One of the biggest challenges for the built environment is reducing greenhouse gas emissions. Earth building has been around for centuries, houses nearly half of the world’s population and is arguably the pinnacle of sustainable best practice. But not according to NaTHERS.
“The best approach to heating and cooling is about maximizing gains through harnessing natural conditions like solar gain, breezes and the cool of night in naturally conditioned ventilated buildings,” said Peter Hickson, president of the Earth Building Association of Australia (EBAA).
“This recommended design paradigm differs significantly from the sealed and insulated box model supported by the Energy Efficiency Provisions in the National Construction Code (NCC), which concentrates on minimizing losses from conditioned spaces through the building envelope.”
Hickson argued that this best practice approach is more suited to Australian climates and climate change predictions, unlike the singular focus on a well-insulated and sealed envelope. In addition, energy efficiency isn’t implemented at the expense of indoor air quality and occupant health and safety when using this method.
Other Earth Building Advantages
- The techniques have been developed for different climates
- Wall densities can be varied to maximise performance in any climate
- Earth is approved in BAL Flame Zone
- Earth is non-toxic, non-allergenic, doesn’t rot, and isn’t attacked by vermin and termites
- It can be load-bearing and is durable
- It has the best embodied energy figures and, being dense, it has excellent sound isolation
- Earth balances and stores temperature and humidity
- Earth is abundant and available everywhere locally
- Earth protects and preserves timber
- Earth walls block electromagnetic radiation
But earth building is continually being challenged by new legislation and requirements to comply with statutory regulations. The most challenging recent legislation involves finding ways of complying with tightening energy efficiency in the area of space heating and cooling.
“Earth builders believe existing earth buildings already comply,” Hickson said. “But passing House Energy Rating assessment tools has been a challenge in colder climates for earth buildings. Difficulty in gaining approval has led to a serious contraction of our industry in Victoria and the problem may well spread to cold regions in other states as they adopt the Nationwide House Energy Rating Scheme, NatHERS.”
Hickson argued that a singular focus on building envelope is not the answer to building energy efficiency.
“NatHERS is focussed on improving the performance of the external envelope of brick veneer project homes fitted with air conditioners, buildings mostly built without regard for simple climate responsive design principles and without ‘effective’ mass,” he said. “Why the focus on the envelope? Because poorly designed, effective lightweight project homes are the reality and the problem.”
Hickson pointed out that the great majority of postwar housing in Australia uses lightweight construction and doesn’t follow even basic climate design principles. Two-thirds of new homes are fitted with at least one refrigerated air-conditioner. Western Australia (WA) is the exception to this preference for lightweight building.
In WA, the building stock is predominantly full brick masonry and rammed earth, though this is changing through the introduction of energy efficiency measures. So recently, lightweight construction is gaining a foothold in WA.
Once a proposed building plan is presented to the NatHERS assessment process, all that can be done to these buildings to make them more energy efficient is to seal them tightly, insulate them well and control ill-placed windows with shading and/or double glazing.
“It is remedial action, not best practice,” said Hickson. “It is like spending the entire health budget on giving sick patients triple bypasses rather than spending something on preventative measures like promoting a healthy diet and exercise.”
In her book House Rating Schemes: From Energy to Comfort Base (Green Energy and Technology), Maria Kordjamshidi states that House Energy Rating Schemes (HERs) from around the world are unable to adequately model anything but sealed insulated conditioned buildings. In line with this, Hickson says NatHERS does not have even basic ventilation logic.
“It doesn’t model these buildings as they are operated in reality or as they need to be operated for the health and safety of occupants with minimum air changes,” he said. “It doesn’t allow for modelling using appropriate ventilation logic to maximise efficiency.”
The problem, he added, is made worse because, due to its design limitations and protocol, NatHERS is discouraging and disallowing naturally conditioned buildings with more effective energy efficiency outcomes.
“It is actively promoting poor building outcomes,” he argued. “This may be unintentional but it is a real consequence. If it cannot model earth buildings that are in effect mass-linked ventilated buildings then to use it to model these buildings gives erroneous results.”
This, Hickson said, sends the wrong message to designers, architects, building assessors and certifiers, builders and clients. He is at a loss as to why bureaucrats and politicians worldwide have legislated the industry down this path and counter to the intentions of professional thermal modelling experts.
So what is the reason? According to the NatHERS administrator, major project builders constructing those ubiquitous lightweight buildings support NatHERS because they can use the same design in any climate, on any site, in any orientation and still easily comply with NatHERS.
“To me, this is an indication of failure of the scheme to improve design and that it simply about mitigating problems with poor designs,” said Hickson.
“The CSIRO Chenath engine is sound and there is no doubt that thermal modelling can be useful in optimising design. We need NatHERS to be capable of modelling naturally conditioned buildings, all buildings with minimum air changes and building designs not just building envelopes.
“Buildings proposed for tropical Darwin with a latitude just 12.5 degrees south of the equator should look totally different to buildings proposed for a much colder Hobart, 42 degrees south of the equator. The age-old approach of designing buildings to suit climates is the one I support.”