Tunbridge Wells Retrofit
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as PDF Retrofit of a 1950s, 3-bed, semi-detached property in Tunbridge Wells. Focus on improvement of the building envelope to a very high level, with high-performance insulation and airtighting. Mechanical ventilation with heat recovery and a boost from independent solar collector. Heat provided by solar thermal and woodburning stove to a thermal store, ensuring minimal dependence on gas and electricity grids, and provision of sustainable wood supply chain. Sophisticated remote controls and monitoring provided to tenant. All works carried out with tenants in-situ, to minimise disruption.
Retrofit for the future ZA636L
Tunbridge Wells Retrofit : 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 | 2004 kWh/yr | 1774 kWh/yr | - |
|---|---|---|---|
| Natural gas use | 19938 kWh/yr | 1239 kWh/yr | - |
| Oil use | - | - | - |
| LPG use | - | - | - |
| Wood use | - | 2134 kWh/yr | - |
| Other Fuel | - | - | - |
| Pre-development | Forecast | Measured | |
| Primary energy requirement | 363 kWh/m².yr | 107 kWh/m².yr | - |
|---|---|---|---|
| Annual CO₂ emissions | 69 kg CO₂/m².yr | 17 kg CO₂/m².yr | - |
| Annual space heat demand | - | 32 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 | 107 kWh/m².yr | - |
| Annual CO₂ emissions offset by renewable generation | 17 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 | 18.5 W/m² demand |
Airtightness
| Date | Result | |
| Pre-development air permeability test | - | 8.04m³/m².hr @ 50 Pascals |
|---|---|---|
| Final air permeability test | - | 6.93m³/m².hr @ 50 Pascals |
Project description
| Stage | Design (pre-planning permission approval) |
|---|---|
| Start date | 31 August 2010 |
| Occupation date | 30 November 2010 |
| Location | Tunbridge Wells Kent England |
| Build type | Refurbishment |
| Building sector | Public Residential |
| Property type | Semi-Detached |
| Construction type | Masonry Cavity |
| Other construction type | 100mm filled cavity |
| Party wall construction | Uninsulated 300mm masonry cavity |
| Floor area | 77 m² |
| Floor area calculation method | Treated Floor Area (PHPP) |
| Building certification |
Project Team
| Organisation | Town & Country Housing Group |
|---|---|
| Project lead person | Town & Country Housing Group |
| Landlord or Client | Town & Country Housing Group |
| Architect | |
| Mechanical & electrical consultant | Bryant and Reina |
| Energy consultant | CEN Services Ltd |
| Structural engineer | |
| Quantity surveyor | |
| Consultant | Baily Garner |
| Contractor | Jenner Construction Ltd |
Design strategies
| Planned occupancy | Single mother with 3 children |
|---|---|
| Space heating strategy | Heating input to a thermal store by solar thermal panels and a woodburning stove, with gas boiler backup. Outputs to radiators across the house. Heat recovered from ventilation exhaust, with boost of pre-warmed air from SolarVenti on sunny days. |
| Water heating strategy | Water heating by heat exchange with the thermal store, inputs from solar thermal panels in summer and woodburning stove in winter with gas boiler backup. |
| Fuel strategy | Mains gas. Mains electricity. Supply chain to be set up for local, sustainably sourced, high quality wood supply. |
| Renewable energy strategy | None. |
| Passive Solar strategy | On sunny days the independant, solar-powered SolarVenti system will automatically boost the ventilation system with pre-warmed, dry air, acting as a powerful dehumidifier. |
| Space cooling strategy | A hybrid ventilation system is proposed. When outside temperatures are greater than 9C, passive stack ventilation will be in operation. When the temperature falls below 9C, the system will automatically switch to mechanical ventilation recovering heat from exhaust air. The house will also retain sufficient internal thermal mass to buffer peaks. |
| Daylighting strategy | Windows moved outwards if necessary, to reduce shading from increased reveals due to external wall insulation. |
| Ventilation strategy | Mechanical winter ventilation with heat recovery, to run permanently at a low level and with automatic boosts through a VentMiser system connected to hot water usage in the bathroom and the cooker in the kitchen. The SolarVenti system will provide a boost on sunny, cold days, providing pre-warmed dry air. Passive stack ventilation in summer (or whenever temperatures are greater than 9C). |
| Airtightness strategy | A membrane will be introduced under the timber floor, and sealed to the walls and at the join with the concrete floor. External render and high-performance windows and doors will stop air leakage through the walls. A rigorous works program will be implemented, with regular air pressure tests and all contractors given individual responsibility for sealing any penetrations of the building fabric. Up to 5 days will be allowed at the end of works for the sealing of joins, electrical connections and any other paths of air leakage. |
| Strategy for minimising thermal bridges | External phenolic insulation will be exchanged for waterproof extruded polystyrene at low levels, and this will be excavated into the ground to minimise the ground floor thermal bridge. Details at the soffits will ensure that the wall insulation meets the loft insulation. |
| Modelling strategy | Modelling carried out in PHPP and SAP whole house extension. |
| Insulation strategy | Thorough analysis and top-up of cavity wall insulation if necessary. External wall insulation will be added to bring wall U-values to 0.14W/m2K Phenolic boards between rafters and additional mineral wool in the loft will bring roof U-value to 0.10W/m2K Insulation between joists under the timber floor will bring U-value to 0.19W/m2K Perimeter insulation and thin aerogel overlay will bring concrete floor U-value to 0.48W/m2K High-performance windows and doors will have U-values of 0.8W/m2K |
| Other relevant retrofit strategies | All measures will be implemented with the tenants in-situ, minimising disruption and making the solution replicable. |
| Contextual information | In order to obtain planning permission, it has been necessary to overlay part of the external wall insulation with brick slips. |
Building services
| Occupancy | NULL |
|---|---|
| Space heating | NULL |
| Hot water | NULL |
| Ventilation | NULL |
| Controls | NULL |
| Cooking | NULL |
| Lighting | NULL |
| Appliances | NULL |
| Renewable energy generation system | NULL |
| Strategy for minimising thermal bridges | NULL |
Building construction
| Storeys | |
|---|---|
| Volume | - |
| Thermal fabric area | - |
| Roof description | NULL |
| Roof U-value | 0.00 W/m² K |
| Walls description | NULL |
| Walls U-value | 0.00 W/m² K |
| Party walls description | NULL |
| Party walls U-value | 0.00 W/m² K |
| Floor description | NULL |
| Floor U-value | 0.00 W/m² K |
| Glazed doors description | NULL |
| Glazed doors U-value | 0.00 W/m² K - |
| Opaque doors description | NULL |
| Opaque doors U-value | 0.00 W/m² K - |
| Windows description | NULL |
| Windows U-value | 0.00 W/m² K - |
| Windows energy transmittance (G-value) | - |
| Windows light transmittance | - |
| Rooflights description | NULL |
| Rooflights light transmittance | - |
| Rooflights U-value | 0.00 W/m² K |