Solar orientation

Natural light makes dwellings more attractive, pleasant and energy-efficient. Housing layouts should be designed to maximise daylight and sunlight while taking into account other factors, such as privacy and the attractiveness of the wider streetscape.

Solar energy generation relies on (and is closely linked to) the layout and orientation of roofscapes to maximise opportunities for solar PV generation. South-facing roofs and the use of reflective surfaces provide the maximum opportunities to benefit from solar gain. However, this arrangement may not always be achievable when combined with other contributing factors.

Understanding the importance and benefits, opportunities and constraints of solar gain is a core principle of any proposed development layout and should be considered at an early design stage.

A building’s form, orientation and window proportions are all aspects that do not add extra construction cost, but if optimised within the design can significantly improve the building’s efficiency.

Notwithstanding the usual best practice principles and surrounding context, development and building form should be as simple and compact as possible. This will reduce the exposed surface area for heat loss. Avoid or limit the use of stepped roofs, roof terraces, overhangs and inset balconies as these features will decrease the building’s energy efficiency.

The orientation and massing of the building should be optimised if possible, to allow useful solar gains and prevent significant overshadowing in winter. Encourage south facing dwellings with solar shading and prioritise dual aspect. Overshadowing of buildings should be avoided as it reduces the heat gain from the sun in winter.

Getting the right glazing-to-wall ratio on each façade is a key feature of energy efficient design. Minimise heat loss to the north (smaller windows) while providing enough solar heat gain from the south (larger windows). It is much easier to design smaller windows facing access decks and larger windows facing balconies. Therefore, try to orientate access decks to the north and balconies to the south.

Micro-climate

All new developments must consider the impact and creation of micro-climates as a result of decision making at planning stage, particularly wind impact on exposed sites or where taller buildings are proposed. This affects the usability of the public realm and the energy demands of buildings.

Overheating can be a consequence of inadequate design, ill-conceived layouts and a lack of climate change resilience. Overheating is a known risk and can be reduced through good design:

  • Ensure glazing areas are not excessive i.e. not more than 20 20-25% of facade on south or west façades.
  • Avoid fixed panes and maximise opening areas of windows. Side hung windows typically allow more ventilation than top hung.
  • Favour dual aspect homes to allow cross ventilation.
  • Provide appropriate solar shading. South façades should have horizontal shading over the window and the west façade should ideally have movable vertical shading e.g. shutters.
  • Avoid relying on internal blinds, which can be removed by residents.
  • Select a g g-value (the solar factor indicating how much heat is transmitted from the sun) for glass of around 0.5 where possible.
  • Use Good Homes Alliance overheating checklist for risk assessment.

Page updated: 18/05/2022


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