new build The store is heated firstly by 7.8 square metres of solar thermal panels. If these are not keeping the tank hot enough, immersion heaters kick in, topping up the heat at times when the solar PV panels on the roof are generating electricity. If necessary, the immersion heater can also take advantage of ‘Economy 7’ low cost night-time grid electricity – but only between 2am and 6 am (and for the top of the tank only), just to ensure there is some hot water first thing in the morning. This has worked well, with most of the heat coming from the renewables, throughout the year. With all that heat sitting on the landing, even though the store is insulated, enough passes out into the living space to keep the house warm too, with direct electric heating only being deployed occasionally. The client says: “It’s an all electric house, and although I haven’t kept close track of the running costs, I estimate we are using slightly less electricity than we are generating, so we are in energy balance more or less. We do need to make some minor changes to the system, as at the moment there is no heat dump for the excess hot water in summer, which can lead to the house overheating. It’s easy enough to deal with this by opening the windows, though.” They are happy with the MVHR too: “We find it very straightforward. It’s extremely quiet, we like to ask our visitors if they can hear it, and they can’t. It’s tremendous – we’re very happy with it.” Although this is only EcoArc’s second completed passive house project, Andrew Yeats admits he is now “very evangelical” about the standard – clearly with some success, as a large proportion of his subsequent clients have also commissioned passive builds. “When clients come to me, I tell them this is what we do: there would have to be a very good reason not to do passive house.” One potential obstacle raised by EcoArc’s clients is cost. Having delivered cost-effective masonry build passive houses for Lancaster Cohousing, Yeats was keen to demonstrate cost-effective passive house in timber frame as well – and believes he has succeeded. His Lake District clients needed to build “on a shoestring” after buying quite an expensive plot (this, says the client, is why they have not had the house certified – they just didn’t have the money left over). The final build cost was £1370/m2. “Some architects would struggle to do a regular home for that,” Andrew Yeats points out. He believes this offers good value for a home that really performs. “After all, architects can be very good at spending other people’s money on things that don’t really mean anything!” He continues: “We kept the costs down by the way we ran the contract. We have had terrible experiences with competitive tendering for passive house. Until they have enough confidence to price fairly for passive house, without the scare factor, virgin passive house builders tend to whack the rates up: they think of how much it will cost to build, then double it! “So what we did was, the client employed the (mainly local) contractors for the separate
trades — including some being paid on an hourly rate — and set up an account at the builders’ merchants. That way everyone was paid fairly, but no-one was making a massive profit. It came in on budget and on time.” With no single contractor carrying the can for passive house quality, instead, they built in quality assurance separately. “We arranged it so that the timber framers would be paid only when the shell was airtight to below 0.6. For the insulation installation, we employed a local independent consultant to check the insulation fill thermographically as it was going in, to ensure there were no gaps. For the ventilation system, a local plumber did the installation, then Green Building Store came and commissioned it.” Building on this positive experience, especially the speed of erection on site, EcoArc have started to work with a local timber frame firm, Eden Frame, to develop their own passive house timber frame system. “We do more of the construction offsite — the panels are pre-insulated, that makes it even quicker to erect. The panels then slot together with thermal bridge free dog-leg joints at the corners: there are not many joints though — the panels are really large,” Andrew says. “This means a frame can go up in one day, and the roof goes on the following morning.” It isn’t just EcoArc, but the clients too, who hope more homes like this will be constructed in the area. In their design, access and environmental statement to the planning authority (the Lake District National Park) the clients stressed the need to develop housing solutions in the area that protect and sustain the environment – that means homes that are energy efficient, sustainable and cost-effective. Their own house certainly shows just exactly how this can be done.
SELECTED PROJECT DETAILS Architect: EcoArc (Andrew Yeats) Timber frame: MBC Timber Frame Contractors: Sam Nelson & Jim Crawford Civil & structural engineering: Peter de Lacy Staunton Passive house consultant: Passivate Cellulose insulation: Warmcel Glass wool insulation: Knauf Quantity surveyors: Bushell Raven Mechanical contractor: Nick Dent Electrical contractor: Phillip Townson Airtightness testing: Paul Jennings Additional wall insulation: Kingspan Airtightness products: Siga/Ampac Windows & doors: Ecohaus Internorm MVHR: Green Building Store Solar thermal collectors: Consolar Solar PV: Lakes Renewables Thermal store: Akvaterm Cladding: Marley Eternit Building boards: Fermacell Concrete block: Aggregate Industries Rainwater harvesting system: Rainwater Harvesting Ltd
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