Sturdy and waterproof frost protection
Frost protection of a building
Frost protection is one of the fundamentals of construction. Frost protection must function reliably for at least 50 years. Replacing frost protection later is expensive and laborious. The most important feature of frost protection is reliability! The freeze-thaw-resistance properties of any product intended to be used as frost protection should be specified. Taking the margin of safety into consideration, a freeze-thaw test provides a solid representation of the conditions to which frost protection is exposed to in the ground.
In passive and zero-energy houses, the waste heat leaked through the foundations is so minimal that the thickness of frost insulation must be increased by 50% along the walls and even up to 100% in the corners. Another option is to extend the frost insulation wider, installing 3 panels side by side, for example, which provides a frost insulation width of 1.8 meters.
Consistent and closed cell structure
Finnfoam is very durable even in challenging conditions, such as during floods or if the performance of the drainage system is reduced. Finnfoam's completely consistent and closed cell structure does not allow tree roots, water or soil carried by water to penetrate it. Finnfoam frost protection does not need protective plastic or drainage systems to be functional. However, you should keep in mind that subsurface drains are a significant component for the proper functioning of other building elements and should never be omitted.
Finnfoam Frost Protection Guide
A functioning and long-lasting frost protection is maintenance-free, and it should remain functional throughout the design lifetime of the building. Therefore, you should specify sufficient technical requirements for the frost insulation during the design process. With regard to frost protection, frost insulation is one of the most cost-effective and reliable methods of preventing damage.
Finnfoam Oy has produced a guide for professionals, which includes the key principles of frost protection when using Finnfoam insulation products (XPS). The principles are based on the instructions of the Finnish Association of Civil Engineers RIL and VTT Technical Research Centre of Finland.
The guide consists of seven sections:
1. General information (Requirements specified for frost insulation)
2. Designing the frost protection for a heated building
3. Frost protection for cold structures
4. Frost protection for yard areas
5. Frost protection for water and sewer pipelines
6. Frost protection for streets
7. Frost protection for roads
Actual thermal conductivity is measured using the lambda U value
The declared thermal conductivity λD specified for thermal insulation and frost insulation products specifies the optimal thermal conductivity of the product when dry. However, in designing and dimensioning thermal/frost insulation you should always use the actual thermal conductivity of the product, i.e. the lambda U (λU) value, which factors in the negative impact on thermal conductivity caused by moisture, for example. To be able to calculate the λU for insulation used in the ground, for example, we must know the water absorptivity of the product when immersed and by diffusion, as well as after freeze-thaw-resistance testing.
Included below are lambda U values calculated for Finnfoam and FF-EPS insulation products when used on the ground, i.e. in slab-on-ground foundations, as vertical insulation inside/outside the footing or as frost insulation. In addition, we have also listed actual lambda U values of other EPS insulation products used in similar applications for comparison.
The Lambda U values in the enclosed table have been calculated using the following formula based on the EN 10456 standard and the RIL 225 instructions, which are being finalized:
λU = λD x FT x FM x Fa
λD = Lambda Declared, FT = Temperature conversion factor, FM = Moisture conversion factor, Fa = Aging conversion factor
Finnfoam is waterproof
Frost insulation must remain dry at all times. Waterlogged frost insulation does not insulate properly and may break as it freezes, which means that frost insulation products must always be subjected to freeze-thaw-resistance testing. Finnfoam's completely consistent and closed cell structure is waterproof, even if it is fully immersed for long periods and freezes occasionally. Included here are the results of long-term immersion testing.
Finnfoam resists compression
In addition to the ground pressure from above, horizontally installed frost insulation is also subjected to other loads. These usually consist of concentrated loads, such as vehicle traffic and landscaping elements. A soil layer of 30 cm laid on top of the insulation can be used to distribute the impact of these load points over a larger area. On the other hand, frost insulation is most effective when it is installed as close to the ground surface as possible.
Due to the high compressive strength of Finnfoam, the insulation can also be installed under the foundation. Finnfoam can also withstand the weight of heavy machinery. Thus, it is important to choose a product with the correct compressive strength for each location. For example, F-300 is the right product for a regular yard area with typical traffic, while the yard of a truck terminal would be better served by F-400.
Finnfoam insulation panels are very resistant to the strains resulting from casting while constructing a split footing. The sturdy Finnfoam simultaneously functions as footing insulation and casting mold panels, which ensures efficiency. The smooth surface of Finnfoam allows it to be removed intact after casting, as it does not stick to the concrete. If you do want the insulation to adhere to the concrete, the Finnfoam surface must be roughened or fluted slightly. Finnfoam insulation can be later installed on top of the footing using renovation mortar, for example. The Finnfoam panels may be coated with a thin coat of plaster, which should be done according to the manufacturer's instructions.
Transition wedge evens out frost heave
Below the insulation, the ground releases heat as it freezes. This additional heat is proportional to the area marked A. As the area of A becomes larger, the amount of additional heat generated under the insulation also increases. The effect of frost protection is at its highest when the thermal insulation is installed as close to the ground surface as possible. A transition wedge will even out frost heaves, but it also increases the amount of additional heat generated by freezing.