How do you top designing and constructing Australia’s first carbon neutral building, currently the nation’s greenest? You might, Warren McLaren reports, raise the stakes by setting your sights on crafting the world’s tallest apartments built to passivhaus standards.

At least, that’s what you do if you are the team behind the 6 Star Green Star Pixel office in Melbourne. Their new building, ‘Delta’, due for completion in 2014, is expected to set a new record in passivhaus design, when it goes up over the heritage-listed Carlton United Brewery.

Just what are these passivhaus standards that Delta’s developer Grocon, architect Studio 505 and sustainable consultant Umow Lai are striving for?

Passivhaus evolved in Germany as a voluntary benchmark, producing homes up to 90 per cent more energy efficient than the traditional European model, largely by negating the need for ‘active’ space heating or cooling. Passivhauses are sited towards the sun, super insulated, and virtually airtight.

The high build quality and lack of thermal bridging (transfer of heat along highly conductive, ie, non- insulating materials) between the exterior and interior of passivhaus structures means that the inside temperature is effectively quarantined from the outside. This allows for such buildings to often be warmed simply via the addition of fresh air into the space.

Initially trialled in Darmstadt, Germany in 1991, ‘passive house’ construction initially spread throughout the cool Teutonic regions of Germany and Austria, as well as Scandinavia. Professor Wolfgang Feist, the leader of the passivhaus movement, was however inspired, in part, by some demonstration houses built in Canada and the U.S. way back in the 1970’s.

While the Passivhaus Institut in Darmstadt, established in 1996, has over 1,500 entries in its online database, there are thought to be around 30,000 passivhaus buildings worldwide. The concept has been adapted to offices, kindergartens, churches, factories and oddly enough, even a fire station and swimming pool.

Such has been its impact in Europe that there have been calls for passivhaus to become the de facto continental standard for any building that would otherwise require conventional heating systems.

But to date there has been little uptake of the idea Downunder.

Maybe because they’re that bit closer to Antarctica, New Zealand has been quicker to embrace the concept. Passive House Institute New Zealand had its official launch in August 2011. Several NZ

architectural and engineering firms already have designers certified by Europe’s Passivehaus Institut (Eight designers, at last count, none listed for Australia).

One of these, EcoBuild Developments Inc., even has a passivhaus style display home, which they believe is New Zealand’s most airtight house. Earlier this year they had the home tested with a blower door apparatus, which indicated that the house had 0.62 air changes per hour.

They reckon “most new houses leak at the rate of 5-10 AC/Hr.” Commenting on their newly completed ‘eHaus’ Baden Brown and Jon Iliffe explain that the building “will perform between 20-25°C all year round with very little active heating or cooling required. It collects and redistributes the energy in a home that would normally be lost in activities like cooking, showering, lighting, TV and other devices that produce heat energy. Conversely in the summer when it’s hot outside the homes super insulation prevents the heat coming into the house significantly reducing the need for active cooling systems.”

Australia has been slower on the uptake of passivhaus implementation. But Melbourne may be the beachhead for Antipodean interest in the standard. It’s where Grocon is creating their above mentioned 10 storey passivhaus apartments. And where Peter Steudle and James Anderson have set up Passive House Pty Ltd. It’s also the city in which Sustainable Built Environments (SBE) has been busy delivering presentations on the subject.

In one such introduction, SBE noted that if passivhaus standards were adopted in Australia, they’d approximate that of a 9.5 Star House Energy Rating.

However meeting passivhaus standards is more about achieving a high degree of thermal comfort for building inhabitants. Though, to achieve passivhaus comfort benchmarks, rigorous observation of energy usage is required.

Annual heating (and cooling) energy needs are required to be under 15 kWh/(mÇa). The building’s super insulated shell walls should attain a U factor not exceeding 0.15W/(mÇK). Similarly, windows are chasing a U-factor less than 0.80 W/(mÇK). At 50 pascals of pressure, the structure shouldn’t have more than 0.6 air exchanges per hour. (Without such an airtight building, any air entering the building — via leaks — won’t pass through the structure’s important heat exchanger. Warm interior air is also more easily lost and wasted).

The Passive House Planning Package (PHPP) is a tool which models the performance of
proposed passivhaus building designs, via Excel spreadsheet software and a 200 page user manual. It costs around $250 AUD.

Many building practitioners will be familiar with the idea of Passive Solar design: orienting a building towards the sun, allowing radiant heat of winter sunlight to create a slow-release energy store within internal thermal mass.

Aside from added emphasis on super insulation and airtightness, what sets passivhaus apart from Passive Solar is that, oddly enough, it is not entirely passive.

The criteria that the building be almost airtight dictates the need for an effective ventilation system. This is normally managed by a mechanical ventilation and heat recovery (MVHR) unit, with an efficiency of greater than 75 per cent. PassivHausUK suggests that, “to achieve adequate ventilation rates in such an airtight building the occupant would be required to open all the windows at least once every three hours for some 5 to 10 minutes at a time – even during the night.” Hence the use of an ‘active’ or mechanical system instead. These MVHR heat exchanger units run 24 hours a day extracting heat from outgoing internal air and adding it to incoming fresh external air.

One of the reasons passivhaus has not been so readily adopted outside of Europe
is that the
production of such
heat exchangers has
been geographically limited to where the dominant passivhaus market is, i.e; Germany. Viewers of the Grand Designs television show might recall that even England’s first certified (not Britain’s) passivhaus in the Cotswolds had to import a goodly chunk of their home’s products.

Even the Grocon/Umow Lai/Studio 505 ‘Delta’ apartments are likely to be using imported materials to help achieve their passivhaus standard. In this case, a pre- fabricated Forest Stewardship Council (FSC) certified cross- laminated spruce structure is being considered as one way to eradicate thermal bridging. These prefab walls will be insulated with shredded newspaper. Like most other passivhaus structures, Delta will incorporate highly insulative gas-filled triple glazed windows. Something that would astound many Australian homeowners, who are yet to even become familiar with double glazing.

PH (to use its acronym) standards were originally set for housing built close to the cool 60° latitude, where heating is a primary focus in securing indoor comfort. Cooling, in the form of air conditioning, is the more prevalent concern in most of Australia.

Passivhaus design can, in principal, be applied to high temperature, high humidity locations, such as are often found in Australia, but the standards may need tweaking to best suit our spectrum of geographic conditions.

In announcing their foray into passivhaus design, Grocon’s general manager Carlton Brewery, David Waldren, said, “We believe homeowners should have the opportunity to take advantage of technology available around the world and achieve the most sustainable home possible.”

He also noted that, “we must all be ready for a new way of living and working. The carbon constrained economy is upon us.”

Passivhaus methodology may become a vital tool in this new way of working.