Heating and cooling

Evaporative cooling

What is evaporative cooling?

Evaporative cooling units pass warm air through a wet filter, which cools the air as the water evaporates. This cool air is then distributed throughout the building.

Evaporative cooling is very efficient, the only energy required is to power the fan that moves the air over the evaporator and a pump that moves the water. Evaporative systems, however, can use substantial amounts of water – 10 to 30 litres per hour depending on the size and air humidity.

Evaporative cooling systems are available as ducted or single room systems. A ducted system is installed outside, either on the roof or at ground level, in an area with good air flow.

Cross section of evaporative cooling systemCross section of evaporative cooling system

Evaporative cooling in coastal locations

Coastal locations (i.e. eastern Sydney) are not generally suitable for evaporative cooling systems as the humidity can be too high and the system will not operate effectively.

Evaporative coolers will reduce air temperature by approximately 80% of the difference between the dry and wet bulb temperature.

If it is hot and humid, the gap between the dry and wet bulb temperatures is small and the cooler will not be able to lower the temperature of the air by much.

For these reasons, BASIX accepts and awards points for evaporative cooling in appropriate areas (generally non-coastal) e.g., Western Sydney.

If evaporative cooling is selected in BASIX in a postcode where evaporative cooling is not suitable a validation message will be triggered, requiring a change in cooling system selection before the BASIX certificate can be generated.

 

Ground source heat pump

A ground source heat pump makes use of the earth's constant temperature to provide heating and cooling. In addition to the heat pump, the system consists of loops of refrigerant or water buried underground called ground loops. The ground loop extracts the heat from the ground for heating or removes the heat to the ground for cooling. The heat pump transfers heat between the ground loop and the dwelling similar to a reverse cycle air-conditioner.

In addition to heating and cooling, BASIX also allows the heat pump either to provide hot water pre-heating through a desuperheater, or to function as a primary system to deliver hot water at the required temperature.

Diagram of a ground-source heat pump system for heating and coolingDiagram of a ground-source heat pump system for heating and cooling

Some ground source heat pump systems have the ground loop and refrigerant loop circulating as two separate circuits. Water sourced systems refer to systems that have water circulating in the ground loop. For systems that utilize refrigerants in both ground and refrigerant loops, the water sourced option can be selected in the BASIX tool.

Direct exchange systems consist of only a single loop of refrigerant circulated continuously from the heat pump through copper loops buried underground.

The refrigerant or water in the above systems is circulated internally. These systems are therefore called closed loop systems. Less common are open loop systems where water from a well or lake is drawn directly to the heat pump.

Ground loop installation options available in BASIXGround loop installation options available in BASIX

Only closed loop systems are available in BASIX for single detached houses. Check with the BASIX helpdesk if the ground source heat pump system consists of open loops or operates for a multi dwelling development. They will be able to help you determine if you are eligible for an alternative assessment.


BASIX assesses the energy for ground source heat pumps based on:

  • For cooling, the Energy Efficiency Ratio (EER);
  • For heating, the Coefficient of Performance (COP);
  • Whether it is used in hydronic floor heating and/or cooling;
  • Whether it is connected to a desuperheater for hot water pre-heating;
  • Whether it is connected as a primary hot water system – no other hot water systems must be installed.

The EER and COP should be rated in accordance to the relevant industry standards (such as AS/NZS 3823.1.3 or ISO 13256-2). The rated EER and COP values need to be expressed in units such as W/W or kW/kW (and not Btuh/W) for BASIX inputs.

In order for the certifier to ensure that commitments of BASIX certificate relating to ground source heat pump are met, a design engineer or installer needs to issue a verification certificate after the heat pump is installed and commissioned on site. The certificate lists the specifications of the ground source heat pump installed in the dwelling.

The certificate must bear the logo and contact details of the issuing company. It must also be attached with the BASIX certificate corresponding to the same address in the application for an occupation certificate.

Find out more about what a sample verification certificate should look like.

Zoning

What is the importance of zoning?

The larger an area to be cooled or heated, the larger the surface area between the conditioned space and the environment so, the more heat will flow and the more energy will be used to maintain comfort.

Some ducted air conditioning systems have the capacity to be zoned to function between "day-night". This means, the air conditioning will only be able to be used in the living areas during the day and in the bedrooms at night.

By incorporating a zoning feature the required size of the air conditioner is reduced and its use is reduced, since it either cools/heats one area or the other, and not both at once.

 Zoning a building may also reduce the air leakage rate, saving more energy, as walls form barriers to internal air flow.

Electric in-slab heating

Note: electric slab heating is a greenhouse-intensive technology.

 

In-slab heating systems are hot water pipes or electric wires or mats laid in a concrete slab or a concrete topping to a slab to provide heating to living spaces. They do not include on-floor heating systems laid over a slab under tiles or carpet.

Insulation is required at the edge of all slabs with in-slab heating system and underneath any suspended slabs (in all climate zones) to ensure heat is delivered only upwards to the living space and does not leak out of the edge or underside of the slab into the subfloor and/or ground.

The above insulation requirements only apply to concrete slab on ground construction or suspended concrete slabs above a subfloor. A suspended slab above habitable rooms or another dwelling is not one of these floor types and is not regulated by BASIX. 

Cross section of pipes laid in a concrete slabCross section of pipes laid in a concrete slabCross section of pipes laid on concrete slabCross section of pipes laid on concrete slab

Ceiling fans

Ceiling fans are recognised by BASIX and are considered one of the most energy efficient forms of cooling. They are included as an individual cooling system option in the living room and bedroom cooling system menus.

If the ceiling fans are combined with an air conditioning system (ceiling fans + air conditioning) then the energy efficiency rating (star rating or EER) of the air conditioning system must also be specified.

Ceiling fanCeiling fans are considered one of the most energy efficient forms of cooling 

Wood combustion heating

Wood burning contributes significantly to air pollution. Check with your council on local air quality controls and whether wood heating is permissible in your area.

Domestic solid fuel heaters such as wood heaters need to be installed in accordance with the Local Government Act, the Environmental Planning and Assessment Act, the Building Code of Australia and Australian Standard AS/NZS 2918.

Air-conditioning

 BASIX assesses the energy for air-conditioning based on:

  • whether it is a single-phase system or three-phase system;
  • for cooling, the cooling star rating or the Energy Efficiency Ratio (EER);
  • for heating, the heating star rating or the Coefficient of Performance (COP);
  • for systems that serve both the living areas and bedrooms, whether the system is day-night zoned between the areas.

If a reverse-cycle air-conditioner is to be installed for heating and cooling, the system needs to be described in both the heating and cooling sections of BASIX. The air conditioner may have a different energy efficiency rating for heating and cooling.

Air conditioning ducting needs to be installed in accordance with the relevant insulation and sealing requirements of the Building Code of Australia.

Zoning

Some ducted air conditioning systems have the capacity to be zoned to function between "day-night". This means, the air conditioning will only be able to be used in the living areas during the day and in the bedrooms at night.

By incorporating a zoning feature the required size of the air conditioner is reduced and its use is reduced, since it either cools/heats one area or the other, and not both at once.

The larger the area to be cooled or heated, the larger the surface area between the conditioned space and the environment. This means that more energy will be needed to maintain comfort.

Zoning a building may also reduce the air leakage rate, saving more energy, as walls form barriers to internal air flow.

New energy ratings for air conditioners

A new star rating that varies for hot, average and cold climate zones, will be mandatory for all 1 phase, non-ducted air conditioners from 1st April 2020. (This has been voluntary since April 2019). For more information on the new climate-zoned star ratings and how to read the new energy-rating label, visit the Energy Rating website. 

Air conditioners registered before 1st April 2020 may carry the old star rating label and can be sold for the remainder of their 5‑year registration period.

If you have an existing BASIX Certificate that specifies an air conditioner rated under the old scheme, but you would like to change it to specify one rated with the new climate-zoned rating, you will need to revise your BASIX certificate.

Air conditioners rated under the old rating scheme will have different star rating than air conditioners rated under the new scheme. For example, an air conditioner rated 4 stars under the old scheme may only be rated 2.5 stars under the new climate zoned scheme.

If you want to select a product with a high star-rating, check it is available before making an energy efficiency rating selection for your air conditioner.

For air conditioners without a star rating, select the Energy Efficiency Ratio.

Gas bayonet heating

BASIX does not reward the installation of gas bayonets, which are typically used for unflued portable heaters. Apart from the negative health impacts of unflued gas heaters, there is no guarantee that the portable heater will be installed and used.

For more information, see the NSW Health Gas Heaters Fact Sheet.

Gas-fired hydronic system

Gas-fired hydronic system is a system where water is heated using a gas heater and then pumped though pipes under the floor, to convection radiator panels, or both. If gas is not available to your site then you can:

  • Contact a gas retailer to register your interest to connect
  • Choose a non-gas option
  • Contact a bottled-gas supplier for information about using bottled gas

Gas heating

Gas fixed flued heating

Means gas heating that is both fixed and flued.

Gas ducted heating

BASIX does not currently distinguish between gas fixed flued heating and ducted gas heating. If you wish to install ducted gas heating, select gas fixed flued heating.

Gas hydronic heating

Means a system where water is heated using a gas heater and then pumped though pipes under the floor, to convection radiator panels, or both.

If gas is not available to your site then you can:

  • contact a gas retailer to register your interest to connect;
  • choose a non-gas option; or
  • contact a bottled-gas supplier for information about using bottled gas.

BASIX does not reward the installation of gas bayonets, which are typically used for unflued portable heaters. Apart from the negative health impacts of unflued gas heaters, there is no guarantee that the portable heater will be installed and used.

For more information, see the NSW Health Gas Heaters Fact Sheet.