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The house insulation

In order to build a healthy, sustainable, and durable construction, materials and house elements have to be carefully considered. Insulation is one of the keys to making your house comfortable and the interior pleasant. If you are looking to improve bills and save money on energy consumption, insulation can also be the solution.

Why insulate? What are the main locations in the prefabricated house where to install insulation? How to evaluate the efficiency of materials, and what is the choice of products?

This month, we focus on building insulation.


The main objective when installing insulation in a building is to reduce heat loss, but from one material to another, many benefits can come along. The proper insulation, also adapted to the construction, will provide you with many advantages.

Very often, insulation is associated with heat loss; it is essential in the kit house to prevent the heat from escaping through the walls, roof, and other weak points, but not only. Insulation also works as a temperature regulator. If the house is properly insulated, you will benefit from pleasant temperatures inside the dwelling all year round, despite the exterior climate. Not only the house environment will be balanced, as well as the atmosphere enjoyable, but savings will be made on the heating costs, as heating consumption will be reduced. Associated with efficient heating and ventilation systems, good insulation will guarantee a return on investment over time after building a house or improving your old one.

Saving heat and energy will also have a positive impact on reducing greenhouse gas emissions. By doing so, many negative factors contributing to global warming and pollution will also be decreased. Good insulation will help to keep the house steady, ease maintenance, and extend the durability and sustainability of the construction.

The newest regulations regarding construction and the building industry have a lot to do with ecological and environmental aspects. This is why, little by little, standards concerning the efficiency of buildings, energy, and consumption are becoming stricter. These regulations and standards encourage the use of renewable energy sources and efficient and greener materials in construction. The main objectives established for the coming decades include the construction of zero-emissions and positive-energy buildings. Insulation plays an essential role in achieving these ambitious but realistic goals.

Many insulation products possess several features and insulating properties in addition to thermal ones. While maintaining an ideal hygrometric balance, products, which contain air, are able to catch the sound. Therefore, they offer adequate acoustic insulation, providing privacy, reducing disturbances, and improving reverberation in a room.

To benefit from all the advantages that insulation can offer, it is necessary to choose the proper and adapted one. Efficient insulation starts with precise, correct, and suitable house structure construction. The building materials have to be picked according to their uses and quality, and the assembly should be meticulously done in order to reduce air leak points (connections of the materials between two different building materials…) and avoid unnecessary air infiltrations through the buildings, which will make the insulation less efficient and thermal objectives harder to reach.

The elements and parts of a building, which can be insulated at an early stage of the
building construction, should be considered with careful attention. It is the case for the foundations, the crawl spaces, or the basements.

Once the main structure of the house is built, including walls, roof, and floors, the insulation can be installed at almost every required location. In order to build a healthy, sustainable, and durable construction, materials and house elements are essential.


Installing efficient insulation at various strategic locations is essential to decrease the heat loss from the house interior and keep the indoor climate pleasant all year long. It will thus allow you to decrease the annual energy and heating consumption and as a matter of fact, costs linked to the house. Indeed, the need to build more efficient constructions also comes with the fact that approximately 40% of the total energy consumption and 36% of the CO2 emissions are linked to buildings in Europe, making the sector a priority when it comes to innovation, energy-saving, and environment.Buildings are large energy consumers, ahead of industrial sectors.

A house has about 6 major locations through which the heat is mainly escaping. The most substantial heat loss operates through the roof and ventilation holes, through which respectively escapes 25% and 35% of the heat. The same phenomena is observed through other house ducts, which can not be covered, such as chimney pipes.

The exterior walls, windows, and external doors let the heat through if they are not or badly insulated. On average, 35 % of the heat loss operates through the exterior walls and 25% through the windows and doors. This is also why it is recommended to opt for high performance doors and windows. For instance the number of glazing, the frame material, or the glass coating are playing a role in the house insulation. The insulating performance of these elements is therefore calculating and various categories are available in terms of waterproofing, air-proofing, and soundproofing efficiency.

Through the domestic water, up to 15% of the heat can be lost, and another 15% through the house flooring. Proper insulation of the house foundations and perimeter will not only play a role in the comfort of the dwelling but will also protect it from the creation of mold, accumulation of moisture, possible invasion of insects, etc.

Therefore, all the locations mentioned here-upper, from the roof down to the foundations, have to be properly insulated and with high-quality materials.

The location to start with is the roof. As the heat is moving upper, it is not surprising that a substantial quantity of heat is lost through the roof. The insulation used in the attic is usually thicker than in the rest of the house, as this location is often airy. However, good insulation does not mean that the house has to be completely sealed, air needs to properly circulate and keep renewing itself.
Good insulation and adapted ventilation go along, it is why if the air circulation is not efficient, moisture problems can occur inside the dwelling, and its structure.

Insulation should also be installed in the ceilings and between floors. It will allow the temperature to stabilize and provide a more homogeneous climate inside the house and in the different rooms. In addition to maintaining adequate temperature, the insulation will also improve soundproofing.

Of course, the internal and external walls will need to be covered with a layer of insulating material, as well. Concerning exterior walls, windproof and waterproof membranes sometimes reinforce the insulating efficiency. As mentioned, the insulation of the basement, crawl-spaces, and foundations will have a great role in the interior climate of the house. Among others, it will prevent moisture risks, infiltrations, and potential insect infestations. It is possible to use different methods to insulate foundations, and the insulation materials are usually placed at the early stage of the house construction when building the foundations. The junctions between the foundations and house walls and flooring also require great attention and quality materials.

Basement insulation will help to minimize weak thermal points where the air can escape and as a consequence reduce the heat loss, it also protects the damp-proof from possible damages, decreases moisture level, and reduces the risk of condensation on surfaces.

The other house locations you may want to consider insulating – or to insulate the living areas from – are the unheated rooms, such as garages, storage spaces, conservatories, other cold spaces, and joists, for example. Besides, it is good to consider moisture and air control through leaked and weaker locations.


There are three primary manners to insulate a building. The insulating material can be installed from inside the construction, from outside, or integrated into the building structures.

Each technique has its pros and cons, and the choice of the technique to use will depend on various factors, such as the location of the building and moisture level, the material used to insulate, the budget, etc.

Most of the insulating materials available on the market are adapted for the inside insulation technique, even though professionals might recommend certain types of materials more than others, such as rigid foam. In this case, the insulation is placed between the external walls and the house interior. This technique is known to be more affordable than the two others, to provide good phonic insulation due to an efficient sound absorbency, and to fasten the time period to heat the house.

However, the insulation from the inside also has few negative aspects: it slightly diminishes the living area surface because the insulation is installed inside the house. Most of the insulation materials also require to be coated with fireproof covering beforehand. When using inside insulation, the waterproof coating is not protected as it is the case with exterior insulation. The inside insulation technique is more appreciated in western European countries, whereas the exterior insulation technique is commonly used in northern countries, for instance.

The outside insulation technique consists of installing the insulating material on the exterior walls of the house. To nicely finish the walls, the insulation can be covered with cladding, panels, or other products dedicated to this use. In opposition to the previous technique, the living area surface inside the house is not impacted by the insulation thickness.
It also offers substantial waterproofing and, thus, dramatically diminishes the risks of mold growth and moisture in the wall cavities.

Besides, it reduces thermal bridging. The thermal bridges are located where the materials of the house are connecting. The heat can escape through the joists more easily than through other locations, for example. The thermal bridges are mainly located where external walls are connecting with the flooring, interior walls, and window and door frames. Therefore, external insulation provides an efficient overlay, can be used for existing constructions and new buildings.

Among the negative aspects of the outside insulation technique: the cost. Indeed, the outside insulation technique often represents a more significant investment compared to the inside technique.

The third technique consists of integrating the insulation inside the building structure. This technique is mainly applied to wooden and iron frame houses. Yet, it can also be used in traditional building types.

The thermal insulation is placed between the bear-loading joists, and the insulation is provided by each of the building materials. Therefore, no additional materials have to be used. This technique is popular and affordable. The thermal bridges are rarer with this technique than when using the inside insulation technique for instance. However, it also can display a lack of thermal inertia, making it often necessary to be completed by another thin insulating product.


Several indicators allow evaluating the efficiency of insulating materials. When choosing a material, they are essential and provide important information. Among the key indicators of material performance, three of them stand out as essential ones.

  • The thermal conductivity ʎ of a material describes its capacity to transfer and conduct the heat. The lowest the value of ʎ is, the better is the material efficiency to insulate. The thermal resistance, R, calculates the insulation resistance to heat flow. The value of R depends on the ʎ value and the thickness of the material. R is expressed in m² K/W. The bigger R is, the better, as it means that the thermal resistance is good and heat loss is low.
  • The heat transfer U, expressed in W/m²K is the opposite of the thermal resistance R. U evaluates the heat capacity to escape a surface. The smaller U is, the smaller is the heat loss.

To measure the thermal conductivity ʎ, the insulation is placed between two environments with two different temperatures. The difference between the two temperatures is denoted ΔT, the thickness of the material is noted d, and A designated the insulation surface area. The amount of heat transferred (Q) within the material is measured when the flow is stabilized. The amount of energy needed is equal to the thermal flow passing through the material and the amount required to maintain the third temperature at a constant level.

Therefore, ʎ is equal to heat transfer Q x material thickness d / surface area A x temperature difference ΔT and expressed in W (mK). As the thermal resistance R is the ratio between the thickness of the material (d) and the thermal conductivity (ʎ), its value is calculated as followed: R = d (m) / ʎ (W(mK))

Knowing the calculation method of the insulating material efficiency can be beneficial for various reasons:

  • if you are looking to compare different products,
  • if you are not sure about the minimal thickness from which a product is efficient,
  • if you want to check the compliance of material with local regulations, etc.

Let’s have an example: we are looking for the thermal resistance of an insulating material B, which thickness is 150 mm. We know that the thermal conductivity ʎ of the material is 0.0349 (W(mK)). By applying the formula R = d/ ʎ, the value of R is equal to 4.286 m² K/W.
This R-value only concerns the insulation material. To know the efficiency and thermal resistance of a wall, for instance, the R-values of the different wall components should be added.

Despite local regulations and materials availability, the region and country where the house is built, the local weather, the other house materials also affect the choice of the proper insulation materials.


Insulating materials can be classified according to their components and are available on the market under various shapes. Insulating materials include expending spays, rigid boards, batts, or even loose-fill materials. They offer numerous features and are more or less adapted to different locations in the house and uses.

The batt and rigid insulations are mostly used for renovation projects, for which the walls need to be replaced. They are efficient to fill the spaces and can be placed between the building materials. Rigid insulation is well adapted to insulate walls, foundations, and roofs, for example.
The loose-fill materials, usually made of cellulose or glass fibers, are ideal in the attic. They are also excellent to fill spaces hard to reach and for which other insulation types would be harder to install. However, be aware that the loose-fill materials are treated. It is recommended to chose the treatment product with caution, as some of them can interact with the other building materials, such as metal, stone, wood, and possibly damage them.
The expanding spays and blow-in insulations are great to reach areas difficult to access, as they are pretty similar to loose-fill materials. Therefore, they are adapted solutions to insulate old buildings.

Insulating materials can be divided into four general categories, considering their components:

  • Organic polymer components: extended polystyrene, polyurethane phenolic foam, etc
  • Plant and animal components: cellulose, linen, feathers, straw, wood wool, etc
  • Mineral components: glass wool, mineral rock wool, cellular glass, etc
  • Reflective products: products with different layers made of various materials.

On the market, many insulation materials are available to comply with multiple project guidelines, such as budget, efficiency, environmental impact, indoor climate quality, etc. In the construction field, some materials are more common. If you decide to insulate the house yourself, also take a careful look at the product certifications, every insulating material should conform with safety and production standards.

Fiberglass (or glass wool) is one of the most used insulating materials, and its success is due to the great quality-price ratio. The material is composed of recycled glass, sand, and binder. On average, the material contains 40 to 60% of recycled glass.
Products are available in various formats and with different densities, for which thickness and the thermal resistance values vary. The denser products are intended for areas with limited cavity spaces, whereas the thinnest ones can be used for walls and frames.
Among the material assets, its resistance to fire and moisture, and its ease of installation. However, you have to stay careful with the insulation installation, as it sometimes irritates the skin.
Another common material used for insulation is mineral wool. Two main products are part of this category. On one hand, the mineral rock wool product is composed of basalt or diabase. The component is melted until reaching the fusion point, centrifuged, and transformed into fibers. On the other hand, the slag-wool is a material manufactured from metallurgical slags, which is the waste standing at the surface of molten metal. The slags are transformed into fibers, and looking like glass wool. The mineral wool materials are also available in various configurations but are most likely to be found as batts and loose-fill. On average, it contains 75% of recycled components.

Polystyrene insulation is still commonly used, even though the products are composed of styrene, made from crude oil refining. During the manufacturing process, small marbles are catching air. The material is light because it is composed up to 98% of air. It is also colorless and available in different shapes such as blocks, boards, and loose-fill materials. It is possible to find more or less thick polystyrene insulation and with different thermal resistance values.

Note that polystyrene materials have to be used with caution and are not well adapted near electrical installations. If the material is light, easy to install, and low cost, it also stores static electricity, is not well adapted to catch and deal with moisture. It often has lower thermal efficiency too, in comparison with other materials.
Among the three options, mineral wool and fiberglass are the most eco-friendly and mineral wool is particularly environmentally friendly, safer, and healthier. Mineral wool and fiber glass are both safe to install. They are commonly used, yet other green materials are available to insulate a building.

The cellulose insulation is manufactured from up to 85% of recycled paper products, including, for the most part, newspapers. After being crushed, the paper products are fiberized. Mineral borates are added to give the material fire resistance, mold, and insect resistance properties (including termites, cockroaches, ants, earwigs, etc). Compared to fiberglass, cellulose insulation shows less risk for health and a higher thermal resistance value. However, the material is more subject to moisture and needs to be complemented by a vapor barrier. Other disadvantages include the cost of installation and a possible settlement of the material through time, causing the thermal resistance to decrease.
Otherwise, cellulose insulation does not contain free-formaldehyde, ammonium sulfate, fiberglass, and asbestos.

It is also possible to select insulation among natural fibers products, such as cotton, sheep’s wool, straw, or hemp. The cotton insulating materials are composed of 85% of recycled cotton, mainly from the denim industry, and another 15% counting for plastic fibers treated with borate. The advantages of cotton insulation include the safe installation of the material, excellent acoustic and water absorption.

Cotton is an eco-friendly and renewable material. On the other side, the material does not expand rapidly and is more expensive than more traditional insulation materials.

Sheep’s wool insulation is insects, and mold resistant, thanks to treatment. The material has a good level of moisture absorption, is fire resistant and long-lasting, as well as easy to install, and eco-friendly. The disadvantages of the material include a lower thermal efficiency if compared to other products and the costly installation.

Straw insulation, known and used for a long time in the construction industry, also represents a green alternative to most common insulating materials. If it can seem a little drastic, innovations are made by manufacturers, whose interest in the material is renewed. They offer nowadays innovative multiple-layered compressed-straw panels.

Hemp wool material is manufactured from the components of hemp plants. It offers excellent insulating properties, both thermal and acoustic. The material is environmentally friendly and stores CO2. Hemp does not irritate skin, does not contain harmful substances, protects against mold and bacteria, is smell-free, and provides moisture regulation.
About negative side, the material is relatively uncommon, and consequently, not enough tested.

If the variety of insulating materials is large, be aware that some of them, used in the sixties and seventies, are not recommended anymore, as tests and studies highlighted health danger and debatable efficiency. For instance, it is the case of the vermiculite material and urea-formaldehyde foam.


As the construction field is turning greener by proposing larger innovative solutions, eco-friendly constructions, and renewed products to better respond to environmental, societal, and social challenges, insulating solutions aim towards the same objectives. It is not just a global awareness and a need to comply with the newest regulations, but a sincere will to change and to offer more adapted and innovative construction and building solutions, which is now leading the industry.

The green objectives described by the latest regulations include the decarbonization of construction materials, among which the insulation products. Over the past decades, the manufacturers and producers have anticipated the efforts to deploy to make a change. Consequently, the market already evolved to overcome some of the negative impacts of insulating materials on safety and health, while making available high-quality materials with efficient thermal and acoustic insulating properties.

Materials partially composed with renewable components tend to be more ecological, as
the fiberglass products, by integrated 100% of bio-sourced elements.
Bio-sourced and eco-friendly materials are already available. It is the case of cellulose products, wood fiber materials, etc. These products are appreciated for their low carbon footprint, their renewable an environmentally-friendly sides, and capacity to store CO2, but criticized for their cost and lower efficiency, compared to more traditional insulating elements.
To be qualified as bio-sourced material, the product has to be manufactured from renewable components, which origins are whether animal or vegetable. A material produced from another eco-friendly substance (including wood fiber, duck feather, recycled fabric, paper cellulose, etc) can also be qualified as eco-sourced.

However, it is still complicated to qualify an insulating material as 100% green an environmentally friendly, as many of them are not only composed of bio-sourced substances. If some of them are getting close, additional materials need to be added to complete the material features. It is the case with mineral wool, for which a vapor/air membrane is always needed, as they are subject to moisture. If the alternatives to manufactured products are under development and slowly gaining popularity, the more traditional materials such as glass wool or mineral wool are not dethroned yet. Their features are well known and proven for years, installation processes are also easier and fast, and compare to greener materials, they are less expensive solutions with excellent efficiency.


It has always been a goal to create houses with a balanced interior climate, as the temperature variations can have a substantial impact on our daily life and comfort. When it is too hot, we are all seeking a cool place, and when the temperatures are dropping, nothing is better than a shelter where to get warmer. This is true, no matter which century we are coming from.

In ancient Egypt, Egyptians were one of the first to create thick stones out of the mud, to keep the interior of pyramids tempered during the day and the night, when temperatures were drastically dropping down. Without knowing about its toxicity, ancient Greeks were using asbestos to insulate their houses and keep them tempered. They also were the first ones to create gaps in the walls, allowing air to better circulate. The Romans, in addition to being the first civilization with indoor plumbing, were aware of the hot loss operating through pipes. To solve this problem, they were using cork to cover the pipes and diminish the heat dispersal. In the northern countries, particularly subject to drastically cold temperatures, Vikings were sealing the house gaps with mud.

Started from middle age, large rugs were attached to the wall to create an additional insulation layer. The technique (or habit)
persisted for a long time as some buildings and housings from the last century were insulated the same way. Nowadays, this tendency is renewed for decorative purposes.

The need for insulation increase during the industrial revolution. Pipes web were largely used and the heat loss from them became an issue, not only in terms of heat dispersion but also for workers, for example, who could harm themselves. At this point, asbestos was largely employed as insulation and became the major insulating material. Nevertheless, and considering the health problems it causes, the material use decreased from the 70s.

Generally speaking, awareness about the need for insulation in constructions and its benefits increased from the 30s. From this period, the number of insulated buildings started to rise. It is also at this period that the double glazed windows were invented. If efficient, the double glazed windows were also expensive and not everyone could afford them. To this day, it is not uncommon to see buildings with one glass windows, even though they are becoming rarer.

If the insulation need is not new, it is over the past decade that most of the innovation and initiatives have been made to harmonize the interior climate and reinforce the insulation properties of building materials by adding new technology and techniques, while making inhabitants benefiting from the insulation advantages. The industry is still recent and innovation will certainly expand the market in the future, taking into account the health, environmental, social, and societal challenges of our modern society.

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