| Planned occupancy | The proposed property is a 3 bedroom 5 bedspace unit. Current occupancy is 2no.adults and 2no.children |
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| Space heating strategy | Heating from mains gas fired boiler feeding radiators. Controls simple to understand with thermostats & weather compensation. |
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| Water heating strategy | Solar hot water with gas condensing boiler back up |
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| Fuel strategy | Mains Gas. Mains electricity. |
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| Renewable energy strategy | none |
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| Passive Solar strategy | Increasing the solar gain is a prominent part of this project. Window cills on the South elevation have been dropped (the lintels can then be kept) and the amount of frame reduced. The internal layout will be remodelled so the solar gain benefits the whole house through an open-plan design. |
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| Space cooling strategy | The increased solar gain would become problematic during the summer. For this reason an external shade will be added to the southern faade, and opening windows added for night-time ventilation. These have been designed to give maximum cooling impact whilst not impinging on the safety of the home. Thermal mass of the existing structure will be used. |
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| Daylighting strategy | The window design (smaller on North, larger on South) has primarily been driven by energy conservation. However, care has been taken to keep the impact on daylight to a minimum, particularly in the kitchen and living room where the open plan layout will improve matters. |
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| Ventilation strategy | High efficiency whole-house mechanical ventilation with heat recovery during the winter, openable windows and mechanical extract during the summer. The ventilation system has been selected, and will be designed, for optimum energy efficiency. |
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| Airtightness strategy | The aim of the project was to achieve Passivhaus standard (ach @ 50Pa = 0.6). because of the poor air test result this has been slackened to 1.5ach, still a considerable feat. Particular elements which performed badly were: intermediate floors, defects in walls, blocked up chimney, loft hatch & service penetrations. Each of these has been addressed and methods of providing a permanent seal considered, such as removal of lighting wiring in the roof. |
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| Strategy for minimising thermal bridges | The existing building is a perfect example of insulation used badly, with terrible thermal and airtightness detailing throughout. For this reason specific care has gone into designing out thermal bridges. This drove the decision to use external wall insulation and a cold roof. The windows will be mounted within the insulation layer with as much of the frame covered by insulation as possible to reduce heat loss from the frame and surround. All services removed from the cold roof and ground floor, with main distribution within the first floor build-up. This allows the penetrations through the thermal envelope to be minimised. |
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| Modelling strategy | Whole house modelling was undertaken in PHPP & SAP |
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| Insulation strategy | Externally insulate walls with phenolic insulation to U =0.089W/m2K . Phenolic insulation has been chosen because of it's low thermal conductivity. We are aware that this material crumbles easily and so is difficult to use, for this reason we are allowing extra design and site training time. Blown cellulose to roof, replacing existing roll insulation. Blown insulation is used as it is much easier to fully insulate hard to reach areas such as between rafters. U = 0.083W/m2K Internally insulate floor to 50mm using laminated boards. It was intended to provide thicker insulation but due to the low floor to ceiling height typical of this property type it was not possible. U = 0.69W/m2K |
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| Other relevant retrofit strategies | Because the level of retro-fit required is intensive it is intended to remove the tenants during the majority of the work. This is to enable a high standard or workmanship, and to give the team space to solve problems that arise on site. once the design has been optimised (through the testing of phase 2) it is expected the roll-out would enable the occupants to stay for a large proportion of the work. |
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| Contextual information | Because the house is part of a semi-detached the team struggled with decisions affecting the appearance; should we confine ourselves to the asthetic of the other half? We decided to go for a half-way house with changes to the window dimensions but clad in a similar brick slip. |
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