BISF Steel Frame House - 80% Carbon Dioxide emmision reduction through whole house upgrade approach including innovative technologies

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Existing: Steel frame with render and steel cladding; Blockwork and timber frame side extension; Steel shingle roof. Proposed: Existing render and steel cladding removed; New sheathing board, insulation & render cladding; Wall, roof & floor insulation to side extension; Main roof insulation increased to 350mm; Triple glazed uPVC windows; High efficiency gas boiler serving radiators; Flue gas heat recovery; LED lights with 50k hours guaranteed max light output; Decentralised whole house ventilation; 2.7kWp PV and 3.0m2 solar thermal panels; AA++ appliances; Smart metering with display; Shower water heat recovery; Reduced water consumption

Retrofit for the future ZA145M
Images Graphs Figures Description Strategies Building

BISF Steel Frame House - 80% Carbon Dioxide emmision reduction through whole house upgrade approach including innovative technologies : 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 2751 kWh/yr 1406 kWh/yr 4913 kWh/yr
Natural gas use18587 kWh/yr 9593 kWh/yr 2509 kWh/yr
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement 321 kWh/m².yr 165 kWh/m².yr 172 kWh/m².yr
Annual CO₂ emissions 62 kg CO₂/m².yr 32 kg CO₂/m².yr 39 kg CO₂/m².yr
Annual space heat demand - 79 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
2.7kWp PV1914 kWh/yr -
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
111 kWh/m².yr 172 kWh/m².yr
Annual CO₂ emissions
offset by renewable generation
19 kg CO₂/m².yr 39 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 test-15.82m³/m².hr @ 50 Pascals
Final air permeability test-12.51m³/m².hr @ 50 Pascals

Project description

Start date01 March 2010
Occupation date16 April 2010
Location Cambridge Cambridgeshire  England
Build typeRefurbishment
Building sectorPublic Residential
Property typeSemi-Detached
Construction typeSteel frame
Other construction typeRender and steel cladding
Party wall construction250mm block / block cavity
Floor area 88
Floor area calculation method Actual Floor Area (SAP)
Building certification

Project Team

OrganisationCambridge City Council
Project lead personCambridge City Council
Landlord or ClientCambridge City Council
ArchitectPRP Architects
Mechanical & electrical consultant N/A
Energy consultantPRP Environmental
Structural engineerScott Wilson
Quantity surveyor
ConsultantCDM Coordinator: PRP Project Services
ContractorHill Partnerships ltd

Design strategies

Planned occupancyCurrently one elderly resident, but potential for family with three children
Space heating strategyGas fired boiler with flue gas heat recovery feeding radiators
Water heating strategySolar hot water with gas condensing boiler back up
Fuel strategySolar thermal hot water with mains gas back up, PV panels and mains electricity
Renewable energy strategy2.7kWp polycrystaline photovoltaic array; 22.5sq.m, 3.0sq.m solar thermal panels
Passive Solar strategyThe house faces almost exactly due west and has some large windows on the west side. Fenestration patterns will remain as existing and adjustments have been made to glazing g-value to compensate for potential overheating on the west facing elevation.
Space cooling strategyNatural ventilation via openable windows; room layouts allow for cross ventilation and cooling. Adjustments to glazing g-value to guard against overheating.
Daylighting strategyThe house already has good natural daylight through large windows. It was designed at a time when daylight and fresh air where important aspects of new beginings in post war housing development.
Ventilation strategyNatural ventilation via openable windows, plus a decentralised whole house system using continuously running low energy fans drawing air out through wet rooms.
Airtightness strategy Sheathing board with foam / render overcladding and careful detailing around windows and doors to minimise air leakage. High performance seals to windows and doors. Draught sealing around the loft hatch. Ventilation equipment checked for air leakage prior to commissioning and careful detailing around sockets and all other penetrations. Instruction to operatives on best practice at contract stage.
Strategy for minimising thermal bridges Minimisation of thermal bridges at design stage by careful detailing of all material and component junctions to ensure continuity of insulation and thermal performance. House steel frame adjusted locally to allow new windows to be supported in line with overcladding. Continuation of overcladding to below ground level to protect the concrete slab edge. Instruction to operatives on best practice and careful monitoring on site during construction.
Modelling strategyWhole house modelling was undertaken using SAP (with NHER Plan Assessor software) in conjunction with the Extended SAP worksheet. EDSL TAS was used to undertake an overheating analysis. AutoCAD produced plans and elevations were used to assist with visualisation and detailed design.
Insulation strategyGround floor - new timber suspended in living room, 25mm nanogel blanket Resultant U-value 0.43 W/m2K Exposed front, rear and gable walls - 200mm Permarock external insulation Resultant U-value 0.11 W/m2K Sheltered house wall in lean-to lobby & store - 50mm Spacetherm 0.21 W/m2K Stud external wall - 50mm phenolic board plus 50mm Spacetherm 0.17 W/m2K Pitched roofs with flat ceiling - Top up to 350mm mineral fibre quilt Resultant U-value 0.12 W/m2K Windows - Replacement uPVC triple glazed low-e Resultant U-value 1.1 W/m2K Doors - Replacement uPVC with triple glazed low-e Resultant U-value 1.5 W/m2K
Other relevant retrofit strategiesOur proposals are designed to be carried out with residents remaining in occupation. Considering the wider application of Retrofit it will not be practical or economically viable on a large scale to decant residents while the work is in progress. Pre commencement discussion and engagement with residents, plus regular monitoring during and after the works, will help to minimise the degree of inevitable inconvenience.
Contextual informationThe particular form of steel frame construction of this house and the well documented defects that have affected other similar homes have influenced our decision to remove the detriorating and unstable external finishes and substitute a structurally sound and thermally efficient envelope. The poor quality of original internal linings have also influenced the choice of a robust and stable cladding.

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