Anyone who has ventured into a loft in the middle of summer or winter will understand the huge range of temperatures that can be achieved in these places. To make them habitable we need to keep good control of both summer and winter temperatures. The answer here is ventilation, heating, and insulation.

You need to meet a minimum level of insulation performance to comply with the current building regs. While these requirements are slightly relaxed for loft conversions, they still result in the entire new story having a total heat loss figure of less than the existing living room just by itself!

One way to get allot of insulation in a small space is with urethane foam or polyisocyanurate foam (PIR). This is a rigid foam panel that can be bought with foil covering on both sides. Even a little as 30mm of this stuff insulates better than a 9" thick solid brick wall!

It pays to shop around as well. What you see here was about £14 for a 8x4' sheet of 50mm thick foam. The local builders merchant quoted £27 + VAT for the same thing! That would have added more than £1500 to the cost of the build!

Another thing that the insulation is good for is noise reduction. For the internal walls a special panel made from a laminate of bitumus foil, PIR foam, and cork is designed to offer better sound suppression as well as good thermal performance.

Any gaps were sealed up with a can of expanding foam filler.