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Roger R
Basic Member
Posts:131
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| 04 Jul 2013 05:52 PM |
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Lbear,
Thanks for the info. The SIP salesman said to cover the OSB with Tyvek or tar paper prior to installing the metal roof. How would we accomplish the air venting on a 12" SIP roof? How do commercial applications do it?
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Lbear
Veteran Member
Posts:2740
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| 04 Jul 2013 06:09 PM |
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Posted By Roger R on 04 Jul 2013 05:52 PM
Lbear,
Thanks for the info. The SIP salesman said to cover the OSB with Tyvek or tar paper prior to installing the metal roof. How would we accomplish the air venting on a 12" SIP roof? How do commercial applications do it?
Remember, he is a "SIP salesman" and like any salesperson they will tell you things to get you to buy their product. Whether it's a car or a home or whatever. His job is to sell the product. If the product fails 5 years from now, good luck trying to get them to step up and fix the problem. Not going to happen, I promise you that. Here is a wood SIP install company that clearly states one must strap/furr a SIP roof, no questions asked. If you don't want problems you will have to furr it out and let it vent between the SIP and finished roofing material: To Vent or Not to Vent ArticleI submit this article for your answer also: GBA ArticleIn the end it's a gamble you have to be willing to take. Don't furr it out and hope you don't get rotting issues and have to replace the entire SIP roof structure 10-15 years later at insurmountable costs. Pay to furr it out during the install and have peace of mind knowing if it does get wet, it will dry out and not rot. Otherwise forget the wood SIPs and just go with Steel SIPs. |
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Roger R
Basic Member
Posts:131
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| 04 Jul 2013 06:52 PM |
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Posted By Lbear on 04 Jul 2013 06:09 PM
In the end it's a gamble you have to be willing to take. Don't furr it out and hope you don't get rotting issues and have to replace the entire SIP roof structure 10-15 years later at insurmountable costs. Pay to furr it out during the install and have peace of mind knowing if it does get wet, it will dry out and not rot. Otherwise forget the wood SIPs and just go with Steel SIPs.
Good advice - thanks very much. I have found many companies manufacturing OSB/SIP but none metal. Do you know a site that lists the metal SIP factories? I'm in the Pacific NW and the 'local' OSB/SIP factory is about 130 miles from me. |
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Lbear
Veteran Member
Posts:2740
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| 04 Jul 2013 07:20 PM |
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Posted By Roger R on 04 Jul 2013 06:52 PMGood advice - thanks very much. I have found many companies manufacturing OSB/SIP but none metal. Do you know a site that lists the metal SIP factories? I'm in the Pacific NW and the 'local' OSB/SIP factory is about 130 miles from me.
Metal SIPsYou are in lumber country and wood SIPs is probably all they do out there. Metal SIPs have many advantages over wood; one of which is they don't rot and they are not termite food like wood can be, they can span much longer distances, you don't have to strap/furr the exterior roof, and they are also lighter weight over an OSB SIP. You can get away with not having a crane because a crew of 2-4 guys can carry a panel by themselves. A SIP sandwich of 26 gauge steel with 12" of EPS and 26 gauge steel can be carried by two people. One advantage is shipping, if you got a wood SIP factory just 130 miles away, that saves on shipping. All you can do is get the quotes/bids from both and compare the pros and cons and make a decision. Take into consideration the crane rental costs with wood SIPS and the other factors. If you go with Type 2 EPS in 12", you get almost twice the strength vs. Type 1 EPS and your R-Values with Type2 will be R-60 @25F and R-52 @ 75F vs. Type1 which would be R-52 @ 25F and R-46 @ 75F. The R-value of EPS drops with the increasing or higher temperatures. Type 2 EPS is a denser material and has greater strength and higher R-Values. |
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cmkavala
Veteran Member
Posts:4327
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| 04 Jul 2013 07:51 PM |
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Posted By Roger R on 04 Jul 2013 06:52 PM
Posted By Lbear on 04 Jul 2013 06:09 PM
In the end it's a gamble you have to be willing to take. Don't furr it out and hope you don't get rotting issues and have to replace the entire SIP roof structure 10-15 years later at insurmountable costs. Pay to furr it out during the install and have peace of mind knowing if it does get wet, it will dry out and not rot. Otherwise forget the wood SIPs and just go with Steel SIPs.
Good advice - thanks very much. I have found many companies manufacturing OSB/SIP but none metal. Do you know a site that lists the metal SIP factories? I'm in the Pacific NW and the 'local' OSB/SIP factory is about 130 miles from me.
Roger R,
unfortunately most of the metal SIP manufacturers are in the southeast US
2 men easily carry a 6" x 16 foot panels
Metal SIPs Buildings
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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jonr
Senior Member
Posts:5341
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| 04 Jul 2013 07:58 PM |
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Hard to tell where it's going to be put, but what is done to prevent that slab from being a massive thermal bridge from inside to outside?
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Roger R
Basic Member
Posts:131
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| 04 Jul 2013 08:01 PM |
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Lbear,
After reading those two articles, I'm actually wondering if SIP roofs are such a good idea? There was however a photo on the Sip School site, of a back ventilated herringbone pattern (nailers) running from eave to ridge, then the metal roofing is to be laid over the nailers. With a vent ridge cap on the metal roof, and vents at the eave - would this be a safe SIP roof so I don't have moisture problems in the future? I'm in the San Juan Islands (northern Washington State) and it gets cold and rainy here, and since we are on the ocean, the moisture is always in the air, etc, etc.
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cmkavala
Veteran Member
Posts:4327
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| 04 Jul 2013 09:24 PM |
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Posted By jonr on 04 Jul 2013 07:58 PM
Hard to tell where it's going to be put, but what is done to prevent that slab from being a massive thermal bridge from inside to outside?
are you talking about the unconditioned garage in Georgia? |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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jonr
Senior Member
Posts:5341
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| 04 Jul 2013 11:34 PM |
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are you talking about the unconditioned garage in Georgia? I don't know, say here:
http://www.picturetrail.com/sfx/album/view/24382755
Do 6" SIPs even make sense for unconditioned garages? |
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Lbear
Veteran Member
Posts:2740
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| 05 Jul 2013 01:00 AM |
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Posted By jonr on 04 Jul 2013 11:34 PM
I don't know, say here:
http://www.picturetrail.com/sfx/album/view/24382755
Do 6" SIPs even make sense for unconditioned garages?
It's not about the insulating properties of a 6" SIP but about the structural requirements of a SIP to carry loads. Unconditioned or conditioned, it doesn't matter, the 6" panel is about the structural roof load. |
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Lbear
Veteran Member
Posts:2740
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| 05 Jul 2013 01:06 AM |
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Posted By Roger R on 04 Jul 2013 08:01 PM
Lbear,
After reading those two articles, I'm actually wondering if SIP roofs are such a good idea? There was however a photo on the Sip School site, of a back ventilated herringbone pattern (nailers) running from eave to ridge, then the metal roofing is to be laid over the nailers. With a vent ridge cap on the metal roof, and vents at the eave - would this be a safe SIP roof so I don't have moisture problems in the future? I'm in the San Juan Islands (northern Washington State) and it gets cold and rainy here, and since we are on the ocean, the moisture is always in the air, etc, etc.
SIPs are good building methods if applied correctly. Yes, venting would be required in your building location. The roof and ridge vents would be mandatory no matter what the SIP salesperson tells you. Many scientists and engineers have concluded that venting wood SIPs in such a climate is mandatory. They supersede anything a salesperson tells you. A metal SIP would work better in resisting the rot and moisture issues but you are located as far NW as possible away from any metal SIP manufacturer. Shipping would get expensive. |
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cmkavala
Veteran Member
Posts:4327
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| 05 Jul 2013 07:14 AM |
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Posted By jonr on 04 Jul 2013 11:34 PM
are you talking about the unconditioned garage in Georgia?
I don't know, say here:
http://www.picturetrail.com/sfx/album/view/24382755
Do 6" SIPs even make sense for unconditioned garages?
when the eave walls are 16 foot tall, then yes for wind loads along coastal Georgia. but besides needed for span, according to the owner, the interior temperature stayed at 70 degrees (with no interior heat) even when the outside temperature dipped to 34, so in this case the thermal mass of the slab was a benefit,  and in the case of the Haiti SIP project , we changed direction of the roof panels from gable to gable
(this eliminated need for roof beam) the 22 foot long panels are clear spanning 18' - 8", being in a Hurricane zone, 6" was needed for wind load, not insulation 22 foot long panel installed with no lifting equipment on this 10/12 pitch roof . We only has 8foot step ladders |
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| Chris Kavala<br>[email protected]<br>1-877-321-SIPS<br /> |
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dr99dragons
New Member
Posts:6
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| 05 Jul 2013 11:05 AM |
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RogerR,
I had grey cement floors, and with radiant floor heating you don't want to cover the floor with carpet because it reduces the efficiency of the heat system so we decided on stone terrazzo floor tiles and they were pricy. I bought my own pigment and all the cement company needed to do was toss the pigment bags into the truck at the plant and by the time the trucks arrived the cement was colored. I don't remember the exact bump in price, but they did hit me with a cleaning charge for the trucks.
Dan |
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Roger R
Basic Member
Posts:131
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| 05 Jul 2013 02:14 PM |
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Posted By Lbear on 05 Jul 2013 01:06 AM
SIPs are good building methods if applied correctly. Yes, venting would be required in your building location. The roof and ridge vents would be mandatory no matter what the SIP salesperson tells you. Many scientists and engineers have concluded that venting wood SIPs in such a climate is mandatory. They supersede anything a salesperson tells you.
Lebear,
When you say 'vent' a SIP roof - do you mean run the nailers under the metal roof and add a ridge vent system; or do you mean cut holes for typical roof jacks? |
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Lbear
Veteran Member
Posts:2740
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| 05 Jul 2013 08:34 PM |
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Posted By Roger R on 05 Jul 2013 02:14 PM
Lbear,
When you say 'vent' a SIP roof - do you mean run the nailers under the metal roof and add a ridge vent system; or do you mean cut holes for typical roof jacks?
I would follow the techniques as described in the Building Science article. It shows a furred ridge vent area with 2x2s. |
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joeldunn21
New Member
Posts:23
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| 10 Jul 2013 02:21 AM |
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I'm about ready to build my OSB SIP house in west central MN. Typical upper Midwest climate. Hot & humid in the summer. Cold & dry in the winter. After reading this forum & this Buidling Science article a few months back I was convinced that furring the SIP roof & laying a second deck for the roofing material/ridge vent was the way to go. Since that time I have had several conversations with my panel manufacturer and contractor (has been building exclusively with SIPs in this area for 20+ years) about this topic. They both say they have never had a roof failure due to moisture in this area and that I'm wasting money by doing this. They recommend applying the roofing materials directly to the SIP, but still installing a ridge cap vent. I'm not sure what the ridge vent is actually venting with this method however. They say it would still allow moisture to escape in the event that it develops under the shingles. I'm not quite ready to "Drink the Kool-aid" yet. Anyone with experience in my area (or a similar climate) have thoughts on this? |
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jonr
Senior Member
Posts:5341
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| 10 Jul 2013 10:30 AM |
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A few things to consider (ie, may or may not be true). A gap could form a place for humid air to enter and then condense (perhaps caused by night sky radiant cooling effects). It should also help with ice dams (with an uncovered vent at the top and bottom, it provides building heat with a place to go other than the snow cover). Shingles should stay a little cooler with a gap. Shingle roofs eventually fail and then you will have very high humidity immediately under the shingles - not good when combined with asphalt felt and no drying gap. Rotted SIPs aren't so easy to fix. Old school thinking was to never put a vapor impermeable barrier on the exterior in cold climates. Synthetic underlayment directly on a SIP would be that. Tape the OSB joints (both sides) to prevent any air flow through them, even as the joint gap changes size with temperature and humidity.
Overall, I'd use a vented roof gap. |
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vb
New Member
Posts:88
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| 10 Jul 2013 10:07 PM |
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Joelldunn21,
I too agonized over the roof venting issue.
Code did not require it and it was not in my original plans. I ended up venting with a similar system to the one LBear is directing you to.
VENT YOUR ROOF. It is not that expensive and only took us a couple of extra days. Do your research now- but after your project is over and you reflect on the finer points of the vented roof you will be very happy you did it. One problem that Minnesota has is ice damming, this will be mitigated with the vented roof. You also have wind driven rain with your storms. Build your house correctly now while you can do it cheaply and easily. |
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Lbear
Veteran Member
Posts:2740
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| 12 Jul 2013 11:19 PM |
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The only way to NOT vent a SIP roof and NOT have problems is to live in a very dry desert climate or use Steel SIPs. Otherwise you should vent the SIP roof to avoid SIP rot. Once the OSB rots the SIP is compromised and it is NOT an easy fix and will cost you a lot of $$$. It's not like you can simply remove the OSB and nail on new OSB.
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joeldunn21
New Member
Posts:23
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| 14 Jul 2013 09:39 AM |
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Thanks for all the input everyone! Vented roof for me! Peace of mind well worth it! Will 1" furring strips provide enough ventilation? I'd like to keep my fascia to 6-8" wide, and my panels come from the factory with 6" trim already. |
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