Draft PPS18: Renewable Energy
Annex 2 Passive Solar Design: Tool Kit
8. The items in the PSD ‘tool kit’ include:
- Orientation – The capture of solar gain can be maximised by orientating the main glazed elevation of a building within 30 degrees of due south. In urban situations this generally results in an east-west street pattern. Orientation is important for housing and schools, which can make effective use of solar heating and daylight. Using dense materials in construction will enable the building to absorb heat during the day and release it slowly at night.
- Room layout – Placing rooms used for living and working in the south facing part of the building, and locating storage, kitchens, bathrooms, toilets, stairways and the main entrance on the north side will make most effective use of solar heat and light.
- Avoidance of overshadowing – Careful spacing of buildings should seek to minimise overshadowing of southern elevations, particularly during the winter when the sun is low. On sloping and wooded sites careful consideration must be given to siting to maximise solar access. It is possible to achieve high levels of natural light penetration with tight urban form but a balance has to be struck between height and shape of enclosing buildings and the width of intervening streets and spaces.
- Window sizing and position – In housing, smaller windows should generally be used in north facing elevations. On the south elevation whilst larger windows increase solar gain this has to be weighed against greater heat losses in the winter and a risk of overheating in the summer. Sloping roof lights facing the sun will increase the solar radiation received. There are more benefits to be gained from reducing the size and number of north facing windows than by increasing south facing ones.
- Conservatories and Atria – Carefully designed conservatories and atria can contribute to the management of solar heat and ventilation. To avoid problems of excessive heat gains and losses they should be designed and used as intermediate spaces located between the building and the external environment. Conservatories and atria can be designed to assist natural stack effect ventilation in the summer by drawing warm air upward to roof vents. They can also be used as heat collectors during the spring and autumn. The net thermal benefits of conservatories will however be lost if they are artificially heated for use during the winter.
- Natural ventilation – This is particularly relevant to offices and public buildings such as schools. Atria and internal ventilation stacks projecting above the general roof level can be used to vent air as the building warms during the day, with cool air being drawn in through grilles in the building façade. This approach obviates the need for air conditioning (which can be up to four times more energy intensive than providing heating), and on occasions should make for a more healthy and pleasant building environment where measures may be necessary to counteract draughts and air pollution.
- Lighting – In offices the avoidance of deep-plan internal layouts and the use of atria, roof lights and light reflecting surfaces can help reduce the need for artificial lighting and should be used in conjunction with sensor controls.
- Thermal Buffering – In order to reduce heat losses, unheated spaces such as conservatories, green houses and garages which are attached to the outside of heated rooms can act as thermal buffers, the temperature of the unheated space being warmer than that outside.
- Solar shading – To reduce summertime overheating shading devices can be built into the building, for example overhanging eaves or projections above glazing. Alternatively solar shading can be provided by devices such as projecting blinds or brise soleil.
- Landscaping – Landscaping, including the use of earth bunds, is often used as part of an overall PSD approach providing a buffer against prevailing cold winds and shading for summer cooling.