I am building an addition for my parents and want to use the opportunity to stretch my envelope, as it were.
I would love not to use fiberglass insulation. Really wanted closed cell foam. Have heard more warnings lately, though, about it being TOO tight. Price could also be prohibitive.
It’s a partial cathedral, 4 pitch rafters with a flat in the middle.
I was then thinking about a wet applied cellulose, but I’m not sure if the R value is any better than fiberglass. Also don’t know what the price is like.
Could you guys tell me your opinions and experiences. I know I’ve read that some people use the others, but I never have.
Thanks
Glenn
Replies
Also, is the R value much better with cellulose at the same depth?
I can only help a little. I see no one else has, yet.
Don't worry about foam being too tight. Since you are only talking about an addition, there will be plenty of air movement through the envelope of the rest of the structure to satisfy ventilation requirements. Choose based on price and performance.
Unfortunately, the HVAC guy told me of a customer who used closed cell in an addition and had trouble with mold and some other problems ONLY in that part of the house.No one wants to make a mistake. Do it once. That being said, you don't know my mother. Job hasn't started and she is already driving me nuts.Thanks.Glenn
Tashler
Wow since my whole house is sealed with foam (SIP's& ICF's) I should have a ton of mold..
Not so- I wonder if your "guy" is wrong?
(he is) Foam seals beautifully keeping heat in and does a nice job of keeping moisture out.
I wish I could stop all the wrong ideas about new technology that occur but since I can't think of this briefly.. does coffee in a thermos have a problem getting moldy?
No the reason is the foam in a thermos does a better job than fiberglas or celluliose.
Foam also won't be affected if something should happen to leak the way fiberglas and celluliose does.
One final bit. Money How much foam saves over the other insulations.
I had a well insulated stick built house that used fiberglass in the walls and celluliose in the ceiling. it was about a 2500 sq.ft. home.. I tore that down and built a 5500 sq.ft. house. with three times the windows and using the exact same furnace my heating bills were 1/3 of previous! My sister remodeled her house using sprayed in foam, increased the size by nearly 50% and now her old boiler is too warm! Her husband replaced it with an electric water heater as a heat source and anticipates a significant reduction in heating costs.. This is Minnesota 40 below wind chills are common!
Edited 8/18/2008 1:27 pm ET by frenchy
Factory foam and foam on site are 2 different animals. I don't trust foam on site because of the experience I have in my house with foam. Remember if you use site foam, you are at the mercy of the guy with the gun getting the chemicals correct.
Factory foam is usually done with computer controlled mixes, and is inspected before it is shipped to end customer.
Mold is not the result of the foam, but rather the inability of the structure to get rid of the moisture.
Edited 8/18/2008 5:43 pm ET by frammer52
frammer52
Then every home should be nothing but pure mold since you're required to have a vapor barrier between you and the insulation.
No you are not. That is the old school of thinking. In cold climates, vb is on the outside.
"In cold climates, vb is on the outside.In cold climates, vb is on the outside."IF you use a descrete vapor barrier then it is on the inside for cold climates.But in all, but the very coldest climates a descrete vapor barrier rather a vapor retarder system can lead to problems.In all climates the walls need to be designed to prevent accumulation of condensation.Dependend on the year around climate and the types of construction there are number of different ways to accomplish that..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
... and of course the sprayed foam IS a vapor barrier.
Jeff
"and of course the sprayed foam IS a vapor barrier."Not always. Depends on the type and conditons. I might just be an vapor retarder.The open cell foams require something else when used on roofs in very cold climates, above 7000 HDD IIRC.And at least some paints will provide that..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
Yes, I'll give you that - interrupted by studs and so on - air barrier but moisture retarder.
Jeff
Edited 8/18/2008 11:45 pm ET by Jeff_Clarke
frammer52
Well if someone screwed up by all means never use that again.. If your car breaks down to you revert back to a horse and buggy?
Frenchy, I have seen picts. on BT of other areas useing foam with installation problems, so I know it is not a local problem.
The major problem is that in the 70's foam was touted as a panacea, only to have long run problems. I certainly wouldn't want to be the homeowner in a retrofit application who had a problem. Imagine the mess to correct. New construction is not as much of a problem because you can see it as it is being applied.
In retrofit, why use it, when you can use cellulose with proven results?
frammer 52
cellulose has one major weakness.. Water!
If there is a leak or somehow rain penetrates into it cellulose loses it's R value completely (same with Fiberglas). Other problems could happen as well but they are too dependant on the same concerns you have with Foam.. the quality of installation..
If it wasn't a problem we wouldn't be doing so much repair work.
Why use foam? in a word because it's extremely efficent. (plus it adds to the structural strength of the building)
We use insulation to save on energy bills the better the R value per inch the higher the R value.. cellulose has an R value of 3.5 per inch foam can be up to 7 per inch. Plus it's not affected by water..
How is the water getting into the walls?
By the way, if it gets wet, it drys with no problems. Can you say wet install?
frammer 52
Depends doesn't it? If it got wet because of a leak won't it get wet again the next time it rains or snow melts? If those events happen at the wrong time of year it could get wet, freeze and not dry out untill the spring.
As to how leaks happen, well they do. We all know they can and do happen even to the best of us.. Corners get cut, mistakes are made, instructions misunderstood, heck a zillion reasons why leaks happen..
That is the precise reason not to use job site foam on old houses.
Can you elaborate on this?
On site foam is the guy who shows up with the truck and controls the mix "on site", correct? How can this contribute to a mold problem?
My experience with "factory foam" is in the small cans. How can this foam be used in a renovation of an older house?
Greg
"My experience with "factory foam" is in the small cans. How can this foam be used in a renovation of an older house?"That is not factory foam.He is talking about foam that make into sheets or blocks at a "factory". Then cut and applied..
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A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.
This doesn't in and of itself contribute to mold. What I am refering to is the inconsistencies of site made foam, without the controls of a factory.
I assume you have some sort of ventilation plan for your home?-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
NRTRob
Of course! But the fact that it's needed indicates the superior job foam can do..
Just making sure!-------------------------------------
-=Northeast Radiant Technology=-
Radiant Design, Consultation, Parts Supply
http://www.NRTradiant.com
Entire house (walls) here closed cell foam no problems. Outside walls are R-19 - R-21 with 2 x 4 construction. Also have an ERV which we love and use a lot, even in summer.
(summer use example - dump 68 degree nighttime air right into the middle of the house, 2nd floor - no need for A/C sometimes the entire following day).
Jeff
Edited 8/16/2008 2:04 pm ET by Jeff_Clarke
What's an ERV?No moisture, condensation, or mold problems?Who did you have do it, would you recommend them, and, if I may ask, what was the cost like?By the way, where in Jersey are you?Glenn
Energy Recovery Ventilator
No problems - central NJ no winter condensation
Have it mostly for wintertime IAQ since hydronic heating.
Trane/American Standard unit 135 cfm +/- cost around $2500 installed. http://www.trane.com/Residential/Products/AirCleaners/FreshEffects.aspx
Jeff
Cellulose should be a bit better R-value wise. Seems I remember cellulose at 3.7 per inch and fiberglass something like 3.2 (although high density is also readily available these days at probably 3.7/3.8 per inch). Wet applied cellulose fills gaps better in general ... boosting effective performance. As long as you have good ventilation the foam should be good ... but you need good ventilation w/ anything ... or you could create a problem where non existed before. Controlled ventilation is better than uncontrolled. Cellulose may be a problem/difficult in the sloped ceiling depending on if the ceiling follows the roof line. Have a contractor give you a take on that part ... need to maintain roof ventilation w/ cellulose/fiberglass ... unless you seal the ceiling well.
How do you seal the ceiling wall?What ever I put up, I assume I need to baffle the bays all the way up.I have seen articles that say to foam against the roof sheathing and create conditioned space, like in an attic. But this is mostly a cathedral.What is an example of controlled ventilation?
Glenn
Assuming your gable wall (ceiling wall?) has a top plate, you don't have to seal it.
You may have to baffle the entire ceiling/roof joist ... generally only if you use cellulose. Install fiberglass carefully and you shouldn't have problems.
Foaming your roof should be no different than an attic situation, really. It's the same concept.
Controlled ventilation ... fancy word for 'exhaust fans' in baths/kitchen. May want to use a dehumidistat or crank timer to control (or even a time clock) one to ensure consistent ventilation. Older houses will have enough leaks to allow fresh air in through the construction, windows, misc. cracks and holes.
Best advice I can give you is to mosey on over to buildingscience.com
and read deeply into the theory.
Then look up their prescription for your climate zone. For example,
"Mixed Humid Heating Zone." They will have some fully worked out designs with many different variations on wall details, etc. Their
books go into even more detail
I am partial to their cost-optimized designs that use a couple of thin
layers of foam (get polyiso) with staggered seams applied over the
sheathing, with FG added in the stud bays, and airtight drywall.
High performance, low cost.
Thanks. I'll check it out.Sounds pretty involved but I'm very interested.Read their article in FH several issues ago. Like the results but slightly skeptical listening to varied opinions.One of my major character flaws is if I'm not sure exactly how to do something without question, I don't let myself do it at all. Don't want to risk making a mistake.Trying to break myself of that. But really don't want to screw the pooch on my own parents house. I would rather get sued than what I would have to endure.Glenn