PHBdW: Passivhaus Bau der Woche 10

When we ran across the AI Passivhaus blog a few weeks ago, we were stunned at the the level of documentation on their project in the Cotswolds. There is a certain level of sexiness to this project – a restored barn in a protected landscape, an “el”-shaped earth-sheltered addition slipped below the barn, a passivhaus that heavily utilizes passive solar and thermal mass – plus the addition of renewables to achieve carbon neutrality.

To obtain planning permission in the protected district, the architects had to agree to keep most of the existing stone barn. This led to some really interesting structural gymnastics that are well photographed and discussed on the AI blog. That the architects were able to pull this off, despite the protected district, seems to have irked many folks. However, we are intrigued the architect found a way to build a fantastic project without destroying the surrounding views.

Below-grade wall assembly, U-value=0.117 W/m²k (R-48.5)

  • plaster
  • 22 cm precast concrete panels
  • waterproofing/drainage mat
  • 31 cm rigid insulation
  • geotextile
  • backfill

Above-grade wall assembly, U-value=0.153 W/m²k (R-37)

  • plaster
  • 22 cm precast concrete panels
  • 25 cm rigid insulation
  • render (stucco)

Ground slab assembly, U-value=0.146 W/m²k (R-38.9)

  • 25 cm concrete, screed (incorporating 20 tons of recycled glass) and resin overlay
  • 25 cm rigid insulation

Roof assembly, U-value=0.085 W/m²k (R-66.8)

  • 25 cm hollowcore concrete panels & screed
  • 36 cm rigid insulation
  • drainage mat
  • geotextile
  • green roof

Triple pane Alu2Holz windows, manufactured by Optiwin, make the interiors glow. We’ve seen these windows used on a number of passivhaus projects lately – and the low U-value, high VT, high SHGC, airtightness and minimal profile make for some superb windows. They seem to be a much better option than Serious Windows at this point, even taking into account issues of shipping.

Additional ‘green’ features include rainwater recycling, a 40m² solar hot water and a PV array which shades the south-facing windows during summer.

  • Windows: U-value=0.74 W/m²K (R-7.6),
  • Airtightness: 0.22 ACH50 (ridiculously tight)
  • Heating Demand: 13 kWh/m²a (4.12kBTU/ft²a)
  • Primary Energy Demand: 62 kWh/m²a (19.62kBTU/ft²a)
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    The project succeeds on several levels, and the juxtapositions (above/below, modern/antiquated, etc) work really well. The minimalist interior is a great touch. Add in the fact that this is intended to be carbon neutral, and the bar for energy efficient modernism has definitely been elevated.

  • Architects: Seymour-Smith Architects (UK)
  • Location: Gloucester (UK)
  • TFA: 358 m² (3,853 ft²)
  • completed: 2010
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    Further Reading

  • Channel4 write up on the underhill project.
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    One response to “PHBdW: Passivhaus Bau der Woche 10

    1. just beautiful.