SELFBUILDER SURVEY: BUILDING A LOW CARBON HOME
CARBON CALCULATIONS
I
nformation on the carbon impact of individual products is of course crucial to calculate your overall carbon footprint accurately, and while not mandated by law, embodied carbon is a key part of calculating whole-life carbon. Even without including embodied carbon, as stated above, our survey discovered that self-builders were fi nding that calculating the footprint of their build was far from easy however. There are tools available to calculate various aspects of your
build’s carbon footprint, such as heat losses in your envelope’s design using (often free) software, such as ‘Therm.’ As in all other areas, the rigour involved makes it a complex, but necessary process if you want to be truly green. Combining those fi gures produced as a result, and in a way that is usable, is part of the overall challenge. Survey respondents were using a variety of means of obtaining information on their carbon credentials. As well as ‘specialist eco-building advice,’ the top voted option was ‘leaving the calculations to the architect.’ In joint third place was using the PHPP (Passivhaus Planning Package) software,
gaining 20% of the votes, as was using manufacturers’ EPD (Environmental Product Declaration) certifi cates. When it came to embodied carbon specifi cally, 12% of respondents were doing embodied carbon calculations as part of their overall carbon emission fi gures, and were using manufacturers’ Life Cycle Analysis data. Some respondents made anecdotal comments on the
diffi culties they had experienced, with one pinpointing embodied carbon: “Calculating carbon emissions in use is relatively straightforward. Calculation of embodied carbon is much more diffi cult.” They continued: “Many manufacturers don’t have data for this, and there are lots of other variables such as distance to site.” Further complications included the impact on building footprint of choosing lower embodied carbon materials. One respondent gave the simple view that when looking at a wide range of carbon info from a wide range of manufacturers, “the information is varied, and diffi cult to follow.”
FABRIC FIRST T
he building fabric is the core of low carbon design, from maximising insulation to minimising heat losses through thermal bridges and penetrations in the fabric, and achieving the highest air-tightness possible. Renewables work alongside a high performance fabric, but can’t deliver the low carbon goods without it. If you are managing your project yourself, this means working hard with the architect, but particularly the various trades onsite, to ensure that the fabric is correctly specifi ed for your property, the best techniques are used, and corners are not cut during installation. Probably the most crucial area to grapple with to achieve low carbon is to ensure you have adequate insulation. There are clearly more options for those doing a new build
than those retrofi tting, with cavities normally requiring a spray solution. Structural insulated panels are a highly effi cient means of constructing an air-tight, well-insulated house. They are normally offsite-constructed, OSB timber with a sandwich fi lling of rigid insulation, and precisely cut using CNC technology for maximum air-tightness.
Self-builders clearly need to ensure they are as informed as possible in order to embark on the low carbon journey, so we asked our readers how they were sourcing info. Internet websites were the most popular method (60%), followed by magazines (46%). Information sourced directly from product manufacturers was the choice of 36%, info from offsite and kit building suppliers got 33% votes, and ‘specialist eco advice’ received 22%.
PRODUCED IN ASSOCIATION WITH
28
www.sbhonline.co.uk
may/june 2022
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