Passivhaus pilot sets the standard in Bath

With Passivhaus social housing schemes on the rise in the UK, PHT members Powell Dobson Architects have successfully delivered a pilot scheme of four affordable Passivhaus homes in the City of Bath, prompting the commission of a further eight certified Passivhaus units.

Mulberry Park Passivhaus, Image credit: Anna Barclay

As part of a larger brownfield regeneration project, the Passivhaus homes at Mulberry Park were designed to explore options for building high-quality, sustainable neighbourhoods that were not only affordable, but also energy-efficient. Developed by Curo and designed by Powell Dobson Architects, the Passivhaus homes were completed in September 2020, and certified by PHT Patron WARM in October 2020. The homes have since been occupied by local people on the Bath and North East Somerset Council’s waiting list.

We have the in-house expertise through our certified designers to deliver this technical and challenging project with Curo. With our Passivhaus experience and Curo’s energy and drive to provide amazing homes for the community, we delivered the first ever Passivhaus certified homes in the Bath and North East Somerset area in Autumn 2020. The project has been a success and very well received by everyone, with two more terraces now commissioned for a future phase of development at Mulberry Park.

Oliver Henshall, Technical Associate at Powell Dobson Architects

Key Stats

Start date: August 2019

Completion date: September 2020

Certification date: October 2020

Project stage: Complete

Units: 4 Terraced houses

Treated Floor Area (TFA): 343m²

Construction type: Timber stud timber frame

Occupany: 20

Mulberry Park Passivhaus, Image credit: Anna Barclay

Jade and her daughters have occupied one of the four Passivhaus homes. Their previous uninsulated home had demanding winter heating bills, and Jade often found that their living situation was both unaffordable and uncomfortable.

Thanks to a fabric first approach championing insulation & airtightness, their family home is now comfortable all year round, eliminating any draughts or heat losses. The mechanical ventilation system (MVHR) efficiently provides constant fresh air resulting in excellent indoor air quality, both in the daytime and throughout the night.

I feel very excited about the opportunity to live in a low carbon home that also costs less to run. This is a huge improvement from our previous living situation, where we had mainly concrete and timber construction with minimal insulation and only electric heating and hot water. My heating bills were very high in the winter. With three children to look after, this was very difficult for me to afford.

Jade, Mulberry Park Passivhaus occupant

Construction

Wall

Timber stud timber frame & Warmcel
U-value: 0.13 W/(m²K)

Floor

Insulated raft
U-value: 0.12 W/(m²K)

Roof

'Cold roof' with Warmcel
U-value: 0.06 W/(m²K)

The beauty of a Passivhaus project is that they can come in all shapes and sizes, and this meant that the pilot scheme was able to seemlessly integrate into the rest of the regeneration project at Mulberry Park. This is also an advantage for future planning, as more units can be added to the overall scheme without disrupting the collective aesthetic of the site. With its modern yet traditional aesthetic and light brick facade, the terraced houses reflect the traditional colour palette of Bath architecture.

Predicted Energy Performance

Airtightness (≤0.6ACH@50pascals)	0.5 ACH@50pascals
Thermal Energy Demand (≤15kWh/m².yr)	16 kWh/m².yr
Thermal Energy Load (≤10W/m²)	9 W/m²
Primary E Demand (≤120kWh/m².yr)	116 kWh/m².yr

The success of the pilot scheme has meant a further two Passivhaus terraces have been commissioned as part of the overall regeneration scheme, with one terrace currently under construction for the open market (4 units) and a further terrace (4 units) due to be completed in June 2022.

We look forward to seeing more Passivhaus schemes motivate the emergence of energy-efficient and affordable neighbourhoods throughout the UK.

We’re really proud of our work at Mulberry Park, of building these high quality homes that help to create a future proof neighbourhood, designed to encourage and enable healthier lifestyles. These Passivhaus homes will greatly benefit our residents who will enjoy lower heating bills, better year round comfort and indoor air quality.

Stuart Smith, Curo Technical Director