Finishing a house requires us to use various sealing techniques. One of them is applying polyurethane foam. Thanks to its extraordinary properties we can, among others, seal the roof much faster.
Polyurethane foam is a modern material that adheres to various surfaces. It is applied directly to the roof structure, but it also has other advantages, such as thermal insulation. Thanks to its design, it can fill any gap, even the smallest one. The foam is useful especially between the rafters, and also next to the masonry. Then it prevents the formation of the so-called thermal bridges. It also has the advantage that it does not shift over time. Moreover, it does not lose its thermal insulation properties. Open-cell foams are especially recommended for roofs, as they are vapour-permeable and extremely flexible. They are applied using spraying technology.
Several types of polyurethane foam can be distinguished – one of them is closed-cell foam. It is 90 or 95% filled with closed bubbles with gas inside. As a result, it conducts heat very poorly. These bubbles often contain noble gas, which makes it even more difficult for heat to travel – with this type of insulation the heat transfer rate is no more than 0.024 W/(m*K). What’s more, this type of foam has remarkable crush resistance and is used for insulation and waterproofing of roofs or attics. It can also be used for floors or foundations. It is most often applied in layers 3 or 4 cm thick.
Open cell foam has open cells and has a spongy structure, which is also filled with air. The insulation here is at a level of 0.034 – 0.040 W/(m*K). This type of foam is compared to polystyrene or the very popular mineral wool. It is a great choice if you want good sound insulation. Open-cell foam can be used for attic insulation, but due to its low compressive strength, it is not suitable for foundations or floors
Polyurethane foam is applied by spraying the material, which expands so it can quickly fill any gaps. It has high resistance to fungi and mold and is odorless. In addition, there is no need for special preparation of the surface to be applied. It forms a seamless layer, which reduces the risk of so-called thermal bridges. Closed-cell polyurethane foam is applied in several layers, 3 cm each, whereas open-cell polyurethane foam is applied in one layer. By applying the foam in thin layers, we can wait until the foam has time to expand before applying the next layer
Before applying another layer of foam, wait until the one applied earlier expands and sets. However, before we apply the first layer, the surface to be sealed should be degreased. For this purpose we can use a special cleaner, which, just like the foam, is applied under pressure
A single cartridge of polyurethane foam with a capacity of 750 ml costs about PLN 50. Foam gun should be added to the cost. A professional gun costs approximately PLN 150. Importantly, the cost of the foam depends on the surface to be sealed
Polyurethane foam has many advantages. With its help, you can much faster seal the attic or floor. It does not require much preparation and is easier to apply than mineral wool or foamed polystyrene. With its help we also seal windows and walls. It is resistant to moisture and mould, which is useful e.g. while sealing the attic. It has also great heat insulation properties. Moreover, it guarantees good acoustic insulation.