Sean Maxwell

It was Friday night after Day 1 of the recent 2016 South Pacific Passive House Conference, and I wasn’t expecting a huge turnout for a discussion that we, the Air Infiltration and Ventilation Association of Australia, were planning to hold about proposing changes to the National Construction Code. It’s not exactly cocktail-hour talk.

Still, we had nearly 20 people stuffed into the room. There were builders, suppliers, engineers, sustainability experts, architects and a few of people who truly had walked into the meeting because they had seen free beer. No matter – it quickly became apparent that everyone in the room could relate to the topic of air tightness and the building code.

Most people don’t associate quality of life with quality of building, but then it dawns on them, and they’re on your side. Many times over the conference, a theme was repeated: we can spread the message of high-performance buildings by highlighting things everyone can relate to: comfort, quality, value and peace of mind.

Bronwyn Barry, co-president at the North American Passive House Network, made a point in her keynote address that was repeated throughout the conference. To paraphrase, “It’s not about the energy. It’s about comfort.” She showed a chart of monitored temperatures throughout the house, which were dead even throughout cold weather and warm weather, from top floor to bottom floor. No matter where you roam in the building, no matter what the weather, Passive Houses accomplish what humans have been trying to do for millennia, which is to create a true shelter from the elements, and they do it with incredibly little energy.

Not only do they use less energy, they improve air quality. Architype associate Elrond Burrell showed monitored data in school buildings where peak CO2 levels (which make students tired) were actually lower in Passive House schools than they were in conventional schools where windows were the main form of ventilation. Why? Because once you can contain the air with a good envelope, you can control what goes on in the building. Not so with a leaky building or duct system.

These were benefits realised in part by following the mantras of “build tight, ventilate right”, “you can’t control what you can’t contain” and so on. Our meeting focused on the things we can do with the National Construction Code to start moving the Australian construction industry in the right direction.

The NCC is intended to provide basic “performance requirements” of a building, and these are the only legally binding or enforceable elements. For building sealing, the performance requirement for commercial buildings goes like this: “A building, including its services, must have, to the degree necessary, features that facilitate the efficient use of energy appropriate to (f) the sealing of the building envelope against air leakage.”

Well, you can tell the effectiveness of that code language by the state of Australian building air tightness, which to put it bluntly, is miserable on the whole. You may have heard of CSIRO’s study of air tightness of 129 new homes, which found an average air tightness of 15.7 ACH50 (air changes per hour of the building’s volume with a blower door at 50 Pascals pressure). At the Passive House conference, this is particularly mind-boggling because Passive House calls for a maximum leakage rate of 0.6 ACH50 to really tackle energy use and indoor environmental quality. That’s more than 25 times tighter. It’s impossible to argue that the code is accomplishing what it is supposed to when it comes to energy efficiency.

Compare the NCC language with the International Energy Conservation Code. The commercial Section C402.4 of the 2012 IECC (scroll down) calls for a lot more, and the whole thing is legally binding. The commercial section of the IECC provides a way that might make sense for Australian buildings to make progress, and that offers a path that is compatible with the approach of the NCC, which is to give builders choices about how to achieve air tightness, yet also put some teeth into the requirements.

One idea is to offer two paths to compliance: a deemed-to-satisfy path and a performance path. The DTS path would be a checklist not unlike that from the IECC residential sections, outlining specific things that need to be sealed, inspected and verified. Ideally this would be enforced by the building certifier being provided a checklist of air sealing details verified by a qualified inspector.

The performance path is simply doing a blower door test to verify that an air tightness of 10 ACH50 has been achieved. Now let me say this plainly: 10 ACH50 is not hard to get to, and everyone in the room who had done a blower door test would agree.

The difference between buildings with 30 ACH50 recorded by the CSIRO study and 10 (or even 5) ACH50 is not that great in terms of cost, time or effort. How do you get to 10? From some of the builders in the room, it meant simply taping the exterior sarking at the joints. It meant watching for gaping holes at intersections of roofs and walls – the size that a possum can crawl through. It means having a worker walk around for a few hours with a cheap foam gun, tape, foam boards and caulk. This is DIY-level stuff, that homeowners, if they are properly educated, would demand for their homes. But it’s clear that we need to start from the bottom and work our way up.

The victory will be getting something – anything – into the building code that starts us off in the direction of verifying that homes are being built to the energy efficiency standards they claim. Most of the builders in the room attested that once you learn how easy it is to seal up the big holes, you start to ask yourself why you would allow a home to be built with those holes in the first place.

At the meeting, ventilation was another topic of discussion, and everyone is afraid of that old boogey-man condensation. Everyone in the room seemed to have conquered their fear, but how? Builders in cold climates can use a cheap and efficient Energy Star bath fan to keep air moving through the house. Builders in warm climates use an equivalent supply fan. Again, this is not hard stuff, and believe me that it’s been thought through before. We also have the benefit in Australia of some home-grown ventilation companies that can provide ventilation solutions that work.

As the meeting closed, one of the outcomes was a pledge among the attendees to supply the results of their blower door tests to an anonymous database, to better inform the Australian Building Codes Board about what is possible to build in Australia. Everyone in the room was on board, as you will be if you see the sense in what we’re talking about. Blower door tests are one of the most basic yet helpful tools in the building performance arsenal. Let’s use them to help plug the big gap between what’s promised and what’s delivered.

Sean Maxwell is president of the Air Infiltration and Ventilation Association of Australia, a group advocating for better building and ductwork sealing to achieve healthier, more energy-efficient homes.

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  1. While I’m sympathetic to air-tightness efforts in cold climates of Australia, and even in air-conditioned houses & offices all across Australia, any NCC air-tightness requirement should recognize that a tighter fabric may not be appropriate for some building styles (such as in Qld & NT) where the building is designed solely around natural ventilation and not air-conditioning. In this case, higher air-tightness can mean that during unoccupied periods when the house is closed up, the internal temperature can go higher than external temps etc etc. We need to keep our building code flexible and allow for all the different design techniques that work across Australia to continue to be explored.

  2. Tightening up the building envelope is the first step, but what about building codes that talk about ventilation. If all the holes and leaks are plugged up, a simple fan won’t do. You need a proper (heat recovery) ventilation unit providing a minimum level of fresh air, day and night, to keep your home healthy.

  3. Keep up the great work Sean. We have a long way to go in this country to achieve healthier, more energy-efficient homes, but as you say this can be done by implementing some pretty simple solutions that are certainly not cost prohibitive.
    The use of Passivhaus principles can achieve great results and outcomes for Australian housing.