INSULATION
Phenolic insulation between studs Construction - 20 mm cement render
- 100 mm blockwork (1.13 W/mK lambda value) - 50 mm cavity - Foil faced breather membrane - 18 mm OSB
- 120 mm phenolic insulation (0.019 W/mK) between 140 mm timber studs - 52.5 mm phenolic (0.019 W/mK) insulated plasterboard - 3 mm skim
Total depth 383.8 mm
in elements such as the outer cladding, insulation, studwork and inner drylining. The lower the U-value, the more effective the construction should be at preventing heat loss.
A good starting point when setting a U-value for your project is the Notional Dwelling specification. This is an eample building performance ‘recipe’ used as part of the checks to ensure a home is compliant with the energy performance targets in the Building Regulations and Standards. An energy assessor applies the targets to a theoretical building of the same dimensions as your home. From this, the software generates the performance targets that the actual building is compared against. While these U-values aren’t compulsory, they provide a useful guide.
As the Building Regulations and Standards are devolved, there are different U-values set for the external walls of new homes depending on where it is located. These are 0.18 W/m2 England, 0.15 W/m2 0.13 W/m2
K in K in Scotland and K in Wales. Keep in mind that
Mineral wool insulation between studs
- 20 mm cement render - 100 mm blockwork (1.13 W/mK) - 50 mm cavity - Foil faced breather membrane - 18 mm OSB - 195 mm mineral wool (0.035 WmK) between 195 mm timber studs - 52.5 mm phenolic (0.019 W/mK) insulated plasterboard - 3 mm skim
438.8 mm
the lower the U-value of the walls is, the more well-insulated your home should be. As such, there’s no reason why a self-builder in England couldn’t look to meet the more ambitious values set by Scotland or Wales.
CHOOSING INSULATION
When insulating a timber frame wall, the obvious place for the insulation to be fitted is within the caity between the studs. To comply with the updated Building Regulations and Standards, this caity may need to be fully filled with insulation. However, doing this alone may not be enough to ensure your home is properly insulated. This is because the wooden studs are much more conductive to heat than the insulation. If not addressed, they will act as a path for heat to escape – essentially bypassing the insulation. To prevent this, a further layer of insulation could either be fitted across the external face of the studs (sheathing them) or on the internal face (typically insulated plasterboard).
Alongside deciding which of these
approaches to take, it is also important to consider the thermal conductivity (lambda value) of the insulation measure being installed. The lower this value is, the more effective the insulation is at preventing heat loss. In many cases, this may mean that a thinner thickness of insulation can be fitted, compared with worse performing alternatives, while still achieving the desired U-value. Phenolic insulation boards can achieve a thermal conductivity as low as 0.019 W/mK – this is significantly lower than some other commonly used insulation materials. As an example of how the choice of insulation can impact your project, we carried out a comparison of a typical timber frame construction shown below. In each case, we considered the use of different insulation products between the studs while identical phenolic insulated plasterboard is fitted internally. Both constructions are designed to achieve a U-value of 0.13 W/m2
K in
line with the Welsh Notional Dwelling specification.
As you can see, by simply using the phenolic insulation between the studs in place of mineral fibre, it is possible to use slimmer 140 mm studs and reduce the overall construction depth by 55 mm. When every millimetre counts, this can help to make your internal living spaces feel more spacious without having to compromise on warmth or energy efficiency.
A MORE ENERGY-EFFICIENT HOME Getting the fabric performance right from the start should be a top priority for any prospective self-builder. By using insulation materials with lower thermal conductivities, you can often achieve the desired level of insulation performance with a slimmer construction, maximising space within your home.
Matthew Evans is head of technical GB at Kingspan Insulation
56
www.sbhonline.co.uk jan/feb 2024
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
