Passivhaus affordable homes

We were commissioned to design the first Passivhaus standard social housing project for Powys County Council. The seven properties would be constructed as part of a £1.3m development in the village of Sarn, near Newtown, Powys.

We were commissioned to design the first Passivhaus standard social housing project for Powys County Council.

The seven properties would be constructed as part of a £1.3m development in the village of Sarn, near Newtown, Powys.

The properties consist of four two-bedroom bungalows, two two-bedroom houses, and one three-bedroom house. Each one has been designed and constructed to the Passivhaus specification, surpassing the minimum specification required for certification.

In addition, a range of sustainable materials were used in the construction, including Welsh-grown wood for the timber frame.

We set out to design a highly efficient range of homes that surpassed the Passivhaus certification requirements.

A low carbon footprint

We, along with our client and Pave Aways, the main contractors, wanted to create a development with a very low carbon footprint. The main insulating material in the walls and roof space is Warmcel, which is produced from recycled newspaper, providing a huge reduction in embodied carbon against petroleum-based PIR-type products.

The wood used for the timber frames was from sustainable Welsh woodlands. The timber frame design is optimized to reduce wastage, any waste from timber can be re-used elsewhere in smaller sections or even recycled into other timber products.

The use of an insulated raft system, where the floor slab sits on a raft of EPS insulation means that the use of concrete is much reduced. Concrete has very high levels of embodied carbon, so reducing the mass of material used has a huge impact.

Renewable energy

Photovoltaic arrays on each of the buildings can create 4.2kW of renewable electricity which reduces the use of mains grid electricity. This again reduces the carbon footprint and impact on natural resources.

Mechanical heat recovery units also ensure heat created in the building is recycled, thus reducing the need for electric or gas heating systems. This reduces energy use and bills for the household while also cutting the amount of energy required off the mains grid.

The final Pasivhaus air tests saw the buildings achieve 0.3 m3 / hm2. The certification requires at least 0.6 m3 / hm2.

  • Client: Powys County Council
  • Contractor: Pave Aways Building Contractors

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