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Outstanding initial air test results for Exeter City Council Passivhaus housing development

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Image courtesy of Gale & Snowden Architects Ltd.

April 01, 2015

The first in a series of initial air tests at one of Exeter City Council's developments of Passivhaus homes has delivered outstanding results of 0.19 air changes per hour (depressurisation) and 0.2 air changes per hour (pressurisation) at five0Pa.

The development of six houses near Newport Road, Exeter, which will be known as ‘Reed Walk’ is being built by independent contractor, C G Fry & Son.Once completed, it is one of three sites currently being developed by ECC to deliver high-quality, affordable Passivhaus homes for Exeter's social tenants.

The design of the houses utilises dense concrete blockwork walls, wrapped with high levels of external wall insulation and render. The combination of high internal thermal mass, insulation, thermal-bridge-free design, and exceptional airtightness will result in excellent, stable comfort levels and very low energy bills for tenants. Together with the specification of healthy building materials based on Building Biology principles, the houses will provide exemplar living conditions and tackle fuel poverty.

Gale & Snowden Architects Ltd., with offices in Exeter and North Devon are the architects, mechanical and electrical engineers, landscape architects, Passivhaus designers, and permaculture designers for the project.The practice has been delivering low environmental impact, healthy buildings across all sectors for the past 23 years.Structural engineering and civil engineering services are undertaken by StructureHaus, formerly Paul Carpenter Associates.

The recent air test results represent airtightness levels of approximately 1/2fiveth of those currently demanded by UK Building Regulations. Air quality in the homes will be maintained to a high standard via highly efficient mechanical ventilation systems with heat recovery (MVHR).

Jonathan Barattini, Project Architect – Gale & Snowden said: “Air tightness is achieved primarily using wet finishes such as plaster and screed with membranes where necessary. Attention to detail, particularly where junctions between different materials occur is paramount. Gale & Snowden would like to commend the Main Contractor, C G Fry & Son, for their workmanship and site supervision in achieving this.

A fundamental understanding of the Passivhaus principles, particularly regarding the airtightness strategy, is required of any Contractor in order to deliver this type of scheme successfully. C G Fry and their 'airtightness champion' and site manager, George Richards, have consistently worked closely with Gale & Snowden in order to fully understand the details and principles necessary to deliver the requisite 0.6 air changes per hour demanded by the Passivhaus Standard. The excellent results achieved are testament to this collaborative approach to construction. Work on the remaining five units is progressing and they are scheduled for initial air tests in the near future. C G Fry also plans to undertake an intermediate air test once all first fix services and carpentry is completed, prior to plasterboard to ceilings and internal walls being installed. This will allow a simple visual inspection of the integrity of the airtight barrier before it is covered up ready for finishing. The whole team will be hoping for similarly successful results in all subsequent tests.

Kevin Murch, Construction Director - C G Fry & Son said: “C G Fry are pleased to be carrying out this unique project for Exeter City Council and delighted to be working with Gale & Snowden to add our constructional expertise to the challenging targets set for this Passivhaus build project. This is the second Passivhaus project C G Fry & Son has carried out with Gale & Snowden and George Richards, our airtightness champion, has past experience in this specialist field. It is a challenging project, however, we are delighted with the initial excellent results achieved.”

Reed Walk is due for completion in August 2015 and will be the latest of seven developments in Exeter designed and delivered by Gale & Snowden Architects as part of ECC's commitment to build all new homes to Passivhaus standard. Together with sites at Brookway and Bennett Square, this current wave of development will provide 20 new three-bedroom homes for Exeter.