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Nothing more clearly points to the failure of Australia’s residential energy efficiency policy and rating scheme than what we witnessed in the summer of 2016/17.

Modern Australian homes are no longer designed for climate and they are not ready for the challenges of climate change. Australia continues to experience record-breaking temperatures, devastating bushfires and as a consequence of both has required an expensive upgrade to our electricity infrastructure. Peak demand from air conditioners triggered failures in transmission in substations, transformers and lines leading to brownouts and blackouts. In some extreme conditions, these failures lead to bushfires and deaths.

The peak load demand from air conditioners forced an expensive upgrade to transmission infrastructure estimated at $7,000 per small two-kilowatt AC unit valued at $1,500. Now heat waves are testing the peak load capacity of our electricity generators. Maintaining base load generation is a problem especially as we move inevitably to renewable energy through pure economics and to international obligations. Peak loads are the greater problem, and hugely expensive in terms of generation, transmission and management.

Reliance on air conditioners is creating this massive problem and unfortunately they are a necessary part of a sealed and insulated lightweight approach to energy efficiency. However, they are totally unnecessary even in the most demanding Australian climates if appropriate climate responsive designs were used. The problem is that it is difficult to impossible to obtain 5 Stars for a naturally conditioned building. There is nothing wrong with the designs. In actual performance they work well. According to thermal modelling academics and professionals (not NatHERS technicians) naturally conditioned buildings cannot be modelled or adequately assessed using NatHERS.

The situation has created the simplistic and erroneous view that energy efficiency is all about the effectiveness of the external envelope in blocking out the effects of the external environment so that the internal environment can be more efficiently conditioned. Designers, builders, certifiers and consumers have been led to believe that high R-values for external walls are crucial, that buildings need to be sealed tightly and that windows and doors should be double glazed or glazed with smart glass and draft proofed and that this equates to an energy efficient building.

The sealed and insulated model is the bandaid approach to energy efficiency in lightweight construction and it has a load of health, safety and durability implications associated with it. Unfortunately, this leads to a dependence on air conditioners and that requires huge energy loads and high carbon-intensive energy use and leads to those extreme peak loads.

Anyone who has lived with limited resources; affordably, sustainably or wisely knows that the best approach to any form of energy efficiency is to reduce demand both overall and peak as the first principle. Should we continue to think resources are infinite?

It is possible to design and build using appropriate climate responsive principles so that the building minimises the need for either heating or cooling whilst enjoying fresh air. Ventilation ruins the performance in sealed and insulated buildings, though it is crucial to thermal performance of mass-linked ventilated buildings. Before we mandate blower door testing and air exchangers, we should consider mandating Fabric Energy Storage (FES) or thermal mass.

For as long as this planet spins and we revolve around the sun there will be night and day and the average of the two offers a free advanced starting position for thermal comfort using thermal mass storage and thermal lag. An appropriate climate responsive design improves on this simply achieved position to a point where the building is naturally conditioned through simple control of mass-linked ventilation. There is no need for air conditioning.

Thermal mass conditions small daytime air changes and nighttime air in turn conditions mass through large air changes or nighttime purging. Sealing and the R-value of external mass walls are not so important except in very cold climates where walls aren’t exposed to adequate solar gain. In cold climates, a small improvement to the insulation value of mass walls solves the problem.

The CSIRO Report Evaluation 5 Star Energy Efficiency Standard Residential Building wasn’t conclusive about the success of the scheme or what had made a difference between 5 Star homes and lower rated homes. Winter heating energy was reduced in Melbourne, Adelaide and Brisbane climates, but energy required for summer cooling increased in all cities (the current problem). Climate change predictions point to a disastrous outcome if we consider that Melbourne will become a cooling climate and not a heating climate within a few decades. It is a shame that modern NatHERS 5 Star conditioned homes weren’t compared with lowly rated naturally conditioned buildings in the report. The report didn’t include WA, where there is a dominance of buildings with thermal mass envelopes and partition walls.

Anyone who was engaged in design or construction 30 years ago would recall a voluntary government researched and industry endorsed approach to energy efficiency based upon G.M.I. (Glass, Mass, Insulation) used in conjunction with PSD (Passive Solar Design). As a young builder keen on things self-sufficient before the words appropriate, sustainable and renewable were in common use I embraced these concepts of GMI and PSD and I stand by them today.

I built a mud brick home with PSD principles. Cavity brick, rammed earth or concrete would have achieved similar results. It is naturally conditioned using the principles more recently described as mass-linked natural ventilation. It is a 28-year-old design though it uses zero energy in cooling to maintain temperatures of 19 to 24 through summer. In 26 years, it has reached an absolute indoor peak of 28 briefly after three-day heatwave conditions.

Each time we experience a heat wave health warnings are broadcasted whilst at home I am experiencing cool comfort through passive design – no air conditioner. During a recent heat wave, the NSW Minister for Energy praised the managers of an aluminium smelter for suspending production and sensibly urged NSW residents to turn their air conditioners to 26 degrees to minimise consumption and avoid failure in our state’s electrical infrastructure. What conditions are people experiencing in their homes if they need to adjust to 26 degrees when this temperature is rarely reached and just below the maximum recorded internal temperature of a mud brick home built with PSD principles?

Does anyone else see the irony in using high carbon intensive energy to cool homes in an ever-warming climate where the use of high carbon intensive energy is at the heart of human induced climate change?

Mandating blower door testing will achieve very little. It would be more beneficial to mandate inclusion of thermal mass. It is definitely time NatHERS protocol mandated minimum air changes in modelling within Regulation Mode to more accurately predict performance whilst ensuring health and safety have equal status with energy efficiency. It is time we had a tool able to model and assess naturally conditioned buildings. At least a select group of skilled assessors should be licensed to model homes and assess these buildings in Free Running Mode so that architects and designers are once again empowered and encouraged to design appropriate climate responsive buildings that don’t require heating and/or cooling.

When a hiker is “bushed” he retraces his steps to find the right path. I think we are clearly at this point.

 
  • Great read Peter, I'm planning on building an earth sheltered home myself that would use thermal mass in its design and construction.

    • Thanks James and good luck with your project. There seems to be a misconception that I am talking about earth covered or earth sheltered buildings. I am writing about my experience with earth walled buildings specifically mudbrick, rammed earth, cob and light earth.

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