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Old 12-23-2009, 10:41 AM   #16
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Sounds like quite a 'leaky' house! There is agood website you might care to browse through to find out what the current state of insulation etc is - all the things we are talking about - and that is www.buildingscience.com.

There, they outline what you should have - and ways to make what you do have better given that you are in a mixed humid climate zone. And I think one of the better points they make certainly in not-easy zones like yours is the fact that one element can't be used alone without regard to other things. Like don't put up fibregalss insulation if your wall leaks humidity - as that will give wet insulation leading to mould. So there you have to stop the humidty before you can insulate so that the walls shed the water and dry out. So maybe your friends were right about insulating.

Oh and I forgot spray-in cellulose insulation. DIY friendly and cheaper than foam although it would mean even more attention to detail when it comes to air movement in and out of your walls and attic.
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Old 12-29-2009, 10:12 PM   #17
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Thanks for the info and that link. I had read through there a while back but more related to my attic (at the time, i wasn't planning to open up my walls :/) I get confused on there because they say, in the south, don't use kraft faced fiberglass batts in the walls. Does that mean I CAN use the unfaced batts? It also seems that unless you're going to completely seal up your house, you're doomed.

From reading the govn't link below, the map shows that I only need a moisture barrier on the exterior side of the wall. So, to me, this would imply that I can do the spray foam and then put in fiberglass batts. Am I missing it?

But i think another problem i'll have is that my floors are old and have some cracks in between the boards so I'll have to look at getting a moisture barrier there too.
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Old 12-29-2009, 10:19 PM   #18
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Here are some photos of what my walls look like.
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To insulate or not-im000896.jpg   To insulate or not-im000926.jpg   To insulate or not-im000927.jpg  
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Old 12-30-2009, 06:48 AM   #19
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The best way is to spray foam the walls. This gives insulation, air sealing and a vapor barrier. But a hybrid method is less expensive. Spray foam with the DIY kit the outside edges of the studs and maybe 1" deep insulation. Then fill with krafted insulation. This paper is a vapor retarder not a vapor barrier like poly. It is the poly you should not use in warmer zones.
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Old 12-30-2009, 07:58 AM   #20
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Ah-ha...thanks for the pics - we all love them here.

And like I said, those reports from buildingscience won't even be mistaken for easy bedtime reading as they contain a alot of the explanations of what is a complicated subject - but at least they give us all the targets we should try to reach just the getting there is a bit tough.

But the way I read that info in relation to your climate, is that insulation is, well, down the list a bit, after bulk water management and air manangement, so that says to me those are where you should spend the money. Having said that, yes it's ideal to have your house down south there completelly wrapped in Tyvek or some other plastic wrap but not everyone is ready to rip off their siding to stop a few drafts. We do the best we can with what we have.

So then there's air movement. Air movement comprises both heat and moisture movements and is one of the easiest things IMO to manage. You're at the stage where you can affect both, then throw in a bit of insulation and better your conditions in one fell swoop. And Bob nailed it: spray-foam insulation would be the best - although not the cheapest.

The overiding principle is that you want your walls to dry equally towards the inside and outside during the course of a year. You want to prevent hot humid air coming in during the summer, and you want to prevent warm inside air from going out during the winter. So given the to-and-from direction of the air, you don't want a "vapour barrier" that prevents this from happening but you do want to slow it down as much as you can. You need a vapour retarder.

Vapour retarders can be just the drywall you would normally put painted in the colour of your choice; could be the paper facing on the fibreglass batts, could be spray foam and could be a thin sheet of aluminum foil. One of those is what you want - and whether it is the walls or the attic, it comes down to the same: you're trying to slow down the movement of air across your home's 'comfort envelope'.

Now fibreglass batts with the paper give you both insulation and a vapour retarder, so they would be the choice for you - that is unless you plan on ripping off the siding and wrapping the house in plastic. For comparison's sake, up here in colder climates, we use a plastic vapour retarder some places and here we don't use the faced fibreglass (because then you'd have two vapour retarders).

The paper face of the fibreglass ought to go on the warmer-in-winter side of the wall, which in your case is towards the inside. Unfortunately you live in a climate where just the reverse is true for the summer, so basically, you're fighting the elements half of the time. So I guess people just say: "I'll use my painted-drywall as an air barrier" and instead use unfaced fibreglass batts - and that's fine too.

So in your shoes, I'd tackle the bulk water outside the house and make sure everything is OK there; then, I'd put fibreglass batts on the wall, and then put up drywall, and paint that with two coats of good paint.

You're happy - and you're giving your family the gift of a paint job...sneaky isn't it?
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Old 12-30-2009, 03:54 PM   #21
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“In the humid south, vapor diffusion retarders (vapor barriers) should be installed on the exterior of building envelopes. Vapor diffusion retarders or materials which act as vapor diffusion retarders should not be installed on the interior of building envelopes. Most wall coverings and virtually all vinyl wall coverings are vapor diffusion retarders and should not be installed in buildings in the humid south (Figure 4).”
This taken from the paper: RR-9302- Humidity Control in the Humid South, found here: http://www.buildingscience.com/docum...ecommendations
It shows how an HVAC system can add to moisture problems because the blocking at ceiling and floor levels was omitted (pp 16). Another reason to block at drop ceilings, floor levels with balloon framing, and at stairs is found here: http://www.diychatroom.com/f98/how-f...framing-37190/ . A good read to keep you safe.

Spray foam 1” (1.8 perms = semi-permeable) thick will air seal, but is not a vapor barrier, unless 25” thick: http://www.henry.com/fileadmin/pdf/H...l_Brochure.pdf You could spray a primer vapor barrier paint (0.5) over the spray foam, then install un-faced glass batts, then drywall, but no vinyl wallpapers.

Be safe, Gary
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Old 12-31-2009, 12:50 PM   #22
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OK, now we're getting down to the fine print, quite typical for discussions on homes built in the South.

The controversial thinking is that, down South, there is more air-conditioning going on than heating, and so it makes sense to aim any insulation work at the fact that hot, humid air tries to get into cool, air-conditioned homes and therefore the vapour retarder (vr) goes on the outside of the house envelope.

Some say put it on the inside, some on the outside, some say don't put any vapour retarders at all.

Well, since we don't know if the OP's house is air-conditioned at all, it is pointless to even have the debate so no-one can really offer more than general opinions on where the vr should be placed. On top of this there are different kinds of vr's out there, some continous like plastic housewraps and other non-continuous like kraft-faced fibreglass batts...

I happen to like the non-continuous approach to the problem, since faced fibreglass batts are effective and easy on the DIYer. I also like the drywall approach and both comnbined IMO add up to a cost-effective solution for the OP.

Is it ideal? No. But it's practical.
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Old 01-01-2010, 12:06 AM   #23
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ccarlisle, I was showing that the Building Science site says --- not to use one, unless certain conditions are met to use a vapor retarder on the outside, never inside in the South. The U.S. Department of Energy agrees with that, and no mention of AC or not: http://www.energysavers.gov/your_hom.../mytopic=11810

Fiberglass batt paper facing is a Class 2, vapor retarder, not to be used at inside wall face. The Ac and fire-blocking link are showing the OP how important it is, not just for drafts.

Be safe, Gary
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Old 01-01-2010, 11:19 AM   #24
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Yes, Gary, I know but I was making the point that BSC says one thing and for example ASHRAE says another. In fact, the latter says that a discontinuous vapour retarder ought to be on the outside in the south where air-conditioning is important.

And by discontinuous they mean fibreglass batts, kraft- faced and stapled to the studs.
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Old 01-01-2010, 01:59 PM   #25
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Quote:
Originally Posted by ccarlisle View Post
Yes, Gary, I know but I was making the point that BSC says one thing and for example ASHRAE says another. In fact, the latter says that a discontinuous vapour retarder ought to be on the outside in the south where air-conditioning is important.

And by discontinuous they mean fibreglass batts, kraft- faced and stapled to the studs.


Paper facing to the room side, is that correct? Yet, both sites say --paper facing on exterior side (not room) or use none at all. Unless you meant staple the facing to the studs on the outside, under the siding?

Interesting article on discontinuous paper facing: http://www.certainteed.com/additiona..._Retarders.pdf

Side point- housewraps (Tyvek= 80perms, Typar= 16perms.) are water barriers, not vapor retarders (Class III = <10 perms) They are vapor permeable, greater than 10 perms.

Not trying to argue here, just don't want the poster to staple paper facing inside where it would do some harm with the moisture coming through the leaky sheathing boards/siding getting the glass batts wet.
Be safe, Gary
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Old 01-01-2010, 02:16 PM   #26
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LOL! Gary, not arguing either - and I think we see things the same.

We're talking down South in an air-conditioned home. There a discontinous vapour retarder ought to be on the outside to prevent hot humid air from coming in during air-conditioning months. You stop the warm air before it even gets to the insulation. But having said that, there will be times when the same house should have things the other way round, as the OP has in winter.

Furthermore since we don't know about the OP's air-conditioning situation, it is hard for us here to tell him where to put the vapour retarder but since we gather he's trying to keep heat in during the winter, then the faced fibreglass should go inside. But with warnings tho'...

And thanks for the Tyvek detail; I am not knowledgeable about those at all.
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Old 01-07-2010, 12:40 PM   #27
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Thanks for the info guys...greatly appreciated!

I got a quote from one of the local spray foam companies and he is asking $2900 to use 2" of closed cell foam on the exterior walls (against the siding). He said after that, if i wanted more insulation or sound barrier to put in fiberglass batts over it. It looks like the DIY kits are about $1400 for 1200 sqft and 1" thick layer so his cost does not seem unreasonable. I have about 1200-1300sqft of wall space to cover. I think this might be the route I go. He also quoted about the same price to spray under the roof surface and a few hundred less to spray under the floor in the crawl space. He did say open cell foam is not an option for the crawlspace due to the moisture it will absorb and will cause mold issues.
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Old 01-07-2010, 01:11 PM   #28
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Thanks for the follow-up + feedback - that helps everyone. You didn't say if the savings you achieve by doing this will make the paybeck period reasonable, or if anyone gave you any idea about that...?
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Old 01-07-2010, 01:47 PM   #29
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"He also quoted about the same price to spray under the roof surface and a few hundred less to spray under the floor in the crawl space." ------- need a v.b. over, paint,etc. to stop moisture drive: http://www.buildingscience.com/docum...n-crawlspaces/ http://www.buildingscience.com/docum...on?full_view=1
Be safe, Gary
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Old 01-08-2010, 07:56 AM   #30
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James:

I'm not Bob and I don't know what he'll say to your question: how a spray-foam would be useful to you...?

Here's what we know: (a) you're writing from Colorado and (b) spray-foam is polyisocyanurate foam that is used in certain circumstances to insulate houses.

We need a lot more info from you in order to link the two facts.

As for the cost, use $1 per board -foot. Here again, we both need more info in order for that information to be relevant.
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