Our utility room on the lower ground floor is the only part of the original floor slab that we didn’t lower as we didn’t see the benefit of all the disruption involved with such an intervention. The disadvantage though is that we have less opportunity to insulate it to the high standard that we have for the new floor (see earlier post). We are at least able to increase the floor by a maximum of 40mm in order to meet the level of the new (higher section) floor and have specified spacetherm. This is a very thin insulation blanket, which is bonded to chipboard. We opt for 20mm thickness of spacetherm (+18mm chipboard), which gives us the make-up we need. The spacetherm is highly efficient, with an exceptionally low conductivity of 0.013 W/m.K, which impoves the U-value of the floor from the original 0.72 W/m².K down to an acceptable 0.26 W/m².K (approximately the standard required for houses built to 2010 Part L Building Regulations)