# Frame over blanket insulation?



## Just Bill (Dec 21, 2008)

In our climate, this would be a big no-no. It simply collects all the condensation during warm months, and then is useless, and creates mold. Can't say what is correct for the mid country, it might be OK.


----------



## jklingel (Dec 21, 2008)

NEW-B said:


> ... but I'd hate to waste all this insulation.


 You read the article and know what you should do. Excellent. So why are you thinking of postponing throwing all the insulation away, with more insulation and lumber, at a later date? We all try the quick and easy way out now and then, but I THINK I have learned to bite the bullet and git 'er done right; that will be quicker and easier in the long run, right? IMO, think again and follow what you know will work. Forget that some contractor "fixed" your neighbor (which may work; dunno).


----------



## NEW-B (Dec 31, 2010)

Well I started tearing out the blankets and bought 1/2" rigid foam to glue to the wall.

Is it possible to add that blanket insulation in the attic?


----------



## jklingel (Dec 21, 2008)

Typical fiberglass batts are very porous, which is why fiberglass is used for air filters. In an attic, left open to the air, it is the worst insulation you could use. However, if you install it and blow cellulose over it, that "seals" it and it will work better. I would not throw it away, as it will do something just lying around in the attic. It depends on what your time is worth to you. Are you sure 1/2" foam is worth the trouble? R-2.5 or 3 is pretty skinny. I'm a bit of a heat loss freak, so I would not consider anything less than 2". What is the difference is the cost of the various sheets? That, of course, is your call. Good luck on the project; they are only beginning... houses are never finished, I don't think. j


----------



## NEW-B (Dec 31, 2010)

jklingel said:


> Typical fiberglass batts are very porous, which is why fiberglass is used for air filters. In an attic, left open to the air, it is the worst insulation you could use. However, if you install it and blow cellulose over it, that "seals" it and it will work better. I would not throw it away, as it will do something just lying around in the attic. It depends on what your time is worth to you. Are you sure 1/2" foam is worth the trouble? R-2.5 or 3 is pretty skinny. I'm a bit of a heat loss freak, so I would not consider anything less than 2". What is the difference is the cost of the various sheets? That, of course, is your call. Good luck on the project; they are only beginning... houses are never finished, I don't think. j


Since I am still insulating the frame wall I decided that extra 1/2" wasn't worth the extra cost. The price difference was about a couple bucks per sheet, but I'm trying to walk that fine line doing it as cheap as possible without sacrificing quality. Thanks for the replys.


----------



## Jackofall1 (Dec 5, 2010)

Use the XPS or EPS,(XPS is preferred has a higher R value than EPS per inch of thickness) 1" minimum, 2" is better.

You can use the fiberglass insulation between the studs, but you will have to cut slits in the plastic, so as not to create a second vapor barrier.

Another use for the fiberglass insulation would be between the floor joist in the ceiling of the room you are fininshing. It will help eliminate sound transmission.


----------



## Jackofall1 (Dec 5, 2010)

jklingel said:


> Typical fiberglass batts are very porous, which is why fiberglass is used for air filters. In an attic, left open to the air, it is the worst insulation you could use. However, if you install it and blow cellulose over it, that "seals" it and it will work better.


Yes fiberglass is used for air filters, but it is also used for car bodies. The density (#'s/ft3) of the material being used will determine is porousity, saying that fiberglass insulation is the worst insulation there is, is just plain BULL.


----------



## jklingel (Dec 21, 2008)

Jackofall1 said:


> Yes fiberglass is used for air filters, but it is also used for car bodies. •• I've never seen a car body made out of fiberglass BATTS. Both filters and batts are very similar composition and not too far off on the density. Yes, the insulation is more dense than a filter, but it is still a very porous material. Batts are obviously nothing like the matting you use in a fiberglass car body.
> 
> The density (#'s/ft3) of the material being used will determine is porousity, •• That is very true. But, we are talking about fiberglass BATTS here, not mats. Just picking up a roll of mat material demonstrates the difference in density. I believe that very tightly woven fiberglass matting is actually a pretty good insulator, but I am not sure on that.
> 
> saying that fiberglass insulation is the worst insulation there is, is just plain BULL. •• Actually, it is very accurate. FG BATTS are not typically dense enough to stop internal convective loops in a wall, which is one reason they are not a great wall insulator. And, if left exposed, they are very poor at stopping air movement; air movement means btu's flying south. Pick one up and look at it or blow through it. You can read about FG and other insulation materials on buildingscience.com, for one site. Greenbuildingadvisor.com is another. There you will read about fiberglass being blown DENSE PACKED into walls and doing very well, ie, about the same as cellulose. It's called Spider Something. You will also read about BATTS being a very poor choice for most house insulation needs. You are welcome.


 Pls see after the bullets.


----------



## jklingel (Dec 21, 2008)

Jackofall1 said:


> ... but you will have to cut slits in the plastic, so as not to create a second vapor barrier.... •• Actually, Jack, that is not quite right. It sounds good, but it just does not work. The slits account for a very small percent of the vapor barrier's area, so they are not effective unless you have a great deal of wind causing the wall to "pump" (generally not a good scenario). You can read about that on the two sites I mentioned, too. In a wall, we hope, the VB is not moving, so there is not driving force to take advantage of the slits.
> 
> It will help eliminate sound transmission. •• Now THAT it does.


 Pls see after the bullets.


----------



## Jackofall1 (Dec 5, 2010)

jklingel said:


> Pls see after the bullets.


 
All I need ask Jklingel is have you really ever looked at the R-values of the materials

FG Bat - 3.1-4.3
HDFG Bat - 3.6 - 5
Cellulose - 3.1-3.8/in

Bout time you quit spreading incorrect information about the qualities of FG.

And the last time I used insulation, I believe it was surrounded by other structure, if you were to apply the same statement "_And, if left exposed, they are very poor at stopping air movement;" _any insulation, would either blow away or collapse, so your comparison is not realistic.

Fiberglass is actually more stable in an attic than celleous as it will absorb less moisture 1% compared to up to 20% with cellulose, resulting in a more stable R-value. (R-value is reduced as moisture content is increased)

PS Your Welcome


----------



## jklingel (Dec 21, 2008)

you best do some serious studying. partial information is dangerous. j


----------



## Gary in WA (Mar 11, 2009)

Basement Insulation Systems NewB, use the builder's grade (low density) fiberglass in the ceiling without the plastic, slit or not. It would still be a vapor barrier, 99.9% effective even with slits. Read this on low density (think convective loops) f.g. in walls or attic; http://www.diychatroom.com/f98/how-buy-choose-fiberglass-insulation-90438/ It collects the dirt well, though. 
So you probably read this on page #9;

However, walls with 0.75 inches of extruded polystyrene and 3.5 inches of fiberglass batt insulation in the cavity would perform well as long as interior humidity was controlled below 50 percent during the summer. Increasing the extruded polystyrene to 1.0 or 1.5 inches would improve performance even with higher interior relative humidity during the summer months. This part of the analysis assumed that the concrete wall had a relative humidity of 100 percent at the exterior temperature. Since these studies were for a climate location similar to Minnesota, the thickness of rigid insulation (R-value) could be proportionately reduced in milder climates.
http://www.eere.energy.gov/buildings/building_america/pdfs/db/35017.pdf

Gary


----------



## Jackofall1 (Dec 5, 2010)

Well I don't often eat crow, but on further investigation, thanks to links posted by GBR in WA I would say that crow is what I have to eat.

Thanks GBR in WA and to Jklingel I have to say I was wrong or stuck in the 80's.

As far as FG being a total outcast I would never say that, and if you have used cellulose it is extreemly dusty, and the chem's it is treated with for fire and mold resistance are a health hazard, that being said.

A job done well with cellulose as compared to a job done equally well with FG, the cellulose will indeed perform better.


----------



## jklingel (Dec 21, 2008)

Thank you, Jack. You have balls, for sure, and I compliment you on that. Next time I may be the one eating crow, or worse, but I've done that enough that I try to be conservative on my responses; doesn't always happen as planned, though. And, FWIW, I have 13" of FG batts in my walls, and they are doing OK (I have mentioned this on other posts, too, so as to not look like I am a cellulose industry troll or whatever). I also installed 5.5" in the lid, and covered it with a foot or more of cellulose. In 1980 I did not know much about cellulose (hell, I didn't know much about ANYTHING), or dense packing cellulose wasn't around then; dunno. If I may gingerly disagree w/ the borates in cellulose being a health hazard, I will. They are hazardous to bugs and rodents, but not to humans. That is why installers don't need haz mat-type suits, like w/ some foams. Google Robert Riversong, who is back in VT (I think) and has been dense packing cellulose for decades. He has the system pretty well figured out, and is extremely knowledgeable of a variety of building science issues. He teaches it, and is a regular on greenbuildingadvisor.com. I've learned a lot from reading over there and buildingscience.com in the last year or so; pretty educated folks, and a lot of those guys/gals also build. Yep. Dirty fingernails and all. BTW: there is also cotton and rock wool, which I personally would use before FG; I just hate that itchy stuff, besides everything else. Y'all take care. john


----------



## Gary in WA (Mar 11, 2009)

Not a problem! I know what it tastes like too..... 
I was shocked when doing the research on low density f.g. I didn't know about the testing until a few years ago. Not many people know about the convective loops as most sites state it but the gravity of it all doesn't jump at you. I think I may need to change my "How to" title as only a few have read it.

I'm starting another different one on sheathing that is just as interesting......

p.s. Been there, done that, will again.

Gary


----------



## jklingel (Dec 21, 2008)

I have had nightmares about convective loops in my walls. But, it keeps my Exxon stocks moving along.... j


----------



## benb (Feb 4, 2011)

It's obvious you guys know your stuff - but I'm getting lost. So, rip out the blanket insulation, put the foam against the exterior walls, frame to it and then put the fiberglass between the studs?

I need a newbie newbie forum.

Ben


----------



## jklingel (Dec 21, 2008)

That'll work, but I would chit can the fiberglass and use rock wool or wool batts, as they are apparently much less susceptible to vapor, and they are better insulation. 1 or 2" of foam, and no vapor barrier. That is my take on the deal. Have a good one. j


----------



## benb (Feb 4, 2011)

Thanks -

Just when I think I have a handle on it, someone at home depot or lowes asks me about what I am using for a vapor barrier -- I then start to think that I have missed something and read the threads again!


----------



## Do It Right (Feb 24, 2011)

Jklingel,
How do you have 13" of FG in your WALLS?


----------



## tpolk (Nov 7, 2009)

Do It Right said:


> Jklingel,
> How do you have 13" of FG in your WALLS?


sounds like an envelope house with dbl exterior walls


----------



## benb (Feb 4, 2011)

*A question about the building science article*

what does it mean when it says to install a capillary break on top of the footing between the footing and perimeter foundation? When it is not new construction but simply finishing a basement, what can you do to prevent that rising damp or the effects of it?

also, their diagram shows optimal insulation in new construction having rigid foam below the concrete slab floor. Again, with finishing, do you all advise rigid foam on top of the slab (even one that has a good finish that needs no leveling, etc.)?

Great article.


----------



## jklingel (Dec 21, 2008)

Do It Right said:


> Jklingel,
> How do you have 13" of FG in your WALLS?


 I built a 2x6 wall, 12" OC and made a ram for my loader; jammed it right in. Kidding. It is, as mentioned, a double 2x4 wall, in between which I stacked 5.5" batts like hay bales. It was a bit tedious, but it works OK. With two of us in 2400 sf, we average about 750 gallons of fuel a year. My new house will have 19" of dense packed cellulose in the walls. I had planned on only 17 1/2" but when I moved the slab down flush w/ the top of the ICF foundation wall (thermal break) I then moved the wall to cover the foam on the top ICF cord. Thus, 19". I refuse to touch FG insulation again; I hate the stuff. In its defense as an insulation, I have heard that newer stuff is a tad more dense than before, so it has improved; but still not the greatest insulation.


----------



## jklingel (Dec 21, 2008)

benb said:


> what does it mean when it says to install a capillary break on top of the footing between the footing and perimeter foundation? When it is not new construction but simply finishing a basement, what can you do to prevent that rising damp or the effects of it?
> 
> also, their diagram shows optimal insulation in new construction having rigid foam below the concrete slab floor. Again, with finishing, do you all advise rigid foam on top of the slab (even one that has a good finish that needs no leveling, etc.)?
> 
> Great article.


 A capillary break is an EPDM gasket, or such, or DryLok paint. On an old slab that does not have a vapor barrier underneath it, I have not heard of a great solution. Whatever you do on top to stop the wicking will leave the slab wet. All I can think of is to take the whole thing out and re-do it; not a great choice, either. As for insulating now, I think you'd be OK w/ rigid foam and all-weather wood framing, (a couple options there) but it better be vapor open on top (no vinyl flooring, etc) so it can dry. That is assuming that you have a relatively dry basement. But, this is only a guess on my part.


----------



## algored2deth (Jan 7, 2011)

benb said:


> It's obvious you guys know your stuff - but I'm getting lost. So, rip out the blanket insulation, put the foam against the exterior walls, frame to it and then put the fiberglass between the studs?
> 
> I need a newbie newbie forum.
> 
> Ben



Lets get down to some further details here. Yes, rip it all out. When you place your foam board (assume 2" thick here), you will glue it to the walls. Use the right glue and do a good job of applying the glue. You may have to fasten them to the walls as well but that will have to be your call depending on wall configuration. In between the panels, you will want to caulk or spray foam or tape joints. Now if the joints from each side of the foam panels fit together tight, you might be bale to leave out the caulk/spray foam but you should still tape ALL seams. You are looking to make it airtight as possible. If you need to caulk, do it. 2" foam gives you a vapor barrier. No need for any more poly. 

As for the floor, if you have the head space, putting down a 1" of XPS foam and then 5/8" or 3/4" T-n-G plywood is one method. You lose a little less than 2" of headspace this way. If you have the space, great. If you are going to do this, do the floor first then the walls. You will end up screwing the plywood-XPS sandwich to the floor with tapcons or similar. Don't need to glue XPS to the floor. If you do the floor first, then the walls, when you frame in the walls, the bottom plate will then go on top of the floor plywood directly. With a fastener, you will need to go through the bottom plate>plywood>foam>concrete.

Overall you are making a 5 sided pink or blue foam box. You need to make it tight as possible. It is not a cheap method. I would also recommend going over to youtube (if you can watch videos w/o a problem) and search on "holmes on homes basment" or something like that . He demonstrates the method and seeing it done is good. 

New construction may put XPS under the concrete. Unless you are willing to rip the floor up, put it on top.

If you add more insulation between studs, others said to use roxul. That is good.


----------



## Do It Right (Feb 24, 2011)

jklingel said:


> With two of us in 2400 sf, we average about 750 gallons of fuel a year.


Wow...only 750 gals for a year is great.
How is the weather in Hawaii this time of year!


----------

