INSULATION 73 BESPOKE IS BEST
James Hulbert of Knauf Insulation explains how housebuilders can navigate their way to cost-effective Part L 2021 compliance in England.
P
art L was published in December and will bring England’s new build homes closer to net zero, and
its pivotal role is reflected in the speed of implementation. The changes will come into force in June this year. Transitional arrangements allow for a brief grace period where homes with planning permission can be built to the old standard but after June 2023, all undeveloped plots (not sites) must comply with the new standard regardless of when planning permission was obtained. So, housebuilders must get to grips with the implications fast. For many that will be easier said than done. Recent Industry Viewfinder research by Housebuilder & Developer revealed that over half of respondents didn’t understand what Part L’s 31% reduction in carbon would mean for their developments. Furthermore, 80% expressed concerns about the cost implications of compliance. I want to reassure housebuilders
that compliance can be both achievable
USING THE SAP METHODOLOGY ALLOWS HOUSEBUILDERS TO DETERMINE THE RIGHT WHOLE-HOUSE RECIPE FOR THEIR REQUIREMENTS
and affordable. Under the new regulations, CO2
emissions from new build homes must be 31% lower than current standards, which will be delivered by fabric improvements as well as low and zero carbon technologies. But, Part L 2021 does not require a wholesale rethink of the building fabric. Housebuilders retain a large degree of freedom to find the most cost-effective mix of technology and fabric improve- ments that will achieve compliance.
NOTIONAL IS SIMPLY A SUGGESTION The most important message is that the notional dwelling is just one example of how to achieve compliance for a typical home. It outlines a ‘recipe’ for fabric specification; U-values for the walls, roof, floors, windows and doors, as well as parameters for thermal bridging, air permeability and heating design. It’s not the only way, or indeed the best way. Most housebuilders are unlikely to find it is the most cost-effective route to compliance.
The notional dwelling for Part L 2021 includes U-values of 0.11 W/m2 roof and 0.18 W/m2
K for the walls.
Adding more mineral wool insulation to the loft is an easy and extremely cost- effective way of achieving a U-value as low as 0.09 W/m2
K, so 0.11 is arguably
an under-specification. Loft space is usually dead space, so the plot footprint won’t be affected. By contrast, achieving 0.18W/m2 cavity walls is more costly, and may
K in
WWW.HBDONLINE.CO.UK K for the
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 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100
