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I have an addition built onto the north side of my house which, according the newspapers stuffed into the cracks, dates back at least to 1932. As I had a set of taps freeze in there last winter I need to insulate & provide a heat source. The attached photo provides an example of the exterior walls & ceiling/roof. The grey section on the left with the two wires coming out of it is the original exterior wall.
The addition is approximately 15’x 7′. The exterior wall is 3/4″ tongue & groove beadboards covered w/cement shingles. The wall studs are 3.5″ deep. The joices suporting the roof are spaced 22.5″ apart. The high point of the ceiling/roof (left side of attached pic.) is 11’1″. The low point (rt. side of pic.) is 8’4″.
The addition has a stone foundation and a crawl space with a dirt floor underneath. I have placed 6 mil. plastic on the crawl space floor, and used fiberglass batts to insulate the crawl space walls and ceiling (the underside of the addition floor which is tongue & groove pine). The crawl space, which opens to the basement, contains outlet wiring & plumbing for a sink & toilet.
My thought at this point is to replace the current exterior shingles with cedar shingles and to redo the roof with slate (this is in keeping with the rest of the house).
Regarding the exterior walls: Is the proper order (working outward): original beadboard, tyvek house wrap, foilfaced insulation foam board, osb/plywood, ventilation strips, shingles? Does the foil on the foam board act as a vapor barrior or do you still need the housewrap? Should tar paper be used instead? Is the proper method of attaching the foam board with an exterior adhesive (liquid nails?)?
Regarding the Ceiling/roof: My idea is to put in a tin ceiling (attached to drywall) 8′ high so there would be a flat ceiling rather than angled. Am I correct in thinking the tin would act as a vapor barrier (or do I still need the plastic over the drywall) and fiberglass should be installed on top of the tin & drywall?
Finally, any thoughts on the best ventilation method & heating source (radiant panels, elec. baseboard, etc.) for such a space would be appreciated. I know this was long. Thanks a lot for your help.
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Dear Haddix,
This is out of my field but congratulations on providing plenty of info and photos. This will help a lot for those that know.
*Fred & others:I'm curious about Haddix's proposed placement of the Tyvek or tar paper. His quote:"Regarding the exterior walls: Is the proper order (working outward): original beadboard, tyvek house wrap, foilfaced insulation foam board,osb/plywood,ventilation strips, shingles? Does the foil on the foam board act as a vapor barrior or do you still need the housewrap? Should tar paper be used instead?"Other than the guy who posted a question about putting Tyvek on the floor during construction, I've never seen mention of applying housewrap or tar paper on the INSIDE of the walls. I thought plastic sheeting was preferred under the interior wall (wallboard or beadboard or whatever). But I also remember a post about using housewrap as a vapor barrier on the ceiling (interior side of rafters/trusses/joists). The way I understand it (may be completely wrong), the housewrap isn't really a BARRIER, and it breathes in one direction. I guess the tar paper breathes in both directions. But the plastic is impermeable.I understand the concern with housewrap and cedar siding, but if Haddix were using a housewrap compatible siding, would applying housewrap to the interior wall be feasible? Wouldn't it be a lot more $? Does anyone put housewrap or tar paper anwhere except over the exterior sheathing?
*Rufus - housewraps allow moisture to pass through from either side. - jb
*Dear Haddix,Sorry it took this long to get back to you but I will try to add my 2 cents worth.Step 1, forget about most of FreddyL's advice.Step 2, forget about the Tyvek and use tarpaper.Step 3, forget about the foilfaced foamboard.Step 4, forget about the OSB or Plywood unless you are replacing the beadboard.Step 5, do install the strapping and the cedar shingles.Now go inside your addition.Step 6, do insulate the walls between the studs with FG or whatever and if you can't put insulation behind the pipes, do move them forward so that this can be done.Step 7, put a poly over the insulated wall and leave an overlap for the ceiling.Step 8, cover with drywall, panelling or whatever and finish.Step 9, have a beer, you've earned it.Gabe
*Rufus, I did not intend to give the impression I was putting tyvek on the interior. I would be placing it on the exterior of the original beadboard.Haddix
*Gabe, Why do you suggest tarpaper rather than the Tyvek? The foilfaced foamboard is to increase the wall r-value as it is a north facing addition and the studs do not allow for thicker fiberglass. I didn't think I could attach shingles directly to the foamboard & would thus need the osb on top of the foamboard. My layers would be: beadboard, housewrap, foamboard, osb, shingles. You're saying the outer layer of osb is unnecessary? Would the combination of housewrap & foil foamboard cause a moisture trap?Thanks.Haddix
*Hi Brent,I prefer tar paper when properly installed.If you want to increase the R factor, install the additional SM insulation "on" the inside wall, where it will do the most good.Installing every product available on the planet does not ensure a good job, it ensure employment at the lumber yard.Your foundation is existing. To build outward with several inches of construction material means you will also have to flash underneath to prevent little things from entering.Its a lot easier to keep the outside profile as is. By putting the styrofoam directly under your drywall it serves two purposes. The first is obviously insulation and the second is a moisture barrier.The sequence of materials you suggested is better suited to warm weather applications than cold weather locations.(with the exception of Tyvek)Gabe
*Brent:First please excuse Gabe. He can't disagree with someone without attacking him. Sorry.Second, I agree with Freddy, and he gives some good advice as usual. I also agree with Gabe that the poly liner over the walls and overlapped onto the ceiling joists are a good thing.Third, your walls seem fine, although I would put the Tyvek on the outside portion of the wall. So your order would be original beadboard, foilfaced insulation foam board, osb/plywood, tyvek, ventilation strips, shingles. Your foil faced insulation will act as a marginal vapor barrier. There is a good article on vapor barriers and water barriers in Journal of Light Construction in 1994, which I refer to constantly. Tyvek is mainly a water barrier, and is utility (except as a wind breaker and to keep the osb dry) is nominal.Since hot air mainly rises, Freddy is right in that most of the effort needs to placed in your ceiling. Whether you add osb and calk it tight (as Freddy suggests) or add a poly liner and some 5/8" drywall (as I might suggest) is a matter of personal taste. Tin ceilings (if they are the old fashioned nail up kinds) probably will look great, but won't be much of a vapor barrier. But in any event slap enough cellulose to make it R40 and forget it.Freddy is also right about the crawl space: it is either outside or inside. If it is outside, then seal off the floor joists above it and vent it. If it is inside, then seal the foundation holes and insulate it. I pick the former.I can't help you too much on the HVAC sytem, unless this is a complete new installation. I got the idea this was an addition, and you have an existing forced air, baseboard, or boiler system. I would need to know more.
*Hi Scooter,"first please excuse Gabe" Come on, was that called for?Your post would have more credibility if it were based on cold weather experience instead of trying to put me down.Your sequence is wrong and not practical. You have created a moisture trap and even Freddy would agree.Great advice.Gabe
*Gabe, Just to clear the air, I didn't feel attacked in any way. I do live in a cold weather climate. I appreciate the dialogue, although the conflicting opinions leave me scratching my head a bit.You reply to scooter: "Your sequence is wrong and not practical. You have created a moisture trap." Is this due to his use of both foilfaced foam board and tyvek? If I take your suggestion & put the foamboard on the inside under the drywall, would that eliminate the need for a plastic vapor barrier? There seems to be a disagreement of the extent to which the foilfaced board is a vapor barrier. Thanks.
*Good morning Brent,No the comment was because it also included poly, foilfaced foam and tyvek with the OSB sandwiched between the last two. This makes a double sealing.With regards to the putting the foamboard inside, we have to make sure we are talking about the exact same product. I'm refering to extruded blue styrofoam SM not any kind of beaded insulation or any type of insulboard with foil covering.If you use the SM with the shiplapped edging and you fit it correctly, I would still install poly over it.If you do not install the SM and you want to install the drywall directly onto the wood studs that are existing, you must still install the poly.So the sequence would be, drywall, poly, SM styrofoam, studs with insulation between, beadboard, tar paper, cedar shingles.ordrywall, poly, studs with insulation between, beadboard, tar paper, cedar shingles.I have a basic problem with insulation on the outside of the "main" envelope unless we were in a warm climate region. It was a gimmick used by tin siding salesmen and only provide a backing for the flimsy siding to rest against.The one thing that a lot of people are missing with some of the differences of opinions, is that I don't believe that one is more right than the other. We all have varying experiences and what works in one place may not work in another or how one installs a product will not be the same way someone else installs that same product, therefore the results are different.The nice thing about this forum, is that with the arguments, a concensus normally emerges.Gabe
*Hi Fred,Any info on Tyvek degradation vs. wood type? I would suspect that red cedar would be much worse than white cedar.Ron
*Hello Brent,No consensus here. My two cents worth:Air-seal the ceiling completely. You can use poly or unbroken painted sheetrock ceiling. Dump a bunch of cellulose on top of it. If you poke a bunch of holes in the ceiling putting the tin ceiling up it won't function as a very good air or vapor barrier. Glue the tin up.Leave the crawlspace in or out of the thermal envelope. If you keep it in the envelope, it'll be easier to keep the plumbing from freezing. If you leave it out you don't have to worry about soil gasses.The walls are not much of a factor if you get the ceiling tight. FG does not perform very well if the cavity it is in has air leakage. If you do use foam, I think it's better on the inside than the outside. I would do densepacked cellulose in the walls with no poly on the inside, tar paper on the outside, then siding. The densepacked cells will prevent moisture from getting into the walls. It is carried mostly by gross air movement, which the densepacked cels will eliminate completely. Only miniscule amounts are borne into the walls via diffusion. Leaving the poly layer out will allow the walls to dry to either side of the envelope during periods of low humidity.Steve
*Hey Gabe,The foam board I've been referring to is a polyisocyanurate insulation made by Celotex.The examples they use all show their foam board (which has foil on both sides) placed on the exterior of the wall studs which is why I originally had them on the outside.A quote from their webpage re: vapor barrierhttp://www.celotex.com/products/residential/resmain.htm"Celotex foam insulations are tough, resisting both water and vapor. They fight heat transfer, have broad operating temperatures and better fire performance than polystyrene, and are not affected by solvents or ultraviolet light."I like the idea of placing the foilfaced foamboard on the inside to eliminate the need for excessive exterior flashing, but the question remains: would the use of the poly with this particular foamboard create a moisture trap?I've never seen the blue foam you refer to but have used the pink. Thanks.Brent
*Steve, Thanks for your thoughts. I hadn't thought of glueing the ceiling up. I suppose I've been jaded by the fiberglass empire (the dark side?) but I have read enough cautions re: cellulose & its potential as a fire hazard to stay away from it.The crawlspace is definately in the thermal envelope as there is plumbing for a toilet & sink located there.Brent
*Good morning Brent,For this discussion, the pink is the same as blue.Celotex was designed to be installed on the outside of building in warm weather applications.In the sequence that I gave you, the substitution of celotex would not change anything. The poly against the celotex foil wouldn't affect anything. The use of and the need for, the foil inside the envelope, is wasteful.Remember this, the insulation you describe, would be inside the envelope. Not exposed to water, ultraviolet light, solvents etc.Now, keeping this in mind, I don't know what you're paying for either of these products where you are, so I would let my pocketbook do the deciding here.Gabe
*I wish the building inspectors did as much tear out as I did. they would agree with the idea that behind cedar put tar paper. I have restored 100 year old homes with no tar paper, 50 year old homes with tar paper and torn into walls with tyvex. the cedar walls with problems have tyvex
*I don't know what you've read but a wall insulated with cellulose will burn through more slowly than one with fibreglass. Air moves through fibreglass; not as easily through cellulose and practically not at all if dense packed. This is unquestioned among fire protection engineers.
*My concerns regarding cellulose stem primarily from the suggestion that the boron based chemicals which provide the fire retardent break down over time, particularly if they become moist. Just recently, although I couldn't put my hands on it for this mailing, I read where the manufacturer incorrectly mixed the chemical additives resulting in cellulose no where near it's rated fire retardent rate.
*Hi Brent,For what it's worth, as far as I'm concerned, no matter what's in the walls, if your house catches fire, you are in deep s**t. You'll be doing good to get out alive. Seems to me it's more important to have a wall that burns slower than one that's going to act like a chimney once it starts burning. I would think a cells wall even with too little or diminished borax would still burn slower than one that's full of air.From the firefighter's point of view, I've read that cellulose has a smoldering problem. It has to be kept wet and babysat longer or it'll flare up again.Steve
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I have an addition built onto the north side of my house which, according the newspapers stuffed into the cracks, dates back at least to 1932. As I had a set of taps freeze in there last winter I need to insulate & provide a heat source. The attached photo provides an example of the exterior walls & ceiling/roof. The grey section on the left with the two wires coming out of it is the original exterior wall.
The addition is approximately 15'x 7'. The exterior wall is 3/4" tongue & groove beadboards covered w/cement shingles. The wall studs are 3.5" deep. The joices suporting the roof are spaced 22.5" apart. The high point of the ceiling/roof (left side of attached pic.) is 11'1". The low point (rt. side of pic.) is 8'4".
The addition has a stone foundation and a crawl space with a dirt floor underneath. I have placed 6 mil. plastic on the crawl space floor, and used fiberglass batts to insulate the crawl space walls and ceiling (the underside of the addition floor which is tongue & groove pine). The crawl space, which opens to the basement, contains outlet wiring & plumbing for a sink & toilet.
My thought at this point is to replace the current exterior shingles with cedar shingles and to redo the roof with slate (this is in keeping with the rest of the house).
Regarding the exterior walls: Is the proper order (working outward): original beadboard, tyvek house wrap, foilfaced insulation foam board, osb/plywood, ventilation strips, shingles? Does the foil on the foam board act as a vapor barrior or do you still need the housewrap? Should tar paper be used instead? Is the proper method of attaching the foam board with an exterior adhesive (liquid nails?)?
Regarding the Ceiling/roof: My idea is to put in a tin ceiling (attached to drywall) 8' high so there would be a flat ceiling rather than angled. Am I correct in thinking the tin would act as a vapor barrier (or do I still need the plastic over the drywall) and fiberglass should be installed on top of the tin & drywall?
Finally, any thoughts on the best ventilation method & heating source (radiant panels, elec. baseboard, etc.) for such a space would be appreciated. I know this was long. Thanks a lot for your help.