I hear people talk about wraping a framed house with 1″ foam sheets for better insulation and to create a completely insulated break between the exterior and interior. It seems like a great idea but im having a hard time understanding how to apply the siding . Do you use furring strips over the foam? Extra long nails that go through the foam into the framing?(that doesnt seem like a great idea) Please help me understand the process. Thanks alot
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Replies
extra long nails...
where do you live???
matters about yur climate whether the 1" goes to the inside or out...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Jpeaton,
I wish someone would post an answer to your question.
assuming the insulation outside
I think it is an important question.
Edited 9/8/2007 12:34 pm by homedesign
FH Small Homes That Live Large (spring 07) Architect Dennis Parker writes "We used 2x4 framing and wrapped the house with 1" thick ridgid foam insulation. Computer modeling shows that exterior foam makes a better insulated wall (than conventional 2x6 construction)" Dan, do you understand how he applied the hardiboard siding over the foam? I feel like a dope not being able to envision it but i cant seem to let it go. Thanks
I'm sure there are several ways to do it. How many RIGHT ways there are to do it I can't say.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
In most areas, if you have an "adequately insulated" home to begin with (eg, 3" of fiberglass), an inch of foam won't make nearly as much difference as will a really good housewrap job.
Dan, The more I read..the more I think that insulation beyond the stud cavity is a good idea for many/most climate conditions. I think it will become standard in the wall of the future. It (the concept) is gaining momentum today.
Keeping the structure inside the thermal layer reduces the potential for condensation. R-value added on the outside of the structure provides a greater increase in overall wall r-value than adding the same r-value between the studs.
I believe in the concept..I just do not think the construction industry has come up with the best answers yet on how to deal with it. A similar problem/opportunity is developing due to the introduction of rain-screen and drainage space...something that is now mandatory in parts of Canada.
The Building Science is getting there but they can't tell us how to "do it" I think they have made attempts..but they still seem awkward.
I agree with the OP...I don't think using extremely long nails or screws is the solution.
We need ideas and help from the guys in the field...HELP
Yeah, I agree that the general concept has potential. But one inch of foam isn't enough to insulate a house in most of the country, and there are all sorts of issues with regard to door/window openings, sealing, attaching siding, etc. You don't just go and take a conventional home, stick the foam on the outside, and call it good.It wasn't entirely clear, but I took the OP's question to apply to either an existing home (where retrofitting 1" foam would be a PITA around doors/windows) or a new "conventional" home that wasn't designed from the start to have foam on it. In either case a good job of housewrap is far better than a half-arsed job of foam wrap.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
"one inch of foam isn't enough to insulate a house in most of the country" ....i dont think anyone here is talking about abolishing the insulation between studs in favor of 1" foam. does that even need to be said? Im also pretty sure the discussion is about how to correctly install the foam wrap not the "half-arsed" way. It does seem like a retrofit would significantly complicate matters. even in new construction attaching the flanged windows seems troublesome though, i agree.
Jpeaton,
There are methods other than using ginormous siding nails. Lstiburek has done some projects where furring strips are screwed over the rigid and into the framing...then the siding is nailed to the furring strips. The whole window flange thing is another issue.
I am pretty darn sure that it is a good idea to have rigid insulation beyond the structure. It is the technique that needs to be developed, discovered or revealed.
Ray Moore is doing some very intersting work.
I did not say that it would replace the housewrap (or WRB)...Actually Lstiburek recomends that the Insulation goes on top of a "drain-type WRB"and protects it.
Most people seem to assume that WRB goes over the insulation....not so
If you are interested in the subject..I will post some links
John
I've only used these panels on the inside over concrete block, but here's what I would do.Install the foam by applying construction adhesive to the studs. Then install the hardiboard on top of the foam while the glue is still wet. Spread a web of adhesive over the foam panels, slap the hardiboard up, and screw it to the studs. After that glue sets, there won't be any sag to bend screws. If you prefer to use nails, I see no reason not to; I just like screws for this.Don't use just glue. My current house has problems now because they attached the sheet rock with glue and didn't back it up with screws or nails. Forty-five years later, things don't look so good.George Patterson
I'm not saying I'm an expert here but when I've seen / done siding jobs with rigid foam underneath it is usually under vinyl siding wich is very light in comparison to wood and definitely to cement board. I would feel comfortable installing vinyl w/ long nails but the other types I would want to use furring strips screwed to the studs through the foam. When I have set window with foam, I have nailed the flanges to furring strips to bring the flanges out flush to the foam plane. You loose the foam insulation at the window flange but the window doesn't look burried, not to mention I wouldn't trust nailing through the foam due to a windows weight and constant use.
I do however tape all the seams of the foam. I would suspect that detailing the foam is key. if moisture gets behind the foam, there may be some real problems with decay or mold. foam doesn't breath like a housewrap in my understanding. Also, there are many different types of foam (open and closed cell, foil faced, etc.). I'm not even sure what to tell you there. I figure the blue or pink closed cell foam they use under grade would be the best choice but you get higher r values from th foil faced stuff.
that's my 1 1/2 cents"it aint the work I mind,
It's the feeling of falling further behind."Bozini Latini
And what you've probably seen is 1/2" foam sheathing, not one-inch foam on top of the sheathing.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
actually now that you say that your right, it's pretty much always been 1/2""it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
The method you describe seems very much in line with this FHB article.
http://www.taunton.com/finehomebuilding/PDF/Protected/021181088.pdf
he puts solid furring under the window flange as you describe.
near the end of the article it says best practice would be to include furring strips with siding. But does not explain how add this extra layer of "confusion"
He also said that sometimes he includes a housewrap..but does not say where
the Lstiburek wall sections seem to always show the drain-type houswrap (or building paper) under the insulating sheathing.
So I guess my question is: Is anyone out there putting all these things together?The wall described in the article above plus drainage-housewrap(or building paper),furring strips and fiber cement siding? I think the real devil here is around the windows.
Do you have photos?
"So I guess my question is: Is anyone out there putting all these things together?The wall described in the article above plus drainage-housewrap(or building paper),furring strips and fiber cement siding? I think the real devil here is around the windows."See my hand up and waving in the back of the class?????I have no problems around the windows at all. While one might intuit that the foam would compress there, and that is true if you reall try or use sloppy carpenters, when the nailing is spread over the larger surface of about twelve feet circumference of a window, and nails are carefully placed, the foam does not compress and the window is set securely. Then we go in ad rim the window with spray foam gluing it in place. Whether I use furring or not has little or nothing to do with the foam. It has to do more with the type of siding and whether we want a rainscreen wall or not. Sometimes the furring is 3/4" strapping and sometimes it is ripped 5/16" strips. We did one job with the cedar breather type rainwall but didn't like it.
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Piffin, thanks for all this great feedback. I am not a carpenter and sometimes I "intuit" things the wrong way. You must be thinking about this stuff night and day. Now If we could only clone you.
John
"You must be thinking about this stuff night and day."Thanks for the compliment, but half of it is so second nature from doing it so many times that I don't have to think about it except to teach a new guy how.
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"there may be some real problems with decay or mold. foam doesn't breath like a housewrap in my understanding"That is why I asked what his climate is. I am surprised nobody else has brought that up yet. When in a cold climate, the foam goes on th e inside of the studs.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I tend to forget that this board is full of folks from all over. Everyone here just seems local when we chat back and forth. I just assumed he was in my type of climate wich is southern new york. a mixed climate for sure."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
Yeah, I agree that the general concept has potential. But one inch of foam isn't enough to insulate a house in most of the country, and there are all sorts of issues with regard to door/window openings, sealing, attaching siding, etc. You don't just go and take a conventional home, stick the foam on the outside, and call it good.
Dan, you are correct...I have not seen a correct solution (yet). I am looking. These issues are difficult.
Ray Moore may have a solution...do a search on the REFORM wall if you are curious
John
Yeah, I've seen several "systems" that would seem to work, including one for retrofits, but they're all fairly complex and require a lot of detailing. No "home run" so far.If the foam mfgr were to imbed some sort of furring in the foam, that might make a difference. Would still need a way to seal between panels, though, or use a wrap.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
To All, here is a link to a remodel..that has it all(still complex though)
page 37 shows the draining housewrap...page 48 shows the furring strips and window casing(this window is really"built-out")
http://www.buildingscienceconsulting.com/resources/presentations/AffordableComfort/2007/042507_TZE_Case_St_04_sec.pdf
Edited 9/9/2007 9:11 am by homedesign
Edited 9/9/2007 9:12 am by homedesign
I built my house in 1990 with 2x6 walls with unfaced R-19 fiberglass batts and 1 inch foil faced foam over 1/2" OSB. I taped all seams and the bottom of the panels with foil tape, after filling any gap bigger than 1/4" with canned spray foam. Windows and doors went in through the flanges with 10d galvanized nails, and I used long siding nails directly through the foam. I started an addition this spring, and had the opportunity to see how the wall system fared over the last 17 years, and I was really pleased to see the OSB look like new, no evidence of leaks around the doors or windows, and no signs of moisture infiltration. I also have not had any issues with siding sagging. I did space the siding nails 12" apart as insurance though. The only I changed as I put in the new door and windows this time is the addition of Vycor around the openings, and I flashed the nailing flanges with Vycor as well. Oh yeah, I am using closed cell spray foam instead of fiberglass in the new part of the house instead of fiberglass. This may not be the ultimate best solution, but I have not had any problems in the last 17 years.
Yeah, it can be made to work. Problem is it's hard to get regular builders to even tape the housewrap, much less do the detailing you did. What's desperately needed is a "no-brainer" system. I think the closest so far is probably sprayed foam -- uses standard construction, no major investment is special tools or training, doesn't require a lot of detailing to get a good seal. But of course it doesn't provide the full thermal break like the exterior foam does.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I've just finished building my house this year, so I have no history to report on.After much research here, and at buildingscience.com, I ended up using 1" of foil faced polyiso, over 1/2 sheathing and 2x4-16" walls.The windows and doors were flashed to the foam with window wrap, and set in homemade felt drainage pans. All the seams were foil taped, and the horiz. joints sealed with mastic.The windows were nailed right through the foam with 2-1/2" roofing nails. These windows were good quality aluminum clad with al flanges, so that may have helped them hold shape but they fit very well.The sidng is a mix of steel (pole barn) wainscot that is screwed to the sheathing, and cedar claps that were attached with 2-1/2" stainless nails.The nails for the claps are tricky, because of the foam deforming enough to let the nail sink through and split the siding, much patience was required, and I may need to add additonal or different fastners as the cedar shrinks and twists.I could see Hardi getting very wavy without a competent installer.The steel works great, and I assume vinyl would be a no brainer as well.A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.
SOme pics for illustration.
This is window installation, the window wrap hasn't been installed yet, but you can see the foam detailing.
View Image
This shows the steel going up, it is very straight forward, and the standard steel trims work out fine with 2-1/2" roofing nails.
This shows the almost finsihed product, I love the cedar, but the cull rate is pretty high, and the maintenance may cause me to lose my hair.
A medium to large guy named Alan, not an ambiguous female....
NOT that there is anything wrong with that.
Edited 9/9/2007 12:25 pm by bigal4102
Edited 9/9/2007 12:26 pm by bigal4102
Edited 9/9/2007 12:32 pm by bigal4102
I wuz thinking ... (fair warning!)Rather than standard wood furring, it would seem to me that you could get most of the same effect with a piece of relatively thin steel, or perhaps a piece of stiff plastic. They could be nailed/glued to the foam and then the siding attached to/through them. They'd prevent sagging and would also keep the foam from dimpling when siding is nailed to them. And negligible extra thickness.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
"it can be made to work. Problem is it's hard to get regular builders to even tape the housewrap, much less do the detailing you did"OK, I see what your problem is with this system. You need to look around and find carpenters with half a brain and a little bit of integrity.Meanwhile quit deriding the system because you can't find men to do it right. It really is not hard to do at all. Easy as zipping up your fly in the morning.'course some guys have trouble with that too...;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thing is, not 10% of the guys out there are as skilled and conscientious as you are. As I said, you have enough trouble just getting them to tape the housewrap. And they don't want to learn anything new either.Any new system (to be widely adopted) needs to be at least as easy as the old, if not easier, needs to be fast (or the big contractors won't use it), and needs to be reasonably foolproof. I won't say that detailing should be "optional", but if it's not done right all the time it shouldn't result in serious problems.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I think you and piffin are going back and forth unescesarily, I think you both have very valid points. Dan - you are absolutely right on about a new sytem needing to be easy and cost efective or it will be done wrong more often than not and the big guys won't use it at all. For the few of us that are carefull, I think piffin is valid in stating that it's not that hard to do something right if we follow the prescibed process. easy as zipping up our fly (although I've forgotten that step from time to time). I think the origional intent of the thread was to clarify the system itself since there seems to be vague info available."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
benjamin obdyke makes a product called home slicker plus typar wich is a house wrap and drainage plane in one. for use behind wood and fiber cement siding."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
I wouldn't use that one over foam. They have the same rainslicker available without the housewrap attached. The housewrap should go under the foam if you use both, then the rainslicker over the foam.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
the more this thread continues the less I feel confident about what I've been told / taught. why the house wrap under the foam? curious is all."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
For myself, when I use foam exterior, I tape it and don't use housewrap. The foam does a fine job of preventing infiltration when done right. But there are those who do use both and the housewrap should go under the foam. For one thing, it will stay on in the wind better that way untill the siding happens and will not be all torn up.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I'm wondering how you seal the wrap around the windows.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I'm wondering how you seal the wrap around the windows.
mornin Dan,
The details I see that use foam and housewrap all seem to marry the window fin to the housewrap...window fin is under the foam....
Now this is where the window casing issue really seem to get awkward to me.
especially when you add the furring strips on top of the foam.
Piffin, how did you combine all that "stuff" when you used housewrap and foam?
Yeah, I thought I heard Piffin say he puts the fin on top of the foam.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Yes, I do the flange/nail fin on top of the foam. Going the other way would invite water in behind the foam. Don't know why anybody would want to do that.I looked at several of my pictures from jobs where I have used the foam but none showing this detail clearly, just one or two from a distance back showing whole house at that stage.So let me try to detail it verbally again.I sheathe the studs with 1/2" Advantec.
I nail the 1" foam over the sheathing with plasticap nails 1-1/2"
I tape the seams in the foil faced foam.
I cut strips of leftover Rooftopgaurd about 18"W to make my pans for the bottom of the rough openings, staple it in place with the flap hanging down loose over the foam.
I install the windows, nailing the flange through the foam, then use Vycor to seal around the flange.
Then I use canned foam to seal around the window frame from inside , gluing it in place snug.
Then if there is to be ext casing, it goes on then, with caulk to the fins.
On single story homes, the window tops blend into the frieze. On second story homes, the windows get a cap flashing over the head casing and a second Vycor strip over that.
When I want a rainscreen detail, I rip 5/16" strips to go over the foam before the casing
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I was referring to the case where you use housewrap under the foam. How do you seal the housewrap around the windows?
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I've been scratching my head for quite a while looking for an economical super insulated wall. The house I just finished had 2x6 walls on 16" centers, half inch osb sheathing, half inch polyiso, 3/4" horizonal furring strips on top of the polyiso for nailing the vertical cedar siding and finally housewrap on top of it all. The furring strips went around all window and door openings for additional nailing. Soft foam was used to insulate the walls inside and was also used on the roof. All seams were taped on the foam as well as the housewrap. Needless to say it's well insulated but it's downfall is that it's time consuming and expensive.
For the next house I had convinced myself to try the Mooney wall with dense pack cellulose (new construction) but it's a spec and I'm having second thoughts about trying something new (at my expense). Plus my framer looked at me like I had 3 nostrils when I mentioned it to him. I'm sure he'd tack on a couple grand to do it. Now I'm thinking about wraping the exterior in half inch foam again, but without the trouble of the furring strips. Still scratching my head???
Clayton
Your profile says nothing about your climate zone. This is crucial.In a cold location you need the foil faced foam on the inside of the wall assembly.For customer who want good insulation but can't afford to have foam sprayed in place, I use BIBBs in the cavities, then 1"foam over the studs, then horizontal strapping to attach the SR to.I am in a moderate climate where I have the option of the foil faced polyiso on either the outside or the inside.
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I am in a moderate climate where I have the option of the foil faced polyiso on either the outside or the inside.
Piffin,
I am confused I did not picture you to live in a moderate climate...
An Island in Maine?
Our heating degree days runs about six thousand. That can be at the upper limit of what is considered moderate.On the island here we are surronded by the moderating effects of the water, keeping us 10-15° warmer in winter than just a couple of miles inland, and sometimes ten degrees cooler in summer. Being up in a bay, we are somewhat protected from the worst storms by comparison to outlying islands.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Thanks Piffin..when I looked at your picture I thought it must be prety damn cold up there.
JB
I would imagine that, for condensation considerations, etc, the issue is not so much heating degree days so much as the coldest (or warmest) temperature that might be experienced for a relatively sustained period.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
I think Joe L and others do use degree days as a guideline, but there is some truth to what you point out there. It is the extreme differences between interior and exterior that creates the most condensation. When I was roofing in CO, I always knew I would have calls for false roof leaks when the temps dropped below minus thirty for a while and then warmed up.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Piffin,I have had a few of those false roof leak calls in Colorado, too. It was so hard to convince some people that their roof was fine, and the water was only condensation. A lot of the mountain places had drywall gaps at glulam purlin beams, and boy did they weep.Back to the thread topic, I am considering doing foam over the sheathing when I redo my own west wall here in SoCal. The foam will go over plywood, under stucco. I as happy that you have no issues with flange-maounted windows over the foam, as that is so much simpler than the hard packing I was considering. Simpler WRT water detailing, that is.The foam is for a little thermal benefit on the hot afternoon side, and also for an isolation plane between the plywood and the hardcoat stucco. The house has no outside sheathing, and good stucco guys agree that ply under stucco invites cracking. This one wall, however, is the tallest wall of the house at 22', and needs sheathing for racking resistance. 25 years of small temblors have cracked the stucco on this wall more than all the others combined. The stucco has been serving as our shear diaphragm, since the only other bracing is flat steel straps poorly nailed with one Teco per stud.The new ply will tie across two floor systems, and is the simplest way to gain the strength we need. The wall is only 19' wide, so it needs to be stoutly sheathed. Under the first floor is an unbraced (except by the stucco) 2x6 kneewall 4' high. I am planning to use 3/4" CDX. Can't buy Advantec out here.I have been thinking the sandwich looks like this: studs, ply, felt, foam (1/2"), paperbacked lath, stucco. There will be a ledger mounted deck at 13' up which will mean no foam there. I'll tape the foam to itself and the windows, but the primary moisture barrier will be the felt right over the sheathing. The windows need to go over the foam, as the stucco is about 1" thick and the windows (vinyl) protrude only 1-1/4" past the nailing flange.What do you think of my plan? I am open to suggestions.Bill
Sounds good to me.If you are considering replacing windows with all this ( or for anyone else reading the topic and thinking of foam exterior) the Marvin windows have an installation detaill I like that is great for over faom, especially for anyone worried about nailing the flange into foa aand ccompressing it. Marvin windows with finished casings have aa metal tab on the back side fo the frame that you rotate into the room, and pull tight and nail on the inner face of the stud, so no nailing on the exterior to install the window.
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Thank you, sir.I already have my windows/sliding door picked out. I am gradually replacing all the windows in the house, and settled in 1999 on a quality vinyl unit that I like a lot, so all will be the same sort when I'm done. They are made nearby in my county, so factory support is easy to get.I used these same units in my ICF shop in 2003, and got "block frame" units which were installed with screws/shims through the jambs. In that building, the windows sit midway in the 10" wall thickness, with a sloping cement sill to the outside. It's a cool detail, one not possible in my 2x4 framed house, alas.Bill
Edited 9/14/2007 10:34 pm by BillBrennen
Piffin,
I am glad you brought up the windows.(doors included)
It seems to me that the relocation or the elimination of the window fin (flange) is what needs to be considered as we move toward walls with "outside-insulation" and "furring/spacers".
The window and the window opening are critical.
At Joe L's seminar I went to this summer (sorry again for not inviting you down for it!) he talked about this stuff a lot. The foursquare house in Concord, from the pdf someone posted, was his own house. IIRC he used housewrap UNDER the foam largely to seal the windows and doors, which he kept in their original location.
His wife is an architect and she wanted the windows pulled outboard, like you do, for looks. He couldn't get his engineer brain around how that could be a foolproof system so they kept the windows inboard.
everybody has a right to make mistakes on their own home!;)
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Mike,
Are you saying that "Steebrick" admitted that his recomended wall recipe actually causes some serious head scratching when it comes to dealing with the trim around the windows? those windows(in the foursquare project) are really built way out...almost like a window around a window.
He explained how he detailed it in his usual fashion--clearly thought through, with good pictures, and insulting several people along the way!
Well, like I said, I don't use housewrap AND the foam so you would have to get that detail from somebody whop does, along with an explanation why.It sounds like from one of the earlier comments that a drainage screen wrap like greengaurd is required when used under foam and that the foam is used over the window flanges. That would explain why the under drainage would be needed since they are inviting water in to the party.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
OK, I misinterpreted some of your comments to mean that you used the two together occasionally.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
OK, I misinterpreted some of your comments to mean that you used the two together occasionally.
Dan...I think this is where you and I got the wrong impression
"So I guess my question is: Is anyone out there putting all these things together?The wall described in the article above plus drainage-housewrap(or building paper),furring strips and fiber cement siding? I think the real devil here is around the windows."
See my hand up and waving in the back of the class?????
It wasn't that one specifically, but it's not important. Piffin used the term "housewrap" in a context that sounded like he'd used it with foam, but probably it was a combo of his being a hair imprecise and my reading too much precision into the statement.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Dan, I think its easy for all of us to get our minds going down different tracks
I am still interested in this subject (foam outside) and if it is even a good idea for my particular micro-climate
I'm glad to find myself in good company on this question. You might be interested in Lstiburek's Guide to Insulation Sheathing at http://www.buildingscienceconsulting.com/resources/walls/Guide_to_Insulation_Sheathing.pdfIt still doesn't answer all the questions, but there are many examples of detailing for windows, doors, etc.By the way, I'm in Richmond, VA; Mixed Humid climate. As others point out, where you are makes all the difference. I had hoped to help our builder see a simple way to modify/improve on his standard 2 x 4 fiberglas batt insulation. The local electric utility gets deregulated at the end of the year and folks are gonna be shocked when their bills go up 25% or more.Frank Delk
Dotor Science,
Thanks for jumping in
Excellent link....I printed that link out a while back and have been trying to sort it out.
That is where I first saw "the housewrap under the rigid" and how odd that sounded at first.
I have also come across a blurb about housewrap having a "bellows effect"and actually pumping air into the house...so the rigid on top helps
John B
John,I forgot to mention that FHB #181 pg. 88 also ran an article on Rigid Foam Sheathing. There are some good ideas for window installation. I'd really like to use this on the house we're planning to build. There's also a Question in FHB #188 pg. 96 about foam sheathing.Frank
There's also a Question in FHB #188 pg. 96 about foam sheathing.
Thanks again,
the article was mentioned briefly earlier...the Q&A link helps too
Doctor Science, Frank,
you referenced a BSC article with a very good point
Exterior Rigid insulation sheathing can also be a good strategy for cold climates!
Also the FHB article you referenced discusses other advantages for placing the rigid outside.
For your first 2 posts ...nice work
(In any event, it seems like using housewrap under foam would be a problem, if one were going to put the window flanges on top of the foam.)
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Just like always. I can't imagine why it would be any different to seal when the flange goes over foam than when it goes over sheathing
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I see, because of the lack of housewrap.I wrap the window rough frame bottom with Rooftopgaurd with about a 12" flap over the foam, then set the window and use Vycor or other flashing tape at the top and side flanges.
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the more this thread continues the less I feel confident about what I've been told / taught. why the house wrap under the foam? curious is all.
HV,
that is why I feel this is an important subject.
My understanding of the housewrap under the foam is that the foam protects the houswewrap and BSC assumes that water will get past the foam. They do specify a draining housewrap.
what about installing a continuous layer of 1/2" foam, then furring strips 1/2" thick in line with the studs and screwed trhough the foam, then infill between furring strips with more 1/2" foam. then the home slicker? never done it that way but seems like it would work."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
Would work, of course, but is a lot more work, and there would be gaps around the furring.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
That creates a tremendous amt of extra un-necessary work. besides, the radiant barrier of the foam works more effectively with that airspace in front of it.
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implying that the furring strips be placed on top of the foam? by the way, what didn't you like about the cedar breather?"it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
Yes, the furring over foam creates a radiant spacing and allows for a drainage plane/rainscreen wall. The men felt like the Rainslicker product was a pain to work with compared to tacking up the furring strips, it was fairly expensive, and where we had shorts of clapboard say 8" between windows and corner trim or whatever, it was hard to keep from setting the nail too hard and sucking the siding in too tight, compressing the slicker product.
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"there are all sorts of issues with regard to door/window openings, sealing, attaching siding, etc. "What issues are there?
I have done this on most of the additions and homes I have built for twenty some years and I am not aware of any negative issues.
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"I believe in the concept..I just do not think the construction industry has come up with the best answers yet on how to deal with it. A similar problem/opportunity is developing due to the introduction of rain-screen and drainage space..."
One of the features of the rainscreen construction as it is being practiced here, is the emphasis placed on allowing moisture that does enter the stud space to have the opportunity exit the wall to exterior. Gaps are left between sheathing sheets and holes drilled in the closed stud spaces under windows.
I worry about the effect that any wall assembly that covers the sheathing with foam may have on the drying capability of the wall.
One of the features of the rainscreen construction as it is being practiced here, is the emphasis placed on allowing moisture that does enter the stud space to have the opportunity exit the wall to exterior. Gaps are left between sheathing sheets and holes drilled in the closed stud spaces under windows.
F&T,
I just recently noticed that you Canadians are drilling holes under windows and leaving gaps in the sheathing. Does that mean that you are doing your air sealing on the inside? How big are those holes under the window? Does anybody up there use wicking strips or wicking cord under the windows to drain the window opening? I read Ray Moore talking about this wicking concept.
2" holes are drilled in any stud space with no gaps in the sheathing. The interior has a continuous 6 mil poly. v.b. taped and sealed. Electrical boxes are gasketed and the v.b. is sealed to the window flanges.
I haven't heard of wicking strips. The recommended details for window openings are a pretty complex layering of wraps, caulking and peel and stick, which is shimmed under the window to drain to the exterior.
I don't know if all this amounts to the right approach, but it is certainly better than what came before.
It's interesting... Around here, while the usual tarpaper or equivalent is generally wrapped in the window ROs, there's little else done in terms of rain treatment other than to (sometimes) tape the housewrap to the window flange. Certainly noting as elaborate as has been described here.But window leaks (and in general, leaks through the siding) are relatively rare, even when flashing and caulking is only half-heartedly done. I'm guessing it has to do with the weather, though I don't know what the difference would be.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Until the late 90s the emphasis was all on sealing the vapour barrier and stopping moist air from entering the wall from the interior - at the neglect of any exterior detailing - because that was where they had found problems in the typical cold Canadian winters. Someone forgot to tell the building code officials that Canada has more than one climate zone, and we experienced what can only be described as a catastrophic series of building envelope failures on the West Coast. Enough water was entering the walls from the exterior that often remediation involved replacing the joists, and it was not unusual to see condo projects with their entire outside walls removed exposing the rooms within.
It's still not over. The middle school (junior high) in my town is undergoing $4 million worth of repairs to its walls and is less than six years old.
"I agree with the OP...I don't think using extremely long nails or screws is the solution."Why not?
Besides, there is nothing extreme about the length of nail needed. a 2-1/4" SS ring shanked siding nail will work just fine in most cases.
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"In most areas, if you have an "adequately insulated" home to begin with (eg, 3" of fiberglass), an inch of foam won't make nearly as much difference as will a really good housewrap job."Dan, you make a lot of good comments here at BT, but that is unadulterated hogwash.To begin with a 2x4 wall with FG batts is FAR from adequately insulated. batts make the worst insulation commonly used today because of the convection loop that exists in stud voids when using batts.Then it is only R13. Adding an inch of Thermax or similar foam adds another c.50% with R7 per inch and does it more effectively than the batts by disallowing convection loss through it and by stopping thermal bridging. Conversations with my customers where I have used this lead me to think it nearly doubles the effective insulation of a wall assembly. Then too, a well done foam job with taped seams will do the same infiltration protection as a housewrap does so you are getting that protection, plus the insulation itself.
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I stand by my comments. First off, in a typical installation housewraap will about double the effectiveness of that 3" of FG. Plus the reduction in infiltration improves the comfort level dramatically, much more than the mere R factor would suggest.IF (and it's a very big IF) you can install the foam as tightly as housewrap then obviously the foam will be better. But getting a tight foam install is much harder than getting a tight housewrap install.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
Housewrap limits the infiltration, but it does ABSOLUTELY NOTHING whatsoever to prevent the convection loop in stud spaces insulated with FG batts. Do you understand what that convection loop is? The way you ignore it makes me wonder.
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No, I understand the convection in the stud space. But my experience suggests that infiltration into the stud cavity is at least as big a loss. (Of course, I'm sure no reasonably realistic "lab" tests have ever been done to sort out these various factors.)
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
"my experience suggests that infiltration into the stud cavity is at least as big a loss."Sure it is but providing the one does not allow us to ignore or negate the effects of the other.As an example of what you just said here, the first time I ever used housewrap we we doubling the size of an old house and had gotten it framed up by mid-november, when it can be getting pretty cold here.
Each morning, the inside would be just about as cold as the outside . When we wrapped it, I immediately began to notice that the interior temp remained ten degrees warmer than outside. I regularly see that same thing ever since, but that was a pretty dramatic demonstration to me.
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Yeah, that's the effect I'm talking about. Clearly, once you have controlled infiltration then more insulation is the only way to further reduce heat loss. But until infiltration is well controlled it's by far the biggest swinger. And it's amazing how much infiltration you can get in an apparently "tight" (by conventional standards) house.What the industry needs is a new paradigm, kinda like the switch to platform framing. Something that's easy to understand, fairly standardized yet flexible (a major problem with SIPs), reasonably foolproof, and, above all, quick and easy enough to get it adopted by an industry that doesn't easily adapt to new techniques.
So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin
What the industry needs is a new paradigm, kinda like the switch to platform framing. Something that's easy to understand, fairly standardized yet flexible (a major problem with SIPs), reasonably foolproof, and, above all, quick and easy enough to get it adopted by an industry that doesn't easily adapt to new techniques.
Dan, I agree with you
I think it is similar to what Lstiburek is saying. "we need simple solutions and we need elegant thinking" we need to do it soon
Go Dan
I looked at the link earlier for lieberstuck's ideas and it requires really paying attention to the steps and the layering. I don't see that happening in the real world."it aint the work I mind,
It's the feeling of falling further behind."Bozini Latinihttp://www.ingrainedwoodworking.com
As I understand it the fasteners would go through the siding, the foam, and into the sheathing. There was a good discussion of foam in fine homebuilding a couple years back. Also check out this web site: http://www.josephlstiburek.com/designsthatwork/cold/profiles/default.htm . Joseph Lstiburek also has a good book on building for cold climates.
Edited 9/8/2007 2:54 pm ET by wasserman
Thanks for the link. It looks like he is advocating the foam and implying long nails through the foam is the key to attaching the siding. It seems like if you were to come back in 10, 20, 30 years the hardiboard would be sagging wouldnt it?
jpeaton, I cannot speak as to cement board siding , but I did a house in 1978 that had 1" rigid foam over 1/2 sheathing , 2 x 6 studs, R-19 batts and the siding was hand nailed clear verticle grain redwood, long nails . Never had any problems I am aware of with the application. Repeated the technique on other houses afterward with different sidings."Poor is not the person who has too little, but the person who craves more."...Seneca
Lstiburek uses 1-2 inch foam sheathing. The iso which has a higher R value than polystyrene that bigal4102 uses sounds great and looks fantastic. The foam with the insulation between the studs keeps the dew point high enough to keep moisture from building up in the wall. Customer service at hardiboard says the siding won't sag however they don't advise furring strips because the space between won't provide protection if something bumps the wall. I'm really interested and would like to know what fastening you finally decide works best, or how other builders have done this.
What climate zone are you in?
You really need to fill in your profile with pertinent information like that to get accurate answers.
I think I'll read the rest of the thread before commenting further
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I worked on a house yesterday ( Habitat house) that had maybe half an inch of foam on it. It's in northern colorado.
Just a though, but could the half an inch of foam be considered just a thermal break instead of a complete insulation of the house? Insulate the house with insulation in the wall cavities and the attic space, but give it a thermal break outside the studs with a thin (1/2") foam and a house wrap.
Does this make sense?
It has been my understanding that this is what we have been discussing all this time
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It sounds like everyone was talking about much thicker foam and it could cause problems. A thermal break doesn't have to be that thick.
Yes, I use the thicker foam because the cost is less per R level per sq ft. and the labour to install is the same whether you use 1/2", 1", or 1-1/2"Usually when 1/2" is used, it is to replace 1/2" sheathing from what I have heard. like we used to use plywood at corners only for wind bracing, and then black homasote for the rest.
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"A thermal break doesn't have to be that thick."To do what? A foam layer won't eliminate thermal bridging of the wood; it only reduces it by adding R. If you have a 2x6 stud, at say R 1.2 /inch, the stud has a total of R 6.6. If you add a half inch of XPS foam, you increase that to 9.1 and thus cut the heat loss by 27%. Not a whopping reduction, but some. Of course, you add that 2.5 to the whole wall, not just the stud.
Edited 9/17/2007 12:12 pm ET by DickRussell
Is there a difference between the way a thermal break works and the way insulation in general (for lack of a better term) works.
When you look at lofty insulation in the attic space it would ( I'm guessing here) represent insulation at one end of the spectrum.
Conversely, a thermal break would be on the other side.
There must be terms to describe what I'm trying to explain here.
Insulation isn't just one thing. There are different components in the total insulation system.
It seems to me that a thermal break doesn't have to be that thick to work. You are just separating two materials. Granted, you don't want one material to radiate across the separation to the other one. And keeping them separate is much easier if you have something there that keeps them separate. So you nail something on that acts as a spacer and that you can nail something else on to it.
It seems to me that if you start putting on thicker foam you are trying to insulate with it more and bridging less. The insulation of the wall is in the stud spaces.
I live in a fairly moderate climate and I like it that way. So throwing on some 1/2" foam is relatively easy and affordable.
I respect the level of detail and thought it takes to really insulate a house well. My neighbor is having a house built using sips panels. But I wouldn't be able to pay for anything near that. I'd work on one though.
An uninsulated 2x4 wall with drywall, plywood sheating, and brick exterior has an R value of about 1.5
Adding R13 fiberglass, or cellulose, insulation to the wall cavities, brings the total R value up to around R9 or R10 - studs are relatively poor insulators at around R4.5.
Adding a R7 thermal break of 1" foam on the exterior adds R7 to whatever insulation you already have, taking the above example up to around R16 or R17.
The foam is still just insulation, but it cuts the heat loss / gain through the studs by more than half.
I think what you might be trying to verbalize is that there are three ways to transfer heat energy: convection, conduction, and radiation. A thermal break is used to reduce conduction.
So far we have only discussed the benefit of "foam outside" as it relates to Thermal Bridging.
Another reason for the rigid outside is that it is a means of reducing condensation potential in the outside wall assembly.
The optimum thickness and type of the "insulating sheathing" is climate specific.
Was this the foam sheathing, or was it applied over the sheathing?
If your view never changes you're following the wrong leader
Yes it was foam over sheathing. I seems we are shooting for an ideal and can run into some problems. I live in a moderate climate and shoot for moderate solutions. In colder climates I can see how you would want to go to extremes.
To your orginal post (Note- I don't claim to have the expertise of many BT'ers) and to answer your orginal question. I used 1.5" foam on the outside and used the idea of a rain shield to hold the siding on. In the following picure I'm using the Lap siding from GP. I nailed into the furring strips
A rain shield allows air to flow up behind the siding allowing it to dry. I used 1/2 in ply cut into strips which were screwed through the sheathing into the stud with 3" screws. The windows had 2X material nailed to the sheathing with the foam butted up to the 2X. Attached the window to the 2X
The inside can't have a vapor barrier because the wall has to dry to one side so I used blown cellose on the inside w/o a vapor barrier. (I'll get creamed on this one) I used a drop ceiling ( 6 in ) and drilled holes just below the top plate to snake the hose down to blow the cellose. I left the holes open (above the drop ceiling) to allow the moisture to evaporate
Thats how I attached my siding to the foam.
Just a different perspective
Go Cubs
In what kind of climate was this?
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I live in the Chicago area
That would have been a better location for foam inside of the studs. You have enough thickness to help prevent thermal bridging and maybe to eliminate dew point condensation, but the VB on outside means interior moisture can pass into the insulation far enough to collect att eh sheathing and stay there.
Overall the way you describe this is probably fine, but high interior humidity in winter would be a bad thing.
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I realize your point, lots of threads on the topic. I was just throwing an idea at the orginal poster for attaching his siding.
I tried the Mooney wall idea with the foam. Its increadible how warm the house is in the winter and in the summer the AC doesn't kick in for a long time. I realize the exposed cellose above the drop ceiling was unconventional, but they said Henry Ford's idea for the V-8 was crazy.
Go Cubs
in the summer the AC doesn't kick in for a long time
Curley, If your ac does not kick on for a long time,
then your ac is oversized,short-cycling and wasting energy
Or else he hasn't paid his electric bill.
If your view never changes you're following the wrong leader
Or he has an efficient insulation pachage that reduces his need for AC
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An air conditioner does not reach its peak stated SEER until it has been running for quite a while. If the AC is oversize it will cool the house too quickly and shut off.
If it shuts off too soon it will also not dehumidify as well.
It is called short cycling and it wastes energy.
I know you guys in the north do not worry so much about ac..but oversized ac and short cycling is a big deal for us Hot Humids
I see but what I was thinking on was that he may have upgraded insulation package after the AC was already installed, accounting for how it came to be oversized.You are right, we only use out AC about 7-10 days a year here.
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I was refering to when the house is cool in the morning and the day heats up it still stays cool until mid morning when it heats up enough for the ac to kick on
If you listen to Dan H- he'll tell ya about the hot air inside the house
Edited 9/16/2007 2:34 pm ET by curley