Site Use

Considering how a building and site impact on each other, enhancing energy efficiency, comfort and convenience.

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Positioning a Home on the Site

The essential premise of sustainable building design is working with the local climate and natural cycles and rhythms. On most sites, the home should be positioned to maximise the benefit from sun (daylighting, warmth, summer shading), existing vegetation, views and cooling breezes, while minimising undesirable effects from extensive site excavation, cold winds, rain and noise. An aim of sustainable building design must be to minimise the effect of the building on the site biodiversity, improve or restore site biodiversity after construction, and minimise the effect of the proposed building on neighbours.

On small sites, there may be limited choice about building form or location. In such cases, allowing for sun to get into the building is likely to be one of the key considerations.

Sun

To take best advantage of sun, a home should be located where it won’t be shaded for a significant part of the day by obstructions such as neighbouring buildings, large trees or landforms.

: Locating a house to avoid shading
Building close to the south boundary will maximise the solar gain if there are significant obstructions on the northern side – remember that your proposed building will also be creating shaded areas on the site and may be affecting neighbours.

Before starting design, check how much sun the site gets and note current and future shading patterns from trees and other obstructions, both on the site and on adjacent sites. Also consider the shading affect of the proposed building. Remember to consider year-round sun paths. Also see orientation for more about designing to maximise the benefits of the sun, and site analysis for information about assessing a site for sun and sun-path diagrams and modelling.

Views

Views enhance the enjoyment of a home as well as adding to the property value. They may be panoramic, may incorporate framed views (i.e. a strategically placed window or opening in a wall), or may be a view shaft between hills or trees.

: Window framing the view
Careful placement and sizing of windows can maximise the visual effect of a view while maintaining thermal performance and sunlight entry.

To take advantage of views, a house may need to be built higher on the site, or it may need an additional storey or part storey to be able to glimpse a view that is otherwise largely out of sight. Note that a taller building will shade a larger area of the site.

Wind effect/microclimate

The site-specific microclimate, and the wind directions, strengths and frequency, must be considered when positioning a home – it may differ widely from conditions experienced elsewhere in the area.

Ridges or valleys may funnel or buffer winds, and wind strength is likely to be greater at or near a ridge or alongside a park or beach. On some sites, the best location to maximise sun or achieve the most spectacular views may also be the windiest location. The height of the building will also have an effect on wind speeds around the upper levels.

The most common wind may not be the strongest, wettest or coldest. For example in Wellington, 55-60% of wind is from the northwest, and 45-50% is from the south. Easterly winds are much less common.

In deciding where to position the home, consider:

provision of shelter for outdoor living areas by using fences, screens, or using the building to create an enclosed courtyard
the effect on parts of the house (e.g. living room, bedrooms) where wind noise would be undesirable – these rooms should be placed, where possible, on the lee side of the house to the strongest wind direction
the effect on opening doors and windows – windows and doors facing away from the prevailing wind can often be left open even in very windy conditions, whereas those facing into the wind may be difficult to open in windy conditions; if possible, frequently used doors should face away from the prevailing wind direction.

: Designing for ventilation while moderating the effect of high winds
The effect of doors on opposite sides of a building, room or hallway should be considered. If they are both open at the same time, depending on prevailing wind directions, this may lead to doors slamming shut or items being blown around. If external doors are located on sheltered sides of the house, this is less likely to occur.

Also see the site analysis section for information about wind strength and direction.

Topography

Unless the site is flat, the topography is likely to have a significant influence on the location and planning of the home.

To reduce the effect buildings have on the landscape they should be designed to minimise:

the need for extensive excavation or filling – large-scale earthworks can increase costs, increase the risk of erosion by altering soil stability and water run-off patterns, increase sediment runoff during construction, and significantly affect natural biodiversity by removing soils and plants
their footprint on the earth by using low-impact foundation systems such as pole frame construction, which will significantly reduce the amount of site work and the amount of disruption
the visual intrusion of the building form within the landscape – designers can use building form and colour to blend in rather than stand out.

The site’s slope and/or the slope of neighbouring sites can affect access to sun and views. For example, an east-facing hillside will have reduced afternoon and evening sunlight, particularly in winter. A south-facing site may receive little or no sun in the winter months depending on the height and steepness of the slope.

: 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.

Also see the site analysis section for information about sun and soil types.

Site hazards

Site hazards may include contaminants in the soil, and risks of flooding, slips, or erosion. Any potential hazard should be avoided if possible, or be considered and designed for as necessary. See the site analysis section for information about hazards.

Adjacent buildings

Adjacent buildings may influence the siting of a new building. When designing, locate the home to prevent:

shading by neighbouring buildings
unreasonable shading of neighbouring buildings
loss of privacy for its occupants, or for occupants of neighbouring buildings.

District plans include rules that cover building proximity to boundaries, and sun access or height recession planes which are intended to protect properties against unreasonable shading, loss of sunlight, loss of privacy and visual outlook to adjacent properties.

Where an adjacent site is vacant, position the building to take into consideration what may be built on the site in future. This means the designer must know the district plan rules regarding the adjacent site (they may be different from the rules applying to the site you’re designing for) and must aim to provide a design that will mitigate any possible adverse effects from the potential building. This may require:

selecting a building location as far from the adjoining boundary as possible
locating the building on an elevated part of the site to maintain views or sunlight
designing the building to maximise views and sunlight
allowing for future changes such as tree growth on adjacent sites.

Existing vegetation

Existing trees and plants on a site should be assessed for their value to the site. Trees can provide shade, wind shelter, soil stability, a habitat for birds, and be visually pleasing – and a tree will take many years to replace if it is removed. In particular, it is very difficult to fully regenerate indigenous species once they have been cleared and/or replaced with introduced species.

Where possible, building position and design should accommodate established trees and plants that will not easily be transplanted. Design considerations may include:

the degree of shading from the trees or shrubs – the shade provided may be desirable in the summer, but less so in the winter; if the tree is deciduous, winter shade is unlikely to be a problem
the age and condition of trees and shrubs – some may require removal for safety reasons to avoid the risk of damage to the completed building or there may be a risk of damage to foundations from tree root systems
the impact of the building on the existing trees – building too close to a tree may affects its long-term viability
the possibility of incorporating a tree or shrub into the building design, such as designing a house or a deck around it
retention of trees and other vegetation that are protected under the district plan or site-specific documents such as an open space covenant.

Plan the site development to allow space for delivery and service vehicles (e.g. concrete pumps), as well as material and waste material storage during construction to minimise the effect on the existing landform, plants and trees. Specify the protection measures, such as clearance from work activities, for critical items such as protected trees.

Not removing existing vegetation will reduce the risk of soil erosion, slips and sediment runoff from the site. Where removal of topsoil is necessary, this should be saved and reused; salvaged plants, particularly indigenous species, should be carefully removed and stored, then reinstated when building work is completed.

Also see the site analysis section for information about plants and trees, and also about protecting culture and (natural) heritage.

Noise

It may be possible to mitigate the effects of external noise by the positioning of the building, such as locating the building away from noise (if possible), or behind a bank or rise that will act as a barrier to the noise. For more, see noise in the passive design section.

It may also be possible to use excavated materials for noise screening instead of removing them from the site (at a cost for transport and disposal).

Location of services

The location of, and connection to, services is not generally a major influence on the position of a building, as services are readily laid to a site boundary. Where live council services cross a site, the building footprint will need to be kept clear of them – obtain specific minimum requirements from the council. There may also be easements that define the access required to these services. Redundant piped services within the footprint of the building area will need to be accurately located and removed.

If a water tank is required, its location will need to be considered at the preliminary design stage. It should be located on a part of the site where it will not visually intrude, be accessible for maintenance and be on sand base over solid ground (a full 5500 litre tank weighs approximately 25 tonnes). Where a tank is to be below ground it must be specifically designed to withstand the loads from the backfilled soil (note that rotationally moulded polyethylene tanks are not designed for below ground use).

Recycling greywater

Greywater is the waste water from washing. It can be reused to irrigate the garden. As with other services, greywater recycling is unlikely to have a major influence on the position of a building on the site, but should be considered at the preliminary planning stage. Access must be available for maintenance.

For your clients

To help your clients understand building orientation on site, refer them to www.smarterhomes.org.nz/design/orientation.