PHBdW: Passivhaus Bau der Woche 07

foto: Bruno Klomfar

Outside of Vorarlberg (AT) and Freiburg (DE), Tirol is one of the densest Passivhaus strongholds in Europe. Several projects in the region utilize cross laminated timber and a few of them achieve the passivhaus standard. This wooden gem does both.

foto: Bruno Klomfar

The work of maaars architektur is no stranger to architecture blogs, although for some reason Reinhold Hammerer’s own house, a duplex in Sistrans on the outskirts of Innsbruck, seems to have largely bypassed publication. This is just one of many stunningly minimal CLT projects completed by his firm.

foto: Bruno Klomfar

The Doppelwohnhaus Sistrans is a duplex made almost entirely of CLT panels, taken to an insane degree: stairs, shelving, guardrails and even a table made from leftover elements. The detailing is really crisp and the monochromatic, minimalist interior creates an incredible effect. Despite having massive walls, the building appears deceptively transparent from within, providing views in multiple directions.

foto: Bruno Klomfar

Exterior wooden screens can be positioned to block excess heat gain or provide unique lighting conditions. The large lift-slide doors and windows are manufactured by Optiwin, an Austrian manufacturer of high-performance wood windows. These are the Zwoa2holz line, a PH certified triple-glazed window achieving an installed U-value of 0,85 (U=0.15 imperial, R-6.7)

foto: Bruno Klomfar

The uppermost level features a glazed space (perhaps a great studio?) with wooden sunscreen, again on the exterior. This space opens to a roof deck, and at night must create a rather interesting lantern.

Ventilation is supplied by a drexel + weiss Aerosmart XLS,a high-efficiency HRV with heat pump for heating (supplied through ventilation) and DHW. Earth tubes are utilized to precondition incoming air. Additional green features include local wood, rainwater harvesting for garden/toilets and a  PV array for powering the heat pump.

Wall assembly, U-value=0.10 W/m²k (R-56.5)

  • 2.5 cm larch facade
  • 3 cm airspace
  • wind paper
  • 2.2cm agepan (fiber board)
  • 30cm cellulose
  • 10.5cm CLT

Roof assembly, U-value=0.10 W/m²k (R-56.5)

  • wood deck on sleepers
  • ventilated membrane roof
  • 2.2cm agepan (fiber board)
  • 30cm cellulose
  • 14.8cm CLT
  • Floor/cellar: U-value=0.14 W/m²K (R-40.5)
  • Windows: U-value=0.79 W/m²K (R-7), center of glass U-value=0.7 W/m²K (R-8),
  • Airtightness: 0.6 ACH50
  • Heating Demand: 14.00/m²Ka  calculated w/ PHPP (4.43kBTU/ft²/a),  14.00/m²Ka  measured

foto: Bruno Klomfar

This duplex is an excellent example of how passivhaus can be quite affordable for multi-family projects. The elongated plan, while a little deceptive, still allows for necessary compactness of each unit. The utilization of cellulose and local wood keeps costs down and should mean the building has a fairly low primary energy input (initial embodied energy). The superinsulation ensures a quiet, well-tempered interior for a region that can get extremely cold. And the glazed corner of the lower unit is a really nice touch – I wonder how much of a thermal bridge that creates?

  • Architect: maaars architektur (AT)
  • Location: Sistrans (AT)
  • GFA: 410 m² (4,412 ft²)
  • building costs: 793€/m² ( ~$110/ft²)   – this is derived from the  igpassivhaus, which shows total building cost of 325,000 euros. In all likelyhood, this is probably the per unit cost, which would put the number closer to $220/ft².
  • completed: 2008
  • fotos: Bruno Klomfar

Further Reading