Postimees · Home & Construction (Kodu ja Ehitus) · 2025
Which insulation material to choose for a private house?
English translation of the original Estonian article. Original headline: Missugune soojustusmaterjal eramajale valida?
See the original design in the magazineA warm home is much more than just a building that retains heat. It is a place where you feel safe and good and spend quality time with your loved ones.
Building a private house is a big investment in which attention has to be paid to every detail. One aspect that affects a house's energy efficiency and quality of life is insulation.
Correctly installed insulation keeps a house warm in winter and cool in summer, reducing heating costs and ensuring a comfortable indoor climate. Today there is a wide range of insulation materials on the market, differing in properties, price and environmental impact. This article gives a brief overview of the main insulation materials and their advantages and disadvantages, and helps you make a more informed choice.
Mineral wool is one of the most common insulation materials
Widely available on the market is wool made either from artificial mineral fibre mixed with rock – stone wool – or from recycled glass fibres, quartz sand, soda and the like – glass wool. This material's heat retention comes from the air between the wool fibres. If the layers are installed correctly, insulating with this material gives a very good result in the harsh Nordic climate.
The advantages of mineral wool are proper thermal and sound insulation, good fire resistance according to its fire class, a relatively low price and fairly easy installation.
Its drawbacks include the risk that in some cases it irritates the skin during installation, and after installing some types of mineral wool boards, microdust in the indoor air may irritate the airways. In addition, this material definitely needs moisture protection and proper so-called taping at transitions.
So which to choose, stone wool or glass wool? Glass wool can be used to produce a more heat-retaining insulation material; stone wool fibres are much shorter, so less temperature-retaining air fits into the material. Glass wool fibres are several times finer than stone wool fibres, and that is what gives better heat retention.
People with an ecological worldview might also prefer glass wool, because it contains recycled raw material, namely glass. Glass wool is also compressed more tightly, which in turn reduces transport and packaging costs.
Polyurethane spray foam, or PUR foam
When this material is installed, it expands on the surface being insulated, filling every gap and helping to create a truly airtight layer. Because PUR foam is made on site, it rules out large amounts of waste. It is mixed from two components that adhere well to the wall, roof ceiling or foundation of the house. PUR foam is suitable for insulating any part of the house and is available with both closed and open cells.
The advantages of polyurethane spray foam are excellent thermal insulation, covering all irregularities well. Service providers claim that because the material's heat retention is extremely good, the thickness of the building's structures can be reduced. This in turn lowers the construction cost of the whole house. Adhering well to all surfaces and becoming completely rigid when it sets, it helps strengthen the structure of the entire building.
One drawback is the relatively high price, because besides the raw material it requires special machines and workers. It cannot be installed when the temperature is below ten degrees above zero. PUR foam is produced through strong chemical reactions, which may also involve chemicals harmful to the environment.
Expanded polystyrene, known by the standard name EPS
EPS, a light and rigid porous insulation material based on plastic foam, consists of 98 per cent air. The boards are light, easy to handle, don't lose their insulating properties over time and don't deform. EPS insulation boards consist of expanded polystyrene beads tightly bonded together by steam.
EPS insulation is strong and used both in new buildings and in renovating older ones. A building can be insulated with EPS boards from basement to roof. EPS boards offer excellent thermal insulation and high moisture resistance, as they are even suitable for installation in the ground.
Drawbacks include its production process and disposal, because expanded polystyrene doesn't decompose naturally. Since this material doesn't breathe as well as wool, attention must definitely be paid to ventilation between the insulation layers.
Cellulose wool
The main ingredient of this material is recycled paper: depending on the product, 80–90 per cent of it is renewable cellulose fibre. An ecological and sustainable choice with good insulating properties. For many, an important argument is that it doesn't cause allergies. Boron and boric acid added to cellulose wool help prevent the spread of fire. It may also be mentioned that some houses with cellulose wool reportedly don't even need a separate vapour barrier, which means the house can "breathe" naturally.
Like any loose-fill wool, cellulose wool is installed with a special machine. "What's interesting about cellulose wool is that the exterior cladding is sprayed using a wet method. The mixture of glue and water helps fill every gap better and holds the insulation firmly in place," explains Kaimar Kulbin, CEO of Werrowool OÜ.
Wood fibre wool
Made from wood fibres, this material is also preferred by home builders who value sustainability. Ecological wood fibre wool is mostly made from crushed sawdust or wood chips, to which substances are added that protect the material from pests and fire. It also has good heat retention, and as loose-fill wool it can fill every crack to prevent thermal bridges.
Drawbacks include the need to use special machines, as it is installed as loose fill. This, however, can mean longer planning and waiting times and a higher price.
Hemp wool and flax wool can be added to the list of even more natural insulation materials, though their drawbacks unfortunately tend to be below-average availability, a higher price and demanding requirements for conditions.
Hemp wool is a truly natural material for insulating a home. It is environmentally friendly and made without harmful additives, suitable for insulating both new and old buildings. Available as mats and rolls, hemp wool is safe in both production and installation, keeping its shape and functionality. Thanks to its unique moisture regulation, it creates a healthy indoor climate and good sound insulation in the house.
Compared with some other insulation materials, hemp wool may be more expensive than average, meaning a larger construction budget. Second, availability may vary by region and noticeably affect delivery times.
Insulation mistakes that can cost dearly
When insulating a private house, both the right materials and their thickness must be chosen carefully. Often something cheap is chosen that doesn't actually deliver the expected result.
Ainar Albi, representative of Isover insulation materials, places poor installation among the most common mistakes. "An insufficient vapour barrier, poorly sealed joints or the formation of thermal bridges reduce the effectiveness of insulation. Another big mistake in insulating is poor ventilation: in an airtight building, bad ventilation can cause damp and mould."
Mistakes are mostly due to a lack of knowledge. Insulation always involves other work as well, which is often overlooked at first. For example, additional facade insulation: when installing windows and doors, insulation both outwards and inwards has to be planned separately. "Another common mistake with windproof boards is using tape to seal the joints, which is prohibited. Taking the path of least resistance, people still do it. In that case neither the windproof board manufacturer nor the tape manufacturer is responsible for the solution lasting and working over time," says Albi.
When building a house, you need to think long-term, because insulation is really an investment so that heating costs stay consistently low in the future. "Unfortunately, insulation isn't something where you add a bit more after a while and then some more later," Albi laughs, though he mentions as an exception loose-fill wool installed as horizontal insulation, with which you really can do exactly that in some parts of the house.
Everyone can find the best solution according to their personal preferences and means
There are several options for insulating a private house that help ensure a pleasant atmosphere and reduce energy costs. When choosing insulation material, thermal bridges must be avoided. That is why a combination of different insulation materials is often used.
It's important to take the uniqueness of every house into account, because the best insulation solution depends on the house's structure, location, climate, preferences and budget. That is why it is advisable to consult a construction specialist to find the most suitable materials and methods.