the floorplan
The modest 110m2 plan incorporates three bedrooms, integral garage, an open plan living/dining space and first floor terrace off the master en suite bedroom.
suppliers
Architect RDA Architects: rdauk.com
Contractor CLC Build: clcbuild.co.uk
SIPS supplier Kingspan TEK: kingspan.com MVHR consultant Green Building Store: greenbuildingstore.co.uk Passivhaus certifier MEAD: Energy & Architectural Design Ltd: meadconsulting.co.uk Kitchen (design modified by RDA Architects) Comprex: comprex.it/en Pool Endless Pools distributed via Home Counties Pools & Hot Tubs: poolboy.co.uk Windows Living Wood Windows: livingwoodwindows.co.uk Floor tiles Feri & Masi: feri-masi.com/en Bathrooms Supplied by Wet Zone: wet-zone.co.uk Brasswear Cea Design: ceadesign.it
Build costs
Foundations
and structure £145,000 Windows
and doors £30,000
Utilities £40,000
Decorations £10,000 Contractors’
costs £20,000 Bathroom sanitaryware
and brassware £10,000
Swimming pool £80,000
Over the years, the German building standard known as Passivhaus (incidentally, a wholly voluntary standard) has attracted several myths, not all of them helpful. This award-winning project manages to topple several of them, the biggest of which is this: you need deep pockets to build this way. In fact, a self-builder can expect to spend around 3% more for a Passivhaus construction than for a more conventional build route (no more, say, than the cost of upgrading to a top-end kitchen).
Elizabeth spent just £250,000 on construction costs (the pool was an additional £80,000), although you may have to pay more post-Brexit, according to the project’s architect Richard Dudzicki; he states that construction prices in London have shot up by 16% since the referendum.
Richards suggests specifying SIPs (structural insulated panels) or timber frame as a sensible way to keep costs down on a Passivhaus project, along with avoiding the temptation to add underfloor heating. The levels of insulation needed to reach Passivhaus insulation mean that it’s an unnecessary expense, unless the Passivhaus Planning Package (PHPP) software indicates that it’s needed. Likewise, several self-builders have paid for a woodburning stove in their Passivhaus only to find the house far too efficient for their
modest heating needs.
Does building in this way mean that you need to construct a large house? Again, not necessarily. Even though the building physics associated with heat loss and airtightness favour large volumes, this small home still managed to achieve certification. And what of the claim that Passivhaus restricts the architect to the simplest of box forms? Again, this project shows otherwise. “I wanted something that was easy to run but not a box with low ceilings,” says Elizabeth. Her architect has delivered on this, although Richard admits that the integral garage required some ingenuity to overcome potential thermal bridging problems.
Elizabeth’s project also shows that building to Passivhaus standards does not necessarily need a construction crew highly experienced in the methodology, although again, it does help. But it does require careful planning to factor in such site-specific elements as the orientation of the sun and shading. For example, like many urban areas, Elizabeth’s plot was shaded and surrounded by tall buildings — two factors that affect the amount of light and sun reaching the house and had to be factored into the calculations.
The tight plot also meant that the architects had to find a way to balance the need for super insulation without losing valuable floor space. “Normally with other construction routes, super-insulated walls could be up to half a metre thick, but choosing 140mm-thick SIPs [from Kingspan] meant that the total wall build up, including extra insulation, was just under 300mm, similar to a standard construction,” explains Richard. “Using SIPs also gave us a way to build an airtight structure. The finished building achieved an airtightness of 0.43m3/hr, over 20 times better than Building Regulations. We were only able to achieve this by closely monitoring the envelope throughout the build and repeatedly testing and adjusting.”
The architects are now monitoring Elizabeth’s house for temperature stability, humidity, volatile organic compounds (VOCs), particulate matter and occupant comfort for 12 months. They then plan to use the information to adjust the MVHR settings in the property. “So far, we can see that the temperature is very steady, even in the sun, at 19-22˚C,” says Richard. They’ve also noticed that during building works, a lot of dust found its way into the house, so the MVHR filters needed changing. “Looking ahead, Elizabeth can expect to make considerable savings on running costs for the next 20-plus years,” concludes Richard. “The house has an energy rating of less than 15kw/m2, around onetenth of what a normal house of this size uses and far more efficient than current Building Regulations require.”