Given that the most energy efficient building is one that uses no energy at all, then the star studded Naturally Cool session at the National Energy Efficiency Conference 19-20 November, in Sydney, looks like it just might create new aspirational thinking in “cool” for buildings – in both senses of the word.
In a stroke of synchronicity, the Energy Efficiency Council has managed to gather two of the world’s leading experts on natural cooling in one place for its annual conference on 19-20 November.
Professor Per Heiselberg from Denmark and Dr Peter Holzer from Austria both have deep and proven commitments to natural cooling – Heiselberg through what is sometimes called the “stack effect” using night time air to purge heat, and Holzer through low technology/low energy approaches.
They’ll be joined in the Naturally Cool session – a highlight of the conference – in a panel that will also include Mike Rainbow of Ark Resources, who has worked on building design inspired by the physics of termite mounds to create stable temperatures, and Kylie Mills of BluKube Architecture and the Passive House Association, who will focus on how good results in comfort don’t need showy and expensive mechanical systems.
So what’s natural cooling?
If you’re thinking it’s an airconditioning fad combined with a bit of improved thermal performance, hold that thought. Natural cooling has come a long way since. And it needed to.
Fads will no longer cut it.
Climate change, growing interest in natural systems and biophilic design, plus the demands of the more stringent revised Building Code of Australia, are already driving new thinking in design of buildings.
Some of the responses hark back to a time before sophisticated mechanical systems and complex technology. There’s a re-emergence of interest in building fabric and passive ventilation to create indoor comfort.
Per Heiselberg, of Aalborg University in Denmark, for instance, is an expert on natural cooling.
Sometimes called passive ventilation, or the stack effect, the strategy Heiselberg is working on involves using cooler night time air through openings at the ground level, and using prevailing breezes to drive the day’s heated inside air up and into the sky through openings in the roof.
Many of these principles are ancient and traditional in hot and dry parts of the world.
There, buildings often have thick walls and small windows, with shutters on the windows closed in the daytime. Some also use wind towers, solar chimneys, underground pipes and evaporative cooling.
“We are transferring these approaches from warmer areas of the earth to colder areas,” Heiselberg says.
These principles can be used in retrofitting buildings.
“In lots of cases we just use the windows and doors that are already present, but with the addition of automatic control strategies and activators – which is more clever than having to open and close windows manually,” he told The Fifth Estate in an interview ahead of the conference.
Sometimes this might not be straightforward.
It might be necessary to create new roof openings and use solar chimneys with automatically opening louvres in the downstairs windows.
In a hot humid environment, however, a different approach is needed because the temperature and humidity do not change at night time.
In hot and humid conditions that have high cooling energy needs, airconditioning supplemented by other technologies might be needed.
“Australia has different climatic zones,” he said. “It would be applied differently in the south from the north, where it is hot and humid.”
The unplugged house
Peter Holzer is likewise interested in low technology interventions.
“My current fascination has to do with houses for ‘good enough’ comfort using as little technology as possible. My consultancy is always looking for what we can leave out. My ideal is the unplugged house!
“If we pulled the plug, would the quality of living inside still be good? Such a house would have to be able to be run by only the inhabitants if we took out the electricity and the professional mechanical stuff.
“So I want energy efficiency and I’m in love with low technology, to create a good internal environment.”
Holzer is also a fan of the concept of “adaptive comfort”.
“I think it is a big mistake to adopt crazy aims and try to reach them because it can lead us to over specify or oversize (heating and cooling) systems.”
Mike Rainbow of Ark Resources might well agree. The Melbourne based engineer worked on probably the world’s most famous passive commercial building, the Eastgate development in Harare, Zimbabwe, with architect Mick Pearce, inspired by the physics of termite mounds for its passive cooling system.
Managing expectations is important and probably central to the outcomes for comfort, Rainbow says.
If people are well informed about the nature of the building, they will be more forgiving if the indoor temperatures are warmer than they might expect in a high tech building when it’s hot outside.
The design of the building will signal the intent, Rainbow says. So a lot of chrome and glass will signal high tech systems, which create expectations of near perfect conditions. While organic natural materials will signal something more in tune with nature and external conditions.
“So when it’s a bit warm there is a forgiveness factor…in a high tech building people are very unforgiving.”
Design should be about “making the buildings legible,” he says.
“I believe in working with architects; it’s a very collaborative interactive process.
“People will see clues: this is space is very different; it’s more sustainable, using materials that are suggestive of a semi external environment rather than lots of chrome and plasterboard.”
In Australia, clients and builders are slowly but increasingly embracing passive house design, with about 72 projects currently believed to be under way.
But still there are many misconceptions about how it works, according to Kylie Mills. A common question, for instance, is “how do you air you house?”
“The normal way,” she says, “with windows and doors.” Being humans – and sometimes, a tad on the lazy side – we might need some mechanical ventilation to do the work for us, perhaps a dehumidifier to stop mould or a small airconditioning unit if the climate is hot and steamy or particularly cold.
Airconditioning installers typically want to specify big units but seeing the magic light go on when they finally “get” passive house, is very satisfying, Mills says.
Builders are usually the sticking point to building passive. But the big point here, she says, is that in general, all that’s needed is quality building.
Things like “taping up the joints on the outside of the fabric or not creasing the insulation because it doesn’t work unless you keep it fluffy.”
It’s how buildings should be built, she says.
The National Energy Efficiency Conference will take place at Sofitel Sydney Wentworth on 19-20 November 2018. See website for more details.