The super insulated breathing walls, floors and roof have 300 mm and 400 mm of insulation between a masonry walls and timber frame roof structure to give a consistent all over fabric U Value of less than 0.11 W/m2k. The windows will be Low E, Krypton filled, soft coat triple-glazed with insulated spacers to give a centre pane U value of 0.7 W/m2k. Cold bridging is avoided through careful detailing around all reveals. Incidental air infiltration will be kept to a minimum through air tight construction that will provide a target air change rate of 0.75 per hour under 50 Pascal air pressure test in accord with the AECB Gold Standard.
Bio-Diverse Sedum Roof
Proprietary lightweight green roof systems were introduced into the UK over 20 years ago. Within the last five years, real intensification has occurred as architects and clients have realised that green roofs will benefit our changing environment through their ability to negate the increasing effects of CO2 emissions, reduce global warming, curtail localised flash flooding and replace habitats for wildlife. A green bio-diverse roof was installed on the community centre. The key benefits of a bio diverse roof system in this situation include: Environmental Masking: The green roof offers the design potential for the centre to blend into its surrounding landscape and at the same time replaces the permeable land otherwise lost to the construction. Practical Use of Waste Materials: Many recycled materials are used which have minimal impact on the environment. The waterproofing membrane, drainage layers and growing mediums i.e porous brick, are readily used. It is also possible to re-use the secondary aggregate from the original site as the growing medium; this further lessens the impact on the environment by reducing the need for waste disposal to landfill and the associated transportation. Wherever possible, salvaged, reclaimed, recycled or recyclable materials will be used within the Green Roof System. Improved Air Quality: A natural process of plants is photosynthesis whereby they use the energy from sunlight to convert water and carbon dioxide into sugars and oxygen. The chemical equation of photosynthesis shows that six molecules of CO2 and six molecules of H2O are converted into one molecule of sugar and six molecules of O2. The more vegetation that is planted on a site the better the air quality. The vegetation will attract airborne pollutants and dust particles, removing them from the surrounding air. Storm Water Management: Green roofs retain rainwater by storing it in the plants and substrate, which then evaporates back into the atmosphere. By slowing down and reducing the levels of rainwater entering the drainage system, less strain is put on what are normally inadequate public sewage systems thus helping to mitigate flooding. A green roof will retain 40 – 90% of average rainfall, depending on the time of year. Thermal Performance: A green roof will provide greater thermal performance for the roof. Ecological Benefits Creating a Natural Habitat: Both plants and small wildlife are encouraged to remain in the area as a habitat is recreated that would otherwise be lost to the footprint of the construction. Aids Biodiversity: The provision of a living habitat specifically designed to target a species of plant or wildlife. Natural colonisation and cross-fertilisation of plants allows for a truly natural habitat to form, though a helping hand can be given by sowing a specific seed mix. The roof is generally self-sustaining and so requires minimal maintenance. Local sedums can be cultivated in the garden and incorporated in to green roof-growing medium.
Passive Solar Design
The large percentage of the high performance solar glazing, high level clearstory glazing and the entrance passive solar sunspace is orientated southwards to provide passive solar gain to the main spaces. Window openings to predominantly service zones to the north elevation in comparison are reduced to a minimum to reduce thermal loss. Tree foliage and external solar shading will prevent excessive heat gains in summer and internal insulated blinds will reduce heat loss to a minimum to windows at night time.
Site Generated Zero CO2 Renewable Energy
Zero CO2 Photovoltaics, Ground Source Heat Pump & Intelligent Thermal Hot Water Store
Carbon neutral renewable energy are provided to the community centre with integrated solar polycrystalline photovoltaic panels mounted on the south-facing roof to convert sunlight in to domestic electricity. The south-facing roof provides optimum solar orientation with a projected peak output of renewable energy. The panels are formed from matt grey frames with black /blue infill panels and would be integrated in to the sedum roof. A ground source heat pump (GSHP) extracts latent heat deep within the ground to form hot water for under floor space heating. The GSHP is linked to an intelligent stratifying vented thermal hot water store with a series of heat exchangers. The configuration of the intelligent store ensures mains cold water is instantaneously heated on demand via heat exchangers making it mains pressure hot water. The actual water in the hot water store does not come out of the taps, it only gets as far as the heat exchanger off loads its heat to the fresh water supply before returning to the main store. GSHP thermal water heats another heat exchanger, which heats stored water that then flows by convection into the store at various points depending on the temperature it has reached. The advantage of this heat exchanger system is that it can deliver heat on demand.
Wind Assisted Passive Stack Heat Exchange Ventilation
Mechanical ventilation been avoided in favor of a healthy passive wind assisted heat exchange ventilation system to the main hall. This naturally draws air through ducts from internal spaces and vents stale moist air through heat exchanger roof cowling vents without using electricity to power unnecessary fans.
Once a building is super-insulated and airtight the biggest source of heat loss is the ventilation required to maintain good air quality. To reduce heat loss it is necessary to pass supply and extract air through a heat exchanger so the out going warm stale air transfers its heat into the incoming cool fresh air. Traditionally this has been achieved using electric fans via a mechanical heat recovery system (MHRV) that is energy consuming and produces CO2 which is clearly not ideal for a carbon neutral building. Electricity is responsible for three and a half times the amount of carbon dioxide per kilowatt hour as heat is and is four times the price, so for a heat exchange ventilation system using an electric fan to be useful it must save at least three and a half times the amount of heat kWh as the electricity kWh the electric fan uses which, is physically impossible. In a carbon neutral building relying on site generated renewable electric energy it is important to reduce demand to the minimum and avoid all non-essential electric fan loads. In reality the cost of providing PV’s to run a mechanical electrical fan heat recovery system can be prohibitive and space absorbing. To avoid these issues and provide a non-electric sustainable passive ventilation system to replace an electric hungry fan system, 4 No a roof mounted cowls that use wind pressure and stack effect pressure to force fresh air in to the building and suck stale air out of the building via a non mechanical heat exchanger were installed.
Low Energy Appliances
All appliances were be carefully considered to eliminate unnecessary electrical demand and to optimize the efficiency of the required essential items, cooker, fridge, lighting etc. All selected components are category A** rated for maximum efficiency and minimal electrical draw when in use. Excess electricity produced from the proposed on site renewables systems, which cannot be directly used in the building, are dumped into the hot water cylinder & excess renewable electricity is exported to the national grid.
Water Saving Devices.
All domestic community centre water outlets have been selected to be as water efficient as feasible with aerated sink / basin taps, and flow restrictors fitted to external taps or hosepipes. The community centre makes use of Ifo Cera dual flush WC’s which are at present the most water efficient flush toilets available in the UK with a minimum flush of 2 litres. This may be compared with a 9-litre flush, which is commonly found in standard UK WC’s. Given that flushing the toilet accounts for over 40% of our average water use the low flush Ifo Cera WC’s can reduce consumption per toilet from 65,700 litres per year to 20,440 litres per year. Ideally we would include for a Rainharvesting recycling system but the bio diverse sedum roof substrate is not suitable for this purpose.
Cradle to grave embodied energy costs are difficult to determine, but energy intensive traditional concrete and fired brick masonry buildings rely on excavating finite natural resources from the earth which cannot be replaced and also use large amounts of kiln energy to make them strong and stable. The concrete blocks specified for the foundations and masonry walls are 7kN dense Masterblock Enviro blocks made with 100 % recycled aggregate. The roof timber frame are from a renewable resource and sourced carefully from a FSC approved sustainably managed supply. The equivalent number of trees used to make the timber frame structures will be planted on local sites with in the district to ensure that overall there is a net environmental resource gain. Roof insulation id from cellulose recycled newspaper.
Waxed timber floors, natural linoleum flooring, organic non-volatile solvent paints and stains to walls, avoidance of formaldehyde and equivalents combined with natural materials and a natural wind assisted cowl ventilation system will lead to a healthy internal air quality.