I know there has been a ton of discussions, my question is fairly basic…
How do I seal the barrier against a stone foundation? I’ve tried building a concrete sill… i didn’t have the skill. Tried glueing to the stones, didn’t take.
Do I run it all the way up to the sill? this seems problematic.
and what if i just run it to the wall, am i just pushing the moisture to the perimeter?
Today there is nothing so i figure anything is an improvement.
oh yeah, i currently have insulation between joists, still cold so I a considering unfaced on the perimeter. Plan to leave the existing insulation and maybe add an exhaust fan.
appreciate any feedback…
jack in Michigan.
Replies
Try using accustical sealant instead of glue. That stuff sticks to anything.
Normally we just insulate the foundation walls and not between the joist so that some heat from the house can get down there.
Just a thought, Dave
I'm assuming your stone/rubble foundation is so uneven that you can't attach a horizontal metal or pressure treated strip to hold your vapor barrier in place. I've "glued" to darn near everything using one of the many polyurethane adhesives that are available - but wire brushing first is usually necessary to ensure a bond.
I agree with previous responder who, in effect, seemed to be saying that it is better to treat the crawl space as part of the "living space", by cooling or heating as in the above living space. I've been following the newer thinking for years by installing a heavy duty vapor barrier ( sealed thoroughly to the foundation wall), and then insulating the foundation and band joist area. No insulation in the overhead joist bays and no venting. Here in the north, vents open in summer only allow warm & moist air to enter the crawl space, which quickly condenses, often leading to moisture damage. Just some thoughts.
Randy
Thanks. Yes the foundation is around 140 yrs old and resembles a rockpile on interior (with a cistern in the middle). When I attempt to fasten the barrier it bunches up all over leaving gaps. I think I may do my best with this approach and then try to fill the gaps with something expandable (great stuff). Not at all confident though.
As for the joists, I just hate to pull out the existing insulation, I may just "open up" one of the registers that goes below to provide some conditioning.
btw. i hate going into crawlspaces...
PS - the Great Stuff will work as a glue to. Not a big fan of that product, but it does have a nack for getting on (and sticking to) everything.
It is difficult to get anything to stick to polyethylene sheet plastic. I have seen some people here describe it as "greasy".
You could try PL400 polyurethane construction adhesive.
Be aware though that there are hybrid plastic sheeting materials available specifically made for use as vapor barriers, most of which do not have this problem of things not sticking to them. One such material is Tu-Tuff (sp?), and is about 3x the cost of regular poly plastic.
Tu-tuf is a poly so you need something which will stick to poly to apply it. I did some research when using Tu-tuf in my crawl space to find a product which would stick to poly and to the foam ICFs with out melting the form. The only thing I found (and it works great) is Permatite Acrylic Sealant. I called several companies in order to find a product which would work - found there is not much which will adhere to poly.
I got the sealant from McMaster-Carr 1-330-342-6100.
Tu-tuff is a "clean poly" so there are a number of adhesives that will stick to it. I think your situation with finding an ICF compatable adhesive made your expierence very different.
The acrylic sealant also adhered to concrete so I am assuming that it will also adhere to rock. I'm not sure where you got your information on adhesives that will stick to Tu-tuf because when I called the company that sells it they did not seem to know of any. They did make suggestions but none of them were satisfactory.
I'm not saying your acrylic sealant won't work - and actually I've never heard of it is it pretty much just a type of caulk? Maybe it is more common than I am aware, but personally I like to use things that are readily available (not that Tu-Tuff is :-)
I used PL400 on the Tu-Tuff on my own home's crawl space which has cinder block walls. Not only did it stick, but I can't get it off. The termite company wanted to retreat, and we could not get it unstuck. Calling a manufacturer is always a good idea, but checking with people in the field sometimes gives a better real-life picture than checking with office workers. I'm pretty sure I got the PL400 suggestion from someone here at BT.
Like I said, Tu-tuff is very different than regular poly though. I have not been able to find much of anything that sticks to regular polyethylene.
Sounds like this guy needs something thick that can bridge gaps - some of which are large.
I just wish I could install Tu-tuff and maybe even glue it on the homes I build. Unfortunately, home buyers would have to pay for it, and only rarely can I even sell them upgraded insulation. Upgraded vapor barrier was not even installed on the 14 Energy Star certified homes that I built.
Thanks guys, I'll investigate the TuTuff. I still don't think I have an answer for the gaps in the stone, the ground is way not level which will add to the gapping.
So today I went below to investigate and found a couple of add'l things...
The addition that is sitting over the crawlspace has two cinder block pillars, how important is it to get the barrier to run under the pillars? That seems like a nightmare.
My cistern has about 8 inches of water in it. I swear that last year it was empty. I can pump it out but I wonder if the water will come back and then should I do anything special? today there is a sheet of plywood over the hole.
The insulation between the joists is also installed upside down, the vapor barrier is facing down - with writing every 8 inches saying to install it to the living side... crazy. It's also falling all over the place, mostly rodents or gravity. I think I may just rip off the paper.
thanks!
regarding the block piers. The VB doesn't have to go under them. Just get it as tight around them as possible and maybe glue it to them.
Re the cistern - I'm not sure about that... my inclination would be to try to get rid of it(fill it in)... or maybe slope everything toward it and put a sump pump in there if you think it will keep refilling. Maybe pump it out as a test to see if it fills back up again... really not sure.
Re the insulation between the joists, sounds like you need to get some of those insulation supports to hold it in place - they are straight pieces of wire about like coat-hanger material. Re the paper, you can just slit it with a utility knive - zebra style. :-) BTW - the insulation is supposed to be up against the floor.
Just a thought, but I was wondering if nailing something like two by twos from the joists at the wall down and nailing them at the bottom to stakes driven into the crawlspace dirt would work-- glue or staple the VB to the 2x2's.
Other thing might be to spread it across floor, then put concrete or rocks or the like at the walls, then bring it up the walls without fastening it to them and staple it through strips of wood to the mud sill. Sort of like a huge plastic bag only fastened at the top.
Edited 10/29/2006 5:16 pm ET by Danno
some people say that bringing the vapor barrier all the way up to the the mud sill can cause the mud sill and rim joist to rot out. I guess the idea is that the mositure is channeled up to the top of wherever the vapor barrier ends. Don't know that for a fact - I'm not a remudeler. I think it was Bob Walker that said that. He is prettty opinionated, but I trust about 90% of what he says...
On an old foundation like that, IMO don't bother to try to run the VB up the foundation or even seal it to it.
_Especially_ if there isn't much clearance between grade and the sill plate/beam and/or siding.
The last thing you want to do is force moisture up the foundation into the sill or siding.
>>I think it was Bob Walker that said that. He is prettty opinionated, but I trust about 90% of what he says...
In the Tavern, I 'vigorously' express my opinions.
In the substantive sections, my views are based on what I see and don't see day in and day out as a home inspector, and I have had to change my views on construction issues enough that I'm always open to reconsideration.
Edited 10/29/2006 8:04 pm ET by rjw
The part you quoted was ment to be a compliment. Hope you took it that way.
PS: the 90% thing was pretaining to home construction type of stuff...
Edited 10/29/2006 8:18 pm ET by Matt
I'm not sure where you are or what your budget is but closed cell spray foam from the house floor to the poly sheeting on the crawl floor will insulate, air and water seal the crawl.
Garett
The biggest problem with stone foundations isn't getting something to stick to it, although that is a also a big problem, but it's all the unevenness. You'll go crazy trying to get a poly vapor barrier to attach firmly.
To get a good seal pull the poly between a 2x4 and the stone wall, stapling the poly to keep it in place on the 2x. Then shoot a few ramset nails or drill for concrete screws to attach the 2x to the stone and fill the gaps with a spray foam. Done.
Beer was created so carpenters wouldn't rule the world.
The thing I am having a hard time wrapping my head around on my own project is the interaction of the insulation and the vapor barrier on the crawlspace wall. I know I want the VB on the warm side, and will be using FG batts to insulate the walls (maybe not the best choice, but I can't afford the spray foam, and sheet foam needs a fire rated material over it around here. I'm going to price the fire-proof foam). This probably means FG batts down the walls.So, if moisture can rot out a mudsill and siding if the VB allows it to go that high (as mentioned above), won't it just saturate the FG batts. I'm in a dry climate (mountains of CO), which helps, but I don't think it will completely eliminate the issue. Also, if I don't want the VB to include the mudsill, how do I attach the batts. I had planned on bringing them up into the joist bays.
On an older house it is possible to increase the moisture level at the plate by running a vapor barrier up the side of the foundation wall since the wall would normally be loosing moisture along it's exposed faces.
So it's not a big stretch to reason if you plates aren't rot resitant then it's probably not a good idea to run the vapor barrier up the wall.
I've personally never seen crawlspace foundation walls insulated in a way that was both long lasting and effective, so I just don't get excited about it. It seems much simpler to insulate the floor.
An inch of ridgid foam sealed around all edges would seal the floor from any moisture coming into the house and eliminates condensation issues because of the insulation qualities. Cover it with fiberglass if you like, or if you have to for fire code reasons.
Vapor barriers in cold climate crawlspaces seem to be better off if they aren't used with insulation in direct contact. I like the ground vapor barrier to simply stop ground moisture from rising above the ground level. Used in this way condensation isn't a problem since there isn't anything to hold the moisture and most moisture is on the ground side anyway.
Beer was created so carpenters wouldn't rule the world.
So, you are talking about a conditioned crawl space.
You raise some good points, and I don't really have an answer for you but here is some things to think about: 1st The paper vapor barrier on FG insulation is not very effective, so it may not be as critical which way you face it. Also, you actually put the VB toward the moist side not necessarily the conditioned side. So in a very high humidity climate install the VB toward the outside of the home. Likewise, on a basement sometimes you will read here about people putting a VB against the masonry wall then insulation, then sheetrock or whatever.
The fact is that conditioned CSes are great in theory, but the implementation can be a bit troublesome. My guess is that is why they still occupy a significantly small % of what is being done today in many areas. Anyway, check at this web site for a method of insulating your conditioned CS: http://www.buildingscience.com/default.htm
BTW - let us know what you decide.