Insulation survey

[MarkAndDebbie]

I looked at cotton batts (recycled denim) and I would bet the cost is close to spray foam!

A quick googling looks like $.60 sq ft for r19 pink stuff and $1.10 r19 cotton. Any idea what spray foam would be?

[MikeOnBike]

We are building a single story 16x18 with a flat truss ceiling.  I want R30 something in the attic but it seems that if I put R30 batts between the trusses I will have nothing covering the 2x4s of the trusses.  My plan is to install R13 parallel/between the trusses and then lay R20 something perpendicular to them. 

[glenn kangiser]

Sounds like it could isolate the truss chord better.  What kind of trusses are you using?  Open web wood?  Will it be hard to get them in there?

What about blown in?

[OlJarhead]

I've been thinking about this a lot for our cabin which has 6" walls and ceiling.  My thoughts are:

Use 1" foam board for the exterior and 4 1/2" fiberglass inside that on the walls then use 1" foam in the ceiling stood off 1" from the sheeting with 3/1" fiberglass batting.

What are your thoughts?  Will this provide better insulation then just the fiberglass batting?

I've also thought of using spray foam for any hard to reach places (like around headers or areas that are just too tough to stuff fiberglass in (becuase I've made voids by goofing up framing here and there)....

[Okie_Bob]

Thought I'd check in and see what was going on in here these days and first thread I find is one of my favorite subjects..insulation!
Those of you that remember me know that I'm a huge fan of Icynene spray foam insulation. First used it on a garage I built which has an apartment we lived in while building a new house. Fell in love with Icynene and used it in the new house.
One thing I didn't see mentioned much in the above thread was the technique of completely enclosing the attic area with foam where you would never do that with any other material. They spray the bottom of the roof from top to bottom and then the top of the ceiling throughout the entire house. I also sprayed under the floor (pier and beam) and all exterior walls. With foam, you get a very tight house with no air leaks anywhere. I've had the house finished about 2 years now and am very happy with low utility bills from the start.
But, I also put in an 18 SEER HVAC system and good windows.
Total cost of cooling in E TX hot summer per month...about $100 worst case. So far, heating has been under that. Figure it gives a good payback.
Okie Bob

[RainDog]

 Okie_Bob:

Ideally, one could build their whole house out of icynene. If they'd only flavor it and fortify it with vitamins, we could eat it too! haha

Merry Christmas!

[Okie_Bob]

Naw, Raindog, my dog wouldn't even eat it and she'll eat anything!!
Okie Bob

[Kiwi55]

Foam plus?

While I am still quite a way from insulation I'm following this very closely.
Ideally I'd like to spray foam both the roof and walls. I was not intending to foam the ceiling as well.

Cost however may not permit. So other options?
What about spraying the walls with 1" of foam (to create a great seal) and then filling the cavities with batts or other insulation? (studs are 6x2). Would I need a vapor barrier? where? (I'm in mid Mississippi).

Same thing for the underside of the roof? I could spray and inch or so, put in batts, and still put foam board under the rafters.

Note also, I was thinking of using closed cell foam on the roof (for it's insulation value), and open cell foam on the walls (for it's noise dampening qualities).

Thanks...Paul

[poppy]

I am not a fan of fiberglass batts or loose fiberglass for that matter.  I have been trying to find the quote source, but someone has pointed out that fiberglass is a common material used for filters.  A good filter must be pourous which of course describes the typical fiberglass insulation batts or loose fiberglass used in attics.

Why would you want to use a filter of any thickness for insulation? 

Something to think about and also reinforces the notion that air infiltration (pun intended  ) is a main cause of heat loss.

Some builders including Jack A. Sobon advocate the use of rigid fiberglass board which has an R-value of about 4.3 per inch.

I for one, like the idea of any "closed cell" system that is continuous, whether in the form of sprayed or rigid board.

[glenn kangiser]

Thought I'd check in and see what was going on in here these days and first thread I find is one of my favorite subjects..insulation!
Those of you that remember me know that I'm a huge fan of Icynene spray foam insulation. First used it on a garage I built which has an apartment we lived in while building a new house. Fell in love with Icynene and used it in the new house.
One thing I didn't see mentioned much in the above thread was the technique of completely enclosing the attic area with foam where you would never do that with any other material. They spray the bottom of the roof from top to bottom and then the top of the ceiling throughout the entire house. I also sprayed under the floor (pier and beam) and all exterior walls. With foam, you get a very tight house with no air leaks anywhere. I've had the house finished about 2 years now and am very happy with low utility bills from the start.
But, I also put in an 18 SEER HVAC system and good windows.
Total cost of cooling in E TX hot summer per month...about $100 worst case. So far, heating has been under that. Figure it gives a good payback.
Okie Bob

Nice to see our resident Icynene pro checking in BoB.  Great to hear from you.

[Okie_Bob]

Glenn, someone has to keep you guys in line! Or at least check in once in awhile to see how far out of line you have gotten.
I bought a boat a couple of weeks back and the guy I bought it from wants to build a cabin in New Mexico. So, naturally I recommened he check out the site. Found out later he did and says it is just what he was looking for. Unfortunately, I don't know
what name he is using but, he lives in Dallas. I told him to look out for Glenn, Mountain Don and John! So treat him nice, he's a younger guy, not like us old fogies!
Okie Bob

[glenn kangiser]

Without you, BoB, this forum would fly apart, so continue to check in and keep us straight once in a while.

We'll be watching for your friend and try not to damage him.  Us old timers can be a bit rough sometimes. 

[Okie_Bob]

Kiwi, I like your idea of spraying the walls as it gives a great seal even if not the highest R value. But, wouldn't waste
the spray foam on the underside of your roof unless you are going to seal it completely. If you plan on a vented attic the
foam would not be the best choice.
The reason I sprayed the underside of my roof is because it is sealed with no venting at all. So, I don't even need any other insulation in what little attic I have.
If I understand your situation, I'd just go with standard ie: fiberglass, etc. Or, you could also spray just the floor of your attic and that would be great.
Okie Bob

[OlJarhead]

I've been thinking about this a lot for our cabin which has 6" walls and ceiling.  My thoughts are:

Use 1" foam board for the exterior and 4 1/2" fiberglass inside that on the walls then use 1" foam in the ceiling stood off 1" from the sheeting with 3/1" fiberglass batting.

What are your thoughts?  Will this provide better insulation then just the fiberglass batting?

I've also thought of using spray foam for any hard to reach places (like around headers or areas that are just too tough to stuff fiberglass in (becuase I've made voids by goofing up framing here and there)....

Any thoughts on this?  I'm in a remote location so doing anything fancy is pretty unlikely (cost prohibitive) so I'm kinda trying to decide if I do this (foam board then bats) or is I use just bats or if cellulose etc is better and I use that -- or that and foam...

All thoughts welcome

[pagan]

OlJarhead,

Fiberglass will allow air movement, which is why it's used for air filters and also why the manufactures are always telling people to use plastic sheeting as a vapor barrier. Also remember that the R values manufacturers quote are based on laboratory tests where the fiberglass has been installed to their exact recommendations, virtually impossible in the real world, which will have a dramatic negative impact on your R value.

Personally I would recommend the sandwich of one inch Hi-R foam boards with taped seams and then dense pack cellulose in the cavities. Cellulose will not allow any air movement and it will also fill in the entire cavity. Cellulose will give you around R-3.5 per inch, but you'll have no air leakage so it performs far better than fiberglass. If you do sandwich the Hi-R foam boards you'll want to use strapping to secure it to the studs or else when you begin dense packing it'll blow the foam boards off. I've seen sheetrock walls blow out when dense packing cellulose.

[OlJarhead]

OlJarhead,

Fiberglass will allow air movement, which is why it's used for air filters and also why the manufactures are always telling people to use plastic sheeting as a vapor barrier. Also remember that the R values manufacturers quote are based on laboratory tests where the fiberglass has been installed to their exact recommendations, virtually impossible in the real world, which will have a dramatic negative impact on your R value.

Personally I would recommend the sandwich of one inch Hi-R foam boards with taped seams and then dense pack cellulose in the cavities. Cellulose will not allow any air movement and it will also fill in the entire cavity. Cellulose will give you around R-3.5 per inch, but you'll have no air leakage so it performs far better than fiberglass. If you do sandwich the Hi-R foam boards you'll want to use strapping to secure it to the studs or else when you begin dense packing it'll blow the foam boards off. I've seen sheetrock walls blow out when dense packing cellulose.

Thanks for the great reply!

I will have to pack by hand -- does this make any difference?

So if I understood you correctly you're suggesting 1" foam board against the outer wall, tape the seems then begin packing in the cellulose and cover with 1" foam board and a vapor barrier?  Or did I get that wrong?

Thanks again.

[MikeOnBike]

Sounds like it could isolate the truss chord better.  What kind of trusses are you using?  Open web wood?  Will it be hard to get them in there?

What about blown in?

Probably open web.  I'm sure it will require a lot of trimming and fussing and hopefully I won't fall through the ceiling. 

We are fairly isolated so we will do the work ourselves.  I see that you can rent the blower and do your own blown-in insulation so if I can find one of those I might try that.

I wish the spray foam was easier for DIY.  We will have a metal roof and I would really like to spray but can't afford a professional crew.

[MikeOnBike]

Probably open web.  I'm sure it will require a lot of trimming and fussing and hopefully I won't fall through the ceiling. 

We are fairly isolated so we will do the work ourselves.  I see that you can rent the blower and do your own blown-in insulation so if I can find one of those I might try that.

I wish the spray foam was easier for DIY.  We will have a metal roof and I would really like to spray but can't afford a professional crew.

I found a Greenfiber blown-in system in the back corner of HomeDepot.  The blower wants 20amps so I'll have to see if our genset can handle that. 

At R-30 it is about 50 cents a sqft.  I think that is fairly competitive with batt fiberglass and it should be a lot easier than trimming batts to fit.

[pagan]

OlJarhead,

Sorry I didn't get back to you sooner, I had the flu and was out for a while.

Pretty close. Most of what I've done is retrofitting and involved putting one inch Hi-R foam board on the inside of the stud wall using the nails with a plastic washer on the end. I then taped the seams with foil tape. After taping I'd run one inch strapping across the studs, about every sixteen inches or so, screwing through the strapping and foam into the studs. With a knife I cut a small square hole through the foam board near the floor and over any window or door, you can cut a round hole but I've found it's quicker to just cut a small square. This gives you access to the wall cavity. At this point I would take the tube for the blower and snake it up through the hole in the foam and begin dense packing. Once the cavity is done I'd stick the small piece of foam back in the hole and then foil tape it in place. Repeat on every cavity. Dry wall is then screwed to the strapping and finished as usual. Personally I see no reason why you couldn't also attach foam board to the outside of the wall using strapping and then attaching your exterior sheathing to the strapping. This would give you the sandwich of foam board filled with cellulose. Honestly I don't know how this would impact the structural integrity of the wall, perhaps John Raabe, or someone with more engineering experience then me, has some insight on this.

The problem with cellulose is, at least for a wall cavity, you cannot pack it in by hand. You'd either wet spray it in and then allow it to dry in place, or you would dense pack, as explained above. Either method requires a machine. You should be able to rent a dense packing rig. Go to youtube and search for "dense packing cellulose" and you'll find some videos showing how it's done. A lot of good stuff comes up. Also search "wet spray cellulose" to see that application.

If renting equipment is not an option, I imagine that if you also caulk the foam boards to the studs giving you a completely air sealed cavity so that if you used fiberglass it would perform far better than if you used just glass and a vapor barrier alone. In this application you would not need strapping as you would not be filling the cavities with pressurized cellulose insulation. You'd just want to use nails or screws long enough to go through your sheathing material and foam into the studs.

Hope this helps some.
Dave

[Kiwi55]

Kiwi, I like your idea of spraying the walls as it gives a great seal even if not the highest R value. But, wouldn't waste
the spray foam on the underside of your roof unless you are going to seal it completely. If you plan on a vented attic the
foam would not be the best choice.
The reason I sprayed the underside of my roof is because it is sealed with no venting at all. So, I don't even need any other insulation in what little attic I have.
If I understand your situation, I'd just go with standard ie: fiberglass, etc. Or, you could also spray just the floor of your attic and that would be great.
Okie Bob

Sorry for the delay in responding (I've been away working on the house). I'm planning a non vented attic. Insulation under the roof and none over the ceiling.
...Paul

[secordpd]

Don't know if this will help anyone, but thought I'd add since it's some good info this guy has.   His name is Dan Perkins and he has written many roofing article for trade mags.  This particular article this link will bring you to is an article he wrote for the mag 'Journal of Light Construction'.  The article title is Retrofitting an insulated cold roof . 

I actually used this on my 3 season porch which has a cathedral ceiling.  On top of my rafters I used rough cut 1' pine boards. On top of that I used ice & water shield.  Then 2' poly-iso sheets (these were bought used from Insulation Depot .com, they have places all over the country that sell recycled/reused insulation board.  I think I paid 9 bucks apiece. I had to buy a pallet. 80 pieces, but sold some and used rest to insulate the outside of my trailer).

I then covered the poly-iso board with 15# felt paper (in case of leaks), used 2x3 for vertical nailer boards.  Then horizontal strapping that I attached my metal roof to.  For the screening between the vertical nailer boards (top & bottom), I used metal screen gutter guards from Lowes, they formed easily the shape of the 2x3.  I figure if I decide to heat, I can insulate between the rafters and bead board the ceiling

If this sound confusing, read the articles Dan wrote.  He has great pics also. It's basically keeping the heat below and the cold above.     If any one has any questions I will post some photos.

[OlJarhead]

http://danperkinsroof.com/1108_JCL_Perkins_A.pdf

Very interesting article but I wonder about the weight?  That's a lot of 2x4's for example and then a 2nd layer of sheeting on top of that.  It would be ok on a roof framed with 2x8's or larger but what about 2x6 rafters on 2' centers?

In my case I was thinking that I could fill the 5 1/2 space between the ceiling and roof sheeting with 3 1/2 insulation and 1" foam board leaving 1" of venting.

Thoughts on that?

[builderboy]

I did sprayed closed cell foam. Cathedral ceiling R45, walls R30. Not cheap. Of all my over budgets, this took the cake. But wow, it's very tight ie no drafts and the increase in structural rigidity is an impressive bonus. Next time I'd probably just spray the roof & do closed cell sheet foam in the walls myself for less than 1/2. If money means nothing go for it.

[OlJarhead]

I'm still considering 1" foam board followed by 3 1/2" fiberglass batting then the 1" air gap, roof sheeting, 30lbs felt and tin roofing.

I'll vent each bay and finish the inside with pine boards (T&G I'm thinking).

I'll draw it out so it makes sense if my description isn't clear -- I'm mostly wondering if it's worth the money to do this versus 4 1/2 Fiberglass only?

[dougpete]

Greetings all -

I am a newbie planning on starting to build this spring.  Down here in the Ozarks we get it all, hot, cold, dry, wet.  My biggest concern is dealing with moisture buildup inside the house.  I spoke with the local spray foam installer, and they recommend building it tight, then using an air exchanger. 
My only problem with this, besides the obvious one of expense is that I want to build as simply as possible and keep expensive to repair and replace technology out. 
I would prefer to just heat with a wood stove and tough out the summers with fans....what would be my best insulation bet under those circumstances?

Doug