Frost Insulation

Sturdy and waterproof frost protection

Frost insulation is one of the fundamentals of construction. The frost insulation shown here consists of two layers of FINNFOAM FL-300/70 mm.

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 leakage of waste heat 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 further out, installing 3 panels side by side, for example, which would provide a frost insulation width of 1.8 meters.

Impermeability is the most important property of frost insulation.

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 permeate it. FINNFOAM frost protection insulates effectively without protective plastic sheets or drainage systems. However, you should keep in mind that subsurface drains are a significant for ensuring the proper functioning of other building elements and should never be omitted.

Deck foundations should be insulated against frost throughout.
Two layers of FINNFOAM FL-300/50 mm used as frost insulation.

Actual thermal conductivity is measured using the Lambda U value

The declared thermal conductivity of thermal insulation and frost insulation materials (expressed as λDeclared) represents the optimal thermal conductivity of the product when dry. However, the design and dimensioning of thermal and frost insulation should always be carried out using the actual thermal conductivity of the products, i.e., lambda U (λU) in accordance with the RIL 225 guidelines, which take into account the detrimental impact of moisture on the thermal insulation capacity of an insulation product, for example. To ensure that λU can be calculated correctly for insulation products used in the ground, for example, the designer must know the water absorption of the product used when immersed, through diffusion, and after freeze-thaw resistance testing.

Below you will find lambda U values calculated for FINNFOAM and FF-EPS insulation products in ground-based applications, i.e., slab-on-ground foundations, vertical insulation on the inside or outside of foundations, and frost insulation. In addition, we have also listed actual lambda U values of other EPS insulation products used in similar applications for comparison.

Moisture can impact the thermal conductivity of thermal insulations used in the ground depending on water absorption.

λU = λD x FT x FM x Fa

λD = Declared thermal conductivity (Lambda), FT = Temperature conversion factor, FM = Moisture conversion factor, Fa = Aging conversion factor

FINNFOAM is waterproof

Frost insulation must remain dry at all times. As waterlogged frost insulation does not insulate effectively and may break as it freezes, all frost insulation products should 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 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 effect 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.

Footing insulation 

FINNFOAM insulation panels are very resistant to strain resulting from casting during the construction of a split footing. As the sturdy FINNFOAM can be used to both insulate the footing and to construct molds for casting, the work is guaranteed to be efficient. The smooth surface of FINNFOAM allows it to be removed intact after casting as it does not stick to the concrete. On the other hand, if you want the insulation to adhere to the concrete, you should scratch or flute the surface of the FINNFOAM panels slightly. FINNFOAM insulation can be installed afterward on top of the footing using renovation mortar, for example. FINNFOAM panels can be coated with a thin coat of render following the instructions issued by the manufacturer of the render. 

Transition wedge evens out frost heave

Including a transition wedge in frost insulation eliminates frost heave.

Below the insulation, the ground releases heat as it freezes. This additional heat is proportional to the area marked A. The larger the area of A, the more additional heat is generated under the insulation. 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.