Air Barrier vs. Insulation

I tried to ask this question at GBA but couldn't get past the secret log-in code :)

Martin said:

[quote]Allan,
Q. "Is cellulose as good an air barrier as open or closed cell foam?"

A. No. So seal your ceiling before you insulate![/quote]


So I assume drywall is an air barrier for a 2nd floor ceiling that has an attic above it. Are you saying loose insulation above the drywall (cellulose or fiberglass) is not air barrier. If spray foam was used instead of cellulose, does it qualify as an air barrier.

What is the relationship between air barriers and insulation, as well as their individual importance.

Not GBA Allan but I am working on this a lot here in NOLA and just did some bits in Providence at JLC.

Open and closed cell spray foam meet air barrier requirements when in an assembly, roof, wall floor.

The [url=http://www.airbarrier.org/index_e.php]air barrier association of america[/url] has the details and guidelines.

Loose fill, FG and cellulose as well as the other boutique insulation's, do not meet the standards presented by ABAA.

So in a ceiling where the drywall is used as an air barrier, sealed, the loose fill in contact is "approved" as insulation.

Loose fill without an air barrier is a filter. Spray and rigid foam in a cavity forms its own air barrier.

'Zat help?

So, you could have insulation that provided R-60 but is a poor air barrier, or insulation that is a great air barrier but low R value. Of course you want both, but which is more important in terms of energy use and comfort.

Allan, I believe that depends on the climate. Here in the hot/humid I would say an air barrier since the hot moist air invading the building when it meets a condensing surface will develop bulk water which will promote mold and mildew as well as decay.

Having said that you really can't separate them when it comes to energy use and comfort.
See the [url=http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Thermal_Bypass_Inspection_Checklist.pdf]thermal bypass checklist.[/url] and the [url=http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/TBC_Guide_062507.pdf]commentary.[/url]

Seems as though for an approach to energy effeciency at a truly affordable level concentrating on the air barrier is a more practical and realistic aproach than designing these high r assemblied that have so much potential for failure and therefore require throwing a bunch of money, materials and skilled labor making these assemblies out of reach for most folks. Don't get me wrong these intricate high-r assemblies are novel and I guess it's got to start somewhere but before folks start calling them "green" they have to be affordable to the masses and not requrie architects, extremely skilled builders, and wealthy owners to make a difference...currently it's not even close.

Allan,
I'm not an expert in this field, but it's all fresh in my brain from 4 days at the JCL show. Insulation and air barriers work together to keep a building energy efficient, each having a separate job working toward the same goal of energy efficiency. Then energy in our conditioned air moves through convection, conduction and radiation. The insulation keeps the energy in the air from moving through conduction, and the air barrier keeps the energy from moving with the air through convection. Some insulations, like spray foams, act as both air barriers and conductive barriers, others, like loose cellulose or fiberglass, act only as convective barriers, but don't perform at an acceptable level to not require an additional air barrier.

-Steve

The best information I can find on this is the EPA's Energy Star Guidebooks. The EPA has been way ahead of all this for quite some time:

[url]http://www.energystar.gov/index.cfm?c=bldrs_lenders_raters.nh_v3_training_req#che[/url]

I wish I could find the older Version 2.0 Guidebook, although they are rolling out new version of Energy Star, the old Guidebook was much better in detail. ThingofBeauty, you knew about these in one post a while back, do you know the link to the 2.0 book? I just have the downloads which we printed.

I'm actually surprised at the questions on this Thread, I would really recommend reading these books. They helped me tremendously and the thing is, you all currently need to know some of this this stuff under IECC 2009 and even more so under 2012.

I used to do ABAA inspections, it was all commercial. That's some really rigorous stuff, I hope they are not migrating towards residential homes, last I know they had a bubble sucker we'd put on brick ties and suck it down to -75pa and most of them would fail. Pretty hardcore. I hope to get back involved with ABAA if I could ever find the time and now that more commercial is going up.

The short answer Allan is that no, open blown cellulose is not an air barrier according to the EPS's standard. Is dense pack cellulose an air barrier? No, not according to the standard, but it would appear to do a damn fine job in my opinion.

According to the EPS Energy Star Standard:

6. For purposes of this checklist, an air barrier is defined as any durable solid material that blocks air flow between conditioned space and unconditioned space, including necessary sealing to block excessive air flow at edges and seams and adequate support to resist positive and negative pressures without displacement or damage. EPA recommends, but does not require, rigid air barriers. Open-cell or closed-cell foam shall have a finished thickness ≥ 5.5” or 1.5”, respectively, to qualify as an air barrier unless the manufacturer indicates otherwise. If flexible air barriers such as house wrap are used, they shall be fully sealed at all seams and edges and supported using fasteners with caps or heads ≥ 1” diameter unless otherwise indicated by the manufacturer. Flexible air barriers shall not be made of kraft paper, paper-based products, or other materials that are easily torn. If polyethylene is used, its thickness shall be ≥ 6 mil.

Get to know this stuff, IECC 2012 is aligning it's checklist with this language, so I hear, we will know for sure in 13 days.

Any of you vets with this stuff catch the "EPA recommends, but does not require, rigid air barriers."

WTF?

They are willing to allow stuff like Tyvek as an air barrier, or (gasp) even plastic wrap.

David, you took the course and everything, is this new? Wasn't only solid materials permitted under the most recent Version 2.0? Where did this come from? There was no mention of nonrigid air barriers permitted in the old guidebook. I am shocked.

[QUOTE=Ted S.;595527] ThingofBeauty, you knew about these in one post a while back, do you know the link to the 2.0 book?[/QUOTE]

Bill R beat me to it, in post #4:
"See the thermal bypass checklist. and the commentary. " Click on his "commentary" link, it goes to the V. 2.1 TBC Guide.

Yes, thanks that's the good one. But I don't see "EPA recommends, but does not require, rigid air barriers" in that version, only the new version. Up until now it has always been a hard material (or so I thought).

To go back to the question in #3, yes, Allan, you could have boatloads of loose fill and a crappy air barrier, and get into lots of trouble. We've run into that in attic insulation jobs. If we insulate the attic floor without doing a good air sealing job, all the moisture is still getting through, but less of the heat, so the roof sheathing turns into a condensing surface. Bad scene.

As to which is "more important" - tough call. I guess I'd say insulation without air barrier can cause the building to fail, air barrier without insulation means you're pissing away energy but won't screw up the building in the same way.

Dan

I am not talking about sealing cracks and penetrations, I am talking about a solid air barrier like you have on walls. Why don't you need the same in an attic?

Allan, even at the walls there are gaps and cracks unless there is a product in Texas that covers the whole building like a, well like a , well--- a balloon.
Take a look at the abaa specs and you will see it goes from parts and pieces to entire assemblies comprising an envelope.

Capice?

It's either an air barrier or not. A lot easier to establish in new construction than in reno, so if it's not there you need to pull out the foam guns and caulk. But there's no functional difference - drywall and plaster are good air barriers, it's just the cracks, penetrations and seams you need to worry about.

You would certainly need one in the attic - more so than in the walls, I'd argue.

Allan, "air barrier" is applied in a couple of different ways, and they aren't consistent.

In a wall, the insulation is usually enclosed and in contact with an air barrier on all six sides. It's fairly easy to detail walls so that the insulation is exposed to a minimum of wind-washing.

In a crawl space or attic, the insulation is almost always completely exposed to wind-washing on one side. The kraft face is typically against the drywall or the underside of the floor. It does seem to me like both situations could be improved by covering the insulation on the open side. As far as I can tell, this is not usually done because (a) it's hard work, and (b) no one cares that much. I have seen some crawls where Tyvek or another sheet material was installed under the joists, but there are usually a lot of obstructions. If you are building on slab you are avoiding this issue nicely. I know that my crawl is drafty be design, and when the wind's blowing through there I'm sure it degrades the insulation performance, probably by a lot.

I heard this from someone who would know.
ENERGY STAR (and programs that require ES, like LEED for Homes or NGBS) require all vertical insulation to be installed in contact with an air barrier on six sides, because fibrous insulation (ie not spray foam insulation) loses a lot of its insulating value in a vertical install, unless enclosed on the back side, like Mr. Meiland mentioned.
Attic insulation loses some value, not being enclosed by an air barrier on the top, but there is less convection compared to vertical, and more insulation, and "for now [ENERGY STAR] is not addressing that because it would be a pretty big change".
You can read the articles about how blown fiberglass does permit convective loops to form, especially at very high delta T situations. Cellulose is more dense and less succeptible, but overall it's not a huge effect supposedly.

Why not plywood the attic floor (2nd floor ceiling) and spray foam the underside of it.

It is possible Allan however for the cost it makes more sense to design an air barrier at the drywall or plaster line.

Spray foam should be used at the rafters if at all.

[QUOTE=Allan Edwards;595636]Why not plywood the attic floor (2nd floor ceiling) and spray foam the underside of it.[/QUOTE]

If you're building a vented attic, I absolutely WOULD do exactly that. In your price range, it makes perfect sense.

[QUOTE=dgbldr;595647]If you're building a vented attic, I absolutely WOULD do exactly that. In your price range, it makes perfect sense.[/QUOTE]

My only problem with that is here we put a lot of insulation in the ceiling / attic. You could not simply ply over the attic floor b/c that would loose insulation space. Unless you are saying add the ply and then continue insulating over that?

Allan,
Considering the amount of time you spend at GBA and here at JLC, I'm surprised you would even ask the question. Really, now, Allan -- why would you even consider building a ceiling without an air barrier? Once you understand the basics of air leakage, why would you ignore the issue?

Every part of your thermal envelope needs an air barrier. Skipping the air barrier makes no sense -- assuming you are a builder who wants to avoid callbacks.

Your question -- "what's more important, an air barrier or insulation?" -- is kind of like the question, "What's more important, a foundation or a roof?" It reminds me of the old game kids play in the 3rd grade: "What's worse, getting your foot cut off with an ax or being boiled alive in a big pot?"

[QUOTE=Allan Edwards;595636]Why not plywood the attic floor (2nd floor ceiling) and spray foam the underside of it.[/QUOTE]

Allan,
I think you are trying to combine your Insulation and Air Barrier all with the same product (Sprayfoam)
Why not Create an Air Barrier by other means as Bill R suggested
You could detail the ceiling with Airtight Drywall Approach.....or....

I will offer you another "suggestion"
Since You are already using ZIP system for your Wall sheathing.

Why not "ZIP system" the attic floor (above the ceiling Joists)?
Use ZIP tape to "connect" the wall sheathing to the attic floor deck.

You would also need a gasket to "connect" the wall sheathing to the bottom plate
and a gasket to connect the bottom plate to the Slab.

Assuming that you "connect" all the windows & doors to the Wall Sheathing....
You should have a pretty airtight "package"

You could then build a vented attic above "the deck" and pile on the not-so-expensive Cellulose.

Edit to say
I think plywood would a better choice for sheathing

If you look at these weatherization programs, they have really done a good job understanding the air barrier, ventilation, and insulation.

The standards first require air sealing be performed which is blower door assisted. The CFM reduction is monitored but also they tap across the attic plane and measure the connection of the attic space to the house, they keep air sealing until the have made a good air barrier at the attic.

Once they are successful with the air barrier, they bring the attic ventilation up to code. This is also very well thought out with the calculations and such.

Once the attic ventilation is corrected and the air barrier has been established, only the do they increase the thermal insulation. All machines are checked for air pressure/calibration, etc.

It's quite impressive seeing the whole operation working as it does. It's a far cry from "blow and go" from years ago.

The best part is before you can do any of the work, you have to be trained. All these weatherization techs have been through the basic building science coursework.

Like I said, I am surprised at some of the questions on this thread, the basic necessity of an air barrier at the attic ceiling can't be over emphasized. As noted above, the lack of the air barrier could lead to considerable condensation issues within the attic.

The best part about doing down and dirty weatherization is that you can see how effective knowledge can be. You don't need $10k in CCSPF, just a little bit of training, some basic materials, canned foam, and blown cellulose and you can do some great work.

[QUOTE=ThingOfBeauty;595613]I heard this from someone who would know.[/QUOTE]

I'm sorry I lead the thread on a tangent with this. If you look through the new Guidebook that I posted a link too you will see some stark differences between the older (and better IMO) Guidebook that Bill posted.

Every time I call the RESNET folks or my Provider I get conflicting information. We are becoming a Provider this year so hopefully that will take some irons out of the fire. But anyways, these resources are invaluable in my mind, and what is more important is that in some regard they lead code changes.

IECC 2012 is due out in 12 days and supposedly these insulation and air barrier checklists are modeled after the Energy Star Thermal Barrier Checklist (or possibly the newer Thermal Enclosure Checklist) and the Guidebooks go into great detail the items of the Checklists. So it's like looking into an hourglass of what is to come.

John B and others:

What I am asking is what are the various methods and materials used to create an air barrier from a 2nd floor to a non-conditioned, vented attic. Something that is reasonably easy, affordable, and works on large houses with varying plate heights, groin ceilings, semi-vaulted ceings. Don't think of a 30' x 80' rectangular building, that's easy. Think of a 10,000 sq ft home with all kind of offsets, raises, bumps, vaults, 2 story ceilings, etc.

Seems like you might want to figure out your ventilation strategy first - that may drive some of the other decisions.

[QUOTE=Dancing Dan;595743]Seems like you might want to figure out your ventilation strategy first - that may drive some of the other decisions.[/QUOTE]

What would be your ventilation strategy.

That would be telling. I dunno, Allan - if it's all cut up it might be easier to not ventilate, to go for a hot roof and treat all that space as condition. Are you thinking generically or do you have a specific house in mind? Post a roof framing plan if you have one.

All the details are in those Guidebooks, Allan.

The knee walls, partition tops, penetrations, etc. are all the same details whether it a 20x40 single story ranch or 10,000 square foot home. You just have to find the right sub, Ontility should be able to refer you to someone. Knowledge is power with this stuff, or you can pay for SPF.

It the end of the day it comes down to 2 things:

Air leakage
R value

How you get there is your own choice, pay the $$$ or learn the lower cost techniques.

SPF is over-rated and knowledge is under-rated in my opinion.

I have been teaching this insulation air barrier stuff for a few months now, something I never thought I would.

Never-the-less it is the "next thing."

As we understand more about how thermal, air and moisture barriers work there will be many changes in the way we build.

Historically as we moved from living in structures with fire pits to computer-designed hvac systems we neglected the other parts of the structure.

Eureka! House as a System!

I am still working on how to best convey this concept.

Remember when we began to regularly put insulation in buildings and discovered there needed to be a moisture barrier on the inside?
Then everyone did it, an didn't didn't work in all climates.

Now we know that insulation needs an air barrier to work.

We have heard for years that fg insulation needs to be in contact with a solid surface on all six sides in a wall to be effective and now we are wondering how that works in a horizontal application, floors and ceilings.

The federally-funded weatherization initiate which benefitted from a huge infusion is leading the way.

These folks have been at it for nearly 40 years and now with enough money and some great [url=http://waptac.org/WAP-Training-Centers/WAP-Network-Verified.aspx]training centers[/url] the word is getting out.

FYI, I do this training at the [url=http://www.lacapinc.org/]Louisiana Training Center.[/url]

So check [url=http://www.waptac.org/]it out.[/url]

I predict this will slowly be integrated into the regular building practice and since builders are slow to change I will always have a job.

Thanks for the opp.

[QUOTE=Bill Robinson;595749]Builders are slow to change I will always have a job.

Thanks for the opp.[/QUOTE]

Yes you will always have a job. Builders are motivated by getting to the closing table and walking away with a check that hopefully pays off their loans and leaves a small single digit profit. It is hard to worry about saving the planet when you are worried about making next months interest payment.

[QUOTE=Ted S.;595747]
SPF is over-rated and knowledge is under-rated in my opinion.[/QUOTE]

Well put, Ted.

[QUOTE=Allan Edwards;595750]Yes you will always have a job. Builders are motivated by getting to the closing table and walking away with a check that hopefully pays off their loans and leaves a small single digit profit. It is hard to worry about saving the planet when you are worried about making next moths interest payment.[/QUOTE]



Now you have done it, watch where this thread goes now.

Spoken like a true-dat builder Allan.

Maybe construction is the last place a boy can continue recess.

No classroom, no studying and the rules are loosely enforced.

It is play time.

My contractor mentor is cousin Jerry, he has passed but will be forever be remembered for saying "I want I doin' it, I not want to I not doin' it.
A true contractor if I ever saw one.

Jerry never wore a seat belt and died of cancer smoking until the last day he could draw breath.

Is it about saving the planet or something closer to home?

IMO, no matter what we do the planet will survive, maybe not the way we know it but it will survive.

It seems this all began in earnest in 1973 when OPEC decided to limit oil exports with the intent of punishing us for getting involved in mid east political affairs.

From that our response was the DOE, energy codes, and much of what we see now intended to reduce energy consumption.
And a lot of political stuff.

I do not believe the initial intent was to save the planet, just to keep control of our dependance on foreign energy/oil.
If you look at the data we have not done a very good job.

I apologize for taking the bait.

Thanks Bill Robinson,
I like the link you posted for the Louisianna Training Center
thanks

[QUOTE=Allan Edwards;595734]
What I am asking is what are the various methods and materials used to create an air barrier from a 2nd floor to a non-conditioned, vented attic. Something that is reasonably easy, affordable, and works on large houses with varying plate heights, groin ceilings, semi-vaulted ceings. Don't think of a 30' x 80' rectangular building, that's easy. Think of a 10,000 sq ft home with all kind of offsets, raises, bumps, vaults, 2 story ceilings, etc.[/QUOTE]

Just as insulation, vapor retarders, and air barriers have to be designed to work together as a system, the architectural process will have to include that design. Designing a structure that can't easily be constructed isn't much different from designing one that can't easily be insulated, be airtight, and be protected from moisture damage over time.

[QUOTE=Bill Robinson;595749]We have heard for years that fg insulation needs to be in contact with a solid surface on all six sides in a wall to be effective and now we are wondering how that works in a horizontal application, floors and ceilings.[/QUOTE]

The word I got from the top of the food chain is they they most absolutely would like to see both the attic and framed floor assemblies also have the 6 sided air barrier and that their reasoning not to do it is because it is almost prohibitive to do in mainstream construction, the target of many of these programs.

It's nice to know that even our leaders can be reasonable (RRP excluded).

Dick, surely you're not suggesting that we control the owner's desire to have some bling?

Pull-up covers over fg have been long proven to[url=http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/92/920510.html] counter[/url] the effects of convective currents.

I've been using sprayed cellulose in attics since '89, which avoids the problem altogether.

[QUOTE=David Meiland;595769]Dick, surely you're not suggesting that we control the owner's desire to have some bling?[/QUOTE]

Have you hugged [i]your[/i] Fonthill Abbey today?