http://lowenergybuildings.org.uk Project name SOLAR HOUSE 80/50 Project summary Project Description Projected build start date 01 Mar 2010 Projected date of occupation 19 Jul 2010 Project stage Under construction Project location Aylesbury, Buckinghamshire, England Energy target Retrofit for the Future Build type Refurbishment Building sector Public Residential Property type Mid Terrace Existing external wall construction Masonry Cavity Existing external wall additional information Brickwork outer, 50 unfilled cavity, blockwork inner, 250 oa Existing party wall construction Solid blockwork plastered both sides Floor area 99.5 m² Page 1
Floor area calculation method PHPP Project team Organisation Project lead Client Architect Mechanical & electrical consultant(s) Energy consultant(s) Structural engineer Quantity surveyor Other consultant Contractor Places for People Places for People Places for People MEPK Rickaby Thompson Associates Inspace Design strategies Planned occupancy Space heating strategy Water heating strategy Fuel strategy Family with one - three children 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. 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. 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. Page 2
Renewable energy generation strategy Passive solar strategy Space cooling strategy Daylighting strategy Ventilation strategy Airtightness 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. The project has adopted a PassivHaus approach rather than a passive solar 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. 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. 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%. 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. Page 3
Strategy for minimising thermal bridges Modelling strategy Insulation strategy 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. 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. 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. Other relevant retrofit strategies Page 4
Other information (constraints or opportunities influencing project design or outcomes) 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... Energy use Fuel use by type (kwh/yr) Fuel previous forecast measured Electri c 11451 3035 6368 Gas Oil LPG Wood Primary energy requirement & CO2 emissions previous forecast measured Annual CO2 emissions (kg CO2/m².yr) 68 18 38 Primary energy requirement (kwh/m².yr) 288 76 160 Renewable energy (kwh/yr) Renewables technology forecast Solar PV 900 measured Energy consumed by generation Airtightness ( m³/m².hr @ 50 Pascals ) Page 5
Date of test Test result Pre-development airtightness - 15.59 Final airtightness - 6.76 Annual space heat demand ( kwh/m².yr ) Space heat demand Pre-development forecast measured - - - Whole house energy calculation method Other energy calculation method Predicted annual heating load Other energy target(s) PHPP Delivered energy (after PV contribution) 30.5 kwh/m2/yr. Primary energy (after PV contribution) 73.5 kwh/m2/yr. Carbon dioxide emissions 20.0 kgco2/m2/yr. The house is all electic. The above figures were calculated using PHPP. Building services Occupancy Space heating Hot water Ventilation Controls Cooking Lighting Appliances Renewables Strategy for minimising thermal bridges NULL NULL NULL NULL NULL NULL NULL NULL NULL NULL Building construction Storeys Volume Thermal fabric area Roof description Roof U-value Walls description Walls U-value Party walls description Party walls U-value NULL 0.00W/m² K NULL 0.00W/m² K NULL 0.00W/m² K Page 6
Floor description Floor U-value Glazed doors description Glazed doors U-value Opaque doors description Opaque doors U-value Windows description Windows U-value Windows energy transmittance (G-value) Windows light transmittance Rooflights description Rooflights light transmittance Rooflights U-value NULL 0.00W/m² K NULL 0.00W/m² K NULL 0.00W/m² K NULL 0.00W/m² K NULL 0.00W/m² K Page 7
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