Harrow Road Retrofit
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as PDF This 1952 solid wall detached house in Nottingham was extended and refurbished using the EnerPHit standard as a guide. PHPP predicted a space heating demand of 25 kWh/m2.a (assuming 1 ACH at 50Pa). Measured energy demand in the 12 months to May 2014 was 20 kWh/m2.a (although air tightness currently exceeds 1 ACH). Comfort and air quality are vastly better than before the refurbishment, a change which is reflected in before and after datalogger records of temperature and relative humidity.
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Energy and fuel use
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
| Pre-development | Forecast | Measured | |
| Electricity use | 1560 kWh/yr | 1590 kWh/yr | 1445 kWh/yr |
|---|---|---|---|
| Natural gas use | 21800 kWh/yr | 5345 kWh/yr | 4509 kWh/yr |
| Oil use | - | - | - |
| LPG use | - | - | - |
| Wood use | - | - | - |
| Other Fuel | - | - | - |
| Pre-development | Forecast | Measured | |
| Primary energy requirement | 232 kWh/m².yr | 81 kWh/m².yr | 70 kWh/m².yr |
|---|---|---|---|
| Annual CO₂ emissions | 43 kg CO₂/m².yr | 16 kg CO₂/m².yr | 14 kg CO₂/m².yr |
| Annual space heat demand | 202 kWh/m².yr | 25 kWh/m².yr | - |
Renewable energy
| Electricity generation | Forecast | Measured |
|---|---|---|
| PV panels | - | 3108 kWh/yr |
| Other Renewables Tech | - | - |
| Electricity consumed by generation | - | - |
| Primary energy requirement offset by renewable generation | 81 kWh/m².yr | 8 kWh/m².yr |
| Annual CO₂ emissions offset by renewable generation | 16 kg CO₂/m².yr | -1 kg CO₂/m².yr |
Calculation and targets
| Whole house energy calculation method | PHPP |
|---|---|
| Other whole house calculation method | - |
| Energy target | EnerPHit was used as a guide |
| Other energy targets | - |
| Forecast heating load | 1.3 W/m² demand |
Airtightness
| Date | Result | |
| Pre-development air permeability test | - | - |
|---|---|---|
| Final air permeability test | 16 August 2012 | 1.093m³/m².hr @ 50 Pascals |
Project description
| Stage | Occupied |
|---|---|
| Start date | 21 October 2011 |
| Occupation date | 21 October 2012 |
| Location | Nottingham Nottinghamshire England |
| Build type | Refurbishment |
| Building sector | Private Residential |
| Property type | Detached |
| Construction type | Solid Brick |
| Other construction type | 9 inch solid brick wall |
| Party wall construction | |
| Floor area | 125 m² |
| Floor area calculation method | Treated Floor Area (PHPP) |
| Building certification |
Project Team
| Organisation | |
|---|---|
| Project lead person | Tina Holt |
| Landlord or Client | Tina Holt and Richard Middup |
| Architect | Gil Schalom |
| Mechanical & electrical consultant | Andrew Farr - Green Building Store (MVHR) |
| Energy consultant | Alan Budden - Eco Design Consultants (PHPP) |
| Structural engineer | Andy Marlor - Howard Ward Associates |
| Quantity surveyor | none |
| Consultant | none |
| Contractor | McCane Construction & Ian Brown Joinery |
Design strategies
| Planned occupancy | 2 adults, 2 children (1 adult working from home) |
|---|---|
| Space heating strategy | Heating from gas combi boiler feeding radiators. Whole house MVHR. |
| Water heating strategy | Hot water from gas combi boiler. |
| Fuel strategy | Mains gas for hot water and heating.Mains electricity for cooking, lighting etc. |
| Renewable energy strategy | 3.25 kWp PV panel array |
| Passive Solar strategy | The street runs N-S so most windows face east and west. To improve passive solar gain, the new extension includes a south facing window and the new loft conversion has a south facing rooflight. |
| Space cooling strategy | The existing brick walls and new blockwork are externally insulated so provide thermal mass. In very hot weather, windows (and some curtains) are closed, ventilating only with MVHR. Once the outside temperature falls below internal air temperature, windows are opened to allow passive stack cooling. |
| Daylighting strategy | The existing east and west facing windows were already quite generous. Extensive patio doors on the west side provide light into the extension, aided by a light colour scheme.We replaced the solid panels on the stairs with spindles to allow more light into the hall and landing from the reduced north facing windows. |
| Ventilation strategy | MVHR and opening windows (which allow passive stack ventilation) |
| Airtightness strategy | The air tightness layer is internal: plaster on the existing brick walls and the new block walls, air vapour barriers in the attic and the square bay (timber construction). |
| Strategy for minimising thermal bridges | Thermal bridges minimised by careful detailing at all junctions and closely overseen during the build. Heat loss via walls to ground minimised with insulation downstands below ground floor insulation and EWI continuing to footings of the existing house. |
| Modelling strategy | PHPP |
| Insulation strategy | - Application of external insulation to solid brick walls (to achieve U-value of 0.13 W/m2K)- Removal of existing suspended and solid floors and replacement with solid insulated floor (to achieve U-value of 0.1 W/m2K)- Insulation above and between rafters (to achieve U-value of 0.13 - 0.10 W/m2K). |
| Other relevant retrofit strategies | Family moved out and rented a house near by. This was useful to store stripped out items for re-use (e.g. timbers, floorboards) and new items until installation (e.g. windows, MVHR) |
| Contextual information | The house was not bought with a Passive House refurbishment in mind at the outset, and the E-W orientation is not ideal. The plot is narrow so there is little gap between this house and the neighbouring houses to north and south. This made scaffolding for EWI difficult on one side, and means that the original house had no south facing windows.Planning permission was sought to insulate and render all elevations (originally all brick) but in the end the compromise was to use brick slips on the bays.The existing brickwork was spalling badly in places so needed protection of some sort. |
Building services
| Occupancy | As before the refurbishment - 2 adults, 2 children |
|---|---|
| Space heating | ATAG A-rated gas combi boiler (located in an insulated plant room outside the envelope) feeding 5 small radiators |
| Hot water | ATAG gas combi boiler (located in an insulated plant room outside the envelope) |
| Ventilation | Paul Focus 200 MVHR unit with Lindab ducting supplied and designed by Green Building Store |
| Controls | Gas boiler thermostat and MVHR controls in main living area, TRVs on 4 radiators |
| Cooking | Electric induction hob and oven |
| Lighting | Mainly LEDs. Some CFLs. |
| Appliances | A+++ rated fridge freezer. dishwasher. washing machine |
| Renewable energy generation system | 3.25 kW PV panel array on S facing roof |
| Strategy for minimising thermal bridges | Some detailed calcs were carried out in the design of the square bay (which was re-built as the original curved bay was weak). Otherwise standard details were used. |
Building construction
| Storeys | 3 |
|---|---|
| Volume | - |
| Thermal fabric area | - |
| Roof description | Pitched roof with gable end to rear and smaller gable over front bay. Stick built with 150mm rafters, 100mm foil faced PIR insulation above the rafters and 150mm Rafter Roll 32 between the rafters. |
| Roof U-value | 0.13 W/m² K |
| Walls description | 9 inch brick wall (exisitng) and 140mm block (extension) with 180mm Phenolic foam board external insulation finished with render and brick slips on the bays |
| Walls U-value | 0.13 W/m² K |
| Party walls description | |
| Party walls U-value | - |
| Floor description | 300mm XPS under the whole ground floor, with downstands to the footings around every internal and external wall. 100mm upstands of XPS with 20mm foil faced PIR upstands above (keeping the slab and the screed away from the brick walls) |
| Floor U-value | 0.10 W/m² K |
| Glazed doors description | Green Building Store EcoPassiv front and back door |
| Glazed doors U-value | 0.75 W/m² K - |
| Opaque doors description | |
| Opaque doors U-value | - - |
| Windows description | Green Building Store EcoPassiv windows |
| Windows U-value | 0.75 W/m² K - |
| Windows energy transmittance (G-value) | - |
| Windows light transmittance | - |
| Rooflights description | Quad glazed Fakro rooflight with insulated flashing |
| Rooflights light transmittance | - |
| Rooflights U-value | - |