Lena Gardens

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Passivhaus retrofit of a Victorian terrace in a conservation area in London
Images Graphs Figures Description Strategies Building

Lena Gardens : Project images

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CO2 emissionsPrimary energy requirement
Energy target

Energy and fuel use

Fuel use by type
Primary energy requirement
CO2 emissions

Renewable electricity generation This project has used the contributions from renewable electricity generation equipment to either meet the Retrofit for the Future target or otherwise reduce the Primary energy requirement and CO₂ emissions associated with the project.

Measured data from renewable generation is not yet available.

Fuel use

Electricity use 3910 kWh/yr 5050 kWh/yr -
Natural gas use57730 kWh/yr 702 kWh/yr -
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement 391 kWh/m².yr 69 kWh/m².yr -
Annual CO₂ emissions 73 kg CO₂/m².yr 16 kg CO₂/m².yr -
Annual space heat demand 184 kWh/m².yr 12 kWh/m².yr -

Renewable energy

Electricity generationForecastMeasured
PV750 kWh/yr 750 kWh/yr
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
59 kWh/m².yr -10 kWh/m².yr
Annual CO₂ emissions
offset by renewable generation
14 kg CO₂/m².yr -2 kg CO₂/m².yr

Calculation and targets

Whole house energy calculation method PHPP
Other whole house calculation method-
Energy target
Other energy targets-
Forecast heating load 10 W/m² demand


Pre-development air permeability test-20m³/m².hr @ 50 Pascals
Final air permeability test17 November 20100.49m³/m².hr @ 50 Pascals

Project description

Start date11 January 2010
Occupation date18 October 2010
Location London London  England
Build typeRefurbishment
Building sectorPrivate Residential
Property typeMid Terrace
Construction typeSolid Brick
Other construction type230mm
Party wall construction
Floor area 195
Floor area calculation method Treated Floor Area (PHPP)
Building certification  Passivhaus certified building Passivhaus certified building

Project Team

OrganisationGreen Tomato Energy Ltd
Project lead persongreentomatoenergy
Landlord or ClientMr and Mrs Pakenham
ArchitectTom Macmillan-Scott
Mechanical & electrical consultant greentomatoenergy
Energy consultantgreentomatoenergy
Structural engineerRS&J
Quantity surveyor
ContractorPrincedale Ltd.

Design strategies

Planned occupancy4 people, often at home
Space heating strategyHeating through exhaust air heat pump in ventilation system. No radiators, underfloor heating or boiler.
Water heating strategySolar thermal with top-up from exhaust air-source heat pump
Fuel strategyMains electricity. Gas cooking.
Renewable energy strategy1.2kWp PV array
Passive Solar strategyMost glazing faces due south, with bay windows for solar capture.
Space cooling strategyUnderground heat exchanger
Daylighting strategy
Ventilation strategyMVHR (winter), openable windows (summer)
Airtightness strategy Measured airtightness of 0.49ach@50Pa.
Strategy for minimising thermal bridges Careful detailing throughout.
Modelling strategyPHPP
Insulation strategyExternal walls, floors and ceilings insulated internally to achieve U-values of approximately 0.1W/m2K.
Other relevant retrofit strategies
Contextual informationHouse is in a conservation area in Hammersmith & Fulham

Building services

Occupancy4 people
Space heatingExhaust air-source heat pump inputting through ventilation system (PH Compact unit)
Hot waterSolar thermal, topped up by exhaust air-source heat pump (PH Compact unit)
VentilationMVHR (PH Compact unit)
LightingLED and CFL throughout
AppliancesAll appliances A+ or better
Renewable energy generation systemPV array on roof
Strategy for minimising thermal bridgesCareful detailing and THERM modelling, with the use of structural foamglas. All floors rehung inside thermal envelope.

Building construction

Storeys 5
Volume 488
Thermal fabric area 675
Roof description
Roof U-value 0.14 W/m² K
Walls description
Walls U-value 0.10 W/m² K
Party walls description
Party walls U-value 0.27 W/m² K
Floor description
Floor U-value 0.11 W/m² K
Glazed doors description
Glazed doors U-value 0.85 W/m² K installed
Opaque doors description
Opaque doors U-value 1.00 W/m² K installed
Windows description
Windows U-value 0.90 W/m² K installed
Windows energy transmittance (G-value) 0.549 %
Windows light transmittance -
Rooflights description
Rooflights light transmittance 0.6%
Rooflights U-value 0.70 W/m² K