Eco-retrofit Orpington - a multiple house solution

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This whole-house AND MULTIPLE HOUSE solution is applicable to both void and tenanted homes that may or may not be at Decent Homes standards and makes most benefit from shared external spaces between houses. The UK-based SME supply chain includes an innovative ground source heat pump system that does not require a separate hot water tank, reducing disruption to tenants as the borehole is made in external land not in the residents' gardens, potentially bringing a district or shared energy network to the estate.

Retrofit for the future ZA538P
Images Graphs Figures Description Strategies Building

Eco-retrofit Orpington - a multiple house solution : Project images

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Eco-retrofit Orpington_Photo.jpg
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 4361 kWh/yr 6680 kWh/yr -
Natural gas use13603 kWh/yr - -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement 279 kWh/m².yr 176 kWh/m².yr -
Annual CO₂ emissions 57 kg CO₂/m².yr 42 kg CO₂/m².yr -
Annual space heat demand - 88 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
PhotoVoltaic 3.7kWp2467.459961 kWh/yr -
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
111 kWh/m².yr -
Annual CO₂ emissions
offset by renewable generation
27 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 targetsTotal Annual CO2 emissions: 17kg/m2/yr Total Primary energy: 110 kWh/m2/yr. The un-editable figures below in the Phase 2 database (Predicted targets) do not align. For calculations please see SAP worksheets plus extension uploaded separately.
Forecast heating load -


Pre-development air permeability test-7.52m³/m².hr @ 50 Pascals
Final air permeability test-7.43m³/m².hr @ 50 Pascals

Project description

StageUnder construction
Start date05 April 2010
Occupation date30 November 2009
Location Darrick Wood, Orpington Kent  England
Build typeRefurbishment
Building sectorPublic Residential
Property typeEnd Terrace
Construction typeMasonry Cavity
Other construction type100mm (approx) cavity
Party wall constructionInsulated 250mm masonry cavity wall
Floor area 95
Floor area calculation method Treated Floor Area (PHPP)
Building certification

Project Team

OrganisationKeniston Housing Association
Project lead personKeniston Housing Association
Landlord or ClientKeniston Housing Association
ArchitectBroadway Malyan Ltd.
Mechanical & electrical consultant
Energy consultantBroadway Malyan Ltd.
Structural engineer
Quantity surveyor
ContractorTCS Group

Design strategies

Planned occupancyTwo adults occupy the property almost continously, other than the "school run" on weekdays. A further two adults and one young child visit the house on a daily basis for 4-6 hours.
Space heating strategyGround source heat pump solution serving radiators with LTHW @55 deg C. Radiatiors proposed as slimline low water radiators with low efficiency, high output.
Water heating strategyInstantaneous hot water via integrated thermal store within indoor Ground Source Heat Pump unit.
Fuel strategyUltra low all electric solution, offset by roof photovoltaic electricity generation.
Renewable energy strategyHigh efficiency ground source heat pump. Roof mounted photovoltaic electricity (3.7kWp as a maximum - this figure is constrained by the input of the efficiency with SAP for the groud source heat pump, which runs at 400% and not 320%, as inputted.
Passive Solar strategyHigh performance low solar transmission glazing on the property which has windows on South-East and North-West elevations. A garden to both front and rear increase likelihood of tenants opening curtains.
Space cooling strategyComfort cooling is possible via reversible ground source heat pump operation. Openable windows for natural ventilation for most of the cooling season.
Daylighting strategyNo changes to the fenestration were possible in this retrofit proposal, but the new heating system with slimline radiators does allow more flexible planning of furniture, which could allow better daylight access through the existing glazing.
Ventilation strategyPassive ventilation via openable windows and trickle vents. Extract fans in kitchen, bathroom and ground floor toilet.
Airtightness strategy Significant improvement to gaps and cracks in envelope, targetting 3m3/m2hr.
Strategy for minimising thermal bridges Areas considered include junctions between external walls and roof, where refurbishment has taken place since the original construction. Window to wall junctions and door jamb are considered using specially-fabricated "Passivhaus" windows and doors that address thermal breaks.
Modelling strategyWhole house dynamic modelling was undertaken in an iterative manner using ies ve software, SAP 2005 9.81 + SAP extension - see energy forecast below. ies ve software used with SAP interface (SAP2005 9.81 via JPA Designer vr 4.04b1 build 002).
Insulation strategyHigh performance TARGETTED roof insulation upgrade following detailed thermo-imaging report and air tightness testing undertaken during phase 1. Triple glazing with target u-value of 0.7W/m2k is the proposed upgrade to the existing double-glazed windows.
Other relevant retrofit strategiesWe are planning to carry out our package of retrofit measures with tenants remaining in the dwelling during the proposed works. We intend to demonstrate our approach can be undertaken with minimal disruption to the tenants and with no associated temporary re-housing costs. Due to the Landlord owning and managing all external land in between properties, there is the opportunity to install external ground source loops for up to 5 properties with potential to activate 1 property in Phase 2 leaving four ground loops capped off for future use. (subject to funding availability). Low energy lights, appliances, cooking and water-saving devices are also going to be supplied and installed.
Contextual informationAdditional data logging devices and clear metering for easyily controlled technology proposed to provide enhanced monitoring feedback to exceed TSB base specification is proposed, following discussion with current tenants that they are not especially energy-conscious at present and would benefit from support in this regard. The tenants have lived in this property for decades and have habits that might be challenged by the retrofit!

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