What’s the latest on insulating balloon framing
Eldan
| Posted in Energy, Heating & Insulation on
I have a 1920 balloon framed cape, Northern NJ, no insulation in the walls, ratty 40 year-old fiberglass batts falling down from the rafters. Gable vents.
I had originially considered removing some drywall and spray foaming the underside of the roof but I now think it will be too disruptive and expensive so I’m considering cellulose for the entire house instead.
I’ve read some things here and there about insulating balloon framed walls resulting in moisture problems, but the approved practices seem to be constantly in flux. What’s recommended today for retrofit insulation of balloon framing?
Replies
One thing about balloon framing is that you can end up filling the upper floor with cellulose if you don't watch it. Not that this is particularly harmful, but it's a bit of a waste of cells.
(OTOH, my parents had the upper floor of their old farmhouse blown full of cells -- really cut down on sound transmission a lot.)
Do you have
an attic, or is this all cathedral ceilings? Either way, insulating the roof/ceiling/attic is the most bang for the buck, but there are differences depending on what kind of construction you have. If it's attic.... blow in 16" or more of cellulose after air-sealing the floor. If it's cathedral, and you want a vented roof (IMO you DO want a vented roof) then you need to install baffles before blowing, so the ceiling will have to be removed.
Guys that run blow rigs know how to get cellulose into the walls correctly. Get some referrals and have one or two of the good companies come out and talk to you.
Re moisture, the status quo seems to be that walls with no WRB are blown with cellulose, and if it causes a moisture problem, that's the price of trying. If there is water getting into a wall area, and that area is now uninsulated, it may survive quite a long time. Once you insulate it, you change everything. Basically, in uninsulated buildings, a lot of energy moves thru the building shell, and moves moisture with it. Adding insulation slows the movement of energy and moisture.
If you really want to go all the way, you re-side the building and install a WRB (and possibly exterior insulation) at the same time. Obviously this takes many years to recoup.
Thanks for the replies
To answer your questions, it's a cape, so there's an atticy part above the horizontal ceiling, a sloped ceiling part against the rafters, and knee walls with some built-ins. Behind the knee walls is unfinished, plank floored, batts barely hanging to the rafters. There is no scuttle so the condition of insulation above the ceiling is unknown. There may be some fill up there, or there may be nothing. Continuing batts to the peak doesn't make sense due to the gable vents.
I would like to keep the areas behind the knee walls accessible, so yes, vent channels and cellulose held against the roof. I figure the vent channels have to continue up through the sloped part (I sincerely hope this can be accomplished without removing drywall -- do they make 8' long sections of vent channel?), and then another 12-18" into the peak to get above the fill.
Does this sound feasible? I'd love to reside and add XPS but I gotta keep this project affordable.
The most common
approach is going to be: insulate the floor of the side attic spaces from below, insulate the kneewalls from behind, and insulate the ceiling by removing enough drywall to baffle and blow correctly. Your side attics will be outside the conditioned space. You need to create a good air barrier as well as insulating them.
If you insulate the rafters, you don't get the R value you probably want, because the rafter bays aren't that deep, especially compared to piling a bunch of cellulose on top of the ceiling. And, FG batts aren't as good as blown cellulose.
You probably can't do this right without demo'ing some drywall. I suppose you could try to insert baffles up between the rafters from inside the kneewall space, and then blow the lid thru small holes in the drywall, but I would probably either take down some drywall OR create a scuttle in the ceiling so you can simply get inside the attic. If you do that, the scuttle needs an insulated cover installed over it.
Don't be afraid of a little drywall demo, it's easy to fix and you can do a much better insulation job if you do.
Yes
I figured I would cut in a scuttle, probably temporary as there's not much height up there. What I hoped to avoid is removing all the sloped drywall. To be clear my plan was to remove all the batts and insulate the rafters from the soffit up past the sloped ceiling, then using fill above the horizontal ceiling, leaving the space at the peak unconditioned.
It's a shame to lose the conditioned space behind the kneewalls. What about adding some strapping across the rafters to get more thickness, or adding foil faced iso?
If you want
to stick with insulating the roof, that will work, but I don't see how you can avoid removing the angled lids unless they are small areas and you can baffle from above or below. If you are only going to have the rafter bay depth to work with then it's worth considering rigid board between the rafters in those angled areas, and more rigid board in the kneewall roof areas.
The problem with story-and-a-half/"cape" construction is that there's really no ideal way to insulate/ventilate after the fact, at least not without major drywall removal. This is independent of the balloon framing issue. Probably the best approach is to go with a "hot roof" and bring the kneewall area into the "envelope", but that's especially difficult to do well in an existing structure. Otherwise you have to kind of invent things as you go along, since every case is a little different in critical details.
Especially difficult is simultaneously achieving adequate ventilation and insulation in the slope wall area. The one thing you have going for you is that getting all of this perfect is not really necessary in the NJ climate -- the ventilation issues of condensation and ice damming aren't nearly as significant as they would be in a colder climate, and perfect insulation isn't as important as it would be in a less moderate climate.
What the other guy said about the floor between walls is right. You have to consider what will happen when you fill the walls at the open floor juncture. Ditto if it is a crawl ... but that's 'easy' to go into and plug each bay. I had a hole into a basement area ... couldn't figure out why the stud bay took so long to fill ... then I did a Homer ... DOH!!! found my furnace room w/ a large pile of cellulose in it ... had to pack it out of there! Funny really ... Hey w/out stuff like that, life is boring eh?
If you can't get baffles for the sloped ceiling, you could make them (but don't ask me how). I imagine you might by raw cardboard and simply cut, bend, and shape to fit. You should put in a skuttle access to the upper attic.
The corrugated plastic political lawn signs work well for making baffles. Put off the project another couple of months and you'll have access to all you need.
Forget the kneewalls! Insulate the roof, not the walls!
Hi Eldan,
I think you may be confused about balloon framing because your post didn't ask a question related to balloon framing.
Someone above mentioned the "common" way to treat a cape was to insulate the knewalls and floors. Perhaps this is also why they are commonly referred to as "the leakiest type of house you could ever build." With a split level a close second.
I would like to whole-heartedly and categorically disagree with the idea that you would insulate the kneewalls and floor. This is the fundamental building performance issue with capes! This violates all rules of Building Science. This is Building Science 101. Fred Lugano wrote a great article about this for FHB in the 90's. It is available with the search function.
Insulate the roof, not the walls as you were originally thinking. And you can leave every shred of the original plaster intact!
I insulated two capes in Northern NJ for firends/family. One was in Midland Park, the other was in Cresskill. I used densepacked cellulose because thats the business I had. I used spray foam kits as described below.
I will say that you are in a very bad area to try to improve your building performance. Northern NJ is where Building Perofmance goes to die!
You will easily be able to find a spray foam contractor, but cellulose will be a different story. The Midland Park house I did was for a plumbing contractor. He had an endless stream of contractor friends showing up to see the work progress because they had never seen or heard of cellulose. It was not available at any local suppliers, and my cellulose manufacturer didn't even ship cellulose into northern NJ. I trucked everything from Rochester, NY.
Anyways, If you have the budget (and the contractor) for spray foam. You can do the whole job with foam. But you will need the upper attic to be big enough for a person to crawl in. Even if it's tight, they can still get the roof and walls from inside that space. The foam can be sprayed several feet down the sloped ceiling. Most are only 3 to 5 feet of sloped ceiling anyways. They can spray a little from the top and a little from the bottom.
If you cannot stuff a very skinny person into the upper attic to spray foam then you will need to use cellulose. You first densepack the sloped portion from the attic side of the kneewalls. Chunks of fiberglass get stuffed into the rafter bay to hold the cellulose in. While that is being done, extra cellulose is blown into the triangle attic above your flat ceiling. It can even be filled solid if it's a small space.
After that you spray foam the roof rafters from the side attic, and the gable end walls. This was common practice when partnering with a spray foam contractor back here.
If no foam contractor is available, or no budget for it. You can cover the underside of the rafters with foam board and cap nail. Then densepack the rafter cavities as well. In Midland Park I had to "wrap & strap" because the AC unit was in the attic. "Wrap & strap" means you cover the underside of the rafters with housewrap (an air barrier). Then nail furring strips horizontally 16" O.C. Then densepack the cavity. I used a foam kit to spray the gable end walls.
I had to wrap & strap because there was not enough room to manuver foamboard inside the side attics.
The Midland Park house cut their gas bill by over half. They don't even turn the heat to "on" until November. They were absolutely stunned. The next summer I did his mother-in-laws cape in Cresskill. She didn't care about her utility bills at all, she wanted the water to stop running in from the ice buildup. She had her thrid roofer on the job while I was doing the first house.
I could have done 6 or 8 more capes there if I had the time. I have since sold the business, but still go visit with them. They still try to get me to insulate their homes.
You will be very happy with either approach to your cape. Just keep all the work at the roof.
-Rob
P.S. - Don't get too worked up about the resultant R-values either. They are fine for your area, and your house will be magnitudes better for the work.
Thanks again to every one for their responses and ideas, but especially you Robert for your detailed post.
I am confused, not about balloon framing, but about why I would find various "advice" on the internet not to attempt insulating balloon framed walls. I don't understand the extra concern over a similar platform framed wall because it wasn't explained.
Your ideas for handling the roof and attics are similar to mine. I had originally considered closed cell foam and going to a ventless roof, an option recently added to the code, and doing only the roof and exposed gable walls at first, leaving the rest of the walls empty. But now I think staying vented and doing the whole envelope in cellulose will cost less and achieve more. By the way finding a closed cell foam contractor in Northern NJ is not easy.
Looks like they do make that vent channel stuff in 6-ft lengths.
The main concern about blowing insulation into a balloon framed structure is that the stud bays are not (necessarily) closed at the bottom, top, and where floors intersect. Thus the insulation is not well-contained. Beyond that there's the minor problem that you can have a pretty tall column of insulation, and the weight of that could result in "creeping" compaction and some resulting voids at the top. (However, this is probably more a theoretical problem than a practical one.)
More Info
The reason you find "various" advice on the internet is because anyone with a computer has a voice, regardless of their skills, education, or beliefs. So it is up to the reader to filter out the various information available. In 1996 I built my first unvented, exterior insulated foam roof with DP cellulose under the foam. Nearly everyone on this forum said it was a bad idea, etc. Except for a few people that actually knew what they we talking about . They had facts, numbers, experience, and most importantly logic.
The post I wrote to you could be a carbon copy of many I wrote on this site in the '90s and had dozens of flamers waiting to pounce on it. They've apparently all smartended up or passed on because these topics are commonplace now. I eventually moved on, tired of arguing with the mob. But the fact is that the "mob mentality" and "conventional wisdom" are the reason many new homes are still built that perform worse than those 2 capes I did in NJ.
I've since built dozens of roofs like that, and made even more greivous violations of "conventional wisdom." All without a single failure or callback.
Regarding Balloon framing. We densepacked many many many balloon framed walls. The biggest "risk" with these walls is that insulation may go somewhere that you don't want it to go. Big deal. Keep your eyes and ears open, and let the house tell you it's story before you start. The beauty of densepacked cellulose is that it will go everywhere it can, and eventually pack and fill its way back out.
We only had 2 issues with balloon framing. 1) We blew a ton into a bathroom from under the toe kick space on the vanity. A shop vac and some gun foam fixed that. 2) We filled a heat supply duct in a wall. To fix, we unhooked the duct in the basement, stuffed fiberglass in the duct to keep the cellulose in, and vacuumed the trunk out. In this case it was more important to insulate the house than get heat to the room. The room was comfy as could be after that.
And lastly, don't spend a penny on venting your roof. I never did on ANY of our retrofits. On new construction we would put in just enough to make the code inspector happy. We had our builders educated on densepack cellulose as well. It became Standard Operating Procedure for all cathedral roofs. Even some of the toughest jurisdictions in our area were letting us do it. You will get no benefit from it, and are actually consciously and with much difficulty taking R-value out of the roof assembly to keep your roof a few degrees cooler.
Or better said, your spending money and effort to make your gas bill higher forever.
-Rob
Another thought on insulating the sloped ceiling area ... which I did in my own 1895 house I renovated. That is to install 1-2 inches of foam board on the slope and drywall over that (screwing through the foam into the framing). You save tearing out stuff ... the finishing is the same. Plus you're dealing less w/ the space restriction of the rafter dimension.
I thought of this
If I had to remove all sloped drywall I'd consider it, but the ceilings are already so low...
And I thought I was long winded. Wow. I'm a little confused, though ...
" I used densepacked cellulose because thats the business I had. I used spray foam kits as described below."
you switch between mentioning cellulose and foam so much, I'm not sure which you are using ... although you seem to lean toward cellulose.
You also don't say anything about the venting issue. I GUESS you are advocating no roof/attic venting. I think w/out venting you need to ensure your exhaust fan systems are working well (and I don't just mean fans spinning around, but actually moving air out when you need it). I think the venting was part of the original OP's issue/question.
I do have a question ... can you use (not sure of the correct term here) ... wet applied cellulose in open attic rafters by using the standard installed netting and then blowing it? Or doesn't that give it enough support? Could you install lath horizontally say every foot to provide support and get away w/ it?
Hi Clewless,
I lean towards whatever technique will work well, and within budget.
In the NJ case. There was no budget for foam. Foamboard was not available. I had cellulose and spray foam kits as two great tools in my tool box. So thats waht we used.
In retrofits cellulose is pretty much the only option that works. Blowing firberglass into a wall or roof is a waste on many fronts. I do feel the need to be a bit "evangelical" about cellulose at times because it is such an absolutely fabulous material that gets pushed to the side by sexier products with better marketing. It's also got the lowest embodied energy of any insulation product, it's 85% recycled, it addresses all 3 modes of heat loss very well, and it's cheap. There's a lot to love there.
On venting. Keep in mind that the air in the vent channels and the air inside your home should have no relationship whatsoever. Removing pollution and moisture is a must no matter how the home is built. Wet basements are also a big concern for interior moisture. If your attic was helping to remove moisture and pollutants from your home you were in avery bad place (and paying dearly for it.)
I am indifferent on the roof venting issue, but I do not want to jeapordize performance sow e can have venting. In Eldan's case he only has a 2x4 or 2x6 roof rafter. You are eliminating 30% to 50% of the insulation to keep the roof a few degrees cooler. Big deal.
I've actually fixed many attics by "unventing" them. Because the venting was so severely increasing the air leakage rate of the house. Picture that I eliminated roof venting and the condensation and ice damming stopped.
My own house has rigid foam, cellulose, and spray foam with vented and unvented roofs. The key thing to remember is that "roof venting" is a pretty weak tool to try and fix a problem. In general if you are retrofitting roof venting into an existing problem roof you've lost your way in the building performance world.
As far as spraying cellulose in roofs. We did wall spray cellulose in several hundred homes in new construction. The "regular" wall spray cellulose cannot be installed overhead because it is actually stacking on the layers of material underneath it. It is possible to mix glue in with the spray to work overhead but that gets quite a bit more difficult and expensive. At that point spray foam is a better option.
-Rob
I guess we have a new authority.
Lower R values, no roof venting.
You're right, the internet is a place where anyone can be an expert.
My rafters are 2x8, 24" o.c. The actual rafter depth is about 7 5/8". I think I have room for the vent channels and still achieve an adequate R-value with stabilized cellulose in the sloped part. I don't want to place these nice 90-year old rafters at risk.
Agreed
You must have a bigger cape. Even with DP cellulose you will have R-21 in the remaining cavity. This will work fine. I am a big fan of more R-value. But in a retrofit you really have to look at cost/benefit. Right now your roof insulation basically does nothing. You would only save a few dollars a year removing plaster to upgrade R-value in the slopes.
Good luck with the project.
-Rob
"In the attic areas in the
"In the attic areas in the case in point, you are likely still leaking air into the attic space, but what happens next?"
If the OP does as he is planning there will be no more air leakage into the upper attic. The side attics become "indoors" and will share air exchange with the rest of the house. Right now the air leakage is unlimited. After the retrofit air leakage into the attic should be almost nil.
In 1942 Ralph Britton did research for HUD and eventually generated the 1/150 and 1/300 roof venting recommendations. He said if the ceiling plane could be made airtight the ventilation reduirement could be reduced by a factor of 10. So now you are talkin 1/1500 or 1/3000.
When the weatherization work is done there should be almost no air leakage into the attic. We verified by blower door and Infra Red camera. The airtightness is the main reason we were doing work in the first place.
Point source exhaust and indoor moisture sources are addressed before the work begins. We retrofitted many Panasonic bath fans into houses, or added ducts, or rangehoods.
-Rob
I guess the problem I had was that until now, you never mentioned anything about your project doing anything w/ mech ventilation ... your emphasis was only on insulation. You also really didn't mention your intended emphasis on increasing air tightness. You also mentioned nothing about compensating for air tightness with mechanical [controlled] ventilation.
While I understand your enthusiasm for cellulose and insulation, you should have, IMO, coupled it with comments about your goal for increased tightness and your work on mechanical ventilation to provide for and control ventilation. Otherwise the OP may esily get the notion that taking your advice about insulation is all he needs to think about.
The coupling of insulation, air tightness, and controlled ventilation is still new enough that we shouldn't discuss one w/out mentioning the other.
If you assumed you inherently implied the other two when discussing the insulation strategy is a stretch IMO. People frequently focus on the insulation component w/out thinking of the other issues involved. While they shouldn't, they do and we have to support each other by repeating the whole strategy, not just pieces of it.
I guess you're correct Clewless. Apparently no one else posting above wanted to increase airtightness. 8-)