House Energy Star Rating Explained

The Nationwide House Energy Rating Scheme (NatHERS) is a star rating system (out of ten) that rates the energy efficiency of a home, based on its design.

The House Energy Rating scheme provides a ‘measuring tape’ to estimate a home’s potential heating and cooling energy use, NatHERS helps to make Australian homes more cost effective to heat and cool. This gives people building or buying a new home a guide to the efficiency of the house. Often good design can reduce the amount of energy needed to keep a home comfortable with no or little additional construction cost. The more Energy Efficient a house is the higher the rating.

Our overall understanding of house design and energy efficiency has come along way. Houses built in 1990 averaged about 1 star on the scale. And before the introduction of national energy efficiency regulations for houses in 2003, less than 1 per cent of Australian houses achieved 5 stars. These days, however, the national building standard for new homes and renovations is a base of 6 stars.

NatHERS uses computer simulation at design stage to assess the thermal performance of a home. NatHERS looks at elements such as orientation, layout, construction materials, insulation and glazing.

Watch this video for a more detailed understanding of how the rating system works.

An energy efficient Queenscliff Fisherman’s Cottage with a contemporary edge was the design brief from our client.

We certainly achieved this with a 7 Star Energy rating. The rating was achieved by installing high density insulation under the roof in the ceiling and in all external walls. The polished concrete floor throughout the main living areas attract the heat from the North facing floor to ceiling windows and act as a thermal mass. All windows and doors are double glazed, with timber windows used to minimise heat loss/transfer. The main kitchen/living and dining rooms has a high pitched roof with floor to ceiling windows facing north creating an open light and airy feel and well placed windows on the South give good cross ventilation to the spaces.

Passive Heating and Cooling Ideas

• Passive solar design, with house orientation and layout to bring sunlight into all living spaces, while windows are aligned to promote breeze paths through house for natural cooling and “night purging.”
• Eaves designed to let in winter sun and block summer sun.
• Double glazed low emissivity coated casement windows & bi-folds to maximise ventilation.
• Polished concrete floor and recycled & bagged Reverse Brick Veneer walls for thermal mass to store heat in winter and cool in summer.
• Highly insulated, tight building fabric.
• Stairwell door and internal louvre windows to regulate thermal stratification.

Hot Water

• Evacuated tube solar hot water system with 315 litre tank instantaneous gas boost (saves approx. 1.5 tonnes of CO2 a year)

Energy-Saving Technology, Design and Features

• LED and compact fluorescent lighting throughout.
• Greenswitch to turn off standby loads at night or when house is vacated.
• A void in the laundry designed as a drying area, where a hanging rack provides evaporative cooling.

Renewable Energy

• Rooftop solar PV system

Insulation

• Bradford Anticon foil-backed blanket and Tontine Thermal Batts in ceiling.
• Bradford Enviroseal reflective foil and Tontine Thermal and Sound Batts in walls.

Water Saving

• Rainwater tanks to run laundry, flush toilets, & water garden with mains backup.
• Redwater valves to direct ‘cold’ hot water, normally wasted, to the watertank
• Greywater gravity diversion system to underground garden distribution
• Water efficient tapware throughout, 7.5 litre per minute shower roses and 3/4.5 litre flush toilets