Thermal insulation of the external basement wall (perimeter insulation)

Perimeter insulation is the insulation of the basement wall on its outer face. It reduces heat loss from the basement, whether the basement rooms are heated or not. Perimeter insulation should always be installed, so that a later change of use (turning the basement or part of it into a guest room, a sauna or a hobby room, for example) does not require digging out the soil again and insulating afterwards — which greatly reduces the cost of any conversion. You never know if and when you will need the basement for more than storage. The term "perimeter" covers all parts of a building in direct contact with the ground.

Advantages of perimeter insulation with Austrotherm XPS

• high insulating effect — lower energy costs and protection of the environment
• heat does not "drain" from the basement rooms — they are more pleasant to spend time in
• thermal bridges at the foundations and at the basement slab (the slab above the basement) are prevented
• Austrotherm XPS is a reliable insulation material: it does not absorb moisture (water) and takes high compressive loads

Installing perimeter insulation

For a building with standard insulation we recommend 8 cm of insulation (Austrotherm XPS). For a low-energy house you need at least 10 cm. A one-component adhesive (bitumen- or synthetic-based) is applied in dabs to the Austrotherm XPS boards, which are then bonded directly to the waterproofing applied earlier. We recommend boards with a rebate (stepped edges) and staggered joints between adjacent rows. Backfill never in one go but in stages, in layers of about 30 cm, compacting each layer before the next.

In Serbia the maximum permitted U-values ("Umax") for perimeter insulation are Umax = 0.35 W/(m²K) for new buildings and Umax = 0.50 W/(m²K) for refurbishment. Low-energy buildings need at least 100 mm of Austrotherm XPS.

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