Metropolitan Housing Trust London - Hawthorn Road
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as PDF 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.
Metropolitan Housing Trust London - Hawthorn Road : Project images
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Energy and fuel use
Measured data from renewable generation is not yet available.
Fuel use
| Pre-development | Forecast | Measured | |
| Electricity use | 2940 kWh/yr | 1960 kWh/yr | 5321 kWh/yr |
|---|---|---|---|
| Natural gas use | 69696 kWh/yr | 4029 kWh/yr | 10100 kWh/yr |
| Oil use | - | - | - |
| LPG use | - | - | - |
| Wood use | - | - | - |
| Other Fuel | - | - | - |
| Pre-development | Forecast | Measured | |
| 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 generation | Forecast | Measured |
|---|---|---|
| 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 |
Airtightness
| Date | Result | |
| Pre-development air permeability test | 14 August 2009 | 16.47m³/m².hr @ 50 Pascals |
|---|---|---|
| Final air permeability test | 17 January 2012 | 2.53m³/m².hr @ 50 Pascals |
Project description
| Stage | Occupied |
|---|---|
| Start date | 26 July 2010 |
| Occupation date | 20 January 2011 |
| Location | London Borough of Haringey London England |
| Build type | Refurbishment |
| Building sector | Public Residential |
| Property type | Mid Terrace |
| Construction type | Solid Brick |
| Other construction type | solid 225mm brickwork |
| Party wall construction | solid 225mm brickwork |
| Floor area | 109 m² |
| Floor area calculation method | Treated Floor Area (PHPP) |
| Building certification |
Project Team
| Organisation | Metropolitan Housing Trust Limited |
|---|---|
| Project lead person | Metropolitan Housing Trust London |
| Landlord or Client | Metropolitan Housing Trust London |
| Architect | Anne Thorne Architects Partnership |
| Mechanical & electrical consultant | King Shaw Associates |
| Energy consultant | 8 Associates |
| Structural engineer | |
| Quantity surveyor | |
| Consultant | University College London - Bartlett School of Graduate Studies (Monitoring) |
| Contractor | Sandwood Construction Ltd. |
Design strategies
| Planned occupancy | Family house |
|---|---|
| Space heating strategy | MVHR and radiators. |
| Water heating strategy | Gas boiler combined with solar hot water panels. |
| Fuel strategy | Mains gas, mains electricity. |
| Renewable energy strategy | Solar is being utilised for domestic hot water and heating. |
| Passive Solar strategy | |
| Space cooling strategy | Summer - Natural Ventilation (openable windows); night purging during hot weather. |
| Daylighting strategy | Passivhaus 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 strategy | Passivhaus 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 strategy | Passivhaus Planning Package 2007 (English Version). SAP 2005 also modelled for comparison. |
| Insulation strategy | Breathable 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 information | The house is in a conservation area. Consequently the front wall cannot be externally insulated and the front door must be retained. |
Building services
| Occupancy | 1 adult, 2 teenagers |
|---|---|
| Space heating | Mechanical 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 water | A 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). |
| Ventilation | MVHR (Maico Aeronom WS250). Stale air extracted from kitchen and bathroom. Fresh air supplied to all other rooms. |
| Controls | MVHR 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. |
| Cooking | Electric oven and hob. |
| Lighting | Low energy lightbulbs throughout. |
| Appliances | Washing machine, fridge freezer, dishwasher and tumble dryer are AAA rated. |
| Renewable energy generation system | Solar Hot water as part of Rotex unit (see hot water system). |
| Strategy for minimising thermal bridges | Insulation laps window frames. Insulation to party wall extends 1m back from front wall. Chimneys filled with expanded clay balls. |
Building construction
| Storeys | 2 |
|---|---|
| Volume | 250m³ |
| 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 | - |