http://lowenergybuildings.org.uk Project name Self Heating Social Housing- the zero carbon retrofit Project summary The target for this project is to create the first UK PassivHaus retrofit using low/zero carbon technology and to reduce the CO2 generated from a Cornish Type 1 system-built property owned by RCT Homes by 100% Project Description Projected build start date 01 Mar 2010 Projected date of occupation 31 May 2010 Project stage Under construction Project location Aberdare, Rhondda Cynon Taff, Wales Energy target Retrofit for the Future Build type Refurbishment Building sector Public Residential Property type Semi-Detached Existing external wall construction Concrete frame Existing external wall additional information Existing party wall construction 230mm solid brick Low Energy Buildings Page 1
Floor area 73.7 m² 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 RCT Homes Ltd RCT Homes RCT Homes Gaunt Francis WPS BRE WSP Lee Wakemans Design strategies Planned occupancy Space heating strategy Water heating strategy Fuel strategy The planned occupancy will be a small family 3-4 people in full-part time work with children in school on weekdays The Space heating will provided by an Air to water heat pump, boosting a thermal store. This will be delivered via a wet system underfloor/radiant heating.the Solar Wall will provide warm air as a feedstock to the Heat pump raising the COP. M Fully controlled ventilation in the form of Mechanical ventilation with Heat recovery, will be used to provide a comfortable living environment. SolarWall to thermal store, Air to water heat pump (COP of 3) providing hot water delivered via underfloor heating system Dwelling is switching to mains electricity. It will be interesting to see the effects of space heating and domestic hot water heating via electricty as the primary fuel. Renewable energy generation strategy 1.52KW P.V array circa 8 m2. microgeneration in the form of Photo voltaic panels. This has been used in the appropiarte context. i.e property faces south. Low Energy Buildings Page 2
Passive solar strategy Space cooling strategy Daylighting strategy Ventilation strategy Property is on a east/west axis. living rooms is orientated to the south. Window proportions have been size for maxium daylight and passive solar gains. Shading stratergy has been considered to prevent summer overheating risk. Optimised using PHPP. As the passivhaus standard is being implemented, the high levels of insulation and excellent air tightness levels will help to moderate the heat gains into the building during summer. Controlled ventilation will be used during the night time, increasing the air flow rates at the coldest periods. This will be used in conjunction conventional with shading systems. e.g Roller blinds, overhangs etc. reduce excessive solar gains Night purging maybe required during heat waves. Existing thermal mass from the existing precast concrete frame will also help moderate summer heat fluctuations All kitchens achieve a minimum average daylight factor of at least 2% All living rooms, dining rooms and studies achieve average daylight factor of at least 1.5% In line with the legislative requirements of the Welsh housing quality standard and design quality requirements for Wales Comfort ventilation will be provided by the MVHR unit. In conjunction with the passivhaus approach (i.e Super insulation, and excellent air tightness. ) this will provide a pleasant internal environment. With regular filter exchange and maintenance to the MVHR unit, heating can be supply by air. This can also help to regulate the fresh air intake and alleviate respiratory illnesses. Low Energy Buildings Page 3
Airtightness strategy Strategy for minimising thermal bridges Modelling strategy Insulation strategy Other relevant retrofit strategies Other information (constraints or opportunities influencing project design or outcomes) Airtight membrane over roof structure sealed to outside face of Inner OSB SIPS. Internal Plasterboard walls parged to provide continuous air barrier with membrane. Suspended floor air barrier sealed direct to masonry wall. Party wall will have a parging coat to ensure air tightness and mitigate thermal bypass. Air tightness membranes and tapes: Air tightness products will be used were necessary using high performance tapes and 'intelligent' vapour checks can help buildings achieve the high levels of air tightness required for Passivhaus buildings, as well as protecting building structures from condensation, mould, rot and damp. Thermal bridging analysis undertaken for all primary junctions interfaces (in order to assist with value engineering.) Continuous insulation maintained throughout. Geometric thermal bridges minimised. Junctions assessed include: Ground floor junction, external corner, party wall, party roof, party floor, eaves, verge, window jamb, head and sill, door jamb, head and threshold. Whole house modelling was undertaken using SAP+extenstion sheet. Phase contact would use PHPP throught the entire design process. Dynamic simulation may also be used to assess the impact of the proposed solar-wall combined with the heat pump heating system. Continuous insulation in the form of SIPS the precast concrete frame over, improves energy efficiency by diminishing the negative effect of thermal bridging. The excellent moisture resistance of OSB intergrated into the SIPS coupled with sealed joints also serves as an air and moisture barrier. The property is currently void an therefore disruption to tenants will not be a problem for this project. However as some components are prefabricated off site this could help save time on-site and cause less disruption to tenants. Low Energy Buildings Page 4
Energy use Fuel use by type (kwh/yr) Fuel previous forecast measured Electri c Gas 39377 Oil LPG Wood 1885 2677 5506 Primary energy requirement & CO2 emissions Annual CO2 emissions (kg CO2/m².yr) Primary energy requirement (kwh/m².yr) previous forecast measured 125 21 44 678 91 187 Renewable energy (kwh/yr) Renewables technology forecast measured 1.52kW P.V panel 1m2 1244 - Energy consumed by generation 1244 Airtightness ( m³/m².hr @ 50 Pascals ) Date of test Pre-development airtightness - - Test result Final airtightness 01 Jan 2013 3.2 Annual space heat demand ( kwh/m².yr ) Space heat demand Pre-development forecast measured - 29 - Whole house energy calculation method SAP Extension for Whole House Other energy calculation method Predicted annual heating load - Other energy target(s) Building services Occupancy Space heating Hot water Ventilation Low Energy Buildings Page 5
Controls Cooking Lighting Appliances Renewables Strategy for minimising thermal bridges Building construction Storeys Volume Thermal fabric area Roof description Roof U-value Walls description Walls U-value Party walls description Party walls U-value 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 NULL 0.00W/m² K NULL 0.00W/m² K NULL 0.00W/m² K Low Energy Buildings Page 6
Project images Low Energy Buildings Page 7
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