Passivhaus Affiliate

Life-changing Cambridge Passivhaus Almshouses

Dovehouse Court redefines accessible housing for the over-55s, blending independent living with community spirit. Designed by Mole Architects, these 3 timber-frame Passivhaus certified blocks provide 15 quiet, draft-free, comfortable homes. 

Dovehouse Court, Mole Architects © David Butler

Built for Girton Town Charity, the fully electric homes feature air source heat pumps and mechanical ventilation systems. Triple-glazed windows ensure a tranquil environment, effectively muting the noise from the nearby A14. To reduce heating bills, the design incorporates passive solar principles, optimal orientation, and deep overhangs for shading. The development overcame planning & site challenges without compromising on Passivhaus certification.

Key stats

  • Construction: Prefabricated timber structure

  • Number of homes: 15 apartments

  • Build start date: 2021

  • Completed: 2023

  • Certified: Passivhaus

Dovehouse Court, Mole Architects © David Butler

The three new Almshouses face a car-free central garden, promoting well-being and social interaction. Each home's brightly colored front door aids recognition, especially for residents experiencing dementia.

Resident quote, Dovehouse Court

Construction 

A panelised timber-frame and lightweight Larsen trusses create thick walls that accommodate 300mm of cellulose fibre insulation. The timber frame panels are made from Spruce soft wood sourced from Scandinavia and manufactured in Welshpool. 

MOLE Architects Dovehouse court

 

 

Architect’s view

The presence of trees around the site perimeter and in neighbours’ gardens resulted in piled foundations and suspended block-and-beam floors, creating challenging potential thermal bridges. These were designed out using aerated concrete blocks and extending external wall and cavity insulation below ground.

Further challenges were caused by the 3m level change across the site. Floor levels along the terrace of bungalows, which run up the site, had to be stepped along party walls. Additional insulation lines the party wall floor and wall junctions as well as on the gables. Careful modelling of the thermal bridge’s PSI values prevented these areas becoming points for heat loss.

We were able to accurately calculate timber fractions in the walls and roofs using the timber frame manufacturer’s shop drawings. Lowfield Timber Frame’s Larsen Truss wall system maximises insulation volumes and minimises timber to 13 per cent (nearer 19 per cent for the two-storey houses) of the overall wall volume. The load is transferred down the inner 89mm-deep leaf, and the outer stud cantilevered. The void is pumped with 300mm of cellulose fibre insulation. An additional layer of wood fibre insulation wrapped the buildings beneath the render.

Ian Bramwell, director, Mole Architects

 

MOLE Architects Dovehouse court apartment plan view

 

U-values 

Floor

 0.09W/m2K

Wall

 0.11W/m2K

Roof

 0.10W/m2K

MOLE Architects Dovehouse court ground perimeter detail

 

Dovehouse Court, Panelised Timber frame © Mole Architects
Dovehouse Court, Panelised Timber frame © Mole Architects
Dovehouse Court, Insulation © Mole Architects
Dovehouse Court, Hybrid Airtightness © Mole Architects Dovehouse Court, Ducting © Mole Architects Dovehouse Court, MVHR duct sunpipe © Mole Architects

 

Building performance 

For airtightness testing, the bungalows were treated as a single unit, with knock-through holes left between units until after the testing was complete. Airtightness layers included a mix of internal structural sheathing, airtight vapour control membrane and airtight sealing tapes. A membrane below screed formed the airtightness layer at ground level.

 

Designed energy performance 

Airtightness n50 (≤ 0.6ACH @ 50 Pa)                           

 

0.6 @ 50 Pa

 

Space Heating Demand (≤ 15 kWh/m².a)

 

15.51 kWh/m².a  

 

Heating Load (≤ 10 W/m²)

 

10.48 W/m²

 

Primary Energy Demand (≤ 120 kWh/m².a)

 

130 kWh/m².a

 

Primary Energy Renewable (PER) Demand (≤ 60 kWh/m².a*)    

 

57 kWh/m².a

 

 

*+/-15 kWh/m².a allowance if offset by energy generation. See Passivhaus criteria

 

Dovehouse Court, Mole Architects © David Butler

Dovehouse Court, Mole Architects © David Butler

 

Services 

Dovehouse Court employs a fully electric scheme, encompassing Air Source Heat Pump (ASHP), hot water generation, and Mechanical Ventilation with Heat Recovery (MVHR) systems for consistent, fresh filtered air. The property's chimneys, mimicking those of Girton's stone and brick cottages, house each unit's individual MVHR ducts.

 

Engineer’s view

The PER (primary energy renewable) criteria of the Passivhaus calculation couldn’t be satisfied with using electricity directly for heat so the project responded by using it more effectively. The opportunity for external air-source heat pumps or heat pump-led heat networks was limited on the site. The response was to place the heat pumps inside.

Ducted air-source heat pumps are integrated with a hot water cylinder to use around a third of the electricity associated with this load, the largest demand given the low space heating needs. The ‘heat pump’ is a small compressor similar in scale to that of a domestic fridge.

The tanks behave exactly as electric hot water tanks and the space heating is provided by a simple electric radiator. Simplicity is retained and efficiency is increased, with occupant satisfaction delivered with lower bills – a good engineering outcome.

Joel Gustafsson, founder and director, JG Consulting

 

Client quote, Dovehouse Court

 

Girton Town Charity Dovehouse Court Girton Town Charity Dovehouse Court

 

Key team 

  • Client: Girton Town Charity

  • Architect: PHT member Mole Architects

  • Contractor: Barnes Construction

  • Structural engineer: Conisbee

  • M&E consultants: JG Consulting/ Hoare Lea

  • Timber frame: PHT member Lowfield Timber Frames

  • Passivhaus Certifier: PHT Patron WARM

Dovehouse Court, Mole Architects © David Butler

It's wonderful to see this beautiful Passivhaus scheme with so many fulfilled residents and informed, ambitious clients who understand the benefits of Passivhaus. Cambridge is becoming a Passivhaus hotspot in the UK, with several certified Univeristy buildings and large scale housing developments in the pipeline. Learn more about the Passivhaus developments along the Oxbridge corridor at the UK Passivhaus Conference 2024.

 

You may also like 

Looking in-depth at Passivhaus Care Homes and Alternative housing? Read about other Passivhaus care home case studies linked below or check out the Passivhaus social housing campaign, providing additional guidance for local authorities and social housing providers.

 

Edward's Court Extra Care. Exeter. Image credit: Architype
St John's Almshouses
Marigold House care home. Image credit: Central Bedfordshire

 

 

Further information 

Mole Architects: Dovehouse Court

Passivhaus Social Housing Campaign

Passivhaus Costs & Benefits 

PHT guidance: Qualiity Assurance for large & complex buildings

Cambridge Forum for the Construction Industry: 2024 Award Winners Dovehouse Court

Architects Journal: Loving alms: Dovehouse Court later living by Mole Architects - 13 December 2023

Large & Complex Passivhaus Masterclass: Care Homes - 22 May 2024

Previous PHT story: Passivhaus care development goes large in Bedfordshire – 01 May 2024

Previous PHT story: Exeter City Council: Passivhaus Champions - 21 June 2022

Previous PHT story: Extra-special Extra Care – 22 October 2022

Passivehouse Accelerator: Extra Care for Exeter's elderly - 18 January 2022

4th July 2024


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