building envelope air tightness studies

Hi everyone,

This is a question from Australia, (I think I’m the only Australian member of BPA).

Our national building code is being updated in 2022. We currently do not address air tightness in our building code and the ‘code writers’ are reluctant to include it.

They state, "Unfortunately, air leakage testing of new dwellings in Australia has not been sufficiently extensive to develop an evidence base sufficient to allow the development of new regulation."

Does anyone know of any studies that may be available regarding air tightness of the building envelope?

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      • I get your points.  Interisland flights are plentiful & cheap (you know, for commuters) - this $4K bill likely (I suspect) due to a lack of competition.

        I hear a lot about Hawaii's "mild climate."  On the Big Island, we have a dozen climate zones.  There's snow on Mauna Kea ("White Mountain") right now!  Most of my business is conducted at lower elevations, where it's decidedly not mild.  People are hot.  They're buying AC to cool their uninsulated houses, uninsulated because builders have said it wasn't needed because of the "mild climate."  (I pile R-38 in attics, problem solved.)

        Couple that with the availability of DIY mini splits on local store shelves and it's a new day - this state hasn't had a great track record with updating the IECC.  It's been on the 2006 IECC until now, with the 2015 update.

        Better airtightness is a new thing.

        Thing I wrote!

        Your AC Doesn't Work and Here's Why
        Hint: it's probably not the AC's fault.
        • Blake - I started to not say anything about 'mild climates like Hawaii'. But I read your post again and decided to say it anyway. I did include the explanation about 'no heating or cooling' to try to be clearer.

          And I agree with your points including the $4k bill was likely to be a lack of competition. That said, I have had to deliver what I had promised and then run to catch an airplane. I was writing up the test report on the plane and included far more explanation and recommendation than I usually do.

          I looked at a couple of the blog posts on your web site. I like what I saw.

          • Thanks, man.  It's Aloha Friday and this is contributing to good vibes.  Working on a new blog today!  Thank you for your kind words.

            p.s. plenty of Hawaii is "mild."  but my part is getting down into the 40s at night and we don't have any heat LOL

            • Really intersting points being made inthis discussion. Hawaii is on my list of places to visit one day. 

              Much like Hawaii most porple outside of Australia think that Australia is hot.  We actually have tropuical climate, deset climate, and temperate climate. A few hours from where i live we have ski fields, (yes we have snow). Our large intertior desert land mass affects our coastal climate in ways that differ from comparable climates elsewhere in the world. 

              The application of a 'one size fits all' approach never works and can tend to make things worse. 

              Good luck with your struggle I Hawaii. I hope good science and common sense will prevail.

  • Greg,

    To provide direction, it would be helpful to have more information on the basis of decision making. I'm sure the rationale is not that physics is different in the Southern Hemisphere, or is it? In the U.S., the Department of Energy does cost effectiveness evaluations for each new code update. I'm sure costs are different for you, but the method and order of magnitude might be applicable. These are all published.

    There has also been lots of great work out of Lawrence Berkeley National Lab on testing actual homes. Lots of then, and all over the U.S. They have studies on air tightness over time, ventilation, you name it.

    One final comment that might resonate is that a tight house is less susceptible to smoke from fire (and other pollutants) leaking in. That would seem important.

    Good luck,



      Thanks Sydney,

      I have found out a bit more about the thought process at regulatory level here since I first posted my question. The underlying issue is that they don't know how to implement air pressure testing without the physical capability to do it. There aren't many blower doors in Australia. It may be a case of implementing visual inspections in the next code with a move towards blower door testing in the next. Our code is updated every 3 years so that would mean blower door testing in 2025.

      You've obviously heard about our recent fires. They were bad. We had worse ones in 2009 and codes were changed accordingly. Unfortunately, many of the measures were well intended but caused more problems. (We implemented a degree of tightness without vapor permeability and without ventilation. Now we have a lot of moisture issues).

      The concept of a building as a system has not gained traction here.

      Slightly off topic, I am actually just old enough to remember the fires of 1974. These fires burnt twice the area of the recent fires and I remember being terrified as child. We had a family farm and I remember Dad coming and going, his black from the soot. I have since fought fires myself. Fires are always a threat here in summer. Our fire season isn't over yet. Even though this summer has been colder than usual there is still a big fuel load so we are always on our guard. (Eucalyptus trees have been described as explosive devices disguised as trees. Our forests are 99% eucalyptus).

      Thanks for your advice. I will keep pursuing higher performing houses here. Time will tell what the code will do.

  • There are many studies and papers available. For residential - search for authors Lstiburek, Olsen, Nelson or Brennon. For commercial there is less available but start with authors Persilly & Sherman. There are many more but those come to mind quickly.

    You probably need to look more for code related studies. I don't have any specifics off the top of my head but there are some available.

    The big thing I recommend is to use the air tightness requirements of the International Energy Conservation Code (IECC). The 2009 IECC had ACH50 recommendations but you could meet the code with a visual inspection. Starting in 2012 IECC the inspection was removed and blower door testing was required. Some people are recommending air tightness that may be more costly than would ever be justified by energy savings - IMHO. Passiv Haus is one of those. But you can use PH requirements to show what *could* be done but may not be justified for code.

    • Thanks very much Kent. I greatly appreciate your suggestions. I have read a lot of Joe Lstiburek's papers. I will investigate his information further in relation to air tightness.

      I will also look into the IECC paper. We have Passivhaus here but there is a big gap between that and the standard house. We can do a lot better with our standard houses with minimal cost impact if we begin with a reasonable air tightness strategy.

      Thank you again. 

      • Greg -

        Note the IECC is not a paper. It is the energy code adopted across most if not all of the United States.

        IECC - ICC
        Overview of the International Energy Conservation Code® (IECC®) Internationally, code officials recognize the need for a modern, up-to-date energy co…
        • Thanks Kent,

          It is interesting looking at the development in this area in North Ameriaca over the last 15 years or so. For the last 10 years here we have unfortunately not advanced in Australia. I remain optomistic though.

          Thanks again for your help, it is greatly appreciated.

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