Can i use loft insulation in stud walls: Insulation FAQs | Knauf Insulation

Insulation FAQs | Knauf Insulation

Can Loft Roll be used in my stud wall or in between rafters?

No, Loft Roll is only designed for use on horizontal applications i.e. as ceiling insulation in cold ventilated roofs.  Loft Roll is a lightweight product designed for optimum thermal performance and ease of application, as such it will not withstand the forces of gravity when installed vertically, nor does it offer any “friction fit” properties.

How do I cut Loft Roll?

Knauf Insulation Loft Rolls are available as “Combi Cut” for ease of application, however if sizes do not match requirement then the whole roll can be cut when in the pack using an insulation saw or sharp knife with a plain or serrated edge.

What is the thermal conductivity of Acoustic Roll?

Acoustic Roll is not assigned a discrete thermal conductivity as it is produced to meet the min 10kg/m3 as per building regulations. If a thermal requirement is also requisite other Knauf Insulation products that meet the minimum density requirements can be used. Contact our Technical Services Team for further information on 01744 766 666

Note: for Robust details certain density criteria above the minimum may be required to achieve compliance.

Can any Loft Roll product be used in applications where acoustic absorbance is needed?

Only Loft Roll 40 can be used in horizontal applications where acoustic absorbance is required in relevant Approved Documents  where a product with a  minimum density of 10kg/m3 is deemed to supply the required acoustic absorbence.

Note: for Robust details certain density criteria above the minimum may be required to achieve compliance.

How does the density of Glass Mineral Wool insulation affect its acoustic performance, and is there an optimum?

In acoustic terms virtually all glass and rock mineral wool products are relatively low in density, this means that unless there are specific frequency’s to be damped, products in the range of 10 – 60kg/m3 will as a rule of thumb give similar results.

Note: Insulation products alone do not give a sound reduction value, only systems or construction elements give this value. Therefore any sound reduction numbers quoted will be in reference to a built system e.g. a partition wall or separating floor not a slab or roll of insulation.

Why do you not declare the density of some of your products?

Knauf Insulation products purposed primarily for thermal insulation are manufactured to meet the requirements of the relevant harmonized standard, and as such density is not declared characteristic. In the case of thermal performance density alone is not a parameter that will relate directly to R or K value. This is the case as each product is designed not only for thermal performance but also for suitability in the application intended, where a product is like to be used for Acoustic insulation as well as thermal we do confirm the minimum density. Please contact our Technical Services Team for further information on 01744 766 666

Does density relate directly to thermal performance?

As above; not directly in many cases as products are manufactured to meet application demands as well as thermal performance. Select your product in accordance with the intended application in the first instance and match up to the required thermal performance or R value, finally you may need to take into account density from the point of view of acoustic absorption.

What is meant by reaction to fire?

REACTION TO FIRE is the inherent combustibility of a material.  

What does Euroclass A1 mean?

Euroclass A1 means that products meet the highest possible level of non-combustibilty for thermal insulating products when classified to BS EN 13501-1, this classification is a requirement of the relevant harmonized standard as a part of CE marking. A1 means that the product has an extremely low amount of combustible material within it and therefore will not contribute to a developing fire in terms of adding fuel

What is the difference between reaction to fire and fire resistance?

REACTION TO FIRE is the inherent combustibility of a material  

Fire resistance relates to the ability of a built system or element of a building to resist the effects of a developed fire, fire spread and more importantly allow occupant escape and safety. It takes into account how; the system maintains its structure as a loadbearing elements prevents the spread of the fire and provides protects adjacent spaces or buildings from the heat of the fire.

Do you offer a service to collect waste mineral wool?

We do not accept waste mineral wool at present. Although we have investigated and continue to investigate several possibilities for accepting waste mineral wool insulation back into our facilities and so diverting it from landfill, there are several challenges that we have yet to overcome:

  • Mineral wool insulation is a relatively low-density material. Transporting large quantities uncompressed is relatively inefficient in energy and emissions terms. That’s why we compress the new product as much as we can when we pack it in the factory. 
  • Our glass mineral wool already contains around 80% recycled materials. One lorry can bring some 20 tonnes of the recycled materials to the Veolia glass recycling facility adjacent to our St. Helens plant; but a large articulated truck wouldn’t hold more than 3 or 4 tonnes of waste mineral wool insulation.
  • Differentiating rock mineral wool insulation from glass mineral wool insulation can be difficult, especially if the product is older. However, rock mineral wool and glass mineral wool are made in quite different processes and couldn’t be reprocessed together. 
  • Any contamination can cause serious damage to our production equipment. Cleaning recovered waste erodes the environmental benefits of recovering.

As technology improves and segregation at building sites and refurbishment projects improves, so may our ability to accept and recycle the waste. As such this is an area which we are monitoring very closely so that we hope to offer this service to our customers in the future.

Can DriTherm® Cavity Slab be used below DPC level?

DriTherm® Cavity Slabs are a non-hygroscopic, glass mineral wool slab that incorporates a silicon enhanced Ecose® binder designed for use in masonry cavity walls. DriTherm® Cavity Slabs can be used in situations where they bridge the DPC in walls. Tests by the British Board of Agrément confirm that DriTherm® Cavity Slabs will not transmit water to the inner leaf, nor will they transmit moisture by capillary action across the cavity or from below damp proof course level.

Does full filling with DriTherm® Cavity Slab eliminate the need for cavity barriers?

A full fill cavity with KDriTherm® Cavity Slabs will meet the requirements of the Building Regulations 2010 Approved document B (Part 6), therefore cavity barriers will not be required. DriTherm® Cavity Slabs have the highest Euroclass Classification, Euroclass A1 Reaction to Fire Classification, in accordance with BS EN 13501-1 : 2007 as the insulation fully fills the cavity, no cavity barriers are required. (For more details please see: BBA Certificate 95/3212)

What do the numbers on some of your product names mean?

The numbers on our product names are related to the thermal conductivity of the product. So the lower the number, the better thermal performance that product will give. For example Loft Roll 40 will give a better thermal performance than Loft Roll 44.

Can You Use Loft Insulation in Stud Walls?

Loft insulation is a requirement in locations that experience cold winter. During winter times, you want to keep as much heat in your home as you possibly can. A stud wall is common within houses due to its affordability and ease of maintenance. 

Is it possible to get the benefits of loft insulation and apply it to stud walls?

Yes, you can use the same insulation finish used in lofts for stud walls, however, it is far from ideal. The main difference between loft insulation finishes and other insulation finishes is that loft insulations specialize more in keeping the heat inside the house since heat usually escapes through the roof. As such loft insulation was not designed for walls.

In this article, we will be going more into loft insulation, stud walls, and how to insulate your stud wall properly.

What is loft insulation?

Loft insulation is a barrier that prevents heat from escaping through the roof. A good chunk of it leaves the building through the roofing. This is troublesome for homes in locations that experience winter as low temperatures can cause damage to the building.

Designing your house in such a way that minimizes the amount of heat loss during winter will save you money during the winter months when you have to use temperature controls to keep your house warm.

Types of loft insulation

There are four different types of loft insulation, each with their own pros and cons. As a rule of thumb, check which type of insulation would best address your insulation needs.

Blanket type insulation

Blanket type insulation is when the material is woven into a blanket—installed as a “cover,” which acts as a barrier.

Fill type insulation

Fill type insulation, as the name implies, is using granules of material to fill a certain space.

Blown-Fibre insulation

This insulation type will require professional help to install. Blown-fiber insulation involves blowing in the materials to fill up space, particularly useful for areas that are harder to reach.

Sheet loft insulation

This type of loft insulation is installed on the roof. The sheets are usually hard, stiff, and their applications can range anywhere from preventing moisture build-up, to acting as a fire retardant.

Materials for Loft insulation

Here is a brief list of the common materials used in loft insulations and a description on why they work well as insulators:

Material Description
Fiberglass Fiberglass is either made into a blanket type insulation or a fill type insulation. Fiberglass is relatively cheap and easy to install. There are, however, numerous health deterrents if mishandled.
Mineral Rock wool As the name suggests, mineral rock wool is a cloth-like material made from rocks. Mineral rock wool provides not only insulation but also fire protection when needed. This type of insulation can also serve as a sound dampener.
Cellulose Cellulose is a plant fiber used for building insulation. Cellulose filling insulation is applied by filling the crevices between utilities and the walls, which prevents air from escaping or entering a loft.

The stack effect explained

The stack effect is used by architects to plan how air circulates inside a building. Most notably, what causes the stock of it is not the air itself but the temperature of the air.

The difference in air density between an indoor area and an outdoor area may cause one of two effects:

  1. Either the air goes in in the case that the air density inside the building is lighter
  2. The air goes out if the air of the building is heavier compared to the air outside.

Architects utilize this phenomenon by designing houses in such a way that allows a sort of “breeze” to form inside the building.

During the wintertime, what happens is that the hot air rises to the top of the building, and as hot air rises, cold air will take its place at the bottom. If the inhabitants downstairs feel too cold, they would raise the thermostat, and the reverse what happened. Since there is hot air at the bottom, then the cold air from the top would start going downwards.

Understanding the stack effect and why loft insulation is designed as it is, is essential information when considering what loft insulation type should be used for stud walls.

Stud walls explained

A stud wall is a hollow wall, usually used as a partition between spaces. It can be made with either metal studs or wood studs. The main difference between the two is they provide different solutions for different problems; in other words, the best type is situational. In the case of insulation, however, the wood-type stud walls would be better because they are easier to manipulate.

The purpose of a stud wall is the same as any other wall, which is to hold up any windows, utilities, doors, and to provide insulation.

The main benefits of stud walls over other walls are how light a stud wall is, the ease of access that it provides for utilities compared to other wall types, and it’s affordability in construction.

When to use loft insulation in stud walls

The principles for loft insulation can also be applied for stud wall insulation. The main difference is that for stud wall insulation, you probably want to use only a blanket type.

The purpose of insulation will also be the same, which is to keep heat inside the house and to prevent water vapors from condensing. As much as possible, you don’t want any heat going into the walls; instead, the objective of wall insulation is to make sure that heat goes to the air of the room instead.

Other measures you can take to keep heat inside the building

The following are ways in which you can keep your house warmer during the colder months of the year:

  1. Let sunlight into your window. If the sun happens to shine during these times, open the blinds and allow the free heat to entire your house.
  2. Use your curtains, when there is no sun, to prevent the air in your room from interacting with colder temperatures.
  3. Check for any opening that the cold can use to enter your house.
  4. Close your doors, especially in rooms that don’t need as much heat. This is to prevent the heated air from moving around too much.
  5. To save on electricity, don’t turn up the heat when it gets cold; instead, use your temperature in such a way that prevents your house from getting too cold in the first place. Using timers works well for this method.
  6. Remove obstructions from heat sources. This allows the heated air to better circulate around the room or the rest of the house instead of being absorbed by objects.
  7. Maximize your heat sources by adding reflectors in the nearby area. This could be anything from aluminum foil to radiator panels.


Insulation is a vital part to consider, especially when you live in colder climates. Think of insulation as an investment rather than an expense for your house as it prevents damage to the building, improves comfortability, and reduces energy consumption.

When it comes to insulation for stud walls, although you cannot use the same insulation finish used in lofts, you can apply the principles of loft insulation on stud walls.

For stud wall insulation, as much as possible, you don’t want any heat going into the walls; instead, you want to make sure that heat goes to the air of the room instead.

Insulation of the ceiling of a frame house: interstorey 2nd floor

In the frame structure, all surfaces must be insulated through which heat can escape from the house and cold air can penetrate. Insulation of the floors of the first and subsequent floors, as well as the attic floor of a frame house, is carried out by analogy with wall insulation, but has individual characteristics for each type of floor.

  • 1 Purpose of the attic
  • 2 Insulation of the attic
    • 2.1 Insulation functionality
    • 2.2 Composition of the cake
  • 3 Interfloor insulation
    • 3.1 Frame house storeys
    • 3.2 Combination of insulation and sound insulation 90 008
    • 3.3 Types of sounds
    • 3.4 Impact noise and floating floor
  • 4 Variety of insulation
    • 4.1 Mineral wool
    • 4.2 Isolon
    • 4.3 EPPS
    • 4.4 Fiberboard
  • 5 Floor insulation scheme
  • 6 Polyurethane foam
  • 7 Inexpensive insulation
    • 7.1 Sawdust-clay mortar
    • 7.2 Expanded clay insulation
  • 8 Additional recommendations

Purpose of the attic

to smooth out temperature differences between outdoor and indoor air. During the daytime, the air temperature in the attic is always slightly higher compared to the outside. It is cold in the attic in winter, and unnecessarily hot in summer.

In case of insufficient insulation of the attic floor:

  1. All the heat in winter comes out through the ceiling;
  2. When touching the ceiling, the heated air cools down and settles down – an increased reverse circulation of air flows is created and drafts are formed;
  3. When hot air and cold ceilings come into contact, condensation forms under the ceiling, which leads to the formation of mold;
  4. In summer, a very heated attic transfers heat to the room.

Proven heat losses through uninsulated floors reach 30%, which in case of normal insulation will save up to 30% of fuel for heating.

Insulation of the attic floor

The attic in the house is considered an auxiliary unheated room. Its operation is usually minimal:

  1. Storage of unclaimed things;
  2. Conclusion through the room ventilation systems;
  3. Installation of horizontal connecting chimneys and electrical wiring.

Insulation functionality

Usually attics do not have floors in the full sense of the word, there are enough board technological passages. Low requirements for the attic in terms of operation largely determine the type of insulation:

  • It can be slab, roll, sprayed, bulk;
  • Thermal insulation materials do not need to have good soundproofing properties, unless the roof is made of metal sheets;
  • Attic insulation may not have good environmental performance – all harmful fumes will be blown out of the attic space – therefore, as an option, it is possible to use expanded polystyrene or polyurethane foam, and other heaters that should not be added to interfloor ceilings;
  • The characteristics of heat-insulating and auxiliary materials of the attic insulating pie must be no worse than wall and even exceed them.

Cake composition

  • Assignment of layers of heat-insulating cake from bottom to top:
  • Facing, decorative;
  • Heat reflective;
  • Vapor barrier;
  • Insulating and noise absorbing;
  • Waterproof.

Insulation between floors

Insulation between the floors of the house, in the case of the construction of the second floor or the conversion of the attic into a residential attic, is necessary to ensure:

  • Autonomous regulation of the thermal regimes of the upper and lower rooms;
  • Insulation against the penetration of steam and moisture, normal for the operation of one floor, to another where it is not needed;
  • Reduction of heating costs and in case of termination of heating of one of the floors;
  • Sound insulation between floors.

Number of storeys of a frame house

Frame houses above two floors are rarely built in Russian conditions. There are many reasons for this, the main of which is the significant weighting of such a structure, which means the need to give it additional depravity and strengthen the foundations. As a result, the original meaning of frame construction is leveled: simplicity, lightness and low cost.

Although in the USA and Canada, where the technology of building frame buildings has been worked out to the smallest detail, their height reaches 5 floors.

If the builder builds a house with a height of more than two floors, then the interfloor insulation is identical at all levels.

Combination of insulation and sound insulation

Any insulation has, to a greater or lesser extent, soundproof properties, the structure of the floor depends on them, and the design of insulation layers begins with determining the parameters and the origin of possible noise.

Noise level up to 40 dB is quite comfortable for a person, above 80 dB it becomes dangerous for hearing.

Types of sounds

In a residential building, sounds are divided into airy and percussive. When they are combined in various combinations or transformed, they become structural:

Airborne sounds: loud conversation or working household appliances and appliances;

Percussion sounds can be attributed to the impact on building elements: drilling, chiselling, hammering, falling.

Insulation and soundproofing of the interfloor ceiling in the construction of a frame house provides for a combination of hard and soft components of the insulating pie. Soft heaters include mineral and glass wool, fibrolite and others – they absorb sounds.

Rigid: Plasterboard, chipboard and other boards reflect sound back into the room.

Impact noises and floating floor

It is very difficult to deal with impact sounds, which are formed not only from falling objects on the floor, but also from just walking on it.

Beam spacers

To dampen the energy of vibrations, special rubber, rubber or cork spacers are laid on the floor beams, along all beams, and in this case, joists without exception. Only after this is the flooring made of boards or other subfloor material.

Floating floor technology

For effective sound insulation in frame buildings, it is recommended to arrange the floors of the second floor or attic without attaching them to the joist beams. Plywood or chipboard of the maximum available sizes is laid in two layers with an overlap. After that, linoleum is laid, preferably on a felt basis.

A perfect connection to the walls is not required, on the contrary, a small gap must be left.

Skirting boards in this case are attached only to the floor or only to the walls.

A variety of insulation materials

Materials for thermal and sound insulation are available on the market in a large assortment. A set of insulation cake is formed based on the wishes and capabilities of the developer.

Beam floor can be insulated with:

  1. Glass or stone mineral wool;
  2. Fiberboard boards;
  3. Synthetic rubber vibration damping materials;
  4. Extruded polystyrene foam;
  5. Foam polyethylene – isolon;
  6. Silica mats;
  7. Mats and slabs made of natural natural insulation – flax, damask, building felt;
  8. Cellulose ecowool;
  9. Bulk insulation: expanded clay, sawdust;
  10. Steloholst;
  11. Sandwich panels of various designs.

The choice of material by the developer should be based on the calculation and needs for one or another quality of insulation. The laying of insulation, regardless of brand, brand or type, should be as dense as possible, without gaps – this is especially true for sound insulation. If there are even a minimum of through holes in the ceiling, the sound insulation stops working.

Mineral wool

Mineral wool has good heat and sound insulation performance, it is the most accessible and understandable floor insulation with a vapor barrier film in the cake.

So that the insulation does not crumble, it is better to use ready-made mats. In them, the mineral wool is closed from the possible ingress of harmful particles of glass and basalt with a non-woven canvas. In addition, mineral and glass wool have a small price.


Excellent for isolon floors, mounted from the ground floor and facing down with foil. Performs several functions simultaneously:

  • Reflects heat back into the room;
  • Attenuates impact noises;
  • Excellent waterproofing agent;
  • Effective insulation.

Minus – a thin layer, insufficient for complete insulation, must be supplemented with something else.


Extruded polystyrene foam will provide adequate noise insulation, is considered a reliable insulation, but it has poor environmental performance, besides it is flammable and releases toxic substances when burned.


Low density fiberboard has good thermal insulation properties. But fiberboards are quite heavy, overloading the floor beams can occur.

Scheme of floor insulation

The technology of floor insulation consists of the following steps:

  • All floor beams must be covered with antiseptic and flame retardant compounds.
  • Laths of approximately 30 X 40 mm are sewn to the beams from the bottom on the sides for the device between the flooring beams – rolling for laying insulation layers.
  • The reel is made of a thin board (thickness depends on the weight of the insulation) or plywood or other lightweight sheet materials.
  • A layer of vapor barrier from a film is laid on the reel with a 10-15 cm launch on the side surface of the beams, fixed with a stapler.
  • A layer of insulation, preferably soft or semi-rigid, is laid on top of the vapor barrier, close to the beams, or even on top of them.

The insulation is again covered with a vapor barrier film from above.

Next, the floor covering is arranged – rough and finish.

Mounting foam

If foam plastic was used for insulation, then the joints between it and the floor beams can be filled with mounting foam. It is a good insulation, it will tightly close the cracks and fasten individual sheets of sheets.

Foam can be used in hard-to-reach places for warming, as well as for correcting defects in work.

Inexpensive insulation

If there are difficulties with the budget, then you can insulate the attic with sawdust, clay, expanded clay. Relatively recently, there were few effective heaters, but frame construction has existed for a long time and it was local natural materials that were previously used.

Sawdust-clay mortar

Clay-sawdust mixture is quite possible to insulate the attic, if the frame is made soundly, and the foundations are calculated with a good margin. Filling order:

  • Pre-soak the clay for 3-5 days;
  • Sawdust must be 3 times the volume of clay;
  • Clay mortar must be thin, flowable;
  • Dry sawdust is added to the clay solution and the mixture is thoroughly mixed;
  • To combat mold, add a little copper sulphate to the finished solution;
  • Moisten beams and rolls with a little clay milk for better adhesion of the mortar;
  • Fill gaps between beams flush with their top;
  • Leave to dry in an open attic for 7-10 days.

Expanded clay insulation

Lay a waterproof membrane along the roll, install a plastic geogrid between the beams. It is necessary so that expanded clay pellets do not spread and do not stray into one place.

Next, pour expanded clay into the geogrid along the upper mark of the beams. expanded clay insulation does not absorb water, so it does not require additional shelter.

Additional recommendations

When choosing insulation for floors, special attention should be paid to their environmental component. For example, insulation of the floor of the 2nd floor, made of linen natural fiber or seaweed, may be inferior in characteristics to other materials, but the general atmosphere, healthy air of a frame house is guaranteed not to harm those living in it.

Practical tips:

  • Select insulation materials according to their soundproofing parameters – in this case, the thermal insulation will remain at a normal level, but steps on the second floor will not be heard;
  • In the attic, you still need to make a draft floor: it will come in handy in case of a roof leak and the need in this case to replace part of the insulation;

Almost all types of insulation materials can be inhabited by rodents, this should be considered in advance and appropriate measures taken, and there is a large choice of them.

Simple attic floor insulation – variants

After the walls are insulated, which many developers consider to be the main thing, the process of insulating the house stops. People are ready to do anything, installation of a heating system, interior decoration, external decor, but not further warming.

And only the coming winter puts everything in its place – slowly but surely, the average temperature in the house begins to fall, and no powerful heating boiler can correct this situation. All the heat injected by the boiler into the heating system and given off to the interior by radiators flies away through the uninsulated attic floor.

It turns out that the insulation of the attic floor is a more important process than all other housework at the stage of insulation of building envelopes.

When to insulate the attic floor

It’s time to insulate the attic floor after the walls have been insulated. In the case when external wall insulation is performed, and it is usually done in the warm season, immediately after it you can do the attic.

If you have an emergency situation – you bought an old uninsulated house and you need to move or a similar one, then you can first insulate the attic, and only then deal with the walls. Heat, it is known to all, tends to rise. With completely uninsulated building envelopes, the house loses 60 percent of heat through the ceiling, 30 percent through walls and windows, and 10 percent through the floor.

It is necessary to insulate the walls and leave the floor and ceiling uninsulated, you will begin to lose up to 80 percent of heat through the ceiling and the remaining 20 through the floor.

How to insulate the attic floor

To the question of how to insulate the attic floor, I will simply answer – with what is at hand, what can be easily bought and what can be bought cheaply.

It is possible to insulate the attic floor with basalt wool.

And it is possible to blow polyurethane foam between the floor joists to insulate the attic.

It is better to insulate the attic floor with an excess of shareware lightweight insulation than with an insufficient amount of expensive effective insulation.

It is possible to insulate the attic with polystyrene foam, basalt wool, resol foam plastic, foam glass, ecowool, polyurethane foam, adobe.

It is not necessary to insulate the attic with any heavy insulation, such as clay with straw or other heavy hygroscopic material. This insulation shows itself quite well in the walls or in the attic of small buildings, such as a bathhouse. But for the home, it poses a potential danger. It can be saturated with moisture and bring down the attic floor.

Why, for example, clay with straw in the attic of a house is not allowed, but expanded clay is possible? After all, it seems to be the same clay.
Because expanded clay is expanded clay with cavities inside the granules. And even in a situation where expanded clay will be saturated with moisture, its weight will still remain much lower than the weight of the same layer of clay-straw insulation.

Attic insulation thickness

How much insulation to put on the attic floor? The answer is simple – the more the better. Within the framework of the new SNiP, when it is important to achieve the thermal resistance of enclosing structures at the level of almost European standards, for MO it is R = 3.2 for walls and 4.5 for ceilings and floors, the thickness of the insulation may be slightly excessive.

The thicker you put the insulation at the stage of warming the house, the less you then pay for fuel to heat your home. Maybe earlier, with cheap gas, it didn’t matter so much, but now, when gas prices rise 2 times a year, you can already start thinking about overheating your home.

The more expensive the energy carriers, the thicker the insulation layer in the attic.

And if you are heated by pellets, electricity or your house is heated by a diesel boiler, then excess insulation is not a luxury for you, but a necessity. When the boiler burns expensive diesel fuel or is powered by no less expensive electricity, it is no longer necessary to insulate to the standard heat resistance R = 3. 2 and 4.5, but to excess R = 4.6 for walls and 6.0 for the attic floor and floor .

To obtain the R value according to the SNiP standards, 150 mm of basalt wool for the Moscow region and 200 mm of the same insulation for the regions of the Urals and Siberia are sufficient.

But to get a really warm house while saving diesel fuel or electricity for heating, you need to think about 300 mm of basalt wool or polystyrene.

Errors in floor insulation

What are the main mistakes made by the owners when insulating the attic floor in their house?

Firstly, the biggest and most unforgivable mistake is an attempt to save on insulation. For some reason, there is still enough courage to hang 150 mm of basalt wool on the walls. Why then put only 100 mm on the ceiling? The attic floor should be insulated 1.5 times better than the walls and 1.2 times better than the floor. This is an axiom.

Secondly, foam plastic is often used to insulate the attic of wooden and frame houses. Should not be doing that. Styrofoam crumbles between the lags of the attic floor and eventually forms a layer of fine crumbs under the waterproofing membrane.

One spark is enough to start a fire that is unlikely to be extinguished. Styrofoam chips and dry rafters and crates are a very dangerous combination. Styrofoam can be used to insulate an attic floor made of reinforced concrete slabs on a brick or block house, especially if it is a flat, exploitable roof.

Do not insulate the attic of a wooden house with polystyrene foam – if a fire occurs, it is unlikely to be extinguished.

And speaking of waterproofing. When using basalt wool as an attic insulation, do not forget to cover the top of the wool with a membrane. Let you already have a waterproofing layer installed between the roofing material and the battens.

This insulation needs separate protection against moisture and wind. Basalt wool fibers are very light, and a good wind blowing under the rafters will carry it far.