Insulation-a continuation from MISC. section

From the responses given in the “Miscellaneous” section about “attic insulation” comments in reports, it’s obvious that most HI’s have not studied or grasped the idea of airsealing for energy conservation purposes.

In an attic before adding any/more insulation, airsealing MUST be done. As insulation levels of up to R50 will be installed, this most likely will be the last time attic efficiency will be addressed, so do the airsealing; no one is likely to go back into the attic at a later date to lift up batts or dig through blown insulation to airseal.

Fiber insulations do slow down air movement (infiltration/exfiltration) a bit but this is not a solution! With a poorly done job (insulated but not airsealed), you will actually be encouraging/creating a condensation problem. The heat loss by conduction to the attic space will be significantly reduced resulting in a much cooler/cold attic but upward air exfiltration is only slowed down a bit.

Above the attic insulation, this interior warm moist air is now cooled below its dew point and is looking for a cool/cold surface to condense on- attic framing and sheathing. Now we have a problem that most likley did not exist before the insulation was added!

So we then have to add more attic ventilation to try to solve the condensation problem that could have been prevented by airsealing before the insulation was added or upgraded.


Yes good info Mr.B .I have closed My attic up tight and no longer roof vents to the out side .17 inches of insulation and 8 inches of foam and gasketed the attic Hatch Soffits still open will close in the spring .
Foamed all wire and box opening in the attic. All attic boards and rafters look like new and it is 22 years old

The suggestion of airsealing is not with in the scope of the Home Inspector. The inspector report what he finds and suggests a solution but the rest is really up to the professional. The insulation contractors and roofer are the one who really need the education. It is good for the Home Inspector to know about it and that way he can mention it but if the home owner doesn’t buy into it and doesn’t call in a person who knows about it then nothing happens. Cellulose insulation does more than just seal a bit. I’ve tested several houses that had great results.

If you are going to recommend air sealing, do you think it might be important to do blower door testing (test in/test out) accompanied with CAZ testing? Why?

I clicked on this thread by “An HI”, and he/she states “it’s obvious that most HI’s have not studied or grasped the idea of air sealing for energy conservation purposes”.
I didn’t click on any other threads in the Miscellaneous/attic insulation section.
I seriously doubt the claims most HI’s do not grasp the idea of air sealing is valid. Just because some/a few don’t agree with “An HI’s” ideas of air sealing (regardless of whether it’s right or wrong), does not equate to most HI’s not grasping this idea.
I’d venture to say most HI’s do grasp the idea of air sealing.

Air sealing is important, as is a vapor barrier. I recommend open cell spray foam un the underside of the roof deck, as opposed to the ceiling, and close all ventilation to the attic area. This is the best solution to handle all issues. Keep the building envelope narrow.

Hope this helps;

The argument started on the other thread is because some HI’s, that are energy auditors, said cellulose does not have an air sealing factor to it. I argued that cellulose does, but fiberglass does not. It went over their heads and they got confused.

I agree that dense-pack cellulose does seal more than either loose or batt fiberglass in walls but it cannot be considered as part of the air barrier system when uised as loosefill in attics.

We’re talking about attic insulation in this thread and the fact that adding insulation to the attic without prior airsealing is a mistake.

In homes with combustion appliances, a whole house airsealing program should be accompanied by CAZ testing for safety.

By just airsealing in the attic, you have put a positive cap on a lot of the stack effect working in the house- the basement negative pressure that may cause backdrafting will then be reduced, a positive effect. This is why I have no problems with airsealing the attic without CAZ testing.

In post after post, I see no mention of it. They should be willing to show off their knowledge.

“Air sealing is important, as is a vapor barrier.”
98-99% of moisture movement of interior house moisture to the attic or wall cavities through is by air leakage and only 1-2% is by vapour diffusion through permeable materials. Therefore concentrate on the air barrier system in the retrofit of older homes and not the vapour barrier.

From a 1977 Canadian government publication:
“Where possible, in adding insulation, install a vapour barrier on the warm side of the insulation but, if this is difficult to do because it requires a great deal of cutting and fitting (such as in an attic-my comment[size=2]),[/size] it can be omitted and the effort be concentrated on the creation of an air barrier. Generally, the interior finish will provide sufficient resistance to vapour diffusion…”

“Make every reasonable effort to turn the building shell into a complete air barrier by finding and sealing as many potential air leaks as possible.”

When airsealing and insulation retrofits are conducted on any building, control, reduction and/or removal of interior moisture by ventilation or other means must be addressed.

“I recommend open cell spray foam un the underside of the roof deck,”
I would hope you are doing or recommnding the utmost to keep the attic air very dry. Long, cold winters with a constant significant vapour pressure differential in favour of movement to the exterior may encourage condensation in the foam at the sheathing. I would personally recommend the higher density closed cell foam.

An HI, It’s going to be really hard for most to want to even discuss subjects with you when you fail to provide the common courtesy of posting a name and location like pretty much everyone else here.

I agree. I am always suspicious when no name, no area, non-member people post and do so with the air of authority. We have had a lot of non-member anonymous people posting in the past, claiming to be experts and all, and seeming to dominate the conversations.

Not accusing, just suspicious.

Darn ,read through for first time and was going to ask qualifications.
Notice Linas and Roy think this is J.B…:slight_smile:

Non-Typical mis-spell for J.B…however.

Now you and I however are another story.

Not even close Bob , I am sure I know who it is and he is not a NACHI member and he is a Canadian .
If you have followed the NACHI Canadian Posts over the years it is Obvious who this person is .
Thanks for trying Bob , I do appreciate your efforts … Roy
and Yes B was your Clue

He’s Canadian, but I think Brian has more brains than this “expert”.

Wow i cant believe you bashing trevor on this. Hes still learning and his posts are mostly philosophical. This is much too specific. Leave him alone he hasn’t caused you any grief in a while. Go ahead and have a round at your other favourite punching bag. I promise you I can take it. Just do me the favour of not quoting that 75% or is it 80% actually arent we up to 90-95% failure rate for new HIs its getting old now lol!

Give it time, you’re still a greenhorn. How’s business?

Who’s Brian? He’s never posted in this thread.