Energy efficiency of the HomeSmart Home

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Keeping the heat in 

Passive solar design 

The HomeSmart Home is designed with living areas and bedrooms on the northern face of the house and the garage to the south.  Most of the home’s windows are along this northern side with no windows facing south.  This maximises use of the sun’s warmth while minimising heat loss through the relatively cool southern windows.


The HomeSmart Home’s walls and ceilings were well-insulated with R4.6 insulation (inserts and a blanket) in the ceiling and R2.6 insulation in the external walls.  The concrete floor however, was a rib raft floor with edge insulation only.  Rib raft floor have been shown to be poor thermal performers in BRANZ testing.

Preventing heat loss through windows 

Most of the home’s windows are along the northern side with no windows facing south. Northern windows were U-PVC-framed and double glazed.  Thermal curtains were used to further prevent heat loss.

Using free energy

Energy generation 

The HomeSmart Home featured a grid-linked solar power system capable of producing in excess of 2100kWh per year. The system is made up of three main components: solar modules, inverter and array frame.  The solar modules comprise eight Sharp 175W 24V panels with a total surface area of 10.4m2. The panels, mounted at an angle of 28° facing north-west-west, are fastened onto the roof using a Conergy solar array frame.  The DC power produced by the solar panels is fed into a SMA Sunny Boy 1700 inverter which converts the energy to 240V AC. The resulting energy is connected to the switchboard in the house and then either used to meet the power needs of the home, or fed to the grid.

Using less energy 

Space heating 

A small wall-inset electric heater in the lounge is the only space heating provided in this house.  The HomeSmart Home relies on solar passive heating combined with good thermal envelope insulation for retaining warmth.

Water heating

A 310 litre Rheem heat pump hot water system with a 4 star energy rating provided water heating.  This is an all-in-one system with the cylinder and heat pump together in the utility area at the back of the house, below the bathroom and not far from kitchen and laundry.  This system is eligible for Energywise heat pump water heating grants and in the North Island, can save up to 62% of the energy used by a conventional electric hot water cylinder.


The HomeSmart Home is equipped with energy efficient appliances - a 4 star washing machine, 3.5 star dishwasher, and a 4 star fridge/freezer.


Energy efficiency was also a consideration when planning the lighting.  With large north facing windows in living areas and bedrooms, the house has good natural light where it is needed.  LED light bulbs are used throughout except for the kitchen where halogens are used for task lighting.  Most importantly, there are no downlights inset into the thermal envelope - downlights are only used in the bottom storey where heat cannot be lost through the ceiling.

Standby system

The HomeSmart Home featured easy reach switches and a remote control to turn off appliances on standby.

Home Energy Rating 

These features added up to an impressive HERS (Home Energy Rating System) thermal rating of 8 stars out of a possible 10.


Energy efficient fridge freezer

Energy efficient dishwasher

Energy efficient appliances can make a considerable difference to energy use in a household