Room to move
Strict Building Regulations relating to insulation can mean thick external walls that eat into the available living area. Kingspan Insulation’s Adrian Pargeter explains how to comply without compromising on space
F
or many years, the major stumbling block for eager self-builders has been the challenge of finding a suitable plot.
However, the introduction of the Self-build and Custom Housebuilding Act 2015 at the start of April should help to change things. The Act requires local authorities to keep a full register of interested self-builders within their catchment and to permission sufficient plots of land to meet that requirement. Of course, once you have a plot, the key
question is how to get the most from it? One of the primary reasons people choose to self-build is to gain a bit more space to stretch out and enjoy, but the home also has to meet the increasingly strict energy requirements in the Building Regulations and Standards. If you’re planning on sticking with a conventional cavity walled construction, this could lead to a potential problem.
Walls closing in
The most recent changes to the regulations governing the energy performance of homes significantly raised the levels of insulation
40 selfbuilder & homemaker
www.sbhonline.co.uk
required for a building to reach compliance. As a result, the overall thickness of the external walls, and consequently the footprint of your building, could increase considerably. If you aren’t able to increase the footprint size, or simply don’t want to, then the only other alternative is to reduce the size of the internal space. This can lead to ugly compromises on the dimensions and layout of rooms, making them feel cramped and unwelcoming. Beyond these considerations, there is an additional problem. Most contractors simply do not like traditional masonry cavity wall constructions to be much wider than 300 mm. Larger cavities have other knock-on effects, such as the need for longer wall ties and bigger foundations, all of which can add to the time and cost of construction.
Keeping it slim
A typical cavity wall construction would be a 100 mm medium density concrete block inner leaf with a 100 mm brick outer leaf. That leaves only a 100 mm void for the insulation and cav- ity. So what options are available to meet the
regulatory requirements and keep within the pre- ferred 100 mm void? The first thing to look at is the thermal conductivity of the insulation to be used, otherwise known as lambda. The lower the lambda value, the more efficient the insulation is, so the thinner it can be to meet or exceed the required thermal performance, or U-value, for the construction. For example, the table below shows the thicknesses required for commonly used insula- tion materials to achieve the same level of thermal performance (R-value).
Lambda W/m.K
0.018
0.020 0.022 0.038
Type of Insulation
Advanced Phenolic
Phenolic PIR
Thickness 55 mm
60 mm 65 mm
Mineral Fibre 110 mm
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