Celotex roof insulation between rafters: Pitched Roof Insulation Under Rafters

Pitched Roof Insulation Under Rafters

Arguably the most popular pitched roof solution, installing insulation between and under the rafters uses the depth of the structural timbers to best effect. Its versatility is the key to its popularity, whether being used to achieve:

• an efficient room-in-a-roof in a new-build property where over-rafter insulation is not desirable
• a refurbishment of an existing roof with head room to spare below the ceiling, or
• a project converting a loft space into a room in the roof

It allows insulation to be installed in a watertight roof, either after the roof covering has been fixed on a new build, or without disturbing an otherwise sound existing roof covering as part of a renovation.

Modern U-value targets mean installing insulation between rafters only is rarely a viable option. Using a thermally efficient material to get the maximum benefit from as much of the rafter depth as possible means the under-rafter insulation layer can be kept to a minimum, making installation easier.

Rigid polyisocyanurate (PIR) foam insulation boards (such as Celotex XR4000 and GA4000) are among the most thermally efficient commonly available insulation materials on the market. Depending on the specifics of the roof, it may be possible to fully fill the rafter depth or, in most cases, leave a 25mm or 50mm air gap between the top face of the insulation and the sarking membrane.

The level of thermal performance required then dictates the thickness of insulation required below the rafters – usually anything from 25mm to 65mm of PIR foam. That can be a general application board (Celotex TB4000 and GA4000 can be considered) followed by a separate plasterboard. Alternatively, using a thermal laminate featuring rigid PIR insulation pre-bonded to a plasterboard (such as Celotex PL4000) means fitting the insulation and ceiling lining in one operation, reducing storage, cutting and fixing.

ISOVER glass mineral wool (GMW) is another option for the between-rafter insulation as a roll or batt. The flexible nature of GMW means that the roll or batts can be accurately-cut and friction-fitted between the rafters – thereby minimising air gaps and maximising thermal performance. In addition, GMW (such as ISOVER Metac) also has inherent acoustic benefits that will help to improve the acoustic comfort of the room-in-roof area as well as the thermal comfort. Once installed, the rafters will be finished in much the same way – either with a thermal laminate or with a general application PIR board followed by a separate plasterboard.

When using Celotex or ISOVER products, you need to satisfy yourself that use of the product meets all relevant national Building Regulations and guidance as well as local, national and other applicable standards relevant for your construction or application, including requirements in relation to fire and applicable height restrictions. In addition to the product datasheet, please refer to the following product documents:

• BBA certificates – where applicable to the application
• Declarations of Performance
• Health & safety datasheets

The building detail is for illustrative purposes only. It does not constitute advice and should not be relied upon.

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Insulation products

Product Name	Thickness Range	Sizes	Lambda
Celotex GA4000	50-100mm	Width 1200mm, Length 2400mm	0.022
Celotex PL4000	25-65mm (+12.5mm Plasterboard)	Width 1200mm, Length 2400mm	0. 022
Celotex TB4000	20-40mm	Width 1200mm, Length 2400mm	0.022
ISOVER Metac	50-200mm	Width 1.2m, Length 3.2 – 9.3m	0.034
Celotex XR4000	110-200mm	Width 1200mm, Length 2400mm	0. 022

Roof Insulation with Celotex GA 4000 Insulation Board

Pitched and Flat Roof Insulation Solutions

Proper roof insulation should be ranked high on your list of priorities, so if you are planning on building a home or reconstructing and upgrading the existing one, now is the perfect time to consider insulating your roof. Namely, regardless of whether you are having (or planning on constructing) a flat or a pitched roof, both require adequate protection, simply due to the fact that conducted studies have shown that a vast amount of heat is lost through a poorly insulated roof. Another valuable fact that should also be considered is that it is not uncommon nowadays for people to convert their empty and unused loft space into a living space, which should never be done without insulation installed. There are many solutions for roof insulation, so we are here to suggest one why we offer a Celotex GA 4000 guide for your pitched and flat roof insulation.

Celotex GA 4000 Characteristics and Advantages

Prior to undertaking your insulation project, you need to be aware of some basic characteristics and advantages of Celotex GA 4000 PIR insulation boards. They are very versatile since they can be used in various insulation applications, including roofs, walls and roofs, since highly efficient, easy to install and available in a number of different thicknesses ranging from 50mm to 100mm, why they can meet different requirements. It is consisted of a rigid PIR core covered with low emissivity foil facings, for improved performance. No harmful blowing agents were used in the manufacturing process which makes the boards extremely eco-friendly and sustainable. Due to its low thermal conductivity (of 0.022 W/mK), it enables great thermal performance with only one layer of insulation, though it can also be used as a part of an insulation system, upgraded with some other insulation solutions. It comes in standard size of 1200mm x 2400mm, with grid markings which make the installation process even easier.

Before moving onto Celotex GA 4000 roof installation, one should make sure that the boards are stored in dry conditions, and if stored under tarpaulins, additional protection from damage must be ensured. When cutting the boards so they suit the specific application, make sure to use adequate face masks and eye protection, alongside proper equipment, including dust extraction tools. Since edges of the boards can be sharp, make sure not to slide bear hands over the edges.

Celotex GA 4000 in Roof Insulation

The upper mentioned advantages probably persuaded you that GA 4000 boards are the best solution for your roof insulation, why we shall move on to the installation process in both pitched and flat roofs.

Pitched roof sarking

Celotex insulation boards offer a thinner, single layer solution and create a highly efficient warm roof construction.

Before commencing the installation, please keep in mind that specific fixing instructions may depend on specific requirements, such as the location and dimensions of the roof. The first step involves installing timber battens across the rafters, whereas the stop battens installed should correspond to the size of the boards, since they are butted directly against these battens. When installing the boards, their edges need to be supported by the rafters, and their longer sides parallel to the rafter lines. In words of thermal regulation, it is best that the unprinted side of the boards to be placed face adjacent air cavities. Since the joists need to be closely butted, use adequate saw to cut the boards to splay and rake at verges and the ridge. The boards should be temporarily fixed with some large headed nails.

Then install counter battens of minimum 38mm x 50mm over the boards and nail it directly to the stop batten. Use stainless steel helical spike fixings whose length should correspond to the sum of insulation thickness, depth of rafter penetration and depth of the counter batten. These should be fixed at maximum 400mm centres and the holes in the counter batten pre-drilled in order of minimizing the risk of splitting the timber. A breather membrane should be draped over the counter battens and secured with tile battens, which are fixed to the counter battens at an adequate gauge, depending on the selected tiles or slates. A vapour control layer is also necessary and should be installed to the rafters’ underside. Finally, some sheet material such as plasterboard should be fixed to the rafters. Note that when the rafters are exposed, you can alternatively fix the plasterboard directly over the rafters before installing the insulation, where a vapour control layer should be fixed directly onto the plasterboard.

Between and over the roof rafters

Celotex GA 4000 PIR boards are ideal to be used between and over the rafters, since these can create a habitable under roof space and are especially applicable whenever headroom is limited, with no water tanks and pipes insulation required.

When installing the boards over the rafters, install timber battens across the rafters, whereas the stop battens installed should correspond to the size of the boards, since they are butted directly against these battens. When installing the boards, their edges need to be supported by the rafters. Since the joists need to be closely butted, use adequate saw to cut the boards to splay and rake at verges and the ridge. The boards should be temporarily fixed with some large headed nails.

A breather membrane needs to be installed over the insulation material. Then install counter battens of minimum 38mm x 50mm over the breather membrane and nail it directly to the stop batten. Use adequate fixings whose length should correspond to the sum of insulation thickness, depth of rafter penetration and depth of the counter batten and fix them at maximum 400mm centres. The holes in the counter batten should be pre-drilled in order of minimizing the risk of splitting the timber. Finally, fix the tile battens to the counter battens at an adequate gauge, depending on the selected tiles or slates.

When insulating between rafters with the GA 4000 PIR board, the following guidelines apply. Prior to cutting the boards, you need to measure the width between the inside face of the rafters. In order of ensuring a friction fit, cut the boards at an angle so that the board width is lightly oversized on one surface. The board is then pushed between the rafters so that it lays tight against the insulation layer. The boards can be held in place with battens along the rafters’ side. The insulation should be fit to the ridge plate and wall plates butted at eaves. A vapour control layer should be installed to the rafters’ underside. Finally, add some finish such as plasterboard fixed to the rafters.

Flat roof – between and under joists

Celotex GA 4000 can be used for creating ventilated cold roof construction and is best combined with Celotex PL 4000 plasterboard, which will drastically decrease the installation time and provide flexibility due to the tapered edge plasterboard.

It is important to leave at least 50mm of ventilated airspace above the Celotex GA 4000 insulation boards, so take this into account when you determine the joist depth. The battens should be fixed to the inside of the joists, whereas the bottom of the battens should be approximately 50mm below the decking. Prior to cutting the boards, you need to measure the width between the inside face of the joists. You can choose specially designed clips that are fit at one metre maximum centres and require no additional fixings. Then, the Celotex PL 4000 plasterboard is secured to the underside of the joists. Finally, in order of creating a vapour control layer, all joints between the boards need to be properly taped and jointed.

Find out more about the Ga 4000 Insulation Board and the various roof insulation systems we offer by reading product specifications and descriptions on our website. Get a free quote for your insulation project and a fast delivery by placing your order online with Insulation Shop. For any additional information contact us through our live chat support system or send us an email to [email protected].

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How to Insulate Your Roof Without Any Kingspan or Celotex • Multifoil-Insulation.com

This step by step guide shows how to insulate a roof using our Triple Layer System – Exclusive to Multifoil-Insulation!

The benefit of our system is that there is no requirement for Rigid PIR Insulation, such as Kingspan and Celotex.

Our Triple Layer system is proven to save on cost, space, wastage & installation time.

Both SuperQuilt and BreatherQuilt included in this system are fully certified. These certifications include LABC & BDA Kiwa. Multifoil Insulation’s Triple Layer system will achieve a minimum U-value of 0.18 on a pitched roof. You are able to retrieve a PDF document displaying the U-value achieved, which can be simply forwarded to building control. To get a copy of this document, please visit our Free to use Online U-value Calculator – Click Here to Use!

Multifoil-Insulation are the leading UK & European distributor of Multifoil Insulation products. We offer free next working day delivery to the UK Mainland (Order before 2pm)

Method Steps

1. Install first run of BreatherQuilt

   Firstly, install YBS BreatherQuilt on the external of the pitched roof. Ensure the reflective foil is facing inwards. Starting at the bottom of the rafters, staple BreatherQuilt to the first rafter using 14mm staples (Max 300mm spacing). Roll BreatherQuilt horizontally across each rafter, stapling continuously. BreatherQuilt should sag between the rafters as opposed to being pulled taught. Ensure that once the tile battens are installed, there is a clear 10mm gap between the top layer of BreatherQuilt and the tile battens.

2. Install next run(s) of BreatherQuilt

   Tape a line of 50mm Thermaseal Double Sided Tape along the top edge of the material. Next, install the next layer of BreatherQuilt, overlapping the product by 100mm. Staple as previously and ensure the tape is secured and sealed. This is to be repeated dependent on how many runs are required for the roof. Additional rolls on the verticals should be butt jointed on the rafters. Ensure the butt jointed rolls are stapled as previous and taped using waterproof tape.

3. Install Tile Battens & Tiles

   At the eaves, BreatherQuilt should extend onto a suitable eaves carrier. This works in the same method as standard breather membranes. Proceed next by installing horizontal tile battens, on the top of the BreatherQuilt. Finally, finish by install tiles or slates.

4. Install 2 Layers of SuperQuilt Under Rafter

   Both layers of SuperQuilt can now be installed from the internal (underside) of the rafters. The first layer of SuperQuilt is to be recessed in-between the rafters, the 2nd SuperQuilt is a flay layer under rafter. Ensure that there would be a clear cavity between SuperQuilt and BreatherQuilt.

5. Recess 1st Layer of SuperQuilt

   SuperQuilt is stapled to the underside of the first rafter. SuperQuilt is next recessed into the rafter (25mm), and fixed with staples of with battens. The material is then pulled taught and fixed to the opposite rafter. SuperQuilt is then wrapped around the rafter, ensuring stapling regularly, and the procedure starts again. SuperQuilt is overlapped by 50mm, ensure fully tape and seal using Thermaseal Foil Joining Tape over the laps and around the perimeter.

6. Install 2nd Layer of SuperQuilt

   Once the first layer of SuperQuilt is installed, proceed by installing the second layer. Staple or nail the second layer through the first layer into the rafters behind. Ensure this layer is also pulled taught, there will then be a cavity between the two layers of SuperQuilt. As per the first layer, the second layer is also overlapped by 50mm. Ensure again the product is fully taped and sealed using Thermaseal Foil Joining Tape.

7. Internal Finishing

   Once both layers are installed and taped, you are ready for your batten & plasterboard. Start by installing min 25mm battens on the insulation. We advise to cross-batten, however vertical battens can be used. Finish by installing 12.5mm Plasterboard. There is no requirement for a Foiled-back plasterboard or VCL. SuperQuilt works as a high performance Vapour Control Layer when taped and sealed.

Buy Tools & Materials

Disclaimer – This guide is based on 100mm Rafters @ 400mm centres, with access to both the internal and external of a pitched roof.   SuperQuilt and BreatherQuilt should be installed in harmony with the manufacturers certificate, fixing instructions and good building practice. Our Multifoils are to be cut using a craft knife or a sharp pair of scissors – Available in our Multifoil Fitting Kit. No personal protective equipment, clothing or handling is required.

Multifoil-Insulation cannot be held responsible for any losses financially or physically from advice provided in this How-To-Guide.

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What insulation should I consider when insulating my roof and rafters?

If you have not insulated your roof and rafters, they are costing you a lot of money in the form of energy bills for every minute that you are using the heating system. This is not an ideal situation to prevent heat loss and save money as heat will escape through the roof and rafters. And a considerable temperature difference will be created because it is a known fact that hot air rises, and in an uninsulated roof, all the heat is bound to escape through the roof eventually. The insulation of roof and rafters is not an expensive procedure and neither a difficult one at that. There are several insulation options available to choose from.

Celotex insulation is one of the options available for the insulation of your roof. This is especially needed in the case of pitched roofs where much heat is lost because of the void. This space can be made habitable by insulating along the plane of the roof pitch with Celotex insulation; to create a warm roof structure with Celotex insulation, it can be used over the roof structure to work as insulating sarking. It eradicates the issue of thermal bridges at the rafters whilst the foil facings, used in conjunction with taped joints, provide an effective barrier to moisture vapor and air leakage. The Celotex TB4000 is a multi-purpose insulation board developed to provide simple solutions for overcoming localised thermal bridges. Celotex TB4000 is made by using  rigid polyisocyanurate (PIR) which containsa combination of blowing agents that have zero ozone depletion potential (zero ODP) and minimal global warming potential (GWP). When you choose Celotex TB4000 you are specifically aiming insulation for elimination of thermal bridges; it is available in varying thickness other than the commonly used standard size, is conveniently cut and shaped for fitting purposes, includes low emissivity foil facings giving improved thermal insulation performance within cavity air spaces and the chief advantage of all- it is a method for long-term provision of reliable energy saving for structures.

Another option is the Celotex GA4000 insulation boards which are also the general purpose and also used for roofs. This kind of insulation is also made using rigid polyisocyanurate (PIR) and offers the same set of advantages of use as the Celotex TB4000. The major difference in Celotex GA4000 is that it comes in the size options of 50mm-100mm while the Celotex TB4000 comes in thicknesses ranging from 12-40mm, making it the thinnest PIR insulation available, in a standard board size of 1200mm x 2400mm. In structures requiring yet more thickness, the Celotex XR4000 insulation can be used.
Just a single continuous coating of the rafters using Celotex insulation can thus reduce the risk of condensation and also avoid the requirement for a ventilation system for the rafter space. In the case of the headroom and rafter depth being limited, Celotex Insulation may be fitted between and over the rafters.

Coming to the Rockwool Flexi-slab, it is a multi and dual-purpose thermal as well as acoustic insulation material that has a distinct flexible edge at one of its ends. The flexible edge offered by the Rockwool Flexi-slab allows for a perfect fit that is reliably retained between the product and its supporting framework for convenient installation and optimal effectiveness. The benefits of using Rockwool Flexi-slab are that firstly its design which comprises of the Patented ‘Flexi’ edge offers accurate fit to all widths, thus, can also be used for the rafters of a pitched roof where the fitting is of significant importance. Moving on its use is very much suited especially for roofs since it will not slump even if the studs happen to shrink. It is also appropriate for use with all common typical metal as well as timber frame spacing. Along with having excellent thermal, acoustic, and fire properties, it is a noncombustible material.

Use the Knauf flex-slab as the fast and convenient way to handle and install roof insulation for any kind of roof because it has flexible edges on all four of the slab’s sides, making it much easier for installation. The Knauf flex-slab is made using ECOSE Technology and recycled material. It has also been awarded the A+ generic BRE Green Guide rating.

Ecotherm may also be used for roof and rafters insulation. Ecotherm is rigid insulation boards that will quickly and easily achieve the needed thermal standards in pitched as well as flat roofs. The use of Ecotherm Eco-Versal allows you to insulate the roof space without the need to alter the thickness of the construction or your method; this is because it needs about half the thickness of the conventional insulation materials to give the same level of thermal performance and thus space is considerably maximized. Using Ecotherm Eco-Versal you may create a warm roof at the rafters’ level and no pipe or tank lagging is needed. Insulation may also be done over, below, or in between the rafters.

Kingspan TP10 is a high performing, rigid thermostat and fiber-free insulation option which is faced on both of its surfaces with low emissivity composite foil facing. It is also aimed at the insulation of warm roof spaces in the face of unventilated or ventilated pitched roofs. It is commonly used as rafter level insulation for tiled or slated roof spaces which are also pitched. Kingspan TP10 is readily available in different size options and also manufactured according to the size required. Kingspan TP10 boards may be used for insulation between, over and under rafters, and as pitched roof sarking.

Plasterboard is typically used with insulation along with a layer of insulating foam bound to it’s the rear side. Sometimes insulated plasterboard is also placed in conjunction with a vapour barrier. Plasterboard is generally a good performance material for insulation of roofs since it is fiber free and rigid thermostat insulation. It’s most suitable for the purpose of insulation, to place most of the insulation between the rafters with an extra layer placed under the rafters. Plasterboard is good for this simple insulation solution; it can be found in a vast variety of rigid insulation products bonded to it. Such as Celotex PL4000 or Ecotherm Ecoliner or Kingspan K18 and Kingspan Kooltherm. Other well-known brands such as Gyproc manufacture an insulated plasterboard called the Gyproc Thermal Basic, Gyproc Thermal Plus and also the Gyproc Thermal Super. Each type of board performs differently eg. the Gyproc Thermal Basic board is EPS insulation attached to the back of the Gyproc Plasterboard, the Gyproc Thermal Plus board is XPS insulation attached to the back of the Gyproc Plasterboard and the Gyproc Thermal Superboard is Phenolic insulation attached to the back of the Gyproc Plasterboard.

Celotex: A Buyer’s Guide

Celotex Saint-Gobain Insulation UK offer a range of products for thermal and acoustic Insulation. With a strong focus on innovation, their products are of high quality and the company has over 90 years of experience.

 

What Is Celotex?

 

Celotex is a multi-purpose insulation board that can be used around the home for insulating roofs, walls and floors and they come in a range of sizes and thicknesses.

 

 

What is Celotex Made From?

Celotex insulation boards are PIR, (polyisocyanurate), which is produced as foam and used as rigid insulation. This rigid core is usually sandwiched between two aluminium foil facings that are high performance, thus creating a tough, hard wearing yet lightweight insulation board. Performance is high while reducing building or renovating costs. The way in which the boards are made is easy on the environment and has a low impact on global warming.

 

Is Celotex Fireproof?

 

There is no insulation that is fully fireproof, but there are some insulation boards available which are classed as “fire resistant” or “fire proof”, which means the material used in them slows the spread of fire. They are specially designed to resist high temperature and ensure no toxic smoke is released if it does encounter flames.

 

Celotex products will burn if exposed to a fire of sufficient heat and intensity. All organic materials when burnt release toxic gases. Any fire should be fought by trained firefighters according to the combustible materials present and using breathing apparatus. Cardboard and plastic packing materials are combustible too. We advise to store the boards away from all possible sources of ignition.

 

What can Celotex Insulation be used for?

 

Celotex insulation can be used for walls, flooring and roofs in homes and other buildings.

 

We’ve put together this handy table to help you compare the different Celotex products that we sell.

 

Product	Use	Size	Thermal Conductivity W/mK	Available Sizes
Celotex CW4000 Insulation Board	Cavity Wall – specifically for use in partial-fill cavity wall applications.	1200mm x 450mm	0.022	50mm 75mm 100mm
Celotex XR4000 Insulation Board	Multi-purpose – Pitched Roofs Flat Roofs Solid Masonry Walls Timber Framed & Steel Framed Systems Floors	1200mm x 2400mm	0.022	120mm 150mm
Celotex PL4000 Thermal Insulation Board	The ‘underneath’ layer of insulation in between and under rafter and joist applications Insulating solid masonry walls Timber frame lining applications including stud wall insulation	1200mm x 2400mm	0.022	25mm/12.5mm 40mm/12. 5mm 50mm/12.5mm
Celotex TB4000 Insulation Board	Multi-purpose – Pitched Roofs Flat Roofs Solid Masonry Walls Timber Framed & Steel Framed systems Floors	1200mm x 2400mm	0.022	25mm 30mm 40mm
Celotex GA4000 Insulation Board	Multi-purpose – Pitched Roofs Flat Roofs Solid Masonry Walls Timber Framed & Steel Framed systems Floors	1200mm x 2400mm	0.022	50mm 60mm 70mm 75mm 80mm 90mm 100mm

 

Here we will take a closer look at some of the uses in more detail.

 

Using Celotex For Floor Insulation

 

Insulating floors is important for keeping heat in the property and keeping feet warm in the winter as well as being effective at adding a sound barrier between upper and lower floors.

 

The following Celotex Insulation boards can be used for solid floor insulation, with concrete or screed flooring.

• Celotex XR4000
• Celotex TB4000
• Celotex GA4000

 

The Celotex boards are laid on top of existing flooring and then covered by your chosen floor finish. It’s a cost-effective heat-retention measure and in the long term, can save you money on energy bills, making it a very worthwhile investment.

 

For further information on insulating your floors, read our floor insulation guide.

 

Using Celotex For Wall Insulation

 

Insulating walls can be done in three ways:

• Cavity walls
• Interior walls
• Exterior walls

 

 Courtesy of Milivoj Kuhar

 

Cavity Wall Insulation

 

Celotex CW4000 Insulation Boards can be used for cavity wall insulation. This product is aimed specifically at partial fill cavity wall applications.

 

Internal Stud Wall Insulation

 

One of the best ways to insulate internal solid walls is by using stud wall insulation. By packing insulating materials between or over the timber frames, before the wall is finished, you can effectively insulate the area.

 

Solid External Wall Insulation

 

External wall insulation can help your home retain energy and heat, reducing draughts and increasing the lifetime of a wall. They don’t cause disruption in the home during installation either and so can be applied to houses that have already been built.

 

The following Celotex products can be used for exterior wall insulation.

• Celotex PL4000
• Celotex XR4000
• Celotex TB4000
• Celotex GA4000

 

 

Using Celotex For Roof Insulation

 

Roof insulation can be applied in a few different ways and can help with the energy efficiency of a building. The types of roof insulation are:

 

• Loft insulation
• Pitched roof insulation
• Flat roof insulation

 

Using Celotex For Loft Insulation

 

Insulating your loft is one of the easiest and most effective ways to save on household bills and increase energy efficiency.

 

For more information on the do’s and don’ts of loft insulation, check out our guide.

 

Using Celotex For Pitched Roof Insulation

 

Pitched roof insulation is used in situations where loft insulation is not practical. You can use boards or foil.

 

The following Celotex products can be used for pitched insulation:

• Celotex XR4000
• Celotex TB4000
• Celotex GA4000

 

 

Using Celotex For Flat Roof Insulation

 

Flat roofs can typically lose a lot of heat. Spaces such as garages, extensions and utility rooms should all be insulated properly to increase the energy efficiency of the entire home or building.

Our guide on flat roof insulation can help answer questions around the installation process.

 

What Is The Thermal Conductivity Of Celotex?

 

Thermal conductivity is 0.022W/mK for each of the Celotex products we sell.

 

How Long Does Celotex Last?

 

Celotex, if left undisturbed once installed can be expected to last around 60 years.

 

Is Celotex Waterproof?

 

Celotex is moisture resistant. This means it does not absorb water as it has a closed cell structure. This ensures the thermal performance and durability of the product is retained over time.

 

How Should Celotex Be Stored?

 

Celotex boards should be stored flat and clear of the ground, in a dry place. If you are storing the boards along with other materials or under tarpaulins, be careful of rope damage or dents from other items.

 

How Do I Install Celotex Insulation?

 

Celotex insulation should always be installed in accordance with the manufacturer’s guidance. We also have a number of guides available.

 

Celotex boards should not be installed in temperatures below 4°C.

 

When cutting Celotex boards, wear protective face masks, eye protection and sue dust extraction equipment. If your skin is sensitive to fibre irritation, apply a  barrier cream to exposed areas before handling.

 

Benefits Of Using Celotex Insulation

 

The benefits of using Celotex insulation are as follows:

 

• Better thermal efficiency per mm than many other insulation materials
• A lower environmental impact that other typical PIR manufacturers
• An expansive product range suitable for pitched and flat roofs, walls and floors
• Product solutions for both new builds and renovations or refurbishments
• Lightweight
• Low thermal conductivity offering better U-Values and some of the thinnest solutions
• Industry leading

 

What If Celotex Is Not Available?

 

Occasionally we are required to substitute and supply an alternative. When this happens we have a number of excellent brands to choose from, including Recticel, Kingspan and Kooltherm.

 

If you need any help picking the right product, call our experts on 0113 245 9191 or contact us via this website.

 

Whether it’s a DIY or trade project, we offer insulation products to suit a range of uses.

What should i use to insulate between the rafters in my roof?

My attic has been converted into two bedrooms, I have a normal staircase leading up to it. I have 4 hatches around the side walls. Inside these hatches I have noticed,due to the wind and chills, that there is no insulation whatsoever on the underside of my roof tiles. What should I be using to insulte this and what are the legal requirements and regs. ie spacing for ventillation? Do i also need to board over whatever I use to insulate this area.Any help would be greatly appreciated as i have a roll of rockwool and was going to use this and hold it in with sheets of wood. Is this wrong?

i would like to add that the conversion was signed off and certificated but was done before myself and the previous owners lived there. It must be 15 years ago.

Once i’ve used kingspan or celotex does this then require boarding over or plasterboarding?

7

7 Answers from MyBuilder Insulation Installers

Best Answer

B J D BUILDING/ROOFING

Cheltenham • Member since 29 Oct 2008 •

34
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Did you have building regulations in place, as this would have been stipulated, and all of the works including insulation would have been checked by bco.

I think you will have to use Celotex or Kingspan, but make sure that no air flows are restricted.

Best to check with bco as these works will need to be signed of, without certificate of compliance it could affect the sale of the house, should you sell it, as the rooms couldnt be classed as habitable.

2012-01-27T10:10:01+00:00

Answered 27th Jan 2012

GJC Carpentry

Bristol • Member since 23 Jan 2012 •

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There is nothing wrong with that method in princaple is just very tricky, hard work and itchy !!!!! best material to use is 100mm ” kingspan” or ” celotex” foil backed insulation board, easily cut to size to fit between rafters. 100mm based on 150mm rafters leaving 50mm air flow.

Regards

Gary

2012-01-27T10:10:02+00:00

Answered 27th Jan 2012

jd kent

Chorley • Member since 14 Jun 2008 •

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You need 50mm airspace between felt and insulation. We use 100mm kingspan inbetween and 50mm fixed underneath

2012-01-27T10:10:01+00:00

Answered 27th Jan 2012

Apex lofts

Barnsley • Member since 25 Jan 2012 •

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Ok what ever you do , do not insulate directly under the tiles . No matter how well you try and do it you will cause a conflict of areas ( the area that should be warm and the area that should be cold ) your insulation should go above your loft ceiling down the walls and along the lower ceiling . the area you are looking into ( although drafty ) is needed to keep your roof ventilated in the eves and up hopefully to the ridge . It keeps it free from condensation and most types of rot ! 🙂

Now you asked what to use . Retro fitting to the walls you should use a 100 mm 4 ” “cavity battern ” like fiberglass but its cheap enough and slightly ridged .

The floor level / ceiling to get it up to regs you now need as much as 300 mm 12″ thick of fibreglass ” earth wool ” and B and Q had it on offer for a unbelievable 3 £ per roll . good luck hope this made sense .

thanks woody apex lofts barnsley

2012-01-27T10:10:01+00:00

Answered 27th Jan 2012

substructure

Slough • Member since 7 Jun 2008 •

36
jobs,
97% positive
feedback

well its not covered by building regs now ,but by the sounds of it niether is your loft or you wouldnt be having this problem ,so yes insulate with that ,it will stop the cold to a point ,but not as good as celotex or kingspan 120mm thermo board ,and of course rockwool is a lot cheaper

2012-01-27T10:10:02+00:00

Answered 27th Jan 2012

Fresh Approach Design & Build Ltd

Maidenhead • Member since 26 Jan 2012 •

12
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100% positive
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I would personally use celotex cut tightly in-between the rafters. You need to leave a gap to the rear of the insulation between the membrane and the insulation to allow air to circulate around the roof space. You could then simply clad the area with plasterboard etc.

Make sure there are no huge gaps where the breeze is felt as there could be other problems that need to be addressed first.

Hope this helps

Christiaan

2012-01-27T10:10:02+00:00

Answered 27th Jan 2012

Roc builders

Harlow • Member since 25 Aug 2011 •

16
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100% positive
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I presume that as you are concerned about legal requirements and ventilation regs etc,that your loft conversion has been done officially and been signed off by building control. If so,the living space should be as insulated as well as it needs to be already.If it has not been done officially,i would get someone to come take a look at the structural side of things before you insulate anything as your conversion may not be safe or legal.

2012-01-27T10:10:01+00:00

Answered 27th Jan 2012

Rafter system and waterproofing

Consider the features of the installation of a warm roof. The principal design of one of the widespread options for a warm roof (country houses, individual housing construction, etc.) is shown in fig. 5.

5. Roofing “pie” :

1 – vapor barrier; 2 – insulation; 3 – rafters; 4 – intermediate crate; 5 – counter-lattice; 6 – waterproofing; 7 – corrugated board; 8 – crate; 9 – ceiling.

The most common mistakes that cause moisture to form on the interior walls of the room are the absence or poor quality of the vapor barrier (when water from the insulation penetrates into the interior of the room) and insufficient or poor-quality thermal insulation, in which the walls remain cold, and the dew point located on the walls inside the room.

Vapor barrier prevents the penetration of air and steam contained in it from the room into the insulation and moisture from the insulation into the room. When laying it, it is necessary to ensure that the top sheet overlaps the bottom sheet by at least 100 mm, and when joined on a horizontal plane – by at least 200 mm. For tightness, it is desirable to fasten the overlaps with a special connecting tape.

In order to prevent the penetration of moisture into the upper layers of the insulation and prevent the formation of moisture condensate on the corrugated board, waterproofing is provided in the roof structure.

Fig. 6. Lathing and waterproofing :

1 – rafters; 2 – intermediate crate; 3 – counter-lattice; 4 – waterproofing; 5 – crate; 6 – initial purlin

6 shows the procedure for installing the lathing and providing roof waterproofing. The optimal distance between the wooden rafters is chosen equal to 600-900 mm. The beam for the rafters is selected with a size of at least 150×50 mm. When laying insulation between the rafters, as a rule, use all the space possible for this.

The use of insulation imposes additional requirements on ventilation. For good ventilation, it is necessary to ensure air circulation between the insulation and waterproofing. An intermediate crate 50 mm high is stuffed onto the rafters. Waterproofing is rolled out in horizontal layers (stripes) from the bottom up. The layers are stacked on top of each other with an overlap of at least 150-200 mm at a roof slope of at least 30 or 250 mm at an angle of 12-30°. On the ridges of hipped roofs (four-pitched roof with a ridge along the junction of two opposite slopes, Fig. 7), the overlap increases by another 50 mm. The use of a connecting tape is optional. The waterproofing is temporarily adjusted to the crate with a construction stapler, and then it is finally fixed with the slats of the counter-lattice. The counter grating is nailed with galvanized nails and finally attaches the waterproofing film. In no case should you fix the waterproofing “in tightness”. Sagging should be at least 10-15 mm evenly across the entire width of the waterproofing. To ensure ventilation, the film must be at least 30 mm away from the insulation and in no case should it touch it. With this method of installation, a wide range of conventional films can be used as waterproofing.

Fig. 7. Outline of a hip roof

However, this method has a significant drawback: heat is vented from the insulation by air flow along with steam generated as a result of temperature changes in the attic near the “dew point”. In order to eliminate this drawback, it is possible to use waterproofing with a high steam throughput, but at the same time withstanding high water pressure (vapor-permeable films such as Yutakon, Yutavek, Antikon, Tyvek, etc.). Such films also play the role of wind insulation and can be laid on top of the insulation without a gap, since the ventilation of the insulation is provided by the properties of the film itself. In this case, the intermediate crate is not installed.

To create a vapor-tight barrier on the inner surface of the thermal insulation of sloping and flat roofs, films of the Utafol group can be used. They effectively prevent the penetration of steam from the interior of the building.

Before starting work on rectangular slopes, check the squareness of the truss system. If the slope diagonals are not equal (see Fig. 8), they should be aligned with additional spacers under the gable boards and only then proceed with the installation of waterproofing.

Fig. 8. Checking the squareness of the slopes

The initial (lower) purlin must be straight, horizontal, parallel to the cornice and located at the very bottom of the rafters. Upper – as close as possible to the upper corner of the junction of the slopes. To install the crate on the counter-crate, make markings according to Fig. 6. The distance between the boards of the crate (the step of the supports for corrugated board) is 350 mm or more. The crate is made from a board with a section of 100×30 mm, and with a rafter pitch of more than 900 mm – even larger section. The general rule for choosing a pitch is that the greater the slope of the roof, the smaller the distance between the boards of the crate, because in this case they have to carry a large load. In addition, the placement of the crate must be calculated so that the boards fall on the future places of the overlap of the sheets. Fastening of overlaps must be made necessarily.

In places where chimneys and ventilation pipes, skylights, hatches are installed, waterproofing is flanged onto the exit walls.

When arranging a cold attic, it is also necessary to observe the technology of laying the lathing and vapor barrier, as well as the drainage system. Waterproofing is necessary in any case, since the flow of even slight heat from the upper floor, especially in the cold season, will cause condensation to form on the corrugated board. In the case of a cold attic, waterproofing is installed directly under the corrugated board with an air gap of at least 50 mm (Fig. 9). In this case, the temperatures are equalized on the outer and inner sides of the corrugated board, even with significant heat leakage from the room. Particularly good results in this case are obtained by using a film with an anti-condensation coating as a waterproofing. The vapor barrier is laid on the ceiling and covered with a layer of insulation (see Fig. 9). Styrofoam can be used as an inexpensive insulation, followed by sprinkling it with gravel to protect it from fire.

Fig.9. Cold attic room .

1 – ventilated ridge; 2 – profiled sheet, membrane waterproofing, crate, rafter leg; 3 – protective layer, insulation, vapor barrier, overlap.

Roof insulation: scheme, tips, heaters

Roof insulation: scheme, tips, heaters

Roof insulation: scheme, tips, heaters

Roof insulation scheme

If the roof insulation is not installed correctly, the roof truss system can rot and this will lead to the destruction of the entire roof. Heaters tend to accumulate moisture in themselves and when in contact with the rafters, moisture passes to them. This can happen due to improper fixing of the waterproofing. In order to avoid such consequences, it is necessary to know the correct scheme of the roof device along with the insulation. The scheme of roof insulation is nothing complicated. It is necessary to know the correct sequence for installing the insulation and follow several specific rules.

• Measure the pitch between the installed rafters.
• Based on the calculations of the previous paragraph, you need to calculate the size of the insulation, given the small gap.
• Next, you need to lay the insulation between the rafters. Thanks to the gaps taken into account in the previous step, the insulation boards will fit easily and tightly. It is necessary to lay these plates from the bottom up, if possible with a minimum number of seams. It is impossible to leave gaps between the plates, as this will violate the thermal insulation of the roof of the house.
• Fixing waterproofing must be done in such a way that between the insulation boards and the waterproofing itself there is a distance of at least 2 cm. This is necessary to take into account the expansion of many heaters by volume from 10 to 30%.
• The gap when cutting the insulation should not be too large, in order to avoid sagging of the insulation sheets. If such a “sagging has appeared”, then it must be eliminated by additional compaction.
• Next, you need to cover the entire structure with a vapor barrier. At this step, it is very important not to confuse the sides of the vapor barrier film: one side of such a film does not let moisture in, and the other side, on the contrary, brings moisture out. Such a film is fixed with a construction stapler to the roof rafters. If there is a need to overlap the vapor barrier film, then the size of the overlap should not exceed 15 cm. In this case, the seams must be secured with a special sealing tape.
• The last step is to attach the counter grille. The counter-lattice is wooden sheets or beams installed on the rafters, which will serve as the basis for the subsequent finishing of the roof inside.

Insulation selection criteria

In order to choose the right roof insulation, it is first necessary to determine the selection criteria so that, based on their results, the most optimal solution suitable for a particular roof can be made. The most basic criteria are listed below:

• Pay attention to the service life of the material. The insulation should be as durable as possible in order to protect the roof from heat loss for as long as possible.
• Dimensional stability. The better and longer the insulation retains its shape, the better it is.
• Density and weight of the material. The insulation should have an optimal weight and density: it should not be too light or heavy in order to avoid problems with the design and insulation of the roof.
• Resistant to temperature changes. The insulation must retain all its properties, regardless of temperature changes.
• Providing soundproofing. In addition to keeping warm, insulation should reduce noise. This is especially true if the roof is made of noisy material, such as metal.
• Insulation must be made from environmentally friendly material to avoid the release of toxins that can harm the health of those living in the house.

Main types of insulation

Glass or mineral wool is the most suitable material for roof insulation. The best option for roof insulation would be a medium hardness insulation made of mineral material. This option will be more expensive than fiberglass insulation, but the costs are sufficiently offset by a large reduction in heat loss and high environmental friendliness of the material.

The following main types of roof insulation are presented on the modern market:

• Soft roll insulation – such heaters are mainly rolls 8 meters long and consist of wool (mineral, glass or stone). Some manufacturers are made in the form of plates. The thickness of such plates has a value in the range of 75-100 mm.
• Bulk insulation: particles of polystyrene, cork or slate, which are covered with a bag. The weight of such a bag is about 100 kg, it is enough to close 1 square. m.
• Semi-rigid or rigid insulation – made of glass or mineral wool. The thickness of such a heater can vary from 25-30 mm and above. Such material is well suited for warming pitched roofs.

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Technology for the correct roof insulation of a private house: step-by-step instructions

Why it is necessary to insulate the roof

Roof insulation provides the following benefits:

• Reduced heat loss. Since large amounts of thermal energy go through the roof along with heated air that rises, its insulation contributes to significant energy savings.
• Improving the indoor climate. During the summer heat, the heated roof, due to thermal insulation, will not be able to transfer heat to the premises, thereby improving the microclimate and eliminating the need for air conditioning.
• Condensation protection for building materials. When warm air in roof attics comes into contact with cold roofing, condensed moisture appears on its inner surface. As a result, wooden rafters, battens undergo decay, fungus and mold form for them. As a result, the service life of the entire wooden roof truss system is significantly reduced. Insulation plates shift the dew point inside their structure, after which excess moisture evaporates from them and is blown out through the roof ventilation system.
• Possibility of converting the premises under the roof into residential. A heat-insulated attic, as well as living quarters inside the house, can be used as an additional area for temporary or permanent residence of people. If there is an attic floor at the top of the house, it is pre-designed to accommodate residents and must be insulated.

General principles of roof insulation

Heat insulators are used for roof insulation – building materials with the lowest thermal conductivity. At the same time, the greater the thickness of the insulation, the more effectively it prevents heat loss.

In individual housing construction, the most common are pitched roofs with a wooden truss system.

In this case, the insulation is always placed between the rafters. A vapor barrier film must be placed under it. It prevents the saturation of moisture with heaters that have the ability to absorb it from the air.

A vapor-permeable (diffusion) membrane is stretched over the heat insulator. It performs functions opposite to vapor barrier films, that is, it is designed to release excess moisture from heaters, which are formed from its condensation inside the material. Also, the vapor barrier membrane additionally performs the functions of protecting the insulation material from water and wind blowing.

In almost all pitched roofs, ventilation is provided, that is, an additional crate (counter-crate) is mounted on the rafters above the diffusion windproof membrane in such a way that the air blows out the moisture accumulated under the roof covering and evaporated from the insulation.

If the house has a flat roof with a slope of 1 – 2 °, rigid and dense slabs of heat insulators are usually used to insulate it. They are covered with a waterproof carpet made of rolled bituminous or polymeric (PVC, TPO membrane) materials. If a flat roof is intended for operation, arrange an inverted roof. In this embodiment, a waterproofing carpet is laid on the ceiling, a slab insulation is placed on top and poured with a screed. Due to its thickness and strength, the screed is able to withstand the weight of many people without damage to the insulation boards and roll, membrane waterproofing.

Materials for roof insulation and methods of their installation

Almost any heat-insulating material can be used to insulate pitched and flat roofs, with the exception of slag indoors. If the insulation is too soft for use on flat roofs, they, like bulk materials, are placed in a crate.

Styrofoam

Styrofoam is called foamed polystyrene, the plates of which have the structure of porous balls sintered together. The material has a density of 15 to 35 kg / m ³ , thermal conductivity, depending on the structure, 0.35 – 0.5 W / m ° K, water absorption of about 4% in 30 days, has zero vapor permeability.

The disadvantages of polystyrene include its poor resistance to ultraviolet radiation, flammability classes G3 and G4, denoting combustible and highly combustible materials, respectively. Styrofoam fire is also dangerous because caustic and unhealthy black smoke is released during its process.

To increase the strength of the physical characteristics of the foam, reduce its water absorption, pressing technology is used, which makes the material more dense.

High-density foam is used for insulation of flat roofs, where it is able to withstand high loads from poured cement-sand, concrete screeds. The use of the material in the pitched roofs of private houses due to its high fire hazard, installation difficulties and doubts of some users about the environmental safety of expanded polystyrene is less common.

However, it is quite possible to lay foam insulation boards between the rafters, fixing them with mounting foam, and cut off any possible emissions of harmful substances by fixing a vapor barrier film under them from the inside.

Extruded polystyrene foam

This material is obtained by foaming and extruding a polystyrene mass in an extruder. As a result, they have insulation boards with a finely porous structure, which are about 5 times stronger than conventional foam plastic. Extruded polystyrene foam (XPS) with a density of 28 – 45 kg / m ³ , unlike polystyrene, has 10 times less water absorption of about 0.4%, thermal conductivity of the order of 0.028 – 0.035 W / m ° K, low vapor permeability of 0.018 mg / m h Pa.

Extruded polystyrene foam has all the disadvantages inherent in polystyrene, can be used as a heater for flat roofs and pitched roofs. When attaching extrusion boards to wooden beams, it is more practical to use mounting or adhesive foams specifically for expanded polystyrene.

Polyurethane foam

Foamed polyurethane (PPU, PUR) insulation is a rigid board material with a density of 30 to 86 kg/m³ with the lowest thermal conductivity among other heat insulators of the order of 0.022 – 0.03 W/m °K. Its water absorption is 1%, vapor permeability is 0.02 – 0.05 mg / m h Pa. The material is considered environmentally friendly. Its disadvantages include poor UV resistance and a high degree of flammability of class G4.

Polyisocyanurate (PIR) foam boards, which are a modification product of polyurethane foam, are also used for insulation. Modified PIR boards have the lowest thermal conductivity of 0.022 W / m ° K, do not burn and do not support combustion (combustibility class G1). To improve the performance of PIR, the insulation is produced with double-sided corrugated foil, aluminum laminate (multilayer foil), kraft paper shells, fire-retardant carbon coating, bitumen-impregnated fiberglass for direct installation of welded waterproofing.

Polyurethane foam and modified boards are designed for flat roof insulation as well as for use in pitched roofs between rafters. Their connection with each other and with a wooden crate is carried out on adhesive and conventional mounting foams.

According to the TechnoNIKOL technology, PIR boards on pitched roofs are laid on an external planed wooden flooring laid over the rafters.

Stone wool

Mineral wool made of basalt fiber in the form of slabs, sometimes foil-coated, is the main type of insulation in pitched roofs. Its advantages, such as environmental safety, incombustibility, resistance to ultraviolet radiation, a high coefficient of thermal conductivity of the order of 0.035 – 0.04 W / m ° K and vapor permeability of about 0.3 mg / m h Pa, put it in a leading position among others types of insulation materials.

Stone wool insulation boards have a density of 30 to 200 kg/m³, a high degree of compressibility of 20 to 40% and elasticity of 70%, which allows them to be placed directly between roof rafters without cold bridges, without using additional fasteners. The disadvantages of basalt fiber include a relatively high degree of water absorption by volume of 1.5%, which requires mandatory waterproofing when installing basalt wool.

Glass wool

Glass wool with a density of 11 – 180 kg/m³ is an environmentally friendly, non-combustible, lightweight material. Its thermal conductivity of 0.03 – 0.052 W / m ° K and vapor permeability of 0.4 – 0.7 mg / m h Pa are comparable to basalt insulation, while glass wool is an order of magnitude superior to stone wool in terms of its ability to absorb moisture, having a water absorption of 15 %. Lightweight material, although it has high elasticity and compressibility, is not held between the inclined roof rafters, therefore, when laying it, it is fixed with a fishing line or thread stretched between nails driven into the rafters.

Glass wool for roof insulation is produced in rolls or slabs, some varieties have one-sided foil caching.

The disadvantages of the material include the possibility of its caking during operation, if low-quality or insufficiently dense products are used. Also, during installation, due to the causticity of glass fibers, the worker should use a respirator and tight sealed overalls.

Polyethylene foam

Roof insulation uses polyethylene foam rolls or mats of various thicknesses. The material has a density of 20 – 45 kg / m³, has a thermal conductivity of 0.035 to 0.05 W / m ° K and practically zero vapor permeability of 0.001 – 0.003 mg / m.h.Pa and water absorption by weight of not more than 0.8% .

Resilient polyethylene foam boards, sometimes with one or two outer layers of foil, hold well between the rafters without losing their shape or shrinking over time. The disadvantages of foamed polyethylene include its flammability class G2, as well as the undeservedly low popularity of the material, which prevents its widespread use for roof insulation.

Ecowool

Ecowool is a product of processing secondary raw materials, mainly old newspapers and books.

During the production process, crushed pulp (80%) is impregnated with borax (7-10%) to make it fire resistant and repel insects and rodents. The second component of ecowool is boric acid (8-12%), which acts as an antiseptic and prevents the spread of mold, fungus and pathogenic bacteria.

The material has low thermal conductivity and high vapor permeability and is considered environmentally friendly.

Ecowool in the form of a loose gray loose mass is used for thermal insulation of horizontal surfaces, placing it in the cells of a wooden crate. The second common area of ​​​​its application is the insulation of attic floors.

To do this, a wooden crate is made on the walls of the attic, a translucent vapor-tight film is nailed to it and the gray mass is blown into the cut holes with a garden vacuum cleaner.

Construction companies for working with ecowool use special crushing and blowing units (DZA) for blowing.

The filling of the space is controlled through a translucent film; at the end of the work, the holes are sealed with adhesive tape.

If the roof is insulated, plywood is nailed to the rafters from above, a vapor barrier film is fixed from below, after which ecowool is blown into the holes cut in it.

There is also a wet method for applying ecowool. To do this, the paper mass is diluted with water and sprayed between the timber of the vertical crate, the excess is cut off by the rule.

Penoizol

Foam or Teploizol is the name of carbamide foam. The material has a thermal conductivity coefficient of 0.032 W/m·°K, vapor permeability of 0.26 mg/m·h·Pa, sorption humidity – 17.8, does not burn (combustibility class G1). To make roof insulation with your own hands, crushed foam chips with a mass density of 6 – 7 are blown out with a garden vacuum cleaner or DZA. The mixture is fed through the pressure hose into the space between the crate and the vapor barrier film, by analogy with ecowool.

Another option for using loose Penoizol, as well as ecowool, is to blow them from above the roof into the space between the rafters sheathed from below and the vapor barrier film laid on top of them, which is nailed with a counter-lattice.

Sprayed and poured materials

For roof insulation, sprayed polyurethane foams and foam plastics can be used, which have similar characteristics to insulation boards. To carry out this procedure, the rafters on top will have to be sheathed with plywood.

Two-component polyurethane foam is sprayed from below between the rafters and then sheathed.

No less effective insulation for roofs is filler Penoizol. It is injected under pressure into the space between the lathing of the attic walls, the rafters closed from above and their sheathing. The material has a very high expansion coefficient, filling all the free space, resulting in an analogue of SIP panels.

It should be noted that these insulation technologies are practically not used during construction, their main purpose is to repair, restore destroyed or ineffective thermal insulation. For example, Penoizol insulation can be poured directly under the roofing into the ventilation space if it is technically impossible to insulate the roof from the inside.

How to properly ventilate the roof

To ventilate a pitched roof, a counter-lattice is used – a wooden beam with a section of 50×50 mm nailed along the length of the rafters after laying the insulation and diffusion film.

A more modern option is to use in roofing instead of wood, water resistant extruded polystyrene foam (XPS) timber. Similar products with a section of 50×50 mm and a length of 1180 mm under the Carbon Eco brand are manufactured by TechnoNIKOL.

Do-it-yourself roof insulation

It is more rational to solve the problem of how to insulate the roof of a house from the inside with your own hands at the design stage. For example, if it is planned to insulate the roof using basalt wool slabs with a standard size of 1200×600 mm, then the internal distance between the rafters should be laid at 590 mm. This will allow you to lay the insulation boards tightly and without trimming in the space between the rafters. The width of the roof rafters is also calculated, which should correspond to the thickness of the insulation.

Standard

Do-it-yourself typical roof insulation is carried out in the following sequence: If glass wool is used, it is supported by a thread or fishing line stretched from below.

After laying the mineral insulation from below, using a stapler, a vapor barrier film is nailed to the rafters. It is better to use modern materials such as Alpha Barrier 4.0 – foil and mesh-reinforced multilayer films.

To prevent the insulation from getting wet after it is laid, he starts work on the top of the roof. A vapor barrier membrane (Alpha Top) is pulled across the slope, nailing it with stapler staples to the rafters. The diffusion membrane sheets are overlapped by 100–200 mm, connecting the joints with adhesive tape.

Then the rafters are sheathed from below with wood boards or this operation is carried out at the final stage of work.

After laying the membrane over the rafters, a counter-lattice made of wood beams or extruded polystyrene foam is nailed to them along the entire length.

Oriented strand OSB-3 or plywood resin FSF boards for rolled, flexible tiles are attached to the counter-lattice. If composite, metal tiles, corrugated sheets are used as a roofing, a transverse crate made of wooden beams is used to fix them with a step along the width of the roof fragments.

Double

A higher degree of roof insulation can be obtained using the following technology:

Next, a horizontal step-by-step (according to the width of the insulation boards) crate made of wooden beams is attached to the rafters.

A slab of mineral wool insulation is placed between the beam of the horizontal crate, which is subsequently sheathed with wood boards.

Next, the insulation procedure is carried out according to standard technology:

• lay mineral wool slabs between the roof rafters;
• cover them with a vapor barrier film, mount the counter-lattice;
• fix step grating or wood boards under the roofing.

Conclusion

To effectively insulate the roof of a private house with your own hands, you need to choose the right technology and insulation materials based on their operational and physical characteristics. Although the roof insulation of individual houses with pitched roofs can be done in various ways, the generally accepted and time-tested options are those using mineral wool boards, vapor barrier and diffusion membranes, and installation of a counter-lattice for ventilation on the roof.

Pitched roof insulation – penoboard.com

Pitched roofing is the most common type of roof in residential buildings. It provides an air volume and a room that can be adapted to specific needs and that can be used at any time. A key requirement in building a quality home is effective thermal insulation that minimizes heat loss through the roof, provides a reasonable level of occupant comfort, and prevents surface condensation.

Planning

The planned or calculated thermal insulation performance is only achieved if thermal bridges are prevented.

Thermal insulation must be laid over rafters or wood decking, or at least some of the insulation must be laid in a continuous layer above or below the rafters without interruption by any structural element, thus minimizing thermal bridges at the rafters. Loads on the thermal insulation system from the effects that occur in practice, such as snow, wind, as well as the actual weight of the roof, require high strength of the thermal insulation material laid over the rafters. Once installed and tiled, the roof trusses, insulation layer and roof form a compact and durable unit that meets physical, construction, technical and weather requirements.

Application

When insulating pitched roofs over rafters, a rigid thermal insulation material is preferred, which meets the requirements for this application in terms of material properties and work with it. Extruded polystyrene foam PENOBOARD, having a structure with closed homogeneous cells, has the following properties:

• low thermal conductivity
• resistance to moisture
• resistance to alternating temperature changes
• high compressive and flexural strength
• high water and vapour-tightness
• dimensional stability
• low bulk density
• easy to use, can be laid in almost all weather conditions.

Insulation over rafters

In order to prevent thermal bridges, the insulation layer must not be interrupted. This can be achieved by laying thermal insulation over the rafters. This case requires the use of a rigid insulating material with high strength, capable of withstanding loads such as the weight of the roof, snow, etc.

Benefits of using PENOBOARD extruded polystyrene foam for thermal insulation of pitched roofs:

• boards have tongue and groove or stepped joints on all sides and provide a continuous insulation layer without forming a cold bridge;
• boards are impervious to moisture, so protection from rainwater or snow is not required;
• PENOBOARD boards have sufficient strength to withstand the loads transmitted from the roof through the longitudinal rails;
• the entire roof is thermally insulated, protected from stress caused by extreme temperatures;
• the continuity of the surface of the joined rigid thermal insulation boards increases the stability of the roof against horizontal loads;
• easy, weather-independent installation, simple design.

Roofs with visible rafters

Thermal insulation of the roof over the rafters makes it possible to design mansards so that the wooden structures (rafters) are visible from the inside. In this case, usually wood flooring (board sheathing) is laid on top of the rafters and is also an interior finish.

Waterproofing, vapor barrier

Polymer-bitumen waterproofing membrane, laid on board sheathing, acts as a waterproofing underlay, as well as a vapor barrier and is laid under the thermal insulation on its warm side. Another option is to install a diffusion waterproofing underlay directly on top of the thermal insulation. An additional vapor control layer can be installed under the insulation, further increasing the tightness, although this is usually not required by calculations of possible condensation.

Thermal insulation

PENOBOARD boards must be laid with bonded seams following the brickwork pattern with a tight joint, starting from the cornices and resting on a parapet rail, the height of which is equal to the thickness of the thermal insulation, and must be connected to each other in such a way that no formation of thermal bridge. Gaps between heat-insulating boards and connecting structural elements must be filled with polyurethane foam by spraying. Thermal insulation boards are fixed to the rafters through the longitudinal battens and plank flooring using special fixing nails or screws.

The longitudinal rails must be pre-drilled so that they do not crack or split during installation. The dimensions of the fastening system in relation to plates and longitudinal rails must be determined by a specialist engineer, especially in the case of thick thermal insulation.

Roofs with hidden rafters

Thermal insulation

PENOBOARD boards must be laid directly on top of the rafters in the same way as for roofs with visible rafters, starting from the eaves and resting on the parapet rail, the height of which is equal to the thickness of the thermal insulation. Insulating boards – depending on the thickness and distance between the rafters – must not be used as work platforms!

Waterproofing, ventilation, roof finish

A vapor-permeable waterproofing underlay must be laid directly on top of the thermal insulation below the longitudinal battens. It is recommended that the longitudinal battens be at least 40 mm thick to provide adequate ventilation under the roof, as well as a solid base to secure the battens or wooden boards supporting the roof.

Interior finishing

Plank sheathing, dry plaster sheets (gypsum board) on longitudinal rails, etc. can be attached to the bottom of the rafters as an inner lining. Although condensation calculations do not normally require this, an additional vapor control layer can be installed between the interior trim and the rafters to further increase the tightness.

XPS boards store well even outdoors, just avoid direct exposure to sunlight.

Roof insulation in detail. Article 7

The Roofing magazine completes the publication of a series of articles by V.Yu. Nesterov “Under-roof insulation in details” (see No. 3-4 (18-19) 2008 and 1-4 (20-23) 2009). The last, seventh, part of this review is devoted to the topic of the reconstruction of attics from the outside. Our magazine has already published an article with a detailed description of the technology for repairing attics, carried out from the outside (see “Roofs” No. 4-2007). Today we offer a more detailed description of this technology with detailed drawings that will help roofers to correctly and with high reliability perform a complex reconstruction of a damaged attic.

Often it is not possible to carry out repairs from the interior side, as customers set a condition for roofers not to disturb the interior finish. Therefore, one option remains – to disassemble the roofing, roofing film and thermal insulation. Usually, at the same time, the old vapor barrier is also removed so that it is possible to inspect the condition of the rafters and interior decoration, as well as determine the most problematic areas of the roof.

Repair from the outside is quite a difficult task, as it is carried out without the resettlement of residents and it is very important during the work to prevent precipitation from entering the premises.

Fig. 1. Installation technology of conventional
vapor barrier films

Until recently, roofers were forced to use classic vapor barrier films with low vapor permeability (Sd > 40…60 m). The rolls were laid between the rafter legs in the form of a groove, the overlap on the side of the rafters was 50-100 mm (Fig. 1).

To prevent the penetration of warm and humid air from the interior into the roof structure, it was necessary to hermetically attach the film to the wooden rafters along their entire length. Usually, adhesive tapes were used for this – single-sided and double-sided made of butyl rubber or acrylate, which were additionally pressed with slats or bars. However, a reliable connection with such tapes could only be achieved on rafters with a smooth (planed) surface, which was extremely rare.

Fig. 2. Cracks and delaminations in rafters

Special adhesives (eg DELTATIXX) for bonding foils to materials with rough surfaces became available to Russian roofers only five years ago. Therefore, in many cases, the classical repair technology did not give a full guarantee of success. In addition, through cracks and delaminations in the solid wood of the rafters, mauerlats and girders (Fig. 2), moisture could freely enter the insulation and lead to the formation of condensate.

The simplest and most convenient is the installation of a vapor barrier in a single layer between the rafters, along their side faces and from above (Fig. 3a). This significantly reduces the complexity and cost of repairs, and virtually eliminates the risk of leaks during repairs. Moreover, the danger of exfiltration of moist air from the attic into the insulation through the delamination of the wooden elements of the roof structure is completely eliminated (Fig. 3b).

If ordinary vapor barrier films are used, then mold can form in the upper part of the rafters after a few days, since the accumulated moisture will condense on the cold surface of the wooden elements. Therefore, only special films with variable (adaptive) vapor permeability can be used for this repair option.

They are made of polyamide and differ from classical vapor barrier materials by variable vapor permeability depending on air humidity. At normal humidity, the film prevents the convective and diffusive movement of water vapor from the room into the roof structure, since it is completely airtight and has a Sd value of 5 m. But as soon as the air humidity rises, the film stops working as a vapor barrier, and its value of equivalent resistance thickness diffusion is reduced to Sd=0.2 m, which corresponds to the permissible level of diffusion subroofing membranes. Thanks to this unique ability to change its vapor permeability, such a film freely removes excess moisture from the structure and prevents the formation of drip condensate on the surface of the rafters and insulation.

The DELTA®-SdFLEXX membrane manufactured by the German company DORKEN GmbH & Co.KG has been successfully used for the renovation of attics for several years on the Russian market.

To protect the film from damage caused by screws and nails protruding from the interior trim, it is recommended that a thin layer of thermal insulation (3-5 cm) of mineral wool, extruded polystyrene foam or fiberboard be placed between the film and the interior trim. After that, the rafters are processed – sharp edges and burrs are removed from them, which can also damage the film during installation work. Next, an adaptive vapor barrier is laid horizontally across the rafter legs, while the film completely wraps around them from the outside (Fig. 4). Roll overlaps are glued with tape or glue to completely eliminate the convective movement of moist air from inside the attic into the insulation.

Thermal insulation material is laid to the full height of the rafters, while the joints of the insulation layers must be shifted relative to each other to prevent cold bridges (Fig. 5). Insulation can only be made of mineral wool, with a high diffusion capacity. Styrofoam or similar vapor-tight materials should not be used in this construction.

Fig. Fig. 5. Installation of insulation between rafters

6. Sealed gluing
vapor barrier on the gable and cornice

Airtight joints on gables and eaves, valleys, ridges, chimneys, chimneys and windows are made with adhesive or adhesive tape (fig. 6). When performing repairs, maximum attention must be paid to any adjunctions and penetrations. Therefore, roofers must foresee all the nuances and design features in advance. It is necessary to calculate the length of junctions, overlaps and order the required number of accessories. It should be taken into account that the consumption of vapor barrier film, tapes and adhesives will depend on the section and pitch of the rafters.

Fig. 7. Laying diffusion membrane

It is recommended to use DELTA®-MAXX/DELTA®-MAXX PLUS premium-class diffusion membranes as roof underlay membranes, which have a unique ability to combine diffusion and anti-condensation properties (Fig. 7). Such films will not allow wetting of the insulation and rafters with condensate, as they can adsorb (hold) up to 1000 g of drop moisture per 1 m2 of surface and then remove this moisture due to diffusion (Sd = 0.15 m). A mandatory requirement when installing films is gluing overlaps of rolls with tapes, which will protect the roof from heat loss, moisture and freezing.