Metropolitan Housing Trust London - Hawthorn Road

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A Passivhaus-inspired refurbishment of an Edwardian, solid brick, mid-terrace property in the London Borough of Haringey. With a focus on super-insulation, airtightness and mechanical ventilation with heat recovery, this project aimed for maximum levels of building thermal and energy efficiency. The heating and hot water solutions were designed to remove the need for a conventional wet heating system. The project also focused on a solution which works best for residents, utilising simple controls, straightforward systems and strong levels of resident engagement.
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Metropolitan Housing Trust London - Hawthorn Road : 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 2940 kWh/yr 1960 kWh/yr 5321 kWh/yr
Natural gas use69696 kWh/yr 4029 kWh/yr 10100 kWh/yr
Oil use- - -
LPG use- - -
Wood use- - -
Other Fuel - - -
Primary energy requirement 803 kWh/m².yr 87 kWh/m².yr 229 kWh/m².yr
Annual CO₂ emissions 148 kg CO₂/m².yr 18 kg CO₂/m².yr 48 kg CO₂/m².yr
Annual space heat demand 617 kWh/m².yr 26 kWh/m².yr 52 kWh/m².yr

Renewable energy

Electricity generationForecastMeasured
Renewables Technology--
Other Renewables Tech--
Electricity consumed by generation --
Primary energy requirement
offset by renewable generation
87 kWh/m².yr 229 kWh/m².yr
Annual CO₂ emissions
offset by renewable generation
18 kg CO₂/m².yr 48 kg CO₂/m².yr

Calculation and targets

Whole house energy calculation method PHPP
Other whole house calculation method-
Energy target Retrofit for the Future
Other energy targets-
Forecast heating load 16 W/m² demand


Pre-development air permeability test14 August 200916.47m³/m².hr @ 50 Pascals
Final air permeability test17 January 20122.53m³/m².hr @ 50 Pascals

Project description

Start date26 July 2010
Occupation date20 January 2011
Location London Borough of Haringey London  England
Build typeRefurbishment
Building sectorPublic Residential
Property typeMid Terrace
Construction typeSolid Brick
Other construction typesolid 225mm brickwork
Party wall constructionsolid 225mm brickwork
Floor area 109
Floor area calculation method Treated Floor Area (PHPP)
Building certification

Project Team

OrganisationMetropolitan Housing Trust Limited
Project lead personMetropolitan Housing Trust London
Landlord or ClientMetropolitan Housing Trust London
ArchitectAnne Thorne Architects Partnership
Mechanical & electrical consultant King Shaw Associates
Energy consultant8 Associates
Structural engineer
Quantity surveyor
ConsultantUniversity College London - Bartlett School of Graduate Studies (Monitoring)
ContractorSandwood Construction Ltd.

Design strategies

Planned occupancyFamily house
Space heating strategyMVHR and radiators.
Water heating strategyGas boiler combined with solar hot water panels.
Fuel strategyMains gas, mains electricity.
Renewable energy strategySolar is being utilised for domestic hot water and heating.
Passive Solar strategy
Space cooling strategySummer - Natural Ventilation (openable windows); night purging during hot weather.
Daylighting strategyPassivhaus certified triple-glazed timber windows replace existing pvc double glazed windows, new opening to ground floor living room, to increase daylighting to rear room
Ventilation strategyPassivhaus Certified high efficiency Whole House Mechanical Ventilation Heat Recovery system (Maico).
Airtightness strategy Air tightness layer comprises membranes to internal insulated walls, roof and floor, and plaster to external insulated wall with existing plaster parged where necessary. Chimney breast filled, Membranes pre-sealed to new windows and doors, details to AECB gold standard. Precompletion testing
Strategy for minimising thermal bridges Vulnerable points are external wall insulation/internal roof, and internal floor to existing loadbearing internal walls, where strategy is to overlap.
Modelling strategyPassivhaus Planning Package 2007 (English Version). SAP 2005 also modelled for comparison.
Insulation strategyBreathable insulation to roof and internally insulated front wall. External rendered insulation to rear wall. Suspended ground floors replaced with insulated solid floors.
Other relevant retrofit strategies
Contextual informationThe house is in a conservation area. Consequently the front wall cannot be externally insulated and the front door must be retained.

Building services

Occupancy1 adult, 2 teenagers
Space heatingMechanical Ventilation with Heat Recovery and small heater battery. As a back-up, 5 radiators were installed, with hot-water supplied from a rotex gas-solar unit (see water heating strategy below).
Hot waterA Rotex gas-solar unit was installed to provide hot water and back up central heating. This unit comprises a gas boiler and hot water tank combined with solar thermal panels (4.72m2 on rear, south-facing roof). Shower waste water heat exchanger (Recoh-vert from Shower-save).
VentilationMVHR (Maico Aeronom WS250). Stale air extracted from kitchen and bathroom. Fresh air supplied to all other rooms.
ControlsMVHR controls: thermostat in the hallway, which controls the post-heat exchanger and heater battery; programmer/control unit in the kitchen to control summer/winter mode and ventilation speed. The occupants have been asked not to use the MVHR heater battery although sometimes they do. There is no thermostat for the Rotex unit, which provides the central heating. The heat provision is based on return water flow temperature and was commissioned at installation. The five radiators have thermostatic valves.
CookingElectric oven and hob.
LightingLow energy lightbulbs throughout.
AppliancesWashing machine, fridge freezer, dishwasher and tumble dryer are AAA rated.
Renewable energy generation systemSolar Hot water as part of Rotex unit (see hot water system).
Strategy for minimising thermal bridgesInsulation laps window frames. Insulation to party wall extends 1m back from front wall. Chimneys filled with expanded clay balls.

Building construction

Storeys 2
Volume 250
Thermal fabric area -
Roof description Roof - 0.12W/m2K (main) and 0.2W/m2K (rear extension); 350mm/300mm sheeps wool insulation (Thermafleece).
Roof U-value 0.12 W/m² K
Walls description All existing walls were 9inch brick solid wall. Front wall was internally insulated with breathable insulation and finishes. Rear wall was externally insulated with a rendered insulation. Front wall: 0.16W/m2K - 200mm sheeps wool insulation (Thermafleece), intelligent VCL (Intello), 60mm woodfibre board (Gutex), 15mm lime plaster finish. Rear walls: 0.13W/m2K - 250mm external rendered EPS (Jablite).
Walls U-value 0.16 W/m² K
Party walls description Existing 9inch brick solid wall insulated internally with breathable materials - 100mm woodfibre board (Gutex) and 15mm lime plaster finish. However insulation only extends approximately 1m back from front wall - it does not cover entire party wall.
Party walls U-value 0.30 W/m² K
Floor description Suspended timber floor replaced with solid floor: OSB on EPS (Jablite). 150mm of EPS to main house floor achieving a U-Value of 0.12W/m2K. 100mm of EPS to rear extension floor achieving a U-Value of 0.2W/m2K.
Floor U-value 0.12 W/m² K
Glazed doors description Triple glazed (Drewexim)
Glazed doors U-value 0.77 W/m² K installed
Opaque doors description Existing timber front door retained. Triple glazed door with U-Value of 0.77W/m2K installed behind front door, creating a small entrance lobby, which sits outside of the thermal fabric.
Opaque doors U-value - installed
Windows description Timber framed, triple glazed (Drewexim).
Windows U-value 0.77 W/m² K -
Windows energy transmittance (G-value) -
Windows light transmittance -
Rooflights description n/a
Rooflights light transmittance -
Rooflights U-value -

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