Interview: Chris Barnett on shifting the game with high-performance modular homes
Cameron Jewell | 19 February 2015
Whenever the UK’s Grand Designs program is shown on Australian TV, traffic to Melbourne-based modular home company Habitech Systems’ website spikes, according to the company’s managing director Chris Barnett.
What are people searching for, though? According to Barnett, they’re looking to get educated about the high performance housing often featured on the popular UK TV program, but which, sadly, rarely features in Australia’s housing market, as uncovered in our story Explosive report lifts the lid on Australia’s building energy performance sham.
The idea that consumers don’t care about energy efficiency highlighted in that report is beginning to shift, though, Barnett says, and he thinks energy prices are quickly replacing petrol prices as the major hip pocket concern – putting the efficiency of homes front of mind.
The poor performance of Australian homes is what drew Barnett into the “more sustainable” modular design and construction business, he told The Fifth Estate. Trained as an architect, he started Habitech back in 2008, after working in sustainability consulting and doing “a lot of policy work” for a range of players.
Seeing that not much on the ground had changed over the years when it came to improving housing energy efficiency, he decided to throw his hat in the ring.
“I got sick of writing green wash,” he says.
He wasn’t initially attracted to the idea of prefab, but the sustainability benefits from resource efficiency and precision design made it a no brainer – “smarter engineering, smarter material use and less waste”.
Barnett claims his company’s homes can outperform the NatHERS energy ratings estimated by programs such as FirstRate5, contrasted with the typical scenario of “as built” performance being nowhere near the design rating.
A University of Melbourne study confirms the findings, with results showing one of the company’s off-grid homes outperforming energy rating software predictions (see graph).
Depending on climate, the houses typically get to eight star NatHERS easily, he says, and with the right orientation can head up to nine. For occupants this translates to heating and cooling loads reduced by up to 80 per cent.
Being involved in the design process is a crucial element for good sustainability outcomes, Barnett says.
“If you don’t get the design right you can still have a poor outcome with good materials.”
A new well-built but badly designed house can translate to an extra couple of grand each winter on heating bills, he says.
Solar passive design, high levels of insulation and energy-efficient ventilation systems are key to performance.
Getting insulation and air-tightness right
The wall panels Barnett uses have R-values of 4.3 while the roof panels are at R5.3. The precision of prefabrication and panels that come with insulation already packed in means that, unlike most traditional construction, there are no gaps to impact air-tightness, and no opportunities for insulation substitution or removal.
Gaps and poor insulation are a key reason Australian homes aren’t currently up to scratch, Barnett says.
The results of the National Energy Efficient Buildings Project report didn’t surprise him, and he says there is a lack of knowledge in the design and building industries regarding air-tightness and insulation that urgently needs addressing. He points to Australia’s relatively mild climate as a reason why these factors are not given as much attention compared with Europe, where there is “a whole different mindset”.
The reports of building surveyors accepting photos as proof of insulation is worrying, he says, and the importance of insulation should not be forgotten, as even a five per cent gap in insulation coverage can lead to a 40 per cent reduction in thermal performance.
Air leakage is another big one. Barnett says he has conducted a door blower test of a new eight star NatHERS rated house that was found to have an air leakage rate that would put it in the league of 2.5 stars.
The air leakage rates of his own company’s houses, he says, can approach Passivhaus standards, with one home with heat recovery technology having an air-change rate of 1.15 air changes an hour at 50 kilopascals. The Passivhaus standard is 0.6, while a typical new home might be 37.4 (see graph).
“Because our buildings are so well sealed, we actually need to bring in fresh air and exhaust stale air and moisture,” Barnett says.
Passive ventilation is designed into the house and heat exchangers and fans can be incorporated to provide fresh air without greatly affecting temperature. Here, a fan extracts the moist, polluted air from the house, and about 90 per cent of the heat (or cool) is exchanged with fresh incoming air.
“In extreme [hot] temperatures, rather than bringing in 35°C air, it will have cooled down to about 28°C,” Barnett says. Only a bit of cooling is then needed to get the house to a comfortable temperature.
While the market is not yet demanding it, Barnett hopes Habitech can offer certification of a home’s air-tightness as standard in the future.
No room for laggards in the emerging prefab market
The need to progress the prefab construction agenda is critical, Barnett says, because if we don’t develop an industry, we’ll get swamped by the rest of the world.
As independent construction practitioner and advisor David Chandler told the prefabAUS conference last year, “There will be no room for the laggards in tomorrow’s construction industry”. The benefits of prefab – reduced costs, build times and waste, and increased precision – mean it has the potential to shake up the current status quo of construction, the wasteful practices of which would not be tolerated in any other industry, Chandler said.
There’s already some countries where 30 per cent of the market is prefab, Barnett says, and in Scandinavia it can head up towards 70 per cent due the short periods of time available to build.
In Australia, however, the forecast is for 10 per cent of the general market to be prefab in the next 10 years.
Barnett’s company aims to take advantage of this growth. It built its first high-performance house just three years ago and just finished its ninth, with more in the pipeline. The company is also expanding, currently recruiting for new staff.
Aside from the magnesium oxide board used for external cladding, which comes from China where most magnesium oxide is found, Barnett says all panels are made from Australian plywood and timber, with the foam also blown in Australia.
And unlike a lot of prefab construction projects, the modular panels are put together at Bayswater in Melbourne. Aside from supporting the local economy, there’s advantages over importing products in terms of carbon miles and difficulties around accountability associated with long supply chains, Barnett says.
The Victorian government seems keen to see an industry blossom, recently throwing its support behind the company with the awarding of a $22,520 business research and development voucher to advance the development of a long-span flooring panel and test the fire resistance of the wall panel system for use on properties with high bushfire classifications.
Sustainability, or comfort, as key
In addition to the operational performance benefits and associated reduction in carbon emissions, thought has been put into sustainable material selection and designing for recycling or re-use.
The magnesium oxide board used for cladding is a high-performance, low-embodied energy gypsum or fibre-based cladding alternative that incorporates recycled wood as its major component, and, cast at air temperature, absorbs carbon dioxide during manufacture.
Australian plantation timber and plywood is used extensively – another carbon sink.
Being Australian manufactured and delivered in flat packs also reduces transport carbon miles, and the panels are designed for disassembly and reuse.
The major selling point of the homes, Barnett says, however, is the “comfort” gained from thermal performance, ventilation and material selection, a term The Fifth Estate is hearing being used more and more to sell sustainable housing.
“It’s something you really have to experience.”