- Site Analysis
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- Passive Design
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Designing the building and the spaces within it to benefit from natural light, ventilation and even temperatures.
Location, orientation and layout
Layout and orientation must be considered from the beginning of the design process.
On this page:
- Orientation for passive heating and cooling
- Choosing a site
- Building location
- Overcoming obstacles
Orientation, layout and location on site will all influence the amount of sun a building receives and therefore its year-round temperatures and comfort.
Other considerations include access to views and cooling breezes. Orientation and layout will also be influenced by topography, wind speed and direction, the site’s relationship with the street, the location of shade elements such as trees and neighbouring buildings, and vehicle access and parking.
Orientation for passive heating and cooling
For maximum solar gain, a building will be located, oriented and designed to maximise window area facing north (or within 20 degrees of north) – for example, a shallow east-west floor plan. However, this will depend on the site’s shape, orientation and topography. For example, an east-west floor plan will not be possible on a narrow north-south site.
Orientation for solar gain will also depend on other factors such as proximity to neighbouring buildings and trees that shade the site.
For solar gain, as well as considering location, orientation and window size and placement, it is also important to consider the thermal performance and solar heat gain efficiency of the glazing unit itself (see glazing and glazing units for more information).
While solar gain for passive heating is important, other considerations include noise, daylighting, protection from prevailing winds, access to breezes for ventilation, shade to prevent summer overheating and glare, views, privacy, access, indoor/outdoor flow, owners’ preferences, and covenants and planning restrictions.
Where passive cooling is more of a priority than passive heating, the building should be oriented to take advantage of prevailing breezes.
Orientation, location and layout should be considered from the beginning of the design process – ideally, from the time the site is being selected. Once a building has been completed, it is impractical and expensive to reorient later.
Good orientation, together with thermal mass and the right glazing and insulation, can cut the heating requirements in a house by half or more, reducing energy costs and greenhouse gas emissions.
Effective solar orientation requires a good understanding of sun paths at the site at different times of the year.
Choosing a site
Selecting a site is the first and perhaps most important step in the passive design process. If a site is not suitable for passive design, some elements of the passive design ethos may not work in favour of efficiency and comfort.
The most important factor is the amount of sun the site receives, as a site that receives little or no sunlight cannot be used for passive solar design.
A flat site will generally have good sunlight access anywhere in New Zealand, but a south-facing slope or a site adjacent to a tall building or substantial planting on the northern side, will not receive good solar access.
An ideal site for passive solar design will:
- be flat or north-sloping
- be free of obstructions to the north (and be unlikely to be built out in future)
- be able to accommodate a building with a relatively large north-facing wall or walls for maximum solar gain (as well as north-facing outdoor areas if those are wanted).
A site with north-south alignment is likely to receive midday sun and with minimal overshadowing, but may have limited morning or evening sun. A site with east-west alignment is more likely to be overshadowed to the north.
Be wary of covenants that may prevent good orientation, shading to the north from trees or buildings, south-facing slopes or views.
Be wary too of very low-lying sites. The potential flooding hazard could undermine some passive design benefits. Apart from the costs and inconveniences of dealing with floods, homeowners are likely to see limits placed on how they can develop the site. Insurance premiums will be higher for these sites in coming years, and in extreme cases houses in low-lying areas may not be able to get insurance at all.
For maximum solar gain, a building should in general be located near the site’s southern boundary. In most cases, this is likely to reduce the risk of shading from neighbouring properties, and also provide sunny outdoor space.
However, the best location for solar access will vary from site to site depending on site shape, orientation and topography; and shading from trees and neighbouring buildings (or future buildings).
As noted above, other factors such as views, wind, topography, and the location of trees and neighbouring buildings will also influence a building’s location on the site.
In areas where cooling is more of a priority than heating, factors such as access to breezes might be more important than solar access.
Rooms and outdoor spaces should be located to maximise comfort during use. In general, this means living areas and outdoor spaces facing north, and service areas such as garages, laundries and bathrooms to the south. See Room layout for more detail on suitable uses for north, south, west and east-facing spaces.
The shape of a concrete slab also has an impact on how much heat is lost from a house and how comfortable it is to live in, as the diagram below shows. A square-ish slab has the highest R-value, while longer and very irregular-shaped slabs lose more heat.
Layout and house shape also strongly influences how well a house will cope with earthquakes. In the Canterbury earthquakes, regularly-shaped light timber-framed houses performed well, while irregular houses often suffered significant damage that was uneconomic to repair.
It is often not possible to obtain the ideal building orientation on a site (particularly in urban areas) and compromise will be necessary – for example, where the view is to the south, the site has a south-facing slope, there is a source of noise on the north side, or the view and sun face into strong prevailing winds.
Updated: 14 February 2019