Barbrook PassivHaus Retrofit

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Retrofit 2 semi-detached properties to PassivHaus standard.

Retrofit for the future ZA246T
Images Graphs Figures Description Strategies Building

Barbrook PassivHaus Retrofit : Project images

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CO2 emissionsPrimary energy requirement
Energy target
Retrofit for the Future

Energy and fuel use

Fuel use by type
Primary energy requirement
CO2 emissions

Measured data from renewable generation is not yet available.

Fuel use

Electricity use 18830 kWh/yr 798 kWh/yr -
Natural gas use- - -
Oil use- - -
LPG use- 462 kWh/yr -
Wood use- - -
heat from boilers biomass - 2668 kWh/yr -
Primary energy requirement 663 kWh/m².yr 77 kWh/m².yr -
Annual CO₂ emissions 157 kg CO₂/m².yr 9 kg CO₂/m².yr -
Annual space heat demand - 12.9 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
Renewables Technology--
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
77 kWh/m².yr -
Annual CO₂ emissions
offset by renewable generation
9 kg CO₂/m².yr -

Calculation and targets

Whole house energy calculation method SAP
Other whole house calculation method-
Energy target Retrofit for the Future
Other energy targets-
Forecast heating load -


Pre-development air permeability test24 March 20108.5m³/m².hr @ 50 Pascals
Final air permeability test22 July 20110.93m³/m².hr @ 50 Pascals

Project description

StageUnder construction
Start date01 April 2010
Occupation date01 September 2010
Location Barbrook Devon  England
Build typeRefurbishment
Building sectorPublic Residential
Property typeSemi-Detached
Construction typeOther
Other construction typePoured concrete, reinforced steel, asbestos pannelling on exteri
Party wall constructionSolid
Floor area 71
Floor area calculation method Actual Floor Area (SAP)
Building certification

Project Team

OrganisationEnergy Action Devon
Project lead personSophie Phillips
Landlord or ClientNorth Devon Homes
ArchitectClive Jones Ltd
Mechanical & electrical consultant TBC
Energy consultantPhase 1: Rob McLeod, BRE, Phase 2: Sally Johns, WARM
Structural engineerGavin Jones and Curtins
Quantity surveyorRod Burton, Pick Everard (in Phase 1)

Design strategies

Planned occupancy2-3 people, out to work or school for part of the day on weekdays.
Space heating strategyMini-district heating system from single external wood pellet boiler connected to two 300l thermal stores - one in each dwelling. Mechanical heat recovery ventilation, with post heating coil from solar thermal. Distribution system TBC at detailed design stage.
Water heating strategy3m2 evacuated tube solar thermal for summer. Wood pellet boiler for winter. Electric immersion back up.
Fuel strategySite is not connected to mains gas network. Wood pellets, solar thermal and mains electricity.
Renewable energy strategyThe properties back onto the West Lyn river, where there is potential for hydro. However, North Devon Homes do not own a long enough stretch for this to be viable. Lynton Community Development Trust is well underway with the development of a much larger scheme which we intend to support. When operational NDH will purchase electricity from the new ESCo. The East/West alignment and shady valley floor location mean both wind and PV are unfeasible. We are using the small area of south facing hip roof for solar thermal.
Passive Solar strategyLimited oppotrunities for passive solar due to site location and orientation. New triple glazed roof lights, front and back on both dwellings, were planned but after modelling in PHPP we have decided against these.
Space cooling strategyNatural ventilation during cooling season. MVHR otherwise. Existing poured concrete walls retained within thermal envelope as thermal store to smooth temperature fluctuations.
Daylighting strategyMaximise daylight, very limited because of East/West alignment and heavy overshading from steep wooded valley sides. Kitchens achieve a minimum average daylight factor of at least 2%. Living rooms to achieve average daylight factor of at least 1.5%. Use mirrored tiles in in window surrounds in kitchen and bathroom. Deep external wall insulation system has also reduced daylight.
Ventilation strategyHigh efficiency MVHR system with post air-heating coil. Openable windows (summer)
Airtightness strategy External airtight barrier created by parging the external walls to below ground level and lining this continuous airtight barrier with 18mm tape sealed OSB. Over existing roof structure 1 m3/m2 .hr @q50 (design target)
Strategy for minimising thermal bridges Complete overinsulation of existing structure to create thermal bridge free design, including new roof construction. Junctions assessed using PHPP include: Ground floor junction, external corner, party wall, party roof, party floor, eaves, verge, window jamb, head and sill, door jamb, head and threshold.
Modelling strategyWhole house modelling undertaken using SAP 2005 and PHPP 2007, to include local weather data, interstitial condensation analysis.
Insulation strategyExternally fit 300mm Warmcel 500 insulation in new OSB frame (U-value of 0.13 W/m2K). Create new warm roof structure incorporating 350mm Warmcel 500 (U-value of 0.1 W/m2K). Excavate existing ground floor slab and replace to include 220mm XPS board. Perimeter insulation to 1m depth.
Other relevant retrofit strategiesMVHR extract air drying rooms in both houses to obviate the need for tumble driers. To use locally sourced labour and sustainable materials wherever possible - Eg Warmcel 500, FSC OSB etc. To allow tenants input in interior design decisions, and engage them in the entire build process. To heat meter the tenants individually and evaluate this approach to billing where North Devon Homes becomes the ESCo, to assess this is light of the RHI from April 2011. To use the site as a training and demonstration site wherever possible to build new skills and partnerships, Eg invite other housing providers to site to watch installation and network with contractors, deliver training to contractors and potential new specialist suppliers etc.
Contextual informationSite is within Exmoor National Park, fortunately the planning authority are forward thinking and have been very supportive and interested in this proposal. Site has limited external space, minimal south facing roof, at the bottom of a steep sided, wooded valley. Site is not connected to mains gas and lack of opportunities to generate electricity on site mean we will need to purchase mains electricity until the Lynton Community Hydro ESCo is operational.

Building services

Space heatingNULL
Hot waterNULL
Renewable energy generation systemNULL
Strategy for minimising thermal bridgesNULL

Building construction

Volume -
Thermal fabric area -
Roof description NULL
Roof U-value 0.00 W/m² K
Walls description NULL
Walls U-value 0.00 W/m² K
Party walls description NULL
Party walls U-value 0.00 W/m² K
Floor description NULL
Floor U-value 0.00 W/m² K
Glazed doors description NULL
Glazed doors U-value 0.00 W/m² K -
Opaque doors description NULL
Opaque doors U-value 0.00 W/m² K -
Windows description NULL
Windows U-value 0.00 W/m² K -
Windows energy transmittance (G-value) -
Windows light transmittance -
Rooflights description NULL
Rooflights light transmittance -
Rooflights U-value 0.00 W/m² K