| Planned occupancy | Family with one - three children |
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| Space heating strategy | The heating strategy is essentially a variant of the PassivHaus approach. Heat losses will be reduced to a level at which they can largely be satisfied by internal gains (from people, hot water, cooking, lighting and appliances). Whole house supply and extract ventilation will recover the internal gains from the exhaust air by means of a compact electric heat pump, and use them for space heating and supplementary water heating. The Nilan VP18 compact heat pump has a CoP of approximately 3.5. |
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| Water heating strategy | The demand for hot water will be satisfied, as far as possible, by 4.5 m2 roof-integrated solar thermal panels on the South elevation. Heat from solar panels will be supplemented by the exhaust air heat pump. The compact heat pump unit has an integral hot water storage cylinder equipped for solar input. |
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| Fuel strategy | The existing house is all-electric, and this will not change, but the efficiency of the house is greatly improved by the combination of heat recovery with the heat pump. |
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| Renewable energy strategy | The house will be equipped with Viridian Solar innovative, new roof-integrated photovoltaic panels, which have been designed for roof installation by roofing contractors using the same installation principles and a matched aesthetic with the solar thermal panels. The 4.5 m2 solar thermal panels will be used to satisfy approximately half of the demand for water heating, and the PV panels will be used to offset the residual electricity demand after efficiency measures (100% low energy lighting and A++ grade domestic appliances) have been implemented. The PV installation will deliver approximately 900 kWh/yr. |
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| Passive Solar strategy | The project has adopted a PassivHaus approach rather than a passive solar strategy. |
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| Space cooling strategy | There is no cooling in the house. A Nilan VP18 compact exhaust air heat pump provides whole-house mechanical ventilation with heat recovery in winter. In summer, ventilation wil be obtained by opening the windows. |
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| Daylighting strategy | The mid-terrace house is oriented south-north. The existing windows will be replaced, but overall window sizes will be unchanged. Sunpipes will be used to introduce additional daylight into the central parts of the house. |
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| Ventilation strategy | Whole-house mechanical ventilation with heat recovery (MVHR) in winter, provided by the Nilan VP18 compact exhaust air heat pump unit. Natural ventilation in summer. The Nilan VP18 unit has SFP 0.58 W/l/s and heat recovery efficiency 80%. |
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| Airtightness strategy | The air permeability of the house will be improved from 9 m3/m2/hr @ 50 Pa to less than 5 m3/m2/hr @ 50 Pa. This will be achieved by careful attention to the detailing of the new windows and external doors, and the new insulated internal linings, floor insulation and loft insulation, combined with attention to detail during construction. |
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| Strategy for minimising thermal bridges | Significant thermal bridges at the junctions of party walls and extenal walls, and around openings, will be minimised by careful detailing in accordance with current best practice. Attention will be paid to the continuity of the insulated envelope at the floor-wall junction and wall-roof junction - this is made easier by the internal insulation of the external walls. Thermal bridges where floor and ceiling joists are built into exposed walls will be minimised by filling the wall cavities with insulation as well as lining them internally. |
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| Modelling strategy | The house has been modelled using PHPP and using Extended SAP. Neither software is idealy suited to this application, so approximations have been made in both assessments, in order to deliver performance predictions that are as accurate as possible. The comparison between the two is interesting. |
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| Insulation strategy | The aim has been to insulate the house to PassivHaus standards, as far as possible. In practice, the following U values will be achieved: ground floor 0.17 W/m2K; exposed upper floor above porch 0.16 W/m2K; external walls 0.21 W/m2K; roof 0.15 W/m2K; windows and glazed doors 1.2 W/m2K; front door 1.3 W/m2K. |
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| Other relevant retrofit strategies | |
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| Contextual information | There are many dwellings of this type in the immediate area, and 18,563 dwellings in Places for Peoples UK stock of this age. The dwelling that is the subject of this study is a three-storey mid-terraced house built in the early 1990s. It is part of a terrace of five dwellings, all owned by Places for People, and part of a development that includes several such terraces. It has uninsulated masonry cavity walls, a conventional roof with insulation between the rafters (because the second floor accommodation is within the roof), and timber-framed double-glazed windows and rooflights. Heating is by off-peak electric storage heaters supplemented by panel heaters. Hot water is provided by an electric single immersion heater. The house is naturally ventilated by opening windows and by three extract ventilation fans. The house as existing has a SAP energy rating of 62 (just above the HA average of just under 60) and the carbon dioxide emissions associated with heating, hot... |
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