Passivhaus Family Home in Wembury

One of our Architects, Dan Stewart, is building his own Passivhaus in Wembury

Birdsong is a self-build ‘forever home’ designed by one of our Architects, Dan Stewart, as his family home. From the outset of the project, the aim was to create a highly insulated, low energy, sustainable home, and as such the ‘Passivhaus’ standard was incorporated and adhered to. The Passivhaus standard ensures a comfortable and healthy home, in both winter and summer (to prevent overheating), and ensures energy usage is kept at a minimum, reducing long term energy costs.

Accommodation includes three bedrooms one with ensuite, a family bathroom, separate WC, open plan living / kitchen / dining room, separate utility, plant room, and a link-detached garage with home office.

The design is relatively modest, to fit within the site restrictions and Area of Outstanding Natural Beauty design guidelines.

Dan and his family wanted the house to incorporate more than the bare minimum in terms of ecology and biodiversity planning policy targets, and as such increased their ‘Biodiversity Net Gain’ from the minimum 10% as required by planning to 48%, providing significant enhancement with the inclusion of bat roosts, bird boxes, new trees, and hedgerow.

The house has an asymmetric pitched roof, with the largest slope facing just off South and hosting a built-in solar panel array. This, combined with a small battery, and a small air source heat pump, will provide all the energy they require for power and hot water, with excess power sent to the grid. Due to adherence to the Passivhaus standard which demands high levels of insulation, airtightness, and careful design of glazing to harness solar gain, only a very small amount of heating (equivalent to an average hair dryer) will be required. This will come from the towel rails in the bathroom and ensuite. Combined with a whole house ventilation system that recovers heat from outgoing air, and puts this into the filtered incoming air, the property will be warm even in the depths of winter, as well as benefitting from filtered air all year round.

The ground floor slab and external walls are built using Insulated Concrete Formwork (ICF). ICF is two layers of rigid insulation with a gap in-between into which concrete is poured. The concrete becomes the structure, and the insulation can be directly finished internally and externally. Dan chose to use ‘R-Wall’, an ICF product, that uses extruded polystyrene (XPS), which is stronger, and waterproof compared to traditional polystyrene typically used in packaging (and other ICF systems). The XPS is manufactured in the UK, with waste carbon dioxide gas pumped in as it is manufactured. The plastic rails and ties that hold the XPS together are made from recycled PVC window frames. Low carbon concrete that uses waste product from the steel industry as the binder instead of cement further assisting in lowering the embodied carbon, and environmental impact. Key advantages of ICF include cost, high thermal mass (which keeps internal temperatures stable), and speed of construction. The house went from slab to roof level in just over a month!

Dan and his family are passionate about using UK suppliers and local labour where possible. His contractor lives on the same road and has also fortunately previously built to the Passivhaus standard. External timber cladding, and internal panelling is being sourced from local sawmills, using timber from British woodlands.

The house is currently in the process of being built and is due for completion summer of 2024. You can follow their progress on their Instagram: https://instagram.com/birdsong_selfbuild.