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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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.


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.

Take a look at this paper - https://www.buildingscience.com/documents/insights/bsi-053-just-rig...

In it Joe makes the point that blower door testing can be good or it can be nearly worthless. Depend on what people interpret the results to mean.

That's brilliant Kent.

I think Joe is on the money here. My own experience has taught me that it's not that hard to achieve around 3ACH50 for a "normal" house, and the benefeits are great. Our housing stock will improve dramatically with a sensible baseline target. Maybe it's baby steps for us with visual inspections.

I love technical stuff and I like measuring with my blower door but I am always mindfull of cost/benefit and sensible applications..... I grew up on a farm, we just like to make stuff work.

Thanks again. 


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.

I'm in Hawaii and our situation is similar.  I've lobbied heavily for including airtightness in our new version of the IECC, but the arguments against it are real.  In the writeup of the bill for consideration by the Council on my island are comments I cut/pasted below  from a pdf, some formatting is lost, sorry.

There's a chicken/egg quandary for our building departments.  They'd like to include it, but down the road when it comes time for inspections, they can't finalize a building if nobody's around to do the testing.  If there was a requirement, a market would open up for testing, but they don't want to create the market.  With no requirement, there is no big-enough market for that service.

I am heartened that they included the SUGGESTION of a blower door test.  I'd like to believe that my island included it to prep builders for the next round of the energy code, so that if they do make airtightness mandatory they can point to the old code and say, "see? you were warned this was coming."

I did offer them suggestions of which houses would benefit from better airtightness.  In our case, it's typically larger houses that are fully air-conditioned that are sited in hot areas.

They did just copypaste the language on blower door testing from the IRC, as an expression that there is precedent and they're not just making something up.

Another argument against mandating airtightness is that building depts can take a "health & safety" attitude towards codes, and if something doesn't translate immediately to a healthier, safer building like electrical codes or plumbing codes or structural codes do, it shouldn't be their responsibility so they kick the ball back to builders and architects.

I building dept official I like and trust told me a story about a builder on this island who called someone on another island to do a blower door test.  They flew in, tested, failed the building, collected $4000, and flew away.  Now there's a sense that a BDT is an expensive thing that doesn't help because that builder got no feedback on how to actually improve the building.


R402.4.1.2 Testing. The building or dwelling unit [shall] may be tested and verified

as having an air leakage rate not exceeding five air changes per hour in Climate

Zones 1 and 2, and three air changes per hour in Climate Zones 3 through 8. Testing shall be conducted in accordance with ASTM E 779 or ASTM E 1827,and reported at

apressure of0.2inchw.g.(50Pascals).[Wherer-equifedbythe,odeffiei,T3testing

test shall be signed by the party conducting the test and provided to the code Testing shall be performed at any time after creation of all penetrations of the building thermal envelope.

During testing:
1. Exterior windows and doors, fireplace and stove doors shall be closed, but not

sealed, beyond the intended weatherstripping or other infiltration control measures.



Dampers including exhaust, intake, makeup air, backdraft and flue dampers

3. Interior doors, if installed at the time of the test, shall be open.

ventilators shall be closed and sealed.

Exterior doors for continuous ventilation systems and heat recovery

heating and cooling systems, if installed at the time of the test, shall be turned


Supply and return registers, if installed at the time of the test, shall be fully


A. Hawaii County's version of this addition is consistent with the version

adopted by Maui County.
See: § 16.16B.R402.4.1.2, MCC.

B. Maui Justification: Due to concerns relating to timeliness, added costs, and availability ofa certified contractor, this " blowerdoortest"isbeing

madeoptionalinsteadofmandatory.Theregistereddesignprofessional may re q u ire this on behalfofthe o w n e r.

The problem of available test agencies and test equipment was addressed in the 2009 IECC (and IRC) by making BDT optional with a visual inspection. Builders could always do the visual inspection instead of BDT. Over the life of the 2009 IECC, contractors (both builders and test agencies) had time to obtain equipment and learned to identify the 'leak sites' that were important to pass the test.

I am not personally familiar with the climate in Hawaii, but I bet it is mild enough that BDT testing is not commonly needed. If a building (residential or commercial) has no heating or cooling equipment - building leakage is far far less important that in a climate where the indoor conditions are "controlled".

The same argument would apply for some locations in Australia. If there is no heat or A/C, then air leakage testing is a waste of time and money in terms of energy savings. But if the building is supposed to "climate control" the indoor conditions then building air leakage is important. In the case of most US residential buildings, the heating and AC cost are the biggest drivers of building energy consumption. (Of course, there are exceptions so that statement is a generalization.).

As far as the BDT agency that flew in, tested / failed, and flew out. I bet the builder got exactly what they paid for. $4000 sounds high. But I bet most of the cost was travel. If they wanted help identifying and correcting leaks - that takes time and money. In the past, many test agencies build some time (typically an hour) into their BDT estimate for the investigation work. Many of those test agencies have removed that time because they were losing jobs to agencies that considered that an extra cost. Investigation work is usually on a dollars per hour basis. But if a plane is waiting for the investigation to be completed, the cost may be thousands of dollars per hour. If they flew commercial and shipped the equipment, they may not have been able to miss their flight.

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!


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.



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