The siting and orientation of a building is essential in achieving good solar access and hence good energy efficiency. The house needs to be designed according to the site and must respond to site-specific conditions to maximise free solar energy. Moreover, it’s important how the rooms are arranged; the right zoning can significantly help save energy otherwise needed for heating and cooling.
Energy use, occupant thermal and visual comfort are influenced by decisions taken in the first steps of a project, usually by choices made even before the actual design begins. The selection of the site and early decisions regarding site layout, room orientation and building form can determine sunshine conditions in and around a building.
How To Optimise Solar Access
Solar access refers to the amount of direct and diffuse solar energy a building receives. Optimal solar access can improve the thermal comfort, decrease energy requirements, reducing greenhouse emission and therefore, benefiting our environment. It’s important to design your building location in order to achieve a good level of unobstructed winter sun. North-facing windows are no guarantee of good solar access. Obstructions in the form of other buildings or trees to the north, northeast or northwest can block free solar heating. The Australian Bureau of Meteorology (BOM) generally recommends that the sun should shine six hours during winter into the windows. Especially in cooler areas, the BOM also recommends solar access to east-facing windows.
New houses or renovations should always try to maximise the site’s potential free solar energy. Good orientation is a condition for energy efficiency. It is easier and more economical to consider this early in the design rather than upgrading a building once its been built. Correct siting and good solar access is relatively easy to achieve for lower density housing, whereas medium and higher density housing sometimes presents a challenge. Smart subdivisions are a requirement for adequate solar orientation and distances between buildings need to be greater to enable unobstructed sunshine into the windows.
Surface-Area-To-Volume Ratio / Building Shape
The surface area to volume ratio (S/V) is an important factor for the performance of a building. The greater the surface area, the greater the potential heat gain or loss through it. Consequently, a small S/V ratio implies minimum heat gain and heat loss. In order to minimise unwanted losses and gains through the fabric of a building, it’s desirable to design a compact shape, without articulation. In theory, the most compact building would be a cube. This configuration may not be acceptable for many reasons, such as restrictions to daylight access, site and neighbouring character, planning regulations or simply personal preferences. However, to minimise heat transfer through the building envelope, the building shape and accordingly the floor plan itself, should be as compact as possible. When designing your home consider thoughtfully what rooms are really needed. Instead of adding rooms you might need. Create multifunctional rooms, spaces that can be used for more than one function and that can easily adapt to a changing lifestyle.
House Siting
In order for a building to be energy efficient and environmentally friendly in any way, there are many things to consider when searching for a site or placing a house on a site.
Analysing needs and lifestyle – current and future
- What type of home is needed?
(house, apartment, villa; is a large garden required, lifestyle options and access to facilities) - Does the location suit your lifestyle and can it accommodate potential changes in the future?
(family addition, retirement, old age, health and so on) - Is the site close to public transport, work, school, family members or other social activities?
(Proximity may reduce the need of a second car. It will reduce car trips, travel time and carbon footprint, consequently protecting the environment, and saving money). - Determine the true cost of the location.
(A site/ home in the outer suburbs may be cheaper, but will this compensate the higher transport cost and the additional times spend on the road or on public transport?)
Study the site and the local climate
- Seasonal and diurnal temperature ranges
- Direction of hot, cold and wet winds and cooling breezes
- Humidity range
- Effect of local geographic features or climate conditions, like the fall of a site, vegetation or neighbouring properties that might modify air movement and solar access.
- Seasonal characteristics
- Orientation of the site, determine where north is. Will the configuration of the site allow for good solar access, and the positioning of private open space and garden areas facing north?
- Are existing or proposed buildings or trees overshadowing the site?
How to place a building
In hot climates with negligible heating needs, the building should be orientated to maximise exposure to cool breezes. The construction should aim to exclude harsh sun all year around, by minimising window sizes and/ or providing large overhangs or other effective shading devices.
All other climate zones, as well as alpine zones, need to incorporate passive solar heating and cooling. The extent of heating and cooling requirements depends on the climate. To determine if you need mostly passive heating, passive cooling, or a combination of both, you can compare summer and winter energy bills, consult a designer or an architect, or check meteorological records on the Australian Bureau of Meteorology website.
In the southern hemisphere, living areas should be ideally orientated within the range of 15°W-20°E of true or ‘solar’ north (20°W-30°E of true north is considered acceptable). Accurate location and direction will enable standard overhangs to prevent overheating in summer and allow lower winter sun to heat the building with no extra costs or effort from the occupants. On the other hand, a poor orientation will result in heat loss in winter and will lead to overheating in summer, by allowing low angled west or east sun to strike glass surfaces. North facing walls and windows should be set back significantly from large obstructions to the north, like trees, fences and other buildings. Keep in mind that they cast shadows two to three times their height in mid-winter. The distance to a single storey building to the north should be minimum 5.5 metres, to a double storey at least 10 metres.
- If possible, garages, carports and other buildings or structures shouldn’t be placed on the northern side of the site.
- Consider sharing walls with neighbours, especially on the east or west boundary as it will minimise unwanted heat loss or gain through these walls.
How to organise a floor plan
Rooms are utilised for distinct purposes at different times of the day and their placement will influence energy efficiency as well as comfort levels. Zoning means the creation of zones by grouping rooms with similar uses, and closing off unheated rooms, such as laundries or guest bedrooms, to reduce heating and cooling needs. It is important to separate heated and unheated areas with doors, such as glass or bi-fold doors to help retain the open-plan aesthetic if required.
- Daytime living areas such as family rooms, kitchen and rumpus rooms should be north facing.
- Avoid orientation and windows to the harsh west sun, especially for living rooms and bedrooms.
- Locating the garages or carports to the west, east or south can protect the building from summer sun and winter wind.
- Areas that use water (hot water in particular) should be grouped together to minimise heat loss from pipes, plumbing costs and water wastage.
- Create buffer zones to the west and south, as this is where most of the unwanted heat gain or loss will occur, such as bathrooms, laundry or storage rooms.
- Avoid self-shading; deep north facing courtyards, garages or other deep articulations should not overshadow north-facing windows.
- Air-locks to external doors are essential to reduce the loss of heated air when the external doors are opened.
- Allow for cross-ventilation. Openable windows and external doors should be located on different sides of the home, with less than 8 metres distance between them to create air flow.
Conclusion
If medium and high density housing is designed with careful attention to good solar access and other passive design solutions, it will use less energy compared to single storey or detached houses. The reasons for this are due to the shared walls and floors, but also the lower percentage of building envelope per dwelling, and each dwelling may have less area of external wall or roof surface. The less the outer shell is in contact with outdoor air, the less the potential thermal radiation, and therefore unwanted heat gain or loss is reduced. Moreover, a free standing home needs more construction material than high density housing and this starts an endless cycle of additional production, waste, labour and travel time.
The dream of a freestanding home is quickly becoming a distant thought; one dwelling on a block seems like an extravagance as land gets more and more precious closer to the city, forcing people to move further out into the suburbs. This leads to longer travel times, increases the dependency of cars, and consequently increases the greenhouse gas emissions through vehicles. As the population of our cities continues to grow rapidly, we have to think about alternative ways of living and have to restructure and improve our public transport system. We have to create new dreams for our sustainable future and find new ways to make medium and higher density living more desirable.
This cultural shift in how we choose to live may seem insignificant to the individual or single family, but imagine where we would end up if the majority of the population understood the positive effect of a sustainable housing model?
Some food for thought. When you are building according to the passive house standard, the orientation of the house is not as critical any more. Meaning even if you have poor solar access, you can get an extremely high performing home.
Please have a read through other other articles or get in touch with us if you want to learn more about Passive House and why we love this way of building so much.