Passivhaus Affiliate
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Cannock Mill Cohousing

Location: Colchester, Essex
Completion Status: Completed 2020 Occupancy: Occupied since December 2019
Architect: Anne Thorne Architects LLP Consultant: Client-side Passivhaus designer: Junko Suetake/ Anne Thorne Architects LLP, Contractor-side Passivhaus designer: Etude, Thermal bridging calculations: Elemental Solutions, M&E Design: Alan Clarke
Contractor: Jerram Falkus Construction Client: Cannock Mill Cohousing
Certification: 2019 & 2020, Passivhaus Certifier: WARM
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Following the success of Lancaster Cohousing, Cannock Mill becomes the second Passivhaus certified cohousing scheme in the UK. .Cannock Mill Cohousing has been a labour of love for the group who brought the project to fruition over many years. The project combines Passivhaus comfort and efficiency with shared community space and low carbon living. 

Cannock Mill Cohousing scheme. Image credit: Anne Thorne Architects

The 23-unit project is comprised of three separate Passivhaus certified buildings of 1-3 bedroom flats and houses:

  • 5 house block
  • 12 house block
  • 6 flat block

A converted listed mill building is used as the ‘common house’ with a shared kitchen, laundry room and community space. There is shared garden as well as private outdoor space.  The houses are designed to lifetime home’s standards with a space for a future lift and wide staircases to accommodate a stairlift.

 

Key Stats

  • Number of units:  23 (1-3 bed flats & houses)

  • Project cost: £10 million (inc land purchase)

  • Construction: Timber frame

  • Construction started: April 2018

  • Completed: 2020

Cannock Mill Cohousing scheme. Image credit: Anne Thorne Architects

 

Cohousing

Cannock Mill Cohousing is a mutually supportive community with some shared facilities, encouraging social contact and individual space in a community managed by themselves, the residents. All residents agree to the aims and objectives of cohousing, which includes a commitment to consultation and consensual decision making. The residents share many things including cars, ebikes, a ‘library of things’ and more. 

We were concerned about being isolated in our houses in London. We also liked the idea of sharing a lot of things, which reduces expenditure and carbon emissions and makes it more sustainable.

Anne Thorne, Architect and Cannock Mill Cohousing resident

 

Cannock Mill Cohousing scheme under construction

PHPP data

 

 

Treated floor area

Form factor

Space heating

Heating load

Overheating risk

5 house block

655m2

 2.63

15.3kWh/m².yr

10.44 W/m2

0%

12 house block

1200m2

 2.33

10.6kWh/m².yr

10.2 W/m2

2%

6 flat block

316m2

 3.53

14.3kWh/m².yr

10.2 W/m2

4%

 

Cannock Mill Cohousing scheme under construction

Measured Energy Performance

Averaged final airtightness tests and combined electricity & gas bills 2020.

Airtightness 

0.6 ACH@50 pascals

5 house block

41.28kWh/m².yr

12 house block

40.85kWh/m².yr

6 flat block

65.51kWh/m².yr


All results fall within predicted performance in PHPP. 

 

We adopted the Passivhaus standard to meet our core aim to keep our carbon footprint as light as possible. There are two fundamental reasons for this: firstly, we care about the environment and wish to leave planet Earth intact for our children and grandchildren; secondly, we don’t want to be paying high energy bills.

Jane Blackburn, Cannock Mill Cohousing

U values

Walls

  • Timber frame with Warmcel insulation

  • Flats: 0.092 W/m2K

  • Houses: 0.108 W/m2K

 

Floor

  • Reinforced concrete with phenolic insulation (flats)/ PIR insulation (houses)

  • Flats:  0.108 W/m2K

  • Houses:0.135 W/m2K

 

Roof

  • Timber frame with Warmcel insulation. Green roofs for houses.

  • Flats:   0.079 W/m2K

  • Houses  0.111 W/m2K

Cannock Mill Cohousing scheme under construction

Key Challenges

Cannock Mill Cohousing scheme. Image credit: Anne Thorne Architects

Sloping site: The houses had to be designed into a 11 metre  (from the top of the slope to the bottom)  north facing slope. To ensure that the houses could be south facing and optimise solar gain the houses were designed ‘upside-down’ with the balconies and living rooms on the top floor.

Drainage: The scheme has a sustainable urban drainage system to prevent flooding from heavy rainfall. Rainwater from the project’s deep green roofs is taken into temporary storage under the road, which then goes into the mill pond and on into the river.

Planning requirements:  The planning department insisted on two and a half car parking spaces per unit, even though many of the residents do not have cars. For Passivhaus projects it is usually easier if garages are located outside the thermal envelope. However, for this project the most efficient option was to install them as garages within the thermal envelope. This was achieved by using very thermally efficient and airtight bifold doors for the garage space. The garage space is most commonly used by residents as studios or workshop spaces and there is a car club for shared cars..

 

I’m now a total convert (to cohousing). I have seen the many fantastic things that they’re doing on site and the strong sense of community that’s developing. They have a lot of people from different backgrounds and they’re great at problem-solving together. And now I think what they have achieved is a triumph.  

Junko Suetake, Passivhaus Designer working with Anne Thorne Architects

 

Key Team

Client: Cannock Mill Cohousing

Architect: Anne Thorne Architects LLP

Quantity Surveyor: Peter Gittins & Associates

M&E Design: Alan Clarke

Contractor: Jerram Falkus Construction

Structural Engineers: Ellis & Moore Consulting Engineers

Thermal bridging calculations: Elemental Solutions

Passivhaus consultant (to contractors): Etude

Passivhaus certifier: WARM

Air testing: Paul Jennings at Aldas

MVHR & Windows & doors: Green Building Store

Lacuna bifold doors: Passivhaus Store

Warmcel insulation (for wall & roof): PYC Group

Cannock Mill Cohousing scheme. Image credit: Anne Thorne Architects

 

Further information

Cannock Mill Cohousing

Passivhaus and the road to zero carbon

Previous PHT story: Progress for Cohousing striving for Passivhaus – 13 June 2016

Previous PHT story: Cohousing scheme gets green light for 23 Passivhaus homes – 11 August 2015 

Previous PHT story: LoCo Cohousing gear up to build Colchester Passivhaus development – 29 July 2014

Anne Thorne Architects Cannock Mill Cohousing

Suetake Studio 2 Cannock Mill Cohousing