| Planned occupancy | Two people, both at home, one works from home. One is older and has limited mobility due to a traffic accident and sight is imparied. |
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| Space heating strategy | The primary heating source for the dwelling is an air source heat pump (ASHP) The primary heating source is supplemented by a thermal store of phase change material (PCM), sized to provide approximately one day of peak heating energy. Heating for the dwelling shall originate from a central thermal store comprising unvented stainless steel dual mantle mains pressure domestic hot water cylinder and heating buffer. Overall control shall be via a building management system (BMS) which shall include monitoring, self-learning, optimisation and weather compensation for the heating system. This shall be accessible and temperatures viewable via LCD touchscreen. |
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| Water heating strategy | Hot water shall be generated within the central cylinder of the tank-in-tank thermal store. This water is heated indirectly from the heat of the primary buffer, heated via either solar input or heat pump source, to a minimum temperature of 45 degC, and maximum temperature of 85 degC. Water supply to the cylinder shall be disinfected using an inline ultraviolet device (germicidal treatment) to isolate all micro-organisms and allow for lower storage temperatures. Hot water flow shall be blended to provide a mixed temperature to taps of 45 degC. Water supply shall also have a passive magnetic and electrolytic scale inhibitor fitted. |
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| Fuel strategy | The modelling and energy assessment under SAP 2005 assumes retention of the existing Ecomony7 electricity tariff, with no additional fuel types being introduced due to the physical and practical aspects of the chosen sample. Dynamic modelling undertaken by Loughborough University does suggest that by utilising an Ecomony 10 tariff the average seasonal efficiency of the air source heat pump COP could increase as well as offering potential to limit temperature swings by having off-peak 'top-up' periods through the day. The project would investigate the possible change of tariff with the electricity provider in addition to the provision of 'smart meters' for export of any surplus energy produced by the photovoltaic array. |
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| Renewable energy strategy | Both east and west roof aspects have PV arrays sized primarily on the available roof space to achieve maximum yield due to their non-preferably aspect. As the SAP Energy calculations developed the amount of PV proposed is based upon a carbon neutral project, with the electricity generated off-setting lighting and small power loads estimated within SAP |
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| Passive Solar strategy | The windows have been carefully selected to insure that solar gain out ways thermal losses. Window proportions have been optimised using PHPP, resulting in a larger kitchen window and reduced subdivision of windows. A sunspace at the rear (west facing) was considered but was not cost effective for the gains made, a south facing sunspace was not possible. |
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| Space cooling strategy | The use of an external insulation layer has the added benefit of reducing summer-time heat transfer throught the external wall elements when compared to an internal insulation strategy. The effects of the external insulation, combined with glazing elements designed to reduce summer-time solar gain, were assessed via the results of dynamic thermal modelling using TRNSYS. The simulations show that excessively high temperatures (25C or above) do not occur at any time in either living or sleeping zones using a standard 30 minute time-step weather file. Spot modelling using higher than normal summer peak temperatures (to simulate the impacts of clamate change moving forward) also indicate that acceptable comfort levels are maintained. On rare occasions where excessive appliance and metabolic gains (due to changes in occupancy) occur coincident with high summer temps, any tendency to overheating will be controlled by the whole-house MVHR, which will act to effectively ventilate the dwell... |
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| Daylighting strategy | The kitchen window has been enlarged to fill the width of the room and maximise possible daylight, however the window is limited by the height of the kitchen units and ceiling and does not reach our target daylight factor of 2% therefore a sun pipe is being considered in this room. The lounge dinner meets our daylight factor target of at least 1.5%, which we have supplemented with a sun pipe to the rear of the lounge dinner to increase the natural light in this area, due to its high level of usage. |
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| Ventilation strategy | The dwelling shall be served by a central heat recovery ventilation unit providing balanced supply and extract ventilation to meet Building Regulations Part F System 4 approach. The unit reclaims energy from exhaust air and uses this to pre-heat the incoming fresh air, reducing overall heat losses from the dwelling. System 4 removes the need for trickle ventilation allowing the air permeability of the dwelling to be reduced as much as possible. During summer and warm autumn and spring day's ventilation can be provided by opening the windows. Window restrictors will be provided for security and safety. |
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| Airtightness strategy | The property has had an air pressure test carried out achieving a result of 6.86m3/(h.m2) @50Pa. This will be improved by installing good quality windows with joints taped all around. The junctions of external wall to floor and ceiling will be taped to ensure an airtight junction. We will ensure all service penetrations will have taped and sealed joints. The party wall is to be foam filled to ensure air tightness and mitigate thermal bypass. |
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| Strategy for minimising thermal bridges | Our strategy to minimise the thermal bridges has been to insure that a continuous line of insulation is maintained throughout. External insulation is continued through the eaves, into the loft space. In plan the external insulation is taken up to the party wall or retuned on the flank wall to adjoining property. These strategies leave some cold bridging however if the whole block is insulated and rendered this would be avoid and aesthetics improved. The work on the whole block is subject to additional funding. Thermal bridging at the ground floor junction is minimised by digging out in front of the foundation and adding perimeter insulation. A thermal skirting of 40mm Spacetherm to a height of 300mm has been added on the interior of external walls and party walls. Within the loft / party wall junction thermal bridging is minimised by wrapping the roof insulation up the party wall to a height of 1m. |
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| Modelling strategy | Several SAP analysis were conducted together with use of the SAP extension worksheet. PH modelling was used for elements that SAP did not cover, for example Solar heat gain. Electrical and Mathematical modelling by CREST, University of Loughborough was then used to verify and validate the models. |
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| Insulation strategy | After carrying out a through costings exercise weighing up the options for either external or internal wall insulation the final strategy agreed was: Application of external insulation and render to filled cavity wall construction to achieve a U Value of 0.15W/m2K;Application of 45mm Spacetherm insulation and chipboard to existing institute uninsulated concrete floor to achieve a U Value of 0.15W/m2K;Adding additional mineral wool to existing loft insulation bringing it to 400mm thick at ceiling level to achieve a U Value of 0.09W/m2K Replacing existing windows with Sheerframe HED having a U value of 0.8W/m2K |
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| Other relevant retrofit strategies | Due to the occupants health we plan to conduct the noisy and dusty work whilst the occupants are not in the property. The rest of the refurbishment works will be conducted whilst the occupants are in the property. Of great benefit to this feasibility project was the bringing together of a truly integrated design team at an early stage. This team comprised of individuals who together possess many years experience in their domains, and whose knowldge, together with the benefit of a highly effective technical toolkit, resulted in the evolution of what we feel is a very effective integrated strategy. |
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| Contextual information | Our social Housing partner, Aragon Housing, is extremely committed to the success of this project, and fully intends to take advantage of the results of the work in a wide ranging retrofit programme moving forward. The results of the project are also of high value to other providers in possession of the significant numbers of similar dwellings, ie relatively compact housing in off-gas areas, often occupied by low-incloime or other vulnerable people. |
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