I am building a cabin in northern Wisconsin, along the shore of Lake Michigan with a SIPS roof system (OSB, foam, OSB), 30# roof felt, then asphalt shingles. Recently, I was made aware of a Technical Bulletin from the Asphalt Roofing Manufacturers Association in 1997 which states that “..shingle application directly over insulated decks is not recommended unless an adequate free-flow ventilation space is created between the top of any insulation and the underside of a nailable deck. Proper ventilation must be provided to dissipate heat and humidity.”
Although this makes some sense, creating a double roof (i.e. nailers with another layer of plywood) erodes the simplicity of the SIPS idea.
That bulletin was published over 5 years ago, and I am wondering if anyone has had any experience with this and/or warranty problems. Thoughts?
Thanks.
Replies
Here is one article I found on the SIPWEB.com site:
http://www.sipweb.com/learningcenter/tips-roofing.asp
I am also building a SIP house and discussed this issue with my panel provider. He claims that no laboratory tests have substantiated the claim that SIP's shorten the life of shingles. Of course... he is a panel provider and not a roofing supplier. :-)>
Here is the link to my ongoing SIP project - hope to have time for an update pretty soon:
http://forums.taunton.com/tp-BREAKTIME/messages?msg=31536.1
By the way - noticed you were a recent addition to Breatime. Welcome!
Kevin Halliburton
"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity." - I.M. Pei -
Thanks for the welcome and the link to the SIPS link. I guess we'll just have to roll the dice with the asphalt shingles . . . can't afford cedar shingles.
We currently have a finished attick with vented fiberglass bats. I was hoping, when we redo the roof, to redo the attic as well, by gutting it and blowing in foam insulation. The original thought was we'd then get rid of the venting system (which would eradicate 8 roof vents) and ultimately make for a much more comfortably conditioned space and an easier re-roofing job.
So, all that said, it sounds like one problem will be that our shingles may go a lot sooner than the state lifespan? I'm hoping to go with a lighther shingle, or, hopefully, a metal roof (which would be less of an issue, then.)
Is there anything wrong with putting shingles directly on an unvented, but super-insulated deck other than shorter shingle lifespan? (In otherwords, is it doing any damage to the deck itself?)
No, with one possible exception. In the seventies, some jurisdictions were requireing the use a plywood for roof sheathing that had been treated with fire preventive chemicals.
The problem is that ( and it took ten or fifteen years to find this out) it seems that the anti fire spread chemical reacted with the plywood glues at or above a certain temperature that was fairly easy to reach in attics in the south. The chemical reaction broke down the glue so that the plywood became strands of veneer kindling instead..
Excellence is its own reward!
It's not necessaryily directly related to SIPs but there are studies showing conclusively that allowing higher heat to remain behind the shingles surface keeps the asphalt shingles hotter and they off gas the volatile oils sooner. In other words, they will age more quickly, on an average nationwide, about 2-3 years with a twenty degree hotter attic temp.
One way I have observed this is in the northern states, on a roof with a steep pitch, a north face will often have the old fifteen year shingles last thirty years with no trouble while the south facing side is lucky to make it past the fifteen year life expectancy.
A vented attic space behind the shingles lets heat dissipate steadily while Sips or some other systems holds that heat to the back side of the shingles. Some shingle manufacturers have decided to place disclaimers on their warrantees for this kind of apppplication.
Excellence is its own reward!
Presumably this would also apply if one sprayed foam (or DP cellulose, or any insulation that doesn't allow air movement) directly behind roof sheathing. I have this issue in my house (although the cellulose insulation is probably poorly applied, given how things are in the rest of the house). Any ballpark guesses on how much it costs to do the cold roof thing as a retrofit?
didUnencumbered by knowledge or fear...
Just wait until the next time you need a roof. The roofers will tell you then.
What you mention is the other type system I had in mind. It is the coming of conditioned attic spaces with foam being sprayed on the underside of the roof sheathing, especially in the south, that prompted those studies as I recall.
I wouldn't worry toooo much but watch what you have and how it ages. I have laid shingles in Florida with it so hot, it was blistering my fingers and the shingle texture wasn't much beter than wet cardboard. I have seen little blisters raising on the face of shingles within an hour after nailing them down. Choosing lighter colours in that kind of climate will do as much to extend roof life as ventilation will, IMO, but you don't see manufacturers waiving warrantees for red or dark brown shingle colours, do you?
.
Excellence is its own reward!
I have a good test case, I THINK.
I have a continous roof plane that faces west and I am in KC, MO area.
1/2 of the roof is part of a gabled roof with standard attic and ventalation.
The other 1/2 of the roof has a clearstory wall behind it and ceiling valuted to the roof. In that section there are soffit events every couple of feet. But I have not been able to find anything that looks like venting at the top end. But, until the roof is replaced I can't tell for sure.
The roof is 23 years old Timberline and does need replacing because of hail damage.
Nowever, it is impossible to tell any difference in the two sections.
Seems to me that someone used to post that there was a brand of shingles that specifically allowed the use over SIPS with no loss of warranty. You might want to make inquires with shingle manufacturers.
Sorry I don't remember what brand.
Another day, another tool.
We are going to build a SIP house and the builder, who is also the manufacturer of the SIP panels, showed me some asphalt shingles that are the only kind recommended for SIP roofs in our area, TX panhandle, because of the heath.
I didn't pay attention to the brand because it is a moot question for us, as we will be roofing with metal because of the fierce hailstorms we get.
If you want me to, I will ask him what brand they are.
I would have done so already before posting but he is out of pocket for the holidays.
I don't know if it is proper for me to post his name and # here for you to contact him yourself.
Thanks to all for the very good information to be found all over this site, especially about SIP.
There doesn't seem to be much on that around, yet, in other places I could find.
Hey Ruby, I would be interested in that info whether anyone else is or not.
Thanks in advance and a, "welcome to Breaktime" to you too.Kevin Halliburton
"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity." - I.M. Pei -
Sent you an e-mail with his name, address and phone #. Don't know if it is ok to post personal information like that here.
You may have other SIP questions for him.
Thanks for the welcome!
I appreciate it. It is no big deal to post useful information including phone numbers and recommendations for good products. Where the line is crossed is when you start advertising for your own product or company.
My SIP thread is chock full of names and phone numbers of suppliers and service providers. As long as you don't think your builder would mind, go ahead and post his info on the site. Others may be interested in picking his brain too.Kevin Halliburton
"I believe that architecture is a pragmatic art. To become art it must be built on a foundation of necessity." - I.M. Pei -
Good question. Maybe I ought to first run it by him before posting his name and number. He came highly recommended by some friends.
I did give him a print-out of your thread on SIP building as far as it was last week.
He asked for it when I showed it to him.
Seems that building with SIP is still in a steep learning curve for all. I have seen two houses he is working on now and he does excellent work in general. All is neat and carefully done. The wood work is precise and smooth. He is nice and patient to get along with, too, for someone that has many questions, as I do!
Will ask him and post if he gives permission.
I have researched SIPS for several years now, and even designed a house specifically to use them, but have still not built with them. The last time I checked, Elk was one brand of shingle that would honor their full warranty if installed over SIPS. You may want to check with the Structural Insulated Panel Association, at http://www.sips.org.