SPRAY APPLIED POLYURETHANE

Initially expanding foam sprayed on insulation was used in refurbishments to stick the roof covering together. It gained something of a poor image in the industry due mainly to dubious marketing. It is now being adopted by some developers as a quick and easy way of installing insulation in walls and roofs. The lack of a reflective foil face reduces efficiency when compared to PU boards but this is to some extent compensated by the fact that the spray coat is continuous and therefore eliminates air gaps. Renotherm’s technical department provides free 'U' value and condensation risk calculations and gives recommended foam depths to achieve the required Dwelling Emission Rate. 'U' value calculations are carried out using the methods in ISO 6946 (walls and roofs) and ISO 13370 (ground floors). Condensation risk analyses are calculated using the method in BSEN ISO 13788:2002 (and BS 5250 Appendix D): Code of Practice for the Control of Condensation in Buildings. Calculations can be provided for roofs, walls and floors and may be submitted to Building Control Departments to demonstrate compliance with Building Regulations.

The spray application can also help achieve the air tightness test in problem buildings. A spin off of sprayed insulation is noise reduction. Air gaps carry noise. If a property is close to a busy road, railway or airport then sprayed PU foam is well worth considering.

AIRCRETE BLOCKS

There were some, mainly in the timber frame sector, who gleefully predicted the demise of brick and block construction when the new Part L requirements came into force. It was claimed that masonry walls would have to be increased to unrealistic sizes. Block manufacturers, resilient as ever, responded with new lightweight products incorporating more air. Coupled with partial fill cavity insulation it is perfectly possible to achieve 0.27/m2K without any significant increase in the overall dimensions of the wall. The use of larger format blocks or thin joint construction also increases the thermal resistance by reducing the number of joints or the width of those joints. However the construction of thin joint is a more exacting process and is not loved by brickies who prefer a more forgiving mortar joint. However it is achieved the end result is that the desired U values of masonry walls can be met without any significant increase in cavity widths.

Despite some strong competition from timber frame, Aircrete masonry construction still retains a sizeable share of the market. Brick and block still has an emotional hold over wall tapping house buyers particularly at the higher end of the market. A feeling of permanence is a major factor when you are embarking on a thirty year mortgage at five times your salary and the fact that you can't set fire to masonry is also reassuring.