DIY deep retrofit and extension of a 1940s semi
Download
as PDF Adding a single-storey extension and applying thermal upgrades to a 1945 council-built semi. A staged retrofit aiming for EnerPhit standards.
DIY deep retrofit and extension of a 1940s semi : Project images
Click on image to preview full size
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 | 3617 kWh/yr | 2200 kWh/yr | 1841 kWh/yr |
|---|---|---|---|
| Natural gas use | 7362 kWh/yr | 2000 kWh/yr | 2188 kWh/yr |
| Oil use | - | - | - |
| LPG use | - | - | - |
| Wood use | - | - | - |
| Other Fuel | - | - | - |
| Pre-development | Forecast | Measured | |
| Primary energy requirement | 223 kWh/m².yr | 99 kWh/m².yr | 91 kWh/m².yr |
|---|---|---|---|
| Annual CO₂ emissions | 46 kg CO₂/m².yr | 22 kg CO₂/m².yr | 20 kg CO₂/m².yr |
| Annual space heat demand | - | 25 kWh/m².yr | - |
Renewable energy
| Electricity generation | Forecast | Measured |
|---|---|---|
| Solar PV | 2500 kWh/yr | 2900 kWh/yr |
| Other Renewables Tech | - | - |
| Electricity consumed by generation | - | - |
| Primary energy requirement offset by renewable generation | 19 kWh/m².yr | -1 kWh/m².yr |
| Annual CO₂ emissions offset by renewable generation | 3 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 | AECB Silver |
| Other energy targets | - |
| Forecast heating load | - |
Airtightness
| Date | Result | |
| Pre-development air permeability test | - | - |
|---|---|---|
| Final air permeability test | - | - |
Project description
| Stage | Occupied |
|---|---|
| Start date | 02 July 2018 |
| Occupation date | |
| Location | Coton Cambridgeshire England |
| Build type | Mixed |
| Building sector | Private Residential |
| Property type | Semi-Detached |
| Construction type | Masonry Cavity |
| Other construction type | 50mm cavity in existing walls |
| Party wall construction | Double brick |
| Floor area | 78.59 m² |
| Floor area calculation method | Treated Floor Area (PHPP) |
| Building certification |
Project Team
| Organisation | |
|---|---|
| Project lead person | Bart Hommels |
| Landlord or Client | Bart Hommels |
| Architect | ECO Design Consultants - Milton Keynes |
| Mechanical & electrical consultant | |
| Energy consultant | |
| Structural engineer | Watson Hallam |
| Quantity surveyor | |
| Consultant | Green Building Store - MVHR |
| Contractor | SMB: https://smbbuilders.co.uk/ |
Design strategies
| Planned occupancy | Occupied during upgrade |
|---|---|
| Space heating strategy | Wet Underfloor heating driven directly from mains gas boiler using weather compensation controls. Low Temperature radiators on first floor. |
| Water heating strategy | 210 litre Heat Bank with proportionally controlled solar powered immersion element, with gas boiler backup |
| Fuel strategy | Mains gas, Mains electricity |
| Renewable energy strategy | 2.88 kWp roof-mounted solar PV array (SSE orientation, 42 deg inclination, no shading) |
| Passive Solar strategy | Window and roof light positions and roof overhang/shading optimised using PHPP |
| Space cooling strategy | MVHR |
| Daylighting strategy | Window and roof light positions and shading optimised using PHPP |
| Ventilation strategy | MVHR. All windows openable for summer bypass. |
| Airtightness strategy | Extension: all transitions between build elements (walls, floors, roof) taped before wet render/plaster applied.Existing: floor taped to walls. Masonry wet plastered. Masonry between joists in floor voids parge coated where accessible. Vapour tight membrane applied in sloping ceilings and loft. |
| Strategy for minimising thermal bridges | Continuous insulation kept throughout: EWI joined with extension cavity insulation. EWI to extend down to 400mm under DPC, limited by footings depth. New windows and doors in existing house mounted inside EWI layer. 50mm celotex perimeter insulation along all walls internally. |
| Modelling strategy | Whole-house PHPP with options report to reach AECB Silver, EnerPhit standards. |
| Insulation strategy | * All floors U=0.11 or better: screed on top of XPS, EPS or Celotex.* All walls U=0.14 or better: 200mm fully filled cavity in extension, 200mm EPS EWI on existing* Ceilings U=0.11 or better through warm roof with 110mm Celotex in between, 110mm over rafters for extension. Existing ceilings: 50mm celotex between rafters, 100/110mm celotex under rafters. loft floor has 150mm insulation in void. |
| Other relevant retrofit strategies | Extension and refurb undertaken under self-management and contributing to the work. Occupation maintained during entire project. Minimising cost of improvements without compromising on quality.Use of low-embedded CO2 building materials where possible: Glulam beam instead of steel, low-CO2 slates for extension roof, wood for external cladding of extension walls. |
| Contextual information | This is a largely DIY, staged retrofit. |
Building services
| Occupancy | family comprising 2 adults, 1 child |
|---|---|
| Space heating | A-rated boiler driving underfloor heating directly through weather compensation controller. Separate zone for upstairs radiators with smart controls (Nest) |
| Hot water | 210 l thermal store fed by solar energy (PV and immersion element controller) and boiler coil. |
| Ventilation | MVHR: Paul Focus 200, Lindab rigid ducting, calibrated April 2020. |
| Controls | Weather compensation for boiler with own outside temperature sensor. MVHR with three settings. |
| Cooking | A/A+ rated induction hob and oven |
| Lighting | LED lighting throughout |
| Appliances | A(+) rated fridge, freezer, dishwasher and washing machine. Latter 2 on timers to make optimal use of solar PV energy. |
| Renewable energy generation system | Roof-mounted 2.88 kWp Solar PV Array. SSE facing, 42 degree inclination. MCS projection 2550 kWh/yr. |
| Strategy for minimising thermal bridges | New doors and windows in existing mounted outside of masonry, inside the insulation layer with lapped window frame. |
Building construction
| Storeys | 1 |
|---|---|
| Volume | 150m³ |
| Thermal fabric area | - |
| Roof description | pitched roof with clay tiles (existing). Extension has timber warm roof construction. |
| Roof U-value | 0.11 W/m² K |
| Walls description | Aerated block and 200mm full filled cavity (DriTherm 32) for extension, 200mm graphite EPS EWI for existing, with thin render and brick slip finish. |
| Walls U-value | 0.14 W/m² K |
| Party walls description | Wet plastered double brick wall, clad with 100mm acoustic rockwool, resilient bars and double layer of plasterboard |
| Party walls U-value | 0.30 W/m² K |
| Floor description | 80-100 mm screed on top of 300mm EPS/XPS. 50mm PIR perimeter insulation at exernal walls, 25mm at internal walls. |
| Floor U-value | 0.11 W/m² K |
| Glazed doors description | Timber framed triple glazing: Green Building Store Performance range. |
| Glazed doors U-value | 0.75 W/m² K installed |
| Opaque doors description | |
| Opaque doors U-value | - - |
| Windows description | Timber framed triple glazing: Green Building Store Performance range. |
| Windows U-value | 0.75 W/m² K installed |
| Windows energy transmittance (G-value) | - |
| Windows light transmittance | - |
| Rooflights description | Fakro triple glazed |
| Rooflights light transmittance | - |
| Rooflights U-value | 0.85 W/m² K |