insulation w/ no vents

[Guest]

Anyone out there fluent in the "tight pack" cellulose insulation technique, i.e., rafter spaces completely filled w/ insulation and no vents? I've read the studies, but still have a hard time believing it works like the practitioners say it does. Any personal experiences or opinions?

[Guest]

Re: insulation w/ no vents

Dear Kurt,

Yes, I am quite efluent: Lots of experience with sick, wasteful, self-destructing buildings and lots of tricks to fix them including acres of DP cels.

Do you have a question?

Regards, derf

aka derf the dusty, Sultan of Cellulose, Defender of the Dense Pack, Vanquisher of Vents, and Redeemer of Roof Holes

[Guest]

Re: insulation w/ no vents

Yep, a lot of questions. There is a thread going on the ASHI (American Society of Home Inspectors) site regarding insulation between rafters, venting, etc. There are them that believe, & them that are skeptics. I am a skeptic. I like hands on experience, & virtually noone uses dense pack in my area (Chicago). I've read studies, done my own experiments on my little cottage, but have still found moisture in my rafters. Do you have any links, photos, published studies, or anything that would be convincing? I could go into detail on my experiments, if you wish.

Kurt Mitenbuler

[Guest]

Re: insulation w/ no vents

Hi Kurt,

That's Kurt M. right? Saw the same question yesterday on the ASHI boards. Fred Lugano, an insulation contractor in Vermont who has written a number of articles for FHB, is an advocate of dense packing cellulose. His area, like Chicago, has pretty severe winters and he has been dense packing for years and claims near 100% success. One article he did was 'Fixing A Cold Drafty House' in issue #105. If you don't have it, give me a push via e-mail with your fax number and I'll send it to you.

It sounds like derf is also an advocate. Why not pose some specific questions I'm sure he is raring to answer.

ONE TEAM - ONE FIGHT!!!

Mike O'Handley
[email protected]

[Guest]

Re: insulation w/ no vents

Yessir, Michael O, it's me, w/ more specific questions for Mr. Derf, Vanquisher of Vents:

1) How long have the oldest installations been in place & have you opened any up or measured interior rafter space moisture w/ appropriate measurement tools?
2) Got any photos?
3) Any failures or problem installations, & if so, what happened & what was the apparent failure component?
4) If it is so darn good, why isn't the industry flocking to it? (Industry wide adoption of a new practice doesn't necessarily mean it is good, & the same is true of industry wide ignorance of something like dense pack cellulose; it may be great, & the industry is ignoring it for any number of reasons.) Any thoughts?

I remember reading the article years ago, & being skeptical. I am unabashedly conservative regarding new techniques; my own personal ethic is to not use anything that hasn't been around for a decade & proven its worth (w/some exceptions). The US building industry is too full of new ideas that we find either don't work or give us cancer after a couple years. Having installed some of them, I am understandably fidgety about new techniques. I've got buddies in the trades that think I am hopeless, but given the economics of building, I like guaranteed results.

I started in the trades in the early 70's during the "first" energy crisis. We were all feeling pretty relegious about energy efficiency (unlike the current building industry). My own experiment didn't "work". I own a 900 SF cottage in Michigan; gutted to the studs 17 years ago, insulated, vapor barrier, sealed all penetrations, gaskets on electrical boxes, etc. Very tight. Installed 1" blue dow foam on the interior walls & ceilings, taped all seams, caulked, sealed. Very, very tight. Exterior carpentry details are/were as tight as good workmanship could make them, stained, & caulked. Installed drywall, taped, finished. 30# felt on the roof deck, no vents, tab shingles. Tore the roof off last summer, moisture in the rafters. What might have gone wrong, or what might I have done wrong?

Basically, I can see how this can work in the short term (1-10 years), but buildings hang around for 100+ years. Doesn't Mother Nature eventually equalize moisture content in rafter spaces to the ambient exterior humidity? How do you "seal" a lumber building against vapor migration?

I have also seen enough ice in attics to know that fiberglass & vents can create amazing moisture conditions, but at least vapor can equalize back out when atmospheric conditions change. Sealed assemblies of lumber & plywood/vapor barriers don't "breath" adequately to allow things to dry out properly (or so it seems to me, in my experience).

Kurt Mitenbuler

[Guest]

Re: insulation w/ no vents

Dear Mike and Kurt,

Happy New Year to you both.

Mike, you seem like a kindly, and dare I say insightful, sort of fellow. I'm pleased to make your acquaintance. Perhaps I could save you a bit of trouble right off. The article you mention, which I have also read and occasionally use as a reference, can be found online now at http://taunton.com/finehomebuilding/pages/h00021.asp . Isn't that fun? There's another cels article by the same author here: http://homeenergy.org/archive/hem.dis.anl.gov/eehem/98/980508.html

Kurt, After attending 2 conferences in Chicago (((love that Science Museum))), I can say for sure that there are many DP installers there. But I'm still unclear about what you are looking to be convinced of. I am also a very conservative person and don't need the risk or aggravation of experimenting with my clients. And with no government funding or academic station, I don't ever go back to cut into my work for intrusive analysis. So I rely on information that have been proven in tens of thousands of houses by people who have the money and temperament for such things. These mighty thinkers include Leger, Tsongas, Fitzgerald, Rose, Nelson, Tooley, Ten Wolde, Rousseau, Christian, Straube, Derome, Bomberg, et al. After talking with them and reading many others, I have put together a bag of tricks that works that works for me. DP is just one of them. So I can go back to the houses and know that the attics will dry up, the roof ice will stop, the fuel bills will drop, the disease will stop, etc. That's how I measure success.

In a general way, I can tell you that the Weatherization Principles of insulation, air sealing, and pressure and diffusion control do work reliably. That is to say, they make houses safer, healthier, more durable and comfortable, and more energy efficient. Roof venting NEVER improves a house in those terms. As Don Fugler said so poetically, "You can't fix a big hole in the ceiling with a big hole in the roof."

Yes, I did have two failures, both in the Fishman (Phish drummer) house. They were both in a hot tub room under a wildly complex roof I built of EPDM rubber, and standing seam copper. Two areas of DP were soaked and related to electrical work. The first one came from a hole cut into the rubber that allowed water to pour into the roof system. The soaked cels had to be shoveled out. More interestingly, another section of steeply sloped wall/ceiling also got very wet under a perfect roof. The moisture was centered around 2 light fixtures. The cause was condensed interior water vapor. Although we insisted that no poly "vapor barriers" were to be used inside the walls, this section had been heavily painted with art colors into a mural. The paint formed a diffusion barrier, and completed the moisture trap. By contrast, all the other DP areas that could dry to the inside had no problems.

Cels, first installed in Canada (12000 HDD climate) in the 1920's, is the only commercial insulation with any track record. After 50 years, some of the original houses were examined and they looked very good.

Dominique Derome conducted a wonderful experiment in Montreal with a DP in a large climate simulator with very wet results. The DP was done perfectly by Jim Fitzgerald, but she was able to push it to failure with a combination of lots of water vapor, pressure, air barrier holes, and extreme cold over long periods of time. Bill Rose has also reported similar resulted in controlled experiments in Urbana.

The silver lining is that nobody has ever been able to grow mold or wood decaying fungus on the framing behind DP. So while I never depend on DP as a diffusion barrier, I don't loose any sleep over installing it either. When a house has a water vapor problem, stop the evaporation first and then install thermal measures.

Despite many benefits and terrific savings on the cost of home ownership, DP will never be part of production building. The most important reason is that good installers don't want that work. In Anchorage, not one packer will take on private sector projects. The other big issue is that building performance is not a priority for our society. Getting as many people into houses as fast as possible is far more important than making those houses more habitable.

Sorry for word load, but the lawyers telling me to give more complete responses.

Regards, derf

[Guest]

Re: insulation w/ no vents

Derf Dude;

While cutting back & forth to the sites you noted, I think I forgot to post my message; if there are two posts that show up, oops.

Thanx for the response. When I said that noone uses it around here, I meant I never have seen it, & I spend my life in construction projects. It is sounding like the province of the craftsman/artisan builder, not what we get to see in Chicago. The big dirty is about tearing down the City to rebuild the City so that it can be torn down & rebuilt. That's before we tear it down again & rebuild. Stuff just gets thrown up (pun intended). I look @ a surprising number of masonry homes w/ NO insulation. I will post some more questions after I research the links you provided.

Kurt

[Guest]

Re: insulation w/ no vents *NM*

[Guest]

Re: insulation w/ no vents

I'll tell you why the industry is not flocking to it: Owens-Corning and the other big one have huge advertising budgets aimed at the home buyer and builder to convince us that their spun glass crap is better.

[Guest]

Re: insulation w/ no vents

I am sure that is part of it. From what I am gathering on this process, it requires tradesman who are concerned w/ details; those types are in short supply here in Chicago.

Kurt Mitenbuler

[Guest]

Re: insulation w/ no vents

Kurt,

Derf forgot to mention a few things that are near and dear to me, particularly recently.

Our county weatherization crews have been densepacking roofs for years - literally. It is a common method of retrofitting cathedral ceilings and 1 1/2 story type roofs. In New York State they have been doing this for 25 years.

Supposedly, when NY adopts the ICBO later this year, UNVENTED dense-packed and foam-in-place roofs will be specifically allowed - no more grey area. The wording will be specific in regards to cellulose and foam.

Do not EVER rely on roof venting to fix a problem. I came from a house today where they tried to fix interior condensation at the tops of the walls by installing MORE venting. There was no condensation until the siding guy cut in soffit vents and took out all the insulation that was blocking the sacred vent spaces. When the condensation started, the solution was to add vent chutes to "allow the cold air to get out of the soffit." This increased rate of cold air passage was somehow going to raise the surface temperatures in the house above the dewpoint. After 2 years of this charade they called the right person - me. We are going to shove the hose down the vent chute and fill the soffits with cels, dense pack the rafter bays on the way out, and blow a 6" cap over all the flat ceilings.

I do this with complete confidence because the first 57 years of this houses life created no condensation on the roofing, even though unvented. It was also only the second roof the house had seen. 28 years per roof ain't bad.

My advice to siding installers and roofers is that if the roof is dry, LEAVE IT ALONE. If the roof is not dry, call someone that knows what they are doing.

-Rob

[Guest]

Re: insulation w/ no vents

Kurt,

Derf forgot to mention a few things that are near and dear to me, particularly recently.

Our county weatherization crews have been densepacking roofs for years - literally. It is a common method of retrofitting cathedral ceilings and 1 1/2 story type roofs. In New York State they have been doing this for 25 years.

Supposedly, when NY adopts the ICBO later this year, UNVENTED dense-packed and foam-in-place roofs will be specifically allowed - no more grey area. The wording will be specific in regards to cellulose and foam.

Do not EVER rely on roof venting to fix a problem. I came from a house today where they tried to fix interior condensation at the tops of the walls by installing MORE venting. There was no condensation until the siding guy cut in soffit vents and took out all the insulation that was blocking the sacred vent spaces. When the condensation started, the solution was to add vent chutes to "allow the cold air to get out of the soffit." This increased rate of cold air passage was somehow going to raise the surface temperatures in the house above the dewpoint. After 2 years of this charade they called the right person - me. We are going to shove the hose down the vent chute and fill the soffits with cels, dense pack the rafter bays on the way out, and blow a 6" cap over all the flat ceilings.

I do this with complete confidence because the first 57 years of this houses life created no condensation on the roofing, even though unvented. It was also only the second roof the house had seen. 28 years per roof ain't bad.

My advice to siding installers and roofers is that if the roof is dry, LEAVE IT ALONE. If the roof is not dry, call someone that knows what they are doing.

-Rob

[Guest]

Re: insulation w/ no vents

Hi all,
I have some questions on cellulose insulation as well if anyone's still following this thread.
I'm renovating an 1803 townhouse in Charleston SC and am being talked into cellulose in the 4th floor cathedral ceiling. The roof is standing seam tin over the original planking and the rafters are sort-of on 24" centers. The house is balloon framed with brick exterior walls and the brick was carried up in between the rafters right up to the roof decking making air access at the lower roof edge difficult.

One concern I have with the cellulose is how it will affect the sheetrock. Cellulose is heavy and I'm worried about "nail pops". The insulation will be about 9 to 10" thick. The insulator said, "Just have the sheetrockers use screws every 4 inches". Really?
Also, what is to be done with the attic spaces behind the kneewalls? Do they need to be filled completely?
There is also a small attic space above a bathroom which contains the hvac equipment. This space includes about 5' on either side of the ridge line but has cathedral ceiling coming away from it on both sides and ajoins another unit on the "gable" end. No way to get air flow in this space if the ceilings are filled with cellulose. Can it be left unvented?
Finally, would I be better off with a vapor barrier tyvek?) applied to the living side of the rafters or no?

I hope this is intelligible (I'm needing a bed) and I appreciate any opinions.
Thanks,
John
Immaculate Construction

[Guest]

Re: insulation w/ no vents

Hi John,

I think if your drywaller is using 5/8" rock and nails at 4" you shouldn't have a problem. I inspect a ton of homes here where the PUD came in and installed what they like to call a sound/weatherization package in the approach lanes of the airport. It is basically new vinyl windows and a really thick layer of cellulose insulation over the ceilings to muffle the sound of the jets moving through the attic. I've never noticed that any of these homes, many of them 50 and 60's vintage with drywall ceilings, had anything other than the normal minor normalities associated with drywall. No sagging ceilings, no nail pops.

Drywall is a lot stronger than folks give it credit for. Once, during an inspection of an attic, I turned around and was startled to find my Vietnamese client following me through the attic to see what I was seeing. He'd climbed in after me very quietly and I had no idea he was there until I turned around. I was even more shocked to realize that he was standing between two of the ceiling joists with nothing but the drywall supporting him. "Don't move," I said, and then asked him to assume a sort of praying stance with both elbows tight to his sides and hands clenched in front. I moved around behind him, repeated, "Don't move," and then placed my hands under his elbows, lifted him off drywall and then moved him over on top of a joist. My guess is that he weighed about 90 lbs.. I then explained as best I could, because his English was limited, why it was not such a good idea to stand on anything other than the joists when in the attic. Going back downstairs, I was dreading what I'd find when I looked at the ceiling under that spot. I expected to find torn drywall, at least around the fasteners. Nothing, not a dimple, not a tear, nothing. I thanked my lucky stars and made a mental note to lecture all clients after that on the best method to use when moving through their attics.

Kneewalls don't need to be completely packed. You can insulate the ceiling of the living space below and the backside of the kneewalls, densepack the sloped portion of the roof and then make absolutely sure you've air sealed this area really well, so moisture can't migrate into this area. If you subscribe to JLC, look up the article I linked for someone else. It has good details regarding how to air seal homes with kneewalls and goes into some detail about dealing with balloon-framed structures.

As far as your HVAC equipment, if you are burning gas or oil in there you'll need to install dedicated ventilation into that area for makeup air before you insulate. Check with your local AHJ to see what's required in your area.

Finally, Tyvek isn't the same thing as a vapor barrier. Water vapor will pass right through it. If you're interested in preventing moisture from migrating into cellulose filled walls, you may be chasing your tail. Dense-packed cellulose forms a pretty effective air barrier. It is extremely popular out here on Puget Sound, especially for retrofits of older homes. And, even with our 'Seattle sunshine' pouring down from the sky about 6 months of the year it seems to remain dry without causing problems. Of course, air conditioning is about as scarce as hen teeth here, so I can't speak for how it reacts to SC humidity during the cooling season. You might wan't to talk to a couple of local insulation contractors about that aspect of it and install a proper poly barrier if necessary. Also recommend you check out the link I posted for someone else to Joe Lstiburek's site, and review the building details they have there for hot/humid climates.

ONE TEAM - ONE FIGHT!!!

Mike O'Handley
[email protected]

[Guest]

Re: insulation w/ no vents

Mike,

Would appreciate a clarification of your recommendation to insulate both the kneewalls and the sloped ceiling on a cape and airseal the area (I assume you mean the area behind the kneewall)to prevent moisture migration into it. In Paul Bourke's JLC article on Practical Details for Energy Efficiency (Feb.2001; link below) in the section "locating the thermal envelope", he illustrates the preferred method as being when "the rafter insulation is brought all the way down to the wall plates". With an air barrier on the inside of the rafters the thermal envelope encloses the entire area behind the kneewall, so insulating and sealing the kneewall becomes unnecessary. I've read about this in several sources so am confused by your recommendation, and just want to make sure I've not missed something.

Is there another article you were referring to in JLC that offers a different approach to Paul's article?

Thanks, Dave


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