This is an example of how a house can utilise the natural environment to conserve and even generate energy by intelligently enhancing nature
Architects are arguable in one of the strongest positions to create a sustainable, low carbon future. Legislation will continue to set more stringent targets to reduce carbon dependency, but the solution requires a more intelligent approach to energy management through good building design which utilises natural and environmental cycles and force, It should be an integral part of the design not applied after, which is how the regulations tend to work.
The practice is committed to environmental sustainability, low energy demand buildings and high levels of energy conservation leading to a low carbon built environment. For example by using good natural light instead of electric lighting, this however must be offset against the potential for overheating or excessive heat loss due to larger windows.
There are a range of technologies available when considering energy use, these work best when they form an integral part of the building design, however not all are appropriate for every building type, use, or location. For example solar hot water generation is of low value in, an office, for example where the only use is washing hands, however in a healthcare building such as a nursing home, which has very high demand for domestic hot water, it is ideal. Similarly, wind turbines in a sheltered urban location may not be appropriate.
Before recommending any technology Mathews Serjeant Architects would carry out an initial assessment to determine the most appropriate system for the project and which will deliver the best advantage for the investment, so, for example in some buildings, natural ventilation tempered with high levels of thermal mass to cool incoming air may be an appropriate alternative to mechanical comfort cooling using chillers which have high energy demand, are costly to install, maintain and run.
Not all sustainable technologies are necessarily low carbon, for example a biomass boiler system is normally fuelled form wood pellets which are a renewable resource but the Co2 output still contributes to greenhouse gasses as any carbon based technology.
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The materials a building is constructed from are an integral part of its design, but all materials take energy to convert from their raw state to a usable product on the finished building this is part of the materials’ “embodied energy” and varies considerably, it not only includes the energy used in processing the material but also the energy used in transport and ultimately its disposal. A timber frame building, from locally grown timber has much less embodied energy compared to, a steel frame building for example. Steel must be extracted from vast amounts of ore, (probably from a mine overseas) or a concrete frame building which requires the extraction and processing of limestone. These materials also have varying degrees of recyclability, wood may be used again, recycled into the form of pellets or wood pulp once, but 100% of steel or aluminium can be recycled indefinitely and retain its first use value. Similarly, concrete can be crushed and used for hardcore or roadbase but it cannot be re-used for its primary purpose.
Over the last few decades or so we have been experiencing more extreme weather events, even in the relatively stable and mild UK. Water conservation is becoming a significant issue. Household appliances and washroom facilities can now be to minimise water consumption and avoid water wastage. Water supply has until recently been taken for granted, however this can no longer continue so a more intelligent and careful use of water must be adopted. Various technologies can be used to conserve water as set out below but the most significant change will need to be a change in attitude to this precious resource.
Generating hot water for general use, this is most appropriate where there is a high hot water demand, i.e. a nursing home, hospice or other 24/7 occupation building. This is generally a supplementary rather than a primary system. During the height of summer it can avoid the need to run a hot water generation system. The initial instalment, running and maintenance costs are generally relatively low and these will pay back the investment through lower bills quickly. Solar Hot Water panels can also be used to supplement heating system during sunny winter days.
Generating low levels of electricity which can be used during the day to offset some of the demand and feed back into the grid when generation exceeds demand. This technology is rapidly developing and is particularly advantageous because of the high feed-in tariffs currently supplemented by the Government, if and when these tariffs are withdrawn it will be a less economically viable solution because the low levels of efficiency and high cost of PV cells. PV cells must be considered as a whole from mineral extraction processing and manufacturer each stage of which takes energy. If the electrical output over the life of the photocells does not exceed the energy required to produce the product (compared to another form of generation) they will have fail.
Collecting rainwater for various low grade uses i.e. flushing toilets, washing, watering plants, cleaning etc. An appropriate system can be installed where there is a demand for low grade water i.e. a nursery for watering plants under glass where the large roof area can be used to collect water. The system can be used internally for flushing toilets and laundry but requires filtering. As parts of the UK experience periods of water shortage and extreme downfall rainwater harvesting will be an essential factor in water micro-management.
This filters and re-uses water from basins, sinks, showers etc. to flush toilets. Essentially this is using water twice, once for baths sinks showers etc and a second time after filtering for flushing toilets. Ideal where there is high water usage and a large number of toilets. There could be possible contamination issues in healthcare buildings which must be considered.
Burning specially prepared wood pellets. This system cannot burn general timber waste products (see below) It requires specialist installers a large plant room and storage area. It also requires a reliable source of appropriate fuel, for this reason it is often used near a sustainable managed forest. These systems are not good at running for small or fluctuating demand, during for example spring. It is used as a primary system is often requires a back-up system. This is a 100% renewable fuel and is regarded as carbon neutral but it does release CO2 into the atmosphere like any other carbon based fuels. It is therefore not environmentally beneficial. This system burns very efficiently with few particulates and little ash waste. The wood pellets must be maintained at controlled humidity.
Other things you will need to know:
Burning general timber waste products i.e. pallets. This is capable of burning wood chips from any source, it does not burn as efficiently as a biomass boiler, can result in particulates being released into the air and has high ash residue. It may be appropriate in some specific locations
This avoids unnecessary air handling plant by using the natural effects such as high and low pressure zones around buildings to draw stale interior air out and fresh air in. It also uses the natural effects of the buoyancy of warmer air to rise and cooler air to sink to create interior air currents. These characteristics can be enhanced by using the thermal mass of the building and heat exchangers to recover heat from stale exhaust air
If you have ever walked into the cool interior a medieval cathedral on a very hot summer’s day you are experiencing the effects of thermal mass in a building. High mass materials such as stone, brick and concrete absorb large amounts of energy from the ambient air, and can therefore cool the inside of a building, this can be combined with natural ventilation where heat energy is extracted from ambient air as it passes over a high mass surface thereby cooling the interior spaces. Generally this type if system uses night cooling to offset the heat of the day with the lower night temperatures. This system works well with 24 hour occupation buildings where a constant temperature is required, it does not work well where internal temperatures need to be adjusted quickly for example a sports hall, only used occasionally and irregularly. High mass structures often have high embodied energy and are often hard to recycle.
These systems are designed to recover the energy which would be otherwise lost from essential ventilation, hot waste water from baths etc. The financial and environmental cost of generating heat is very high it therefore makes good sense to retrieve that energy.
These use high volumes of low grade background heat from the environment, extract the latent heat from it and produce smaller quantities of high grade heat in the building. The heat itself is free but, there is an electricity cost to extracting the heat. Common examples of these are: Ground Source, which utilise the fact that below about 1.2m the ground remains at a constant temperature of about 10O c throughout the year. Air source, which extract latent heat from the air and Water Source which use a large body of water to extract latent heat from. These are graded according to their coefficient of performance but the choice will be limited by the site and the budget. This appears to be a limitless supply of free energy but it must be borne in mind that it is required energy to extract and use it. These systems are ultimately a form of solar energy, geothermal energy is very rare in the UK and in not considered here.
A good building is designed to maximise natural daylight for heat gain in the winter and solar shading (to prevent overheating) in the summer using orientated, large glazed elements in conjunction with brise-soleil. This reduces the dependence on artificial lighting. You may notice that often many buildings will have lights on during daylight hours. This is an avoidable waste of high grade, very expensive energy (electricity) particularly when there is a plentiful supply of high quality natural daylight available. Well placed windows, sun-pipes, shallow footprint plans and well placed courtyards can bring light deep into the building interior avoiding the need for dependence on artificial lighting. Research is showing that natural light is essential for good physical and mental wellbeing. Although windows are now much more thermally efficient, they are still a source of heat loss through a building fabric and more particularly of heat gain if poorly positioned or inappropriately shaded, however they can also be used to generate heat when the sun is low in winter.
This measure is about eliminating un-planned air leakage through the building fabric through which energy is lost, it appears to contradict the principle of good natural ventilation, however the more thermally efficient and airtight the building the better the ventilation needs to be managed
Reducing energy demand and avoids heat gain in the summer. There are many different types of thermal insulation ranging in efficiency, however some require large amounts of energy to make, or involve the use of environmentally harmful by-products. Natural materials such sheep’s wool or straw bales etc can also be used. Of all the energy saving measures available this is by far the most important; it costs the least and has the greatest effect on reducing energy demand.
Generating low grade electricity which can be used during the day and feed back into the grid out of hours or when demand is low. With this form of micro generation technology it is essential to ensure it is in the right location. As with similar systems an assessment needs to be made evaluating: the probable returns, installation costs and the life of the equipment. Added to this mix, as with Photo Voltaic the input tariffs rate over time need to be taken into account.
The most appropriate solution will include several of the above technologies the decision will be informed by a combination of: the design brief, the site, the project budget, future running costs and your environmental principles all of which we will be happy to explore with you.