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remains an unavoidable thermal bridge. Simmonds says the temperature here is a bit cooler than elsewhere — and by cooler, he means about 19C. Many of these issues are subtle effects he has picked up on while trying to identify the impact of remaining thermal bridges on perceived comfort. This reminds Passive House Plus of the late David Foster Wallace’s essay ‘Shipping Out’, in which the author spends a week in the Caribbean on one of the world’s most luxurious cruise ships. But when the ship docks and another — newer, shinier and even more luxurious — ship docks alongside it, the author starts to become irrationally unhappy with the tiniest details that aren’t right about his own palatial boat. It seems to be human nature that the more comfortable our surroundings, the more we become attuned to the tiniest of things that are out of place. Simmonds agrees: “It’s an absolute illustration of human nature isn’t it — everything’s relative.” What advice would Simmonds have for anyone embarking on a similar retrofit? He recommends thinking well ahead of time, and taking steps to dry out the structure of a masonry building six months or more before upgrading, reducing rising damp loads and “turning off the rain” load by using rainscreen cladding, lime renders or brick creams. These rain shedding measures must continue to allow water vapour to diffuse outwards as this is a crucial drying mechanism. Simmonds says this is important for masonry buildings, so that subsequent insulation — especially when insulating internally — and airtightness work does not have to deal with excessive moisture loads either immediately after retrofit, and on an ongoing basis thereafter. (above) most of the existing brick walls were insulated externally with 250mm of Permarock Platinum EPS insulation; (below left) part of the house also features a green roof with a variety of wildflowers; (opposite) (left) Knauf mineral wool to I-beams on main roof; (right, top) Foamglas Perinsul structural insulation helps cut out thermal bridging while (right, bottom) the new extension floor was insulated with 250mm of Jablite EPS under a reinforced concrete raft

“Anticipating moisture loads, and planning ahead to reduce and manage short and long term risks to the fabric and indoor air quality, is one of the most important technical challenges when retrofitting buildings,” he says. When asked what else he would have done differently, given six years of hindsight, the answers are all non-technical. He would like to have put the MVHR somewhere else, as despite being accessible, easy to maintain and close to the external wall — for short duct

runs — he would like to have installed a window facing the garden in this area downstairs. He says the unit is quite a large prototype that takes up a lot of space. But he adds: “You can’t get everything you want in a smallish urban plot.” His overall message? “This is the most comfortable building we’ve ever been in, compared to all our previous experiences,” he says. “This house is incredibly thermally comfortable in all areas — all year, bright, sunny and calm, the air is consistently fresh and heating bills are extremely low. A joy to live in!”

SELECTED PROJECT DETAILS Clients: Andy Simmonds & Lorna Pearcey Architect: Simmonds Mills Contractor: ECO-DC Project management: Simmonds Mills Energy consultant: David Oliver M&E engineer: Alan Clarke MVHR: Green Building Store Structural engineer: Bob Johnson Consulting Structural Engineers Passive House certified: Passive House Institute Finance: Ecology Building Society Airtightness tester: ALDAS External insulation (supply): Permarock External insulation (install): EJ Horrocks Additional wall insulation: Knauf Pipe insulation: East Midlands Insulation Thermal breaks: Pitsburgh Corning Roof insulation: Knauf Floor insulation (wool): Thermafleece Floor insulation (EPS): Jablite Floor insulation (PUR): Kingspan Airtightness sealants & tapes: Green Building Store Airtightness membranes:Ecological Building Systems Windows & doors: Internorm Roof windows: Fakro Cladding: HW Morgan & Sons Gas boiler: Valiant MVHR ducting: Lindab Water saving fittings: Wickes DIY Carpets: Natural Carpet Company Paints: Earthborn Paints: Keim

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Passive house plus issue 10 (UK edition)  

Passive house plus issue 10 (UK edition)