*
I own a “ranch” home that was built in 1943. The home is located on a major river and is only 20′ from the water. There is a large amount of “dry rot” present in the crawl space. This is presumably from moisture and/or flooding in the crawl space. I have plans to control this moisture by adding additional venting and a vapor barrier over the currently bare ground.
I have several windows that have experienced significant rot on their sills. I would like to replace these windows before the wall sheathing has a opportunity to also rot. When I am replacing the windows I would like to anticipate some future changes. The one major change that we would like to make is to re-side the house. Re-siding would have a couple of advantages: it would allow us to use a exposure that would be more proportional to the house, it would allow us to inspect the rim joist and replace rotten wood more easily, it would allow us to add additional insulation to the existing 2″ mineral bat, and it would allow us to add additional insulation in the form of some EPS on the exterior, behind the new siding. To accomidate the EPS I would need to furr the new windows out, say 1.5″. This means that the window will be quite unsightly until the new siding is installed. This will probably be several years. Perhaps some kind of moulding could be applied at a later date to allow for a change in wall thickness thus allowing the window to be installed tight to the current wall sheathing. I digress. How the window is installed is not a concern at this moment. My main concern is if the EPS could act as a vapor barrier thus causing condensation in the wall. Does anybody have experience or recommendations in regards to installing EPS on the exterior of a older home? What would you do in this situation?
Replies
*
this very question is addressed on the main discussion page today (yes, adding an impermiable layer of foam sheeting on the outside of the house would require any interior moisture to escape some oter way and that needs to be addressed somehow - provide other ventilation, or allow some thru the sheeting (not tape the joints maybe).
Please study the archives for 'venting', 'insulation', etc. and read up on the tons of discussions previously discussed.
Note that not all posters are in the same climatic region as yours, or as each other. This website does not make that easy to tell (poster's locale is not in their header) so any advice taken from here demands consideration of that fact.
good luck and tell us what you decide. or ask more questions as you get your plans more specific.
*I'm at Affordable Comfort Conference 2001 this week (with at least Robb S and Fred L) and spent the entire afternoon in a session on this very topic - with more tomorrow and Thursday.Where do you live - climate wise? Do you have air conditioning? Are there forced air systems? Ducts in crawl space?If you respond quickly I will try to check tomorrow and ask the experts on Thursday!
*I live in SE Wisconsin only a mile from Lake Michigan. This is primarly a heating climate with cooling in the 3 hottest summer months. The house is heated with forced air, with the ducts in the attic. The house is not currently air conditioned, but that is something that should be anticpated in the future. Right now I'm cooling the house with a whole house fan.I wonder if the EPS was sawn into smaller pieces if that would increase it's permiability enough that it won't cause condensation. But how big would the pieces be? 2x2?Thanks for your help!
*Well - come to the conference att the Sheraton near the airport and learn for your self from the "greats" of insulation. I'll ask them directly also but if you can afford the day you will learn a lot.The crawl should be sealed - heavy plastic or better TuTuff (a cross linked poly ethlelne) or epdm -(rubber roofing) across the gorund and up the crawl walls to the sill. Seal the band joist with blocks of XPS (styrofoam - not bead board) and foam in - foam in a can - or buy a big pack of spray foam and just foam them entirely - may be worth it to not spend so much time in the crawl. Then add insy=ulation (not fibreglass) to walls - rigid foam tightly sealed for instance. NO VENTS IN CRAWLS! That has only been repeated a dozen times a day. (If you can't seal the plastic well you might - just might - consider a small - 50 cfm - exhaust fan from crawl to outside on a humidistat to depressurize it, suck inside air down through it, and expell soil gasses, spores, etc.Air seal the interior pressure barrier - all the cracks and joints and holes in the drywall and bypasses in the framing. Foam, caulk, whatever.Insulate ceiling with as much as you can.Then, I don't like foam on exterior but it is popular. Personally, I would blow cells from inside (easy to patch plastwer or drywall or pull a mop board off and drill there) and simply reside - maybe with building paper or house wrap under. If you do use foam, the air and the vapor barrier on the inside should be pretty good. Cover foam with housewrap. If youe siding with vinyl figure that foam and siding are good for 20 years and then replace.But come to ACC and find out for your self. (and meet me and Rob Susz and Fred Lugano - not to mention Lstiburek and Tooley and Fugler and Straub and many others)
*Which airport are you guys at and what are the hours?
*Sorry - General Mitchell - but ends today and I think today is only a few "short courses". I found it to be a very exciting and educational event and look forward to attending next year.If you do wrap foam around exterior - and extruded polystrene or polyiso would be appropriate, not expanded polystyrene (the white bead board stuff) - just make sure that the construction inside is not too impermeable. Drywall with latex paints is ok - but I did ask what happens when this is repainted several times and was told it becomes a vapor barrier - a not good thing. Basically, only one vapor barrier per wall or ceiling.The inside should obviously be air sealed - tight drywall caulked at edges, foam-in-a-can around windows, etc.As important, the new exterior cladding should be a water managed system - some sort of cladding with a drainage plane and a drainage space. Housewrap, vertical furing, and clapboards do this; there are others obviously. This of course has to be coupled with very good flashing, which probably includes drainage pans under the windows all the way through the wall.One slick tip for these windows - use a piece of beveled siding on the sill framing to create a slope and then cover with peel and stick or other waterproof memrane that can be made into a corner.Windows, cladding, doors, etc. all will leak - plan for it.
*Bill,Please explain why your against EPS and for XEPS or Polyiso. If something new has come up at the conference you recently attended ,I would sure like to know why the preference to a specific type of foam.Thanks Al Cobb
*This is an issue that the "experts" are divided on from my listening and reading. I bvelieve that when a rigid foam skin is installed, it will be defacto a vapor barrier (>1 US perm by definition). At most, you want just one vapor barrier in a wall. (I'd prefer none in my house but will leave that argument for another discussion.) EPS does not meet the vapr barrier requirement BUT I know it will hold moisture. Also in climates I have built, it will harbor insects. Its possible to construct a wall with an interior side vapor barrier and use EPS outside based on the premise that any moisture that gets into the wall will dry by difussion through the EPS - but I worry that won't happen and/or bad things will happen in the process - like condensation outside of the EPS on the back of the sheathing. (So to defend against that you apply cladding on furring, and so on.)What I would consider more seriously than I have in the past is this concept of a vapor barrier in the middle of the wall - like Gene's sprayed foam on the inside of the sheathing and framing, then dense pack inside of that. As long as the foam/vapor barrier has sufficient conductive insulation to keep the first condensing surface (inside of foam on spray or inside of sheathing on rigid foam outside) warm enough to not condense, it should work. Rigid foam sealed tight on the exterior would be the same - the inside surface of the foam being the vapor barrier in the middle of the wall and the first condensing surface.Only mentioned was the ability of various materials to store moisture - below a critical mold or condensation level - and release it later to dry by difussion to either the inside or outside or both. Thus my preference for a wood and cellulose wall with wood and gypsum sheathing and either wood or fibre-cement cladding or even real stucco and nothing constituting a vapor barrier or even a vapor retarder (less than 5 US perms).So maybe that' snew and maybe not. I just feel a little more certain of my previous instincts - based on old houses.
*This is what I feared-that the gain of added R-value is not worth the potential trade off of condensation. I was hoping that sombody before me had resolved this problem.Bill do you work in the SE Wisconsin area or were you just visiting?
*I live in the Chicago area curerently (12 years)and am from New England but my interest and study of weatherization are not limited to those climes.You can put foam on the outside but have to think through all the other issues carefully and not create a second vapor barrier. It isn't as "tolernat" or forgiving of system as I prefer - not to mention all teh work and effort and changes to extend the trim and windows and such.
*bill, i don't think you are keeping up with the latest testing and findings about EPS.......i spent 20 years avoiding it like the plague, mostly for the reasons you stated.. but it turns out that they are not true...EPS costs a lot less per R-value...it can be treated for vermin (mostly with borates and marketed as "Perform-Guard" )it comes in at least 3 common densities: 1 lb/cf12.5 lb/cf & 2 lb/cfit will hold moisture , but nothing you can measure...nothing else i have found will return the same cost/benefit ratio.... if i were you , i'd give EPS another look... i did after talking to others on this forum, and it will be my first choice from now on when i'm looking for foam products...
*I don't trust chemical treatments for 100 years - which seems like a reasonable goal. (Of course if your using vinyl then one expects to tear it off - windows and all - and replace every 20-25 years - so that is a different criteria.)I'm not sure what you think I said that was true. Certainly adding it to the outside of an existing building must result in some fussy jamb extensions and trim work. Certainly you agree that EPS doesn't provide the moisture storage capacity of wood and cellulose. And certainly there are dangers to including two vapor barriers in a single wall assembly.I never said that eps is not cost effective for its nominal insulatinon value. (How does it do when wet and after it dries out if it does dry out?)If you want cheap - fine - I'm for fine which isn't necessarily cheapest nor even competitive if profit is your goal.
*EPS doesn't absorb water... since we switched to EPS on the INSIDE of our energy walls, i don't have to worry about a vaport barrier on the wrong side... nor do i have to bother with all the neccessary blocking we used to use when we were putting Polyiso foam on the extriormy point is that you were using polyiso,, or Styro-smor similar products.. which are NOT treated for vermin..having ripped a few of teh energy homes of teh early '80's apart and found the infestation... i won't use anyting in the foundation area or first floor walls that isn't treated..EPS fits the bill, bill...
*I still don't trust a chemical treatment for insects and such to last 100 years. Ain't going to happen.I wasn't sure of the meaning of your comment aboyt vapor barrier on the wrong side but time and time again I've read that eps is not a vapor barrier: perm >1 US perm. No vapor barrier is thinking I do appreciate, if that is what you mean.
*My problem is that I already have a moisture problem. This is due to the house being located very close to a body of water. For that reason I must be extremelyy cautious in that I don't cause any further moisture problems. My current feeling is that a layer of EPS on the exterior could cause moisture build-up inside the wall. Maybe it would maybe it wouldn't; but I can't afford to find out. Which is why I posted here-to get other peoples opinions. For that I thank you.
*Please confirm: You already have moisture build up in the walls?
*Tim, do what Bill says for the crawlspace and your moisture problem will go away; It has nothing to do with being near water, it has to do with the fact that you have a terrible crawlspace, one that is textbook bad. These are all over the place.Your sheathing is probably already rotten (which no one has yet pointed out).The furred out windows don't look too bad. I have mine furred out 2 inches for foam and I used foam and plywood to fur them out for an insulated spacer for the window. I have had increasing quantities of furred out windows on my house for the last 6 years. Of course it is way back off the road....The EPS is a vapor reatrder, and can be applied under the siding with no building paper over it. tape all the joints and nail heads with 3M 8086 tape. Lstiburek calls this out in his cold climates book.The foam will actually cause the temps inside the wall to be higher, preventing condensation. This foam is vapor permeable. It will make a bad situation worse, and you currently have a bad situation. So the issue becomes source control of moisture. Stop the moisture before it gets into the walls. Stopping moisture from getting airborne in the crawlspace is the first step. Stopping convection into the wall is the next step. Applying the foam and raising the temperature of your first condensing surface is the third step.Oh, and your ducts are leaking 20% of your wet heated air into the attic and delivering the air right to the cold roof sheathing, so the roof is probably rotten too. There's that "rot" word again.I am flattered Bill spoke so highly of me, even after meeting me in person!!-Rob
*Bill,I'm still not sure why your down on EPS. The only cons you've stated when comparing it to other foam products are moisture retention and insects.My experience shows all closed cell foams will wick moisture when exposed to soaking conditions. Obviously this kind of condition is not present in your avarage wall. If it is, you've got bigger problems then the perm rating of your foam of choice. The insects issue is also a wash in my opinion. I've personally seen infestation of both XEPS and polyiso foam. As for a so called chemical treatment to EPS, I think your putting borates in a poor light. You are referring to a mineral not a chemical. The material is also called disodium octoborate tetrahydrate and commonly called diatimatious earth. It's a water soluable product that will be around as long as the foam is. However, it has only proven itself effective against carpenter ants and termites. (not insects in general) In addition, I would caution anyone from counting on borate treated foam as the sole means of defense in the war on ants and termites. Just because the foam is treated, dosen't mean the critters won't find another area of the structure that provides food and shelter.Again I ask Why. Your views and comparisons would be appreciated so that I may understand your prejudice.Thanks again, Al Cobb
*Personally, I would avoid all foams whenever possible. I've read and seen of more problems with foams than without. They won't store and release moisture the way wood and other organic products do and they tend to require more careful installation - sometimes beyond the abilities of most installers.I recommend XPS or polyiso where it would be acceptable or desirable to have a vapor barrier. EPS is not a vapor barrier but it doesn't seem to be quite as vapor permeable as wood or drywall.As far as treatments, the fact that it is water soluoble does not seem to recommend it as permanent.And it seems that many materials get rave reviews if they don't fail within a few years. I more interested in 50 or 100 years.
*I doubt if there is any moisture build-up currently in the wall cavity. My moisture problem is currently limited to the crawl space. The moisture is coming out of the ground as it is moist. Not damp (wet), but moist so that the sand will stick to you. The rim joist is rotten to the point that you can rip chunks of it out with your bare hand. The floor joists are dry rotted. They look perfectly normal on the exterior, but they have no modulus. You can get a screw drive to penetrate 1/2" on some of them, yet they look like new. I've been sistering the joists when I can and have added some headers to reduce the joists span.None of this work has been fun, and it has been rather disheartening to find such a nice house to have so much cancer. For this reason I cannot run the risk of causing any moisture build-up in the walls. I wouldn't be able to keep up!In response to Bill's comments about EPS being being used on a home, I would have to agree with him. The product (at least on this application) is a can of worms. As this is a older home the multiple layers of paint would qualify as a vapor barrier. I know that Bill has stated several times that EPS is permeable, it must be very close to being impermeable which would make it a second vapor barrier (and one on the cold side of the wall too!). This would defenitly cause condensation in the wall, which is exactly what I'm trying to avoid! I'm beginningg to think that the only place that foam should be applied is on the room side of a wall (which brings up flame spread/smoke generation issues).I believe that we all agree that trying to crutch a product with a chemical insect treatment is just that: a crutch. I don't intend to live in this house for 100 years, but I do want to do the job right.Bill, I cannot seem to find your comments on reducing the moisture problem in my crawl space. My thought was to add additional ventilation and a ground vapor barrier, but I thought that you contradicted that saying instead to reduce theventilation. Wouldn't that cause additional condensation problems?
*tim... no, we wouldn't all agree that treating EPS is a crutch..and .. i did state that all of our foam is applied to the inside of our wall systemsand.. if you have that much moisture problem in your crawl space.. you also have a problem in your walls..good luck..
*To reduce the moisture in your crawl space you want to prevent the moisture from GETTING to your crawl space. - all run off water diverted 10 feet away from the building - the lot should slope away from the building - they 'floor' of the crawl space should be sealed to prevent ground water from rising up and entering that space (plastic, taped and stuck down to the ground with maybe sand on top, etc, etc).There have been many posts here about how to reduce moisture in crawl spaces, please search the archives and enjoy the arguments that are recoreded there.Only after you have cured this moisture problem would I suggest that you add any more insulation to your structure.working in a crawl space is so awful. The best solution I've run in to is concrete (over a gravel bed and a plastic barrier). Then you can get around on a automotive repair dolley!And no more gophers digging holes!
*Tim,Re: crawlspace moisture and ventingThere has been literature printed in JLC in the last year or so citing studies that conclude that you should not vent crawlspaces except in the most arrid (dry) of climates. In most instances, in the summertime the relative humidity of the outside air is high enough that upon entering the cool crawlspace, moisture must be released from the outside air and it condenses on pipes, framing, etc. It is usually better to keep the crawlspace sealed up as tight as possible or under slightly positive pressure so that you are expelling crawlspace air and it is being replaced with dry air from the interior conditioned space. If there are moisture sources within your crawlspace that make the RH higher than it would be if you diluted it with outside air, then there may be some benefit to venting. But if that is the case, you ought to get that interior moisture source under control, or you'll soon have rot with the windows open or closed.Steve
*Now, I understand the comment about not venting the crawl space.. This was actually contrary to my thinking (more ventilation=less moisturebuild upup). I just finisheregardingng around the house and now have the grade pitching away from the house and 6-8" below the siding (instead of above). I have also installed a subteranian drainage system for the gutters. I know that I need to put a vapor barrier on the ground and topping it with concrete would be a good idea (but a miserable project). When these changes are completed the moisture level should be reduced to a more acceptable level. Thanks for your help. :)
*Tim, the foam on the cold side of the wall will actually make the wall cavity warmer, PREVENTING condensation.I will again make my point - DRY OUT THE CRAWL SPACE!You think the moisture issues is only in the crawl space, that's because you haven't yet looked in the walls. I would suggest some more investigation before spending another dollar on remedial work. You may indeed be throwing good money after bad.-Rob
*
I own a "ranch" home that was built in 1943. The home is located on a major river and is only 20' from the water. There is a large amount of "dry rot" present in the crawl space. This is presumably from moisture and/or flooding in the crawl space. I have plans to control this moisture by adding additional venting and a vapor barrier over the currently bare ground.
I have several windows that have experienced significant rot on their sills. I would like to replace these windows before the wall sheathing has a opportunity to also rot. When I am replacing the windows I would like to anticipate some future changes. The one major change that we would like to make is to re-side the house. Re-siding would have a couple of advantages: it would allow us to use a exposure that would be more proportional to the house, it would allow us to inspect the rim joist and replace rotten wood more easily, it would allow us to add additional insulation to the existing 2" mineral bat, and it would allow us to add additional insulation in the form of some EPS on the exterior, behind the new siding. To accomidate the EPS I would need to furr the new windows out, say 1.5". This means that the window will be quite unsightly until the new siding is installed. This will probably be several years. Perhaps some kind of moulding could be applied at a later date to allow for a change in wall thickness thus allowing the window to be installed tight to the current wall sheathing. I digress. How the window is installed is not a concern at this moment. My main concern is if the EPS could act as a vapor barrier thus causing condensation in the wall. Does anybody have experience or recommendations in regards to installing EPS on the exterior of a older home? What would you do in this situation?