16-1218 v3.0/The Living House/XPS Insulation for Rammed Earth Walls


The Living House will be constructed out of rammed earth and we are planning to insulate the interior of the walls with a rigid insulation product (the wall insulation needs to be rigid to enable the earth to be rammed around it, thus ruling out batt type insulations).

We are looking at using 70mm XPS foam for this insulation as it is a rigid product, with a high r-value, that can be used without additional protection directly against the rammed earth thus reducing materials requirements.

We also looked at using PIR insulation for this insulation as it is Red List compliant however we have come to the conclusion that XPS insulation is the most sustainable solution for wall insulation for this dwelling as we have been advised that if we use PIR for the wall insulation that it will require a 300 micron / 1200 gauge polythene sheet to be wrapped around it to protect it from the rammed earth whereas the XPS can be in direct contact with the earth. Using XPS therefore means that we can eliminate and entire material and waste stream from the project. 

We are aware of I10-E12 9/2010 HFRs in Foam Insulation but would like confirmation that XPS foam can be used in this manner in this way as we feel it is a bit of grey area in terms of this exception as there is another potential red list compliant product that could be used as the wall insulation, although we feel that the red list compliant product is actually an inferior product due to its requirement for additional mechanical and moisture protection. 


Because there is a Red List free alternative product available that provides similar R-value performance, this application of XPS with HFRs is not eligible for I10-E12 HFRs in Foam Insulation. While dematerialization is an appropriate design approach, it does not justify the inclusion of Red List ingredients when a Red List free alternative with similar performance is available.

Post ID 6327

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