Energy

Designing homes to conserve energy and use it efficiently, from sources that cause least environmental harm.

Wiring installation

Wiring requirements differ depending on the construction type and building element.

On this page:

  • timber framing
  • steel framing
  • concrete and polystyrene block
  • straw bale
  • earth construction
  • roof spaces
  • skillion roofs
  • concrete floors
  • timber floors.

For all types of construction:

  • Do not damage the insulation around the wires during installation.
  • Install a conduit or sleeve in the concrete floor slab at the entry point for underground supply cables.
  • Install a sleeve for wiring that passes through polystyrene insulation.

Timber framing

  • Ensure that holes are large enough for the size/number of cables being installed if the hole is too small, the insulation may be damaged as the cable is pulled through.
  • Ensure that drilling and notching does not exceed the limits set by NZS 3604 for the framing size and location.

Steel framing

  • Holes are generally predrilled.
  • Install wiring as for timber framing
  • Install grommets in holes that cables are to be run through to protect cables from damage (some framing has grommets preinstalled).
  • Use self-drilling screws to attach flush boxes, distribution boards and meter boards.
  • Ensure that framing is earthed.

BRANZ recommends that frames be temporarily earthed during installation for additional protection.

Concrete and polystyrene block

  • Plan wiring layout before construction commences so locations of all conduit, flush boxes, and so on have been determined.
  • Install PVC conduits in the walls before the concrete or grout is placed.
  • Protect surface-mounted wiring by running in trunking.
  • Install wooden blocks in polystyrene block construction to provide a solid fixing for wall-mounted fittings such as lights, heated towel rails, heaters.

Straw bale

  • Install PVC conduits through walls to flush boxes and wall light locations.
  • Install a large conduit for mains access to the meter box.
  • Specify the installation of wooden blocks with flush boxes screwed to them into the straw bale construction to provide a solid fixing for wall-mounted fittings such as lights, heated towel rails, heaters, and so on.

Earth construction

  • Install PVC conduit through walls to flush boxes and wall light locations.
  • Install a large conduit for mains access to the meter box.
  • Cut conduit channels with a chainsaw.
  • Use flush boxes designed for use with concrete or concrete masonry.
  • Install wooden blocks for flush boxes to provide solid fixing for wall-mounted fittings such as lights, heated towel rails and heaters.

Roof spaces

  • Keep major cableways away from the manhole access any cables within 2 metres of the manhole cover and where there is more than 600 mm access space must be clipped.
  • Locate extra low voltage and communications cables at least 300 mm from power cable routes (further is better).
  • Do not install power cables over trusses, to avoid the likelihood of a roofing nail penetrating a cable.
  • Clip all wiring to timber battens where the cable is laid at right angles to the main framing.

BRANZ recommends installing lights and power outlets in the roof space to provide power for installations such as a ventilation system, a solar panel pump or for tradespeople to use when working in the roof space.

Skillion roofs

Preplanning is essential, as the installation of additional cables is difficult once the ceilings are lined.

  • Feed cables through holes in the centre of ceiling joists to minimise the likelihood of a roofing nail penetrating a cable.
  • Before installing downlights, check dimension of the roof space to ensure they fit.
  • Specify CA-rated downlights only.

Concrete floors

  • Conduits that need to be located within the concrete slab generally use 25 mm conduit for power, phone, data and TV.
  • The mains cable duct from the meter box is typically 50 mm diameter with a swept bend to allow for the main earth to be installed into it as well. (Note that, if the underground mains cable is long, it may be a multi-core aluminium conductor requiring a 100 mm duct and swept bend).
  • Locate telephone or cable connection conduits a minimum of 300 mm away from the power duct generally use 2532 mm conduit.

Timber floors

  • Run cable under the floor wherever possible, as this gives easier access.
  • Sleeve all wiring that passes through polystyrene underfloor insulation (alternatively specify TPS cable that is not affected by the polystyrene).
  • Clip wires to framing.

BRANZ recommends installing lights and power outlets under the floor if access to the space is needed for maintenance work.