Air leaks remediation and house tightness

Out of all the websites I visited which write about air infiltration into houses and the corrective measures to be taken to correct that situation, only 2 ( and I visited over 40) mentioned that making a house too tight can cause new problems.
If I was to find the sources of air leaks into a house I would explain that sealing ALL air leaks could be worse than leaving them in place, but if one really wants to stop all air leaks (or most of them) I would recommend an HRV or ERV be installed.

Any comments would be appreciated.


Air sealing ceases when additional air sealing is not cost-effective, when the air-leakage-reduction target is reached, or when the minimum ventilation level is reached.

None of this can be determined without a blower door test.

Ideally, a house is completely air tight with all required amounts of fresh air provided through mechanical means where it can be conditioned and filtered. Rarely is this ever achieved.

Hello James
My point was that most of the websites I visited and who use infrared cameras, are talking about finding leaks and lack of insulation or the presence of moisture and the fact that finding the above and correcting them will save the home owner money and make the house more comfortable.
Except for 2 sites, no site mentioned that making a house too tight could make the situation worse.
Also, practically non of the infrared camera users mentioned the use of a blower door test.


That is because an infrared camera is insufficient to address what you are referring to as “house tightness”. It is like attempting to photograph the wind and use your photo to judge its speed and volume.

Lack of insulation has nothing at all to do with air leakage. Insulating an air bypass simply filters the conditioned air as it leaves the building.

So you are OK with inspectors going into houses with their IR cameras, pointing out air leaks and moisture and suggesting that the air leaks should be eliminated without telling the home owner about the consequences of on overy tight hosuse without make-up air systems?

“The sealing of air leakage is very cost effective and can pay for itself in the first year from energy savings that the sealing will generate.”

This is a quote from an inspector’s website.

No mention of the consequences… :roll:

There are no “consequences” if you do it right. A blower door test is essential. An infrared camera is an optional tool to use in addition to a blower door.

No, I am not. Blower door tests are the only means of quantifying air leaks and measuring the effectiveness of sealing them. Not cameras.

No Offence but if your blower door test tells you that the house could be tighter (based on whatever standard for air changes per hour you use) do you start sealing different areas and you perform a blower door test after every stage to see if you achieved the desired effect?
We don’t have an equivalent to BPI in Canada (unfortunately) but we have NRCAN which is somewhat similar but without the teeth :slight_smile: .
Also, what do you use to find the actual leak locations when you use a blower test?

Thank you for your replies so far


Thank you for your replies so far

That would be great except that people are afraid to share thier knowledge in the immediate area surrounding them probably because they are afraid of losing business.
That is why I post here because hopefully people would not be threatened by someone far away.



You are correct! Many home inspectors do not totally understand the actual complexities of house air leakage.  Every change to a house must be viewed in relation to what it may do to another part of the house. For example, to foam the rafters of an existing house without looking at the HVAC sizing would be a mistake. James is correct - the only way to actually quantify the home's leakage and air change per hour is to do a blower door.

No house is too tight. Airtightness improves comfort and saves energy. Since 98-99% of the interior house vapour that moves into wall and celing cavities is air leakage, proper airsealing may save prevent a mould/rot situation in areas of air leakage. Once a house is airtightened, it will need supplemental mechanical ventilation, sometimes as simple as a good bath exahust fan on a timer, or possibly a timed whole house exhaust system. Here’s a brochure that I worked on and updated in the 1990’s:

In the 1980’s while running an insulation/airsealing company, we were installing good exhaust systems and instructing our customers on controlling interior moisture problems from basement dampness, not drying clothes inside/venting dryers to exterior, not storing wet firewood inside, covering aquariums, not too many plants, etc

Thank you for the brochure Brian.

As for your comment that NO HOUSE IS TOO TIGHT, why else would newer houses need mechanically assited air exchangers (HRVs)?

Too tight is obviously a relative term but let’s assume that an older home can be sealed to the level of a new house, wouldn’t you agree that if an HRV is not added that house WILL be too tight to the point that it will be uncomfortable.


Re: The House as a System

Heat Pumps

Get More Details</SPAN>

2,800 ~ 12,000
3,000 ~ 21,000

We had an energy audit on our 1400 sq. ft. Home Electric Base board heat .
Fully Finished Basement Gas fire Place .
Sealed and insulated as recomended

On recommendation of audit Person we put in a Mr. slim heat pump.
it heats our home upstairs great ,Electric heat kicks in at about 14°F/-10°C.
I think we save about 70~ % on our heating and the AC is I think 23 seer and it is great .
Easy 3 hour insulation no changes in Basement cost in Canada about $3,300.00 and about $1,400;00 return from the Government .
Attached Thumbnails

Did you go to my site?

Hope you didn’t miss this page: :wink:

Thanks I am lucky to have a friend who has done this for years
When he did the second Test and I said I had a couple more small air leaks He said No stop now.
Go any further and you will need to put in an HRV .
Been two years now and every thing seem perfect , He had me put on both Bath fans Dryer and Kitchen exhaust to confirm his reasoning .
Humidity at this time is 39% slight moisture on edge of the windows out side temp is 16°F inside 72°F .
Thanks for your concern ,Do you have any thoughts .
. We have some Plants in the home no fish tanks .
Do not dry laundry inside .
Is there any more info you need …
2 adults one dog all Bath exhaust on timers . Gas fire place uses outside air . Gas water heater uses inside air .
Have 4 C/O detectors and 5 smoke detectors .
Electric dry uses inside air

This is exactly what I was writing about.
You must be 1 of the 2 sites that I mentioned (out of over 40 sites) that addresses the issue of over tightening a house when hunting for leaks.


I’m not!

Many people are sold equipment with promises from vendors of being a leader in the field, making more $$$…that’s all you’re both concerned about…making more $$$$$$…and then enter the field with their new service very poorly trained especially in IAQ, backdrafting, etc. If you have not been in the IAQ field for a few years fulltime in a truly professional manner, having previously been trained/mentored by a person with many years of building science, air leakage testing/sealing, HVAC training, you’re putting yourself in danger of being labeled a “charlatan” with complaints and your customer giving you a bad reputation.

It’s not that simple…a 1 or 2 week course from BPI or RESNET is still just a “lead-in” to the field; experience will teach you a lot more…hopefully it’s not costly and a bad experience!

Dense-pack cellulose has been used for many years as part of an airsealing program for homes. It’s been mentioned many times in articles about “projects weatherization” programs. (Home Energy magazine)

Even if it’s not dense-pack, cellulose reduces air leakage in homes. After buying a blower door in 1981, the first house my company insulated was a 1920’s balloon framed 2 storey. We were only contracted to do the walls with the homeowner to do any further interior airsealing at the walls on his own. We did a pre-insulation air leakage test and a second immediately after the walls were blown. At this point nothing else was done to the house…The air leakage at 50 pa had been reduce by 38%.