| Planned occupancy | 2-3 people, out to work or school for part of the day on weekdays. |
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| Space heating strategy | Mini-district heating system from single external wood pellet boiler connected to two 300l thermal stores - one in each dwelling. Mechanical heat recovery ventilation, with post heating coil from solar thermal. Distribution system TBC at detailed design stage. |
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| Water heating strategy | 3m2 evacuated tube solar thermal for summer. Wood pellet boiler for winter. Electric immersion back up. |
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| Fuel strategy | Site is not connected to mains gas network. Wood pellets, solar thermal and mains electricity. |
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| Renewable energy strategy | The properties back onto the West Lyn river, where there is potential for hydro. However, North Devon Homes do not own a long enough stretch for this to be viable. Lynton Community Development Trust is well underway with the development of a much larger scheme which we intend to support. When operational NDH will purchase electricity from the new ESCo. The East/West alignment and shady valley floor location mean both wind and PV are unfeasible. We are using the small area of south facing hip roof for solar thermal. |
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| Passive Solar strategy | Limited oppotrunities for passive solar due to site location and orientation. New triple glazed roof lights, front and back on both dwellings, were planned but after modelling in PHPP we have decided against these. |
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| Space cooling strategy | Natural ventilation during cooling season. MVHR otherwise. Existing poured concrete walls retained within thermal envelope as thermal store to smooth temperature fluctuations. |
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| Daylighting strategy | Maximise daylight, very limited because of East/West alignment and heavy overshading from steep wooded valley sides. Kitchens achieve a minimum average daylight factor of at least 2%. Living rooms to achieve average daylight factor of at least 1.5%. Use mirrored tiles in in window surrounds in kitchen and bathroom. Deep external wall insulation system has also reduced daylight. |
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| Ventilation strategy | High efficiency MVHR system with post air-heating coil. Openable windows (summer) |
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| Airtightness strategy | External airtight barrier created by parging the external walls to below ground level and lining this continuous airtight barrier with 18mm tape sealed OSB. Over existing roof structure 1 m3/m2 .hr @q50 (design target) |
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| Strategy for minimising thermal bridges | Complete overinsulation of existing structure to create thermal bridge free design, including new roof construction. Junctions assessed using PHPP include: Ground floor junction, external corner, party wall, party roof, party floor, eaves, verge, window jamb, head and sill, door jamb, head and threshold. |
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| Modelling strategy | Whole house modelling undertaken using SAP 2005 and PHPP 2007, to include local weather data, interstitial condensation analysis. |
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| Insulation strategy | Externally fit 300mm Warmcel 500 insulation in new OSB frame (U-value of 0.13 W/m2K). Create new warm roof structure incorporating 350mm Warmcel 500 (U-value of 0.1 W/m2K). Excavate existing ground floor slab and replace to include 220mm XPS board. Perimeter insulation to 1m depth. |
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| Other relevant retrofit strategies | MVHR extract air drying rooms in both houses to obviate the need for tumble driers. To use locally sourced labour and sustainable materials wherever possible - Eg Warmcel 500, FSC OSB etc. To allow tenants input in interior design decisions, and engage them in the entire build process. To heat meter the tenants individually and evaluate this approach to billing where North Devon Homes becomes the ESCo, to assess this is light of the RHI from April 2011. To use the site as a training and demonstration site wherever possible to build new skills and partnerships, Eg invite other housing providers to site to watch installation and network with contractors, deliver training to contractors and potential new specialist suppliers etc. |
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| Contextual information | Site is within Exmoor National Park, fortunately the planning authority are forward thinking and have been very supportive and interested in this proposal. Site has limited external space, minimal south facing roof, at the bottom of a steep sided, wooded valley. Site is not connected to mains gas and lack of opportunities to generate electricity on site mean we will need to purchase mains electricity until the Lynton Community Hydro ESCo is operational. |
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