Passive Design

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
  • Layout
  • 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.

If optimal orientation can be achieved, it will reduce some of the heating requirement, reduce energy costs and reduce greenhouse gas emissions.

Effective solar orientation requires a good understanding of sun paths at the site at different times of the year.

Orientation of house for the sun 
Orientation of house for the sun

With good orientation and suitable shading, summer sun is excluded but winter sun is allowed in to keep the house warm.

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.

Building location

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.

Layout

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.

Effect of concrete slab shape on R-value 
Effect of concrete slab shape on R-value

Effect of concrete slab shape on R-value.

Overcoming obstacles

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.

Designing to avoid shaded areas of the site 
Designing to avoid shaded areas of the site

Shade from trees and landforms can be avoided by building higher on a site or by using skylights or clerestory windows. Taller buildings will increase the amount of shaded area on a site.

Design factors for a south-sloping site 
Design factors for a south-sloping site

Clerestory windows can be used to provide solar gain on a south-facing site.

Design factors for a site with loud noise source on the north side 
Design factors for a site with loud noise source on the north side

Where there is noise on the north side, careful design is required to minimise the disturbance caused by the noise while still allowing sun into the house.

 

Updated: 14 March 2016