Reducing carbon emissions and tackling climate change are central to Sarah Wigglesworth Architects, and the practice’s most valued collaborators are part of that drive
When we decided to retrofit our Stock Orchard Street home/office in north London we worked with the environmental consultancy Enhabit. Although cutting-edge for sustainability when it was completed in 2000, the targets for U values, which were set by the Building Regulations of 1995, are now considered pretty low. We wanted to boot it up to at least meet, or preferably exceed, what’s required now.
Enhabit reviewed our energy usage for the previous eight years and looked at our occupancy patterns. They put probes in to monitor the U-values, carried out thermal imaging and did airtightness tests. They created a Passivhaus model to identify where the offending parts were and what we could do to target them with a cost benefit analysis. There were some changes that were obviously needed – some of the windows had visibly warped so they leaked both air and noise – but we were amazed that replacing just one rooflight – admittedly large – would knock 8 % off our energy bills, so that was a no-brainer.
We also realised that we needed to insulate the steel main beams, add loads more wall insulation on the south west side, introduce solar shading, and change all the kit. By picking apart a lot of the building and putting it back together in a more energy-efficient way, we managed to reduce CO2 emissions by 62%.
We spent a lot, but you have to put your money where your mouth is. We were very, very lucky that we managed to complete the work by the end of 2019 just before Covid. With energy bills going the way they have, it’s obvious that improving building fabric is the way forward.
Enhabit combined knowledge of Passivhaus modelling with practical skills. The firm carried out all the testing and analysis that gave us data that could supplement and verify our experience of living in the buildings. Most of all, they helped by offering a cost-benefit menu of options, which helped us target areas for improvement. They spoke in jargon-free language, were honest about potential pitfalls and were great communicators.
There aren’t that many one-stop shop sources for ecological building material supplies that can offer useful advice all round, including practical help for builders and architects – we could certainly do with more of them.
Ecological Building Systems are fantastic. They offered toolbox talks, which are practical demonstrations of how to use their products, as well as really amazing CPDs on aspects of green construction, products and building physics. When we did the retrofit of Stock Orchard, they came to the site to teach our builders how to apply the air tightness tape correctly. This is a real skill, and it was very useful for me to know this too.
EBS also supplied everything we needed for the airtightness on the retrofit. As part of this, we taped around the windows, doors, floor/wall ceiling/wall junctions and around service penetrations and managed to cut our air leakage in half from 12 to 6 m3/hm3. It wasn’t built to be a Passive House building – but we’ve done what we can with the retrofit.
EBS provides confidence when moving into green building design and helps the technical team to specify, construct and maintain its products in the right way.
When Jeremy [Till] and I were teaching at Sheffield, we heard about an amazing project at Sheffield Hallam University’s Design Research Centre being led by Professor Jim Roddis. He was doing research turning recycled glass and resin into terrazzo, a product then called S11 or TTURA. So we went to see him. We liked that it was a recycled material - specifying materials that reuse and repurpose waste streams is something we believe architects will increasing need to do.
We commissioned him to do our kitchen table. It was the largest project the team had made at that point, so was an experiment for them in scaling up. The table weighs an absolute tonne – we had to get the floor strengthened. It stretches 3m inside the kitchen and continues through the wall – with thermal breaks – outside into the deck for another 1.5m. It was cast in Sheffield and polished at Diespecker’s Yard in Peckham before arriving at Stock Orchard Street.
We selected the different colours of glass from a bottle bank, some clear, some coloured, and these were all put into a resin. We ended up with funny bits of blue glass in the table as well – everyone has their favourite chip.
I’m really pleased with it – I think it’s really lovely. It gets a lot of use, doesn't show the dirt and has lasted really well, although the outside is a bit pitted from weathering. The material is now marketed as Resilica and seems to have gone from strength to strength.
We aim to be green, and that does mean selecting materials that tend to be a little less common. We always try to use ethically-sourced materials that are natural products and don’t cause damage to the landscape or communities of origin, and those that have low embodied energy. For carpet, we’ve often used Tretford cord, supplied by Joseph Hamilton Seaton. This has an A+ rating on the BRE’s Green Guide to Specification.
Tretford is carpet made from goat’s hair in the Republic of Ireland, which we like for its texture and colour, its eco-credentials and its wearability. It’s available in tiles and rolls. When we’re designing schools, we need something that’s hardwearing but also soft for when children are sitting on the floor, for example in a reading corner. Tretford’s range is so much nicer that the usual coarse, nylon varieties on offer. When you’re designing for children, colour is really important in making it attractive, and the Tretford colours are just gorgeous – you’ve got heathers, really good blues, bricky red, aubergine and oranges – but if you want it bland you can have natural goat-colours as well. We also like coirs, sea-grass matting and sisal.
We generally work on low cost projects with everyday materials that are ready-at-hand and off the shelf. I think this signals a shift in the way architects will increasingly work in future.
We like working with galvanised corrugated steel, and often use a cladding product with an embossed surface from Hadley Industries in Birmingham. We like its semi-industrial look and it’s cheap as chips. We always work out the embodied carbon on what we specify, and most steel in the UK is actually recycled. We prefer it to aluminium cladding, which has such an energy-intensive process and involves bauxite extraction, which is really destructive to the environment. So we try to avoid using aluminium whenever we can.
We used the corrugated steel to clad the straw walls of our building at Stock Orchard, and also at Deborah House Studios in Hackney where we retrofitted it with external wall insulation– it’s a very easy way of giving a building a facelift. It does weather, but in a way that gives it greater character.