Minutes of BDAA Board Tele conference held 17/12/99

29^th August 2001

BDA SUBMISSION ON NATHERS.

At the outset, it should be stated that the current regulatory focus on energy performance alone has potential to create an incorrect perception amongst consumers that a five star NatHERS rating equates to a five star environmental rating. Energy policy should always state upfront that it is a single issue policy and refer to the broader issues of sustainability especially, water use and waste water, biodiversity impacts, waste generation and minimisation, soil loss, visual and social amenity.

A single issue focus should be discouraged.

This submission addresses three key areas in which NatHERS affects building designers.

Internal issues with NatHERS
The application of NatHERS in a regulatory context.
The interpretation and contextualisation of NatHERS ratings and outputs.

Internal issues with NatHERS.

1) NatHERS is best suited to heating (in WERS sense) climates. The inbuilt assumption that high thermal mass construction is universally beneficial in improving energy efficiency is open to challenge - particularly in cooling climates and mixed climates.

This is particularly true where there is a low diurnal range (less than 6 degrees). In these locations, mass has dubious benefit at best. When the additional embodied energy of high mass construction is taken into account, high mass construction will often cause increased energy consumption on a building lifecycle basis.

2) NatHERS does not adequately address solutions for the 40% of sites on which solar access cannot be achieved.

3) Assumptions that energy will be used for cooling when internal temperatures exceed pre-determined comfort levels can be misleading where mechanical cooling is not used. A free-running version is essential and should be developed as a matter of urgency.

4) NatHERS does not accurately assess multi storey dwellings - particularly in regard to convective air flow, stack ventilation and variable heat loss due to vertical temperature stratification.

5) The measurement of energy use/M²/annum is flawed. It does not reward efficient use of space. A 300m²home with three occupants will score higher than a 150m²home with three occupants because it has a lower ratio of external wall to floor area. Yet the larger building will consume around double the heating and cooling energy and contain double the embodied energy

6) NatHERS is unable to recognise, measure and reward best practice (current best practice exceeds 5 star rating). The proposed solution for this (bar creep) is challengable. Should a 5 star home purchased in 1999 still rate 5 stars when sold in 2010? Bar creep would preclude this. We need to think carefully about this and agree a solution. A five star home is already not a very efficient one. We need to be aiming higher. Continued use of NatHERS in its current format is encouraging mediocrity.

7) Climate banding obscures the actual energy consumption and makes direct comparison of energy use between climate zones more difficult. Whilst this can be argued to be of benefit in helping consumers identify the most efficient home in any given area, the actual energy consumption in mega joules/square metre should be the main focus of regulatory authorities in developing the most effective policy for reducing energy consumption in a given region and climate.

The current focus on banded star ratings rather than actual energy savings has resulted in the introduction of inefficient regulatory policies. eg. In benign climates like coastal south east Queensland and northern NSW, heating and cooling energy can represent as little as 6% of total household energy consumption. In these climates, strict application of HERS based regulation can divert limited budget away from more effective energy saving strategies such as solar HWS, efficient appliances and reducing embodied energy.

8) NatHERS needs to be more transparent in the way that it arrives at a rating. Such transparency would make it more useful as a design tool (in the way the FirstRate and the SEDA Scorecard currently are). The user interface is poor and needs urgent upgrading. The interface is currently at the standard of early 90s software.

9) More sophisticated options for construction systems, insulation and design are required.

The application of NatHERS in a regulatory context.

Reliance on NatHERS ratings as the single measure of energy efficiency in prescriptive applications discourages innovation and development of alternative solutions.

Lack of consistency in application of Energy Smart Homes policies by NSW councils is creating confusion and leading to unjustified criticism of the NatHERS tool.

Exclusive use of NatHERS when other programs (BERS, First Rate) are equally valid and have features not offered by NatHERS is biased in the extreme and anti competitive. (eg. BERS selectable ventilation options, choice of whether mechanical or natural ventilation cooling is used; ability to address discomfort time bands and assess against occupancy patterns).

NatHERS is not designed to address other major energy consumption factors: energy sources, appliances (esp. HWS), embodied energy, occupant behaviour and occupation patterns to name but a few. Failure to address these factors seriously undermines the credibility of energy policies relying on a NatHERS rating as the sole measure of energy efficiency. The problem is not with NatHERS. NatHERS is an envelope/fabric rating tool. The fault is with the energy policy (eg. Energy Smart Homes).

Suggested solutions:

Introduce additional performance based criteria which can be submitted as an alternative to a NatHERS rating or as a supplement. These criteria should demonstrate how equivalent greenhouse gas emission reductions can be achieved by alternative means eg. efficient appliances, reduced embodied energy etc.
Allow the use of alternative programs to encourage competition and further development of software.
It is hoped that many of the above problems will be addressed in NSW by the current review of the Energy Smart Homes policy.

3) The interpretation and contextualisation of NatHERS ratings and outputs.

More attention needs to be paid to developing appropriate energy policies for specific climatic regions.

Whilst a HERS based assessment system may well yield significant, cost effective energy savings in cool and cold climates, a very different policy is required for cost effective reduction of energy consumption in a warm humid climate. In well designed buildings in benign climates, heating and cooling energy share can be low. Hot water heating is often the largest single energy user in these climates. NatHERS does not assess energy used for heating water. This should be factored in.

Embodied energy content of building materials can (in extreme cases) also exceed the heating and cooling energy used, during the lifetime of the building. Embodied energy should be considered when interpreting a rating - particularly in a benign climate.

More consideration should be given to the cost effectiveness of energy policies. Of particular significance is the durability and expected lifecycle of a building. Currently, the entire focus of most policies is on the efficiency of the envelope and fabric. Life cycle and durability issues can be equally important - especially in benign climates.