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Random Quote: Writing at the same time as Shakespeare was Miguel Cervantes. He Wrote Donkey Hote.
The new theory for insulating attics is to apply insulation between the rafters instead of above the ceiling between the joinsts. All venting to the outside is covered; making the attic an interior room and the normal heat from the sun is mostly prevented from getting into the attic by the insulation.
FOAM is the normal method of application, Some builders use Batt insulation (the Pink stuff).
Before this gets kicked to the Chat room, I would sure like to hear from any of you that have done this type of insulation, or know somebody that has. Please either PM me or send a message to me at rspickering@gulftel.com
Thanks for anything you can share. Savings of 40% are the accepted standard when this is done, BTW.
__________________ Rick
Alabama's Gulf Coast
Chaparral 240 Signature (Sold)
I think one reason for insulating between the joists is to make the attic open to airflow through vents and grilles under the eaves, to help prevent mildew. Plus, heat rises, so do you really want to spend money heating an attic?
I suppose you COULD also insulate between the rafters; that might help keep some heat from entering in the summer, and wouldn't change the ventilation pattern I mentioned above.
Be very careful of insulating the rafters. You take a very real risk of voiding your shingle warranty. Some shingles require that the roof be "cold" or vented. I dealt with the issue on my cathedral ceilings. There are many different ways to vent the underside of your roof decking in order to properly use foam.
This is a very hot (no pun intended) topic that has not worked itself out yet that I know of. Best to call your shingle manufacturer before you listen to the spray foam guys. No need to toss a 35 warranty out with the trash.
__________________ 2003 Boston Whaler 255 Conquest w/ twin 200 HPDI's
I've never been a racist. I don't like the white half either.
Mist,
Who has ever really used a 35 year roof warranty? That's almost like expecting print a family photo on paper that is guaranteed not to fade for 100 years. Good point about it "cooking" shingles though.
My point is that if 5 years down the road your roof shingles curl up and turn to garbage who's going to cover it?
I buy 35 year shingles expecting a 35 year trouble free life span. Not to make a claim for them only lasting 30 years. It's the same reason my roof was covered 100% by ice and water shield. By the time the overhangs and valleys were properly covered, it was only 300 more bucks to cover the balance. I do however feel sorry for the SOB who does the first ripper to that building.
As I'm sure you know, it's the hidden damage water creates like rotting the roof deck, starting mold issues, insulation with paint and plaster repair just to get a list started that is more of an issue IMO.
__________________ 2003 Boston Whaler 255 Conquest w/ twin 200 HPDI's
I've never been a racist. I don't like the white half either.
Closed cell foam under the roof is a big no-no.......open cell foam is entirely acceptable. What else can I say since I just had it installed a few months ago.
Isconyne(sp) is commonly sprayed on the underside of roofs here. "Course we don't have to worry about condensation on the underside of the roofing materials. I'd spray the underside of the roof deck AND batt the ceilings. Your location may have different weather conditions.
Savings of 40% are the accepted standard. So......what do you mean by that? Your engery bills are going to drop by 40%? Not calling you a liar, but I find a 40% savings over a properly insulated batt house hard to fathom.
Andy
__________________ Andy Munao Our new parts site: www.simyamaha.com Yamaha Outboard Sales, Parts and Service 1-800-213-3323 parts@shipyardisland.com Click the logo to see our THT Vendor Forum
One big advantage of insulating the attic is reducing the temperature differential on the a/c ductwork. A/C systems in attics lose alot of efficiency by picking heat from the attic, because the ductwork is poorly insulated...r-6 or so.
They make a formed foam air channel that goes between the roof rafters before batt insulation goes over it. This provides about 2" of air channel from the soffit vent to a ridge vent against the underside of the roof sheathing.
I dont know how effective this is at keeping shingles cool, but it's the best system I've personally seen. Can't rember who made the foam channel, but it was pink, so I would guess Owens-Corning.
This was on a cathedral application, but should work physically in an attic as well.
Dont know anything about effectiveness.
__________________ Dog Tired
I'm for a government that is by the people and for the people!
Since this thread started, I've done a lot of surfing and have been surprised by the information that I've learned and/or read. First, my roof is metal with those foam air channels, so the shingle concerns are moot (to me, at least).
Closed cell foam has a higher R-value than open cell and it completely covers the sheathing like paint; as opposed to open cell that breaths and allows moisture to flow both ways. The concept of sheathing rotting for lack of ventilation (with closed cell) seems to be more of an old wives' tale when we think that all wood lasts longer when its covered, whether by paint or otherwise.
In the foam system, the idea is to enclose the attic area just as we enclose new construction; in essence making the attic a part of the home's interior rather than a transition area from In to Out. This if foreign to us, but the idea is that radiated and convected air are what heat the attic, so eliminating that situation results in attics that are about the same temp as the interior rooms. Reducing the attic temp by 15-20 degrees reduces the heat transfer from the A/C flexduct. Makes sense.
Blown insulation or batt insulation hold air and slow heat transfer; that's their purpose. During the summer, that trapped air gets warmer and warmer and soon the trapped air temperature is the temp of the attic air within 3 degrees. I haven't measured that, but it makes sense and that means that the ceiling sheetrock is between 98 degrees on top and 76 degrees underneath. R-value of sheetrock is 0, so the temp of the ceiling ought to be close to 87 degrees and that puts a load on the cooling air from the A/C system.
The cost of foam is about 5X that of batt. The good news is that 5" of foam is R30 while 6" batt is only R19, so installing foam gives 50% greater insulating value. (you can't put R30 batt between 2x6 rafters)
All that said, wrapping the attic with foam is supposed to result in substantial savings. That 40% number comes from the internet, not from me, but all of the players in the foam industry use that number. From my perspective, it ought to be an average. Guys with ranch styles have larger attics should see greater savings, while guys (like me) with 3 stories under the roof have less attic area and should see less savings.
I think that metal roofs that are aluminum (not painted dark) have a high reflective value, which explains why my attic is only 15-20 degrees warmer than the upstairs rooms. It would make sense that hot shingles would increase the attic temp to 20-30 degrees, making foam and even greater benefit to shingle users.
Shingles get heated by the sun, not by what's in the attic. Logic rules, the outside is always hotter than the inside. What foam does is reduce the air temp in the attic, which could ONLY help the sheathing temperature under the shingles. Shingle curl seems to be another old wives' tale.
P.S. I'm a retired GC, so these old wives' tales have been in my head forever, too.
After ALL of this research, I ran across a product called Radiant Barrier film. It looks like aluminum foil and just lays over the attic insulation. The theory is just like those survival blankets that reflect heat. The cost is stupidly cheap and installation is like rolling roofing felt, albeit in confined areas.
Anybody have any experience with either the foam or this Radiant Barrier stuff?
__________________ Rick
Alabama's Gulf Coast
Chaparral 240 Signature (Sold)
For starters I’ve got to say, have any of you ever filed a warranty claim on shingles? Man that warranty sucks the big one! After they pro-rate the age of the shingle and factor in the probable cause(s) of the damage the home owner is left with JACK-SH!T - MAYBE enough replacement shingles to do the roof of a small shed.......grrrrrrr My last home....I had one face that took 20 bundles of 3 in 1 shingles (25 yr. Warranty). Eight and a half years into it the one face was shot! Warranty claim submitted and agreed upon.......payout was 3 lousy bundles!!!!! ......grrrrrr. The shingle warranty does NOT include/ cover labor, felt paper, nails, water & ice or clean up. I told the son-of-a-bitches to shove the 3 f#@king bundles up there arsses.
Any body that knows anything about insulation will all say that closed cell spray foam insulation will provide better R value insulation per inch then any conventional blown in or batting. There is no logical reason to use an open celled spray foam insulation.
Quote:
I think that metal roofs that are aluminum (not painted dark) have a high reflective value, which explains why my attic is only 15-20 degrees warmer than the upstairs rooms. It would make sense that hot shingles would increase the attic temp to 20-30 degrees, making foam and even greater benefit to shingle users.
I guess you’ve never worked up in an attic in the middle of the day in the summer time Rick. Me personally Rick, “I’ve” NEVER seen an attic 15-20° warmer then the inside of a house in the middle of the day in the middle of the summer on a clear day, UNLESS the inside of the house is a 120° or the attic has turbines and is seriously power vented. Even your 20-30° number is unrealistic to what I’ve experienced and had to work in. ALL the attics I’ve worked in, in the summer time, had to be in the 130-140° range......easy 120° by ten o’clock in the morning on clear days.
Quote:
Shingles get heated by the sun, not by what's in the attic. Logic rules, the outside is always hotter than the inside. What foam does is reduce the air temp in the attic, which could ONLY help the sheathing temperature under the shingles. Shingle curl seems to be another old wives' tale.
“Shingles get heated by the sun, not by what’s in the attic. Logic rules, the outside is always hotter than the inside” Maybe it’s the way you’ve wrote this out? But if it’s 140° outside then I’d sure the heck bet you the world it’s going to be hotter inside the attic.
“What foam does is reduce the air temp in the attic”. No, foam will not reduce the temp inside the attic, foam can only reduce the thermo heat from transferring into the attic. So you’ve stated, “P.S. I'm a retired GC,” if so you should know better then to word things like you are.
Shingles curling: from “my” experience, I’ve seen more shingles curl quicker then flowers grow when the shingles are “properly installed” on the south side of an outside porch roof that is open on the underside. I have asked many on why this is so common, I have yet to get a good reply. But I do have a theory.....the sun’s heat/ rays are what they are and shingles are what they are. Now if one applies a greater amount of heat to one side of a shingle then the other I have to figure the shingle or in fact pretty much any other type of material is ALL going to buckle/ curl towards the heat source. Now if this is indeed the case I would have to say directly spraying open or closed foam directly on the underside of the roof’s sheathing could not be a good thing.....regardless of the ventilation issues.
Quote:
The cost of foam is about 5X that of batt. The good news is that 5" of foam is R30 while 6" batt is only R19, so installing foam gives 50% greater insulating value. (you can't put R30 batt between 2x6 rafters).
If you are going to use numbers to present your case, then at least try to do them accurately. Why would you install a 6" batting @ R19 and “only” install a 5" foam? Next off, 6" of foam is going to provide approximately R40 which would be approximately 50% of 6" of R19 batting.
I’d have to ask why anyone would put fiberglass blow in or fiberglass batts on an attic floor, or even consider it? Cellulose blow in is a much better insulating product (IMO). Fiberglass insulation will not stop convection currents, therefore regardless of the R value used in the attic on the floor/ joists there will always be heat/ cold transference. The convection which does occur in fiberglass insulation does not occur in/ through cellulose insulation. Cellulose once settled becomes a self sealing insulation which also prevents air flow.
Now the article below doesn’t indicate what “other materials” are, but I could only imagine they are talking about fiberglass and open celled spray foams.
I think that metal roofs that are aluminum (not painted dark) have a high reflective value, which explains why my attic is only 15-20 degrees warmer than the upstairs rooms. It would make sense that hot shingles would increase the attic temp to 20-30 degrees, making foam and even greater benefit to shingle users.
I guess you’ve never worked up in an attic in the middle of the day in the summer time Rick. Me personally Rick, “I’ve” NEVER seen an attic 15-20° warmer then the inside of a house in the middle of the day in the middle of the summer on a clear day, UNLESS the inside of the house is a 120° or the attic has turbines and is seriously power vented. Even your 20-30° number is unrealistic to what I’ve experienced and had to work in. ALL the attics I’ve worked in, in the summer time, had to be in the 130-140° range......easy 120° by ten o’clock in the morning on clear days.
y'know, Scottish person.....you're too full of yourself and your personallized opinions to be much good to what I'm trying to learn. Take for examply your first ScottishMan's truism about attic temps.
I'm measuring the temps every hour just to develop a database for before and after I do something in the attic...and how much it would be worth it to me depends on how much temp difference there is to start with.
Today is mild summer with temps in the mid 80s since this morning. Interior stays at 79 (-6 degrees from exterior). Attic has been above 90 since 11 and now, mid day, its 94 (+8 degrees from exterior).
Yesterday afternoon from 3-4, exterior was 88 and attic was 97. I used 15-20 to err on the plus side.
This is just one of the condescending statements you have made that are just....plain...false. Am I clear about that? Maybe in scotland the mud huts are all that hot (in your mind), but think about the rest of the world, numbnuts.
You made a mistake. Try to be more helpful, more tactful, and less combative, condescending and foolish-sounding, OK?
__________________ Rick
Alabama's Gulf Coast
Chaparral 240 Signature (Sold)
The cost of foam is about 5X that of batt. The good news is that 5" of foam is R30 while 6" batt is only R19, so installing foam gives 50% greater insulating value. (you can't put R30 batt between 2x6 rafters).
If you are going to use numbers to present your case, then at least try to do them accurately. Why would you install a 6" batting @ R19 and “only” install a 5" foam? Next off, 6" of foam is going to provide approximately R40 which would be approximately 50% of 6" of R19 batting.
.
OK, I'm going to say this really, really slow so you can stay with us on this, ScottishMan.....
First, R40 is to R19 like 200 is to 95. Y'see, its more than TWICE as much, not 50% as you think(?)
Next, why 5" of foam instead of 6"? Well, at $.70/SF/inch, that saves a lot of money. Money is what your mom uses to buy the remedial books you probably don't read anyway.
Finally, the comparison to 6" batts is used because that's the most traditional batting that can be applied to 2x6 rafters. Y'see, you can't install R30 batting because its 8" thick.
Any actual work you've done with roofing or attic might pertain to the bats in your belphry...certainly not in the real world.
You need to learn to.....aw heck, there I go wishin' again!!!!!!!! You aren't going to learn anything else since you know it all.
__________________ Rick
Alabama's Gulf Coast
Chaparral 240 Signature (Sold)
First one is the inside, second one is the outside temp, third one is the attic temp after leaving the temp device up there for 15 minutes. The attic is getting blasted by direct sunlight, the window in the 3rd pic is facing south. Before the renovation I would have guessed the attic easily reached 120 degrees on a 90 degree day.
First one is the inside, second one is the outside temp, third one is the attic temp after leaving the temp device up there for 15 minutes. The attic is getting blasted by direct sunlight, the window in the 3rd pic is facing south. Before the renovation I would have guessed the attic easily reached 120 degrees on a 90 degree day.
Tireless, does that attic temp read 82???? ....and there looks to be foam on the walls, so did you do the sheathing, too? How thick on the sheathing (assuming there're 2x4 studs?)
Wow, this is the first post by somebody that's done this! What difference have you seen in the power usage?
__________________ Rick
Alabama's Gulf Coast
Chaparral 240 Signature (Sold)
First one is the inside, second one is the outside temp, third one is the attic temp after leaving the temp device up there for 15 minutes. The attic is getting blasted by direct sunlight, the window in the 3rd pic is facing south. Before the renovation I would have guessed the attic easily reached 120 degrees on a 90 degree day.
Tireless, does that attic temp read 82???? ....and there looks to be foam on the walls, so did you do the sheathing, too? How thick on the sheathing (assuming there're 2x4 studs?)
Wow, this is the first post by somebody that's done this! What difference have you seen in the power usage?
scroll up to my previous post and click on the link
What difference have you seen in the power usage? What's on the deck between the ceiling joists, blown or Batt?
We have maybe 6-8" of blown and have a metal roof.
Honestly, this is the first I've ever really measured attic temps...before they just all felt like 120. 10 minutes ago there was only a 10 degree spread between exterior and attic (86-96), so wonder whether a metal roof mitigates the advantages of insulation? What do you think and is your roof shingled?
__________________ Rick
Alabama's Gulf Coast
Chaparral 240 Signature (Sold)
bamaboy473 - 6/25/2008 4:06 AM
Any actual work you've done with roofing or attic might pertain to the bats in your belphry...certainly not in the real world.
You need to learn to.....aw heck, there I go wishin' again!!!!!!!! You aren't going to learn anything else since you know it all.
"remedial books you probably don't read anyway." ......well I guess your mommy didn't buy you any for spelling that's for sure.......belphry.........shhhhhhhhhs....belfry. So who's calling who a dick head here?
Attic insulation, Foam or Batt? 
So who's calling who a dick head here? 
