| Planned occupancy | Two residents currently live in the house and the occupancy will remain the same during and after works. Both residents go out to work, but occasionally work from home. |
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| Space heating strategy | The space heating strategy is to reduce heat losses to a level at which they can largley be satisfied by the internal and solar gains, especially in spring and autumn. Heat gains will be recovered by a heat pump from the ventilation exhaust, and redistributed via a thermal store that will also be used for water heating. Heat distribution will be via the existing radiators. |
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| Water heating strategy | Hot water will be provided by roof-mounted solar collectors supplying heat to the thermal store. The store will also receive recovered internal heat gains, via the heat pump. When the temperature of the store is not high enough a small gas-fired combination boiler will be used to raise the temperature of the water to the required level. |
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| Fuel strategy | The house has an existing gas supply. The proposed system will be largely electric, making use of a heat pump and solar photovoltaics, but a small gas-fired combination boiler will be used to bring the domestic hot water to the required temperature when necessary. |
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| Renewable energy strategy | The house will make use of roof-mounted solar thermal collectors to satisfy approximately 50% of the hot water demand. Photovoltaic (PV) panels will be used to offset the electricity demand. |
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| Passive Solar strategy | The project team has adopted a variant of the PassivHaus strategy, rather than a passive solar strategy. This makes the design substantially independent of orientation, which will be an advantage for replication of the improvements on this large estate and elsewhere. |
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| Space cooling strategy | No cooling is proposed. The assisted passive stack ventilation system will operate year-round, and will be supplemented in summer by the occupants opening the windows. Upstairs windows will be opened on warm summer nights to counter overheating. |
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| Daylighting strategy | Although the existing windows will be replaced, no change is proposed to the daylighting of the house. |
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| Ventilation strategy | The house will be equipped with an assisted passive stack ventilation system (with very low fan power). Supply air will be provided by humidity-sensitive trickle ventilators in window heads, and/or wall ventilators. Internal heat gains will be recovered from the passive stack by means of an electric heat pump, which will supply heat to a thermal store for space and water heating. |
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| Airtightness strategy | The target air permeability for the house is less than 5 m3/m2/hr @ 50 Pa; this is the best standard of air-tightness that the project team believes is realistically achievable for this old, solid-walled building. Air tightness will be achieved through careful attention to detailing and to construction on site. Particular attention will be paid to the continuity of the air barrier at corners and junctions between building elements. Where internal insulated dry-linings are installed internal electrical wiring, sockets, switches, etc, will either be relocated on internal walls or accommodated in wiring voids inside the air-tight membrane. |
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| Strategy for minimising thermal bridges | Thermal bridging will be minimised through careful attention to detailing and to construction on site. Critical details will be analysed usng Therm software to ensure an appropriate and cost effective approach. Internal insulated linings on external walls will be returned at least 600 mm along party walls. Subject to Therm analyses, consideration will be given to supporting the suspended floors internally and cutting off the ends of existing timber joists that bridge the internal insulated linings. |
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| Modelling strategy | The performance of the house has been modelled using PHPP and Extended SAP, and the performance predictions below are based on the PHPP analysis. |
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| Insulation strategy | The house will be insulated towards PassivHaus standards. External walls will be insulated internally using Spacethem aerogel-based lining boards, except for the single-storey kitchen wing at the rear, which wil be insulated externally. Loft insulation will be substantially increased. The suspended timber ground floor of the main house presents a challenge: the floor void will be filled with injected graphite-coated 'sticky bead' EPS insulation. Except on the front eleveation, windows will be replaced with new proprietary high-performance, triple-glazed low-emissivity argon-filled units. On the front elevation new double-glazed high-performance windows will be purpose-made to match the appearance of the existing windows. |
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| Other relevant retrofit strategies | |
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| Contextual information | |
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