Fenton House

The brief

David and Jenny Arrenberg wanted a low-energy home on a woodland plot among 250-year-old cedars and oaks, with open-plan living upstairs to make the most of the views over the trees to the Tay estuary.

How we built it

The design keeps the plan to a simple rectangle, which suits Passivhaus and keeps costs in check, then puts the character into the roof: four pitched sections, each with an exposed glulam beam at the apex, so the kitchen, dining and living spaces read as separate rooms within one open floor.

Space on site was tight, so our joiners built the ten timber frame panels on the insulated raft foundation and they were craned into place. The frame is I-joists filled with wood fibre batts, wrapped in a further 100 mm of wood fibre board, with three sections clad in zinc and one in Scottish larch.

Building the airtight layer over the glulam beams took care, and the house tested at 0.66 m³/(h·m²). Bills for all electricity, including heating, hot water and charging an electric car, came to around £106 a month in the first year.

Performance

• Wall U-value0.115 W/m²K
• Roof U-value0.116 W/m²K
• Floor U-value0.124 W/m²K
• Windows0.68 W/m²K, triple glazed
• Space heating demand15.5 kWh/m²/yr (design stage)
• Measured energy use37 kWh/m² in the first year