Boundary Close (End-terrace)

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A small social housing development of 8 dwellings constructed with a super-insulated panellised timber frame and designed to run without a central heating system.
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Boundary Close (End-terrace) : Project images

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CO2 emissionsPrimary energy requirement
Energy target
Near Passivhaus

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 - 6810 kWh/yr -
Natural gas use- - -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement - 164 kWh/m².yr -
Annual CO₂ emissions - 39 kg CO₂/m².yr -
Annual space heat demand - 26 kWh/m².yr -

Renewable energy

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

Calculation and targets

Whole house energy calculation method
Other whole house calculation method-
Energy target Near Passivhaus
Other energy targets-
Forecast heating load 19 W/m² demand


Pre-development air permeability test03 March 2008-
Final air permeability test02 June 20081.58m³/m².hr @ 50 Pascals

Project description

Start date15 August 2008
Occupation date
Location York North Yorkshire  England
Build typeNew build
Building sectorPublic Residential
Property type
Construction type
Other construction type
Party wall construction
Floor area 104
Floor area calculation method Actual Floor Area (SAP)
Building certification

Project Team

Project lead person
Landlord or ClientYork Housing Association
ArchitectPhil Bixby of Constructive Individuals
Mechanical & electrical consultant Nu-Aire
Energy consultant
Structural engineerThermal Timber Frame
Quantity surveyorBrian Stace

Design strategies

Planned occupancyAll dwellings were planned as 3 bedroom units.
Space heating strategyThe main space heating strategy was to design out central heating systems by providing high levels of insulation (all opaque fabric U-vales less than 0.12 W/m2K) and setting ambitious air permeability targets. Electric resistance heating and positive input ventilation air with pre-heated air combine to provide back-up space heating.
Water heating strategyFlat panel solar hot water panels to meet up to 60% of the solar hot water demand and electric immersion to provide back-up.
Fuel strategyThe sole fuel source is mains electricity.
Renewable energy strategyNo renewable energy generation was proposed.
Passive Solar strategyPrinciples of passive solar design were followed: Larger areas of glazing are provided to the southern facing elevations with minimal glazing to the rear of the dwelling.
Space cooling strategyMain cooling is primarily through natural ventilation. Mechanically driven cooling using night-time positive input ventilation is also an option.
Daylighting strategyThe passive solar design assists in providing daylight to the living and some bedroom spaces. Rooflights are used to provide natural light to the first floor bathroom and second bedroom.
Ventilation strategyPositive input ventilation to supply fresh air, with pre-heating provided by passing outside air through solar hot water panel.
Airtightness strategy The primary airtightness barrier is a continuous internal barrier composed as follows: Roof = Panels sized to minimise number of construction joints and panels covered with DuPont Airgurad membrane, lapped and taped to wall membrane. Wall = Continuation of internal membrane on OSB, taped and sealed to all openings and penetrations and down to floor slab. Battened service voids provided internally to protect integrity of air barrier.
Strategy for minimising thermal bridges The construction detailing was developed over a series of two similar, super-insulated timber frame schemes and informed by and developed with input from the contractor.
Modelling strategy
Insulation strategy
Other relevant retrofit strategies
Contextual information

Building services

OccupancyVaries - From 2 to 4 occupants.
Space heating2 kW electric panel heater with additional contribution from a NuAire'Sunwarm' positive input ventilation system.
Hot water2 No. 1.25 x 2.5 solar hot water flat panels from NuAire with backup electric immersion heater.
VentilationNuAire'Sunwarm' positive input ventilation system with a single suppy air diffuser. This unit passes incoming air thorough the solar hot water panels to pre-heat supply air and can reverse this operation during warm nights to provide some cooling. A separate hood extract is provided in the ktichen.
ControlsThe NuAire 'Sunwarm' system is controlled by a single user control panel with one adjustable dial to choose from six supply air speed settings. The single electric panel heater is controlled by a room thermostat and timer.
CookingAll cooking appliances supplied by tenants.
Lighting100% compact fluorescent bulbs throughout.
AppliancesAll appliances supplied by tenants. The one exception to this is that the housing association requires all tumble dryers to be condensing models to avoid the need to puncture the air membrane for a dryer vent.
Renewable energy generation systemNone.
Strategy for minimising thermal bridgesNone calculated.

Building construction

Storeys 3
Volume 253
Thermal fabric area 187
Roof description Double pitched roof finished in plain clay pantiles on a 407mm deep, fully insulated engineered timber joist/rafter OSB clad panel. Prefabricated roof panels span from the wallplate to a ridge beam. An internal service void has been created using 25x50 battens with the ceiling finished with 12mm plasterboard.
Roof U-value 0.08 W/m² K
Walls description Two types of external cladding: Stained softwood vertical board on board cladding to ground floor; Thermowood horizontal boarding above. The cladding boards fixed to 25 x 50mm battens on OSB sheathing on 300mm engineered timber studs lined internall with OSB and fully filled with mineral wool. An internal service void is provided by fixing plasterboard on 25 x 50 battens.
Walls U-value 0.10 W/m² K
Party walls description Timber cavity comprised of the following construction on either side of a 50mm cavity: 12mm plasterboard on 18mm timber boarding on 89mm timber frame. Only one of the two halves of the party wall construction is insulated with mineral fibre.
Party walls U-value -
Floor description Floating floor construction comprised of 22mm tongue and groove timber boards with all edges glued on two layers of 75mm extruded polystyrene insulation on 100mm concrete slab on ground.
Floor U-value 0.12 W/m² K
Glazed doors description Solid stained softwood doors with double glazing.
Glazed doors U-value 2.00 W/m² K uninstalled
Opaque doors description
Opaque doors U-value - -
Windows description Double glazed timber windows with low emissivity coating, 16mm argon fill.
Windows U-value 1.70 W/m² K uninstalled
Windows energy transmittance (G-value) 60 %
Windows light transmittance 70%
Rooflights description Fakro triple glazed rooflights in laminated timber frame.
Rooflights light transmittance 50%
Rooflights U-value 1.70 W/m² K