We're building a simple house ("T" footprint....2 valleys and 2 ridges) with ICF walls and SIP roof.  What are the recommendations for installing metal roofing (standing seam metal roofing)?  We've been told to cover the SIP with a water and ice shield.  Some people have recommended topping that with "Cedar Breather" for venting.  Others have suggested vertical strapping and still others have said to install a secondary roof surface floating over the SIP.  Thanks in advance.  Cathy

First, you should check with your roofing supplier, to see if a solid underlayment is going to be required. I know that many types of true 'standing seam' must have a solid surface directly under the metal to keep it from telegraphing any strapping that might be used underneath and to reduce the chancs of damage from hail, etc. Most of the heavier industrial types of metal can be applied over intermediate structures, such as roof purlins or strapping. Over the years, I have applied metal using all three ways that you mentioned. I prefer the use of the 'cedar breather' method of ventilation over the strapping. Less likely to telegraph. (Also there are other, similar products available that will be less expensive than Cedar Breather)
Recently there have been some test results showing a significant reduction of heat buildup in conventional attics, when ventilation between the metal and sheathing is available. To my knowledge, this testing has not been done in relation to a SIPS roof, to show whether the same holds true, or not.

Thanks Wes.  We're using heavy guage metal and doing a tradition roof (i.e., the metal will be bent on site).  The Cedar Breather is quite expensive.  What other products are out there which would be similar?  BTW, not sure I mentioned but we live in northern NY, in the Adirondack Mountains.  Not sure if location will have any bearing on this topic.  Cathy

I would cover the entire roof with Ice and Water shield as someone else suggested. I did this on a house similar to what you are describing. ICF wall, SIP's roof but this house had to have red cedar shingles over the sips's (deed restriction) I covered the entire roof with the ice and water shield to protect it until the shingle or in your case metal will be installed. We then built a cold roof system above, using 1x strapping vertically up the roof and then over that horizontally. We also put a corrigated vent strip behind the fascia to allow air to flow up under the shingles and out the ridge vent. I would suggest allowing this to vent in some way, the metal directly over the sips roof even with ice and water will get extremely hot. There is a guy in NH that places pex tubing in the space between the strapping and uses this for solar hot water collection. If your intending on putting strapping over the ice and water then think about placing some Pex under the metal to collect hot water. Pex is pretty inexpensive stuff, even if you don't tie it in right away it would be there for future use. Check out Dawn solar in NH he also adds thin film PV to the upper side of the metal and creates a hybrid solar collecting roof. I don't know about the thin film, the efficiency of that stuff is terrible around 7%, but I like the hot water collecting idea and will definetly try this on my next project that has metal roofing.

Tom Pittsley
ecobuilder@aol.com
www.eebt.org

on our most recent project we placed a peel & stick membrane to the sips, installed 7/8" steel hi-hat @14" oc then this permatile metal roof

Hi Cathy,

I would be very careful about applying ice and water shield to the exterior surface of the panels. Ice and water sheild acts as a vapor barrier and there are very few areas in the United States where a vapor barrier is applied to the exterior surface (the deep south being the exception). As a matter of fact, you could create serious moisture problems within the SIP assembly by trapping in any airborne vapor at that point. In many cases, the vapor will condensate at this condensation plane and the moisture will be wicked into the top OSB skin of the panels.

A better method for the assembly would be to have the vapor barrier on the inside of the SIPs. This can be achieved in either the conventional manner using poly/visqueen or by simply sealing the panel seams with caulking and approved SIP tape. Keep in mind; OSB and plywood, technically speaking, are vapor barriers, so it is not necessary to cover the entire surface - just the seams.

On top of the panels, regular 15lb or 30 lb felt can be applied, and then the metal roof. The roof does not have to be firred up, but it is a good idea to do so. This can be acheived using  1 x 2 or 1 x 4 strapping which will allow the exterior surface of the OSB to 'breath' and will also allow any condesation accumulating under the metal to dissipate.

Hope this helps.

Dave

Cathy,
I am no builder  but built my own SIP home.  I did contract out the metal roof, facia and eaves.  My attic is conditioned and sealed (not a conventional "cold roof").  After doing a bunch of research and investigation, I determined that the simple method seemed to be as good as any.  30 lb. felt on the SIP panel (water and ice sheild on the eaves as required by code - kind of a waste given how my roof is = conditioned, but code nonetheless) and the standing seam panels "bent on site" attached to that.  It is only 2 yrs. old, so time will tell.

Kathy,

Hopefully you've decided to use Polyurethane SIP roof panels instead of styrofoam. If you are using styrofoam, Oak Ridge National Laboratories strongly recommends using a radiant barrier and or anti-reflective coatings when metal roofs are used in conjunction with any open cell foam as it can get hot enough to start melting EPS.

Hope this helps and best wishes for your project.

Craig Payne
www.eco-panels.com

Cathy not Kathy, Sorry

CTP ; our EPS is closed cell and have never had any problems with metal roofing applied to SIPs

We had a group tour at ORNL and one of the building scientists from ORNL said that he would strongly recommend against using metal roofing over EPS of any kind unless their was additional protection included: i.e anti-reflective coatings and or radiant barriers. Someone in the group had asked about Icynene and the conversation then moved to SIPS and EPS. They have done extensive testing and I do value their opinion. It's good to hear you have had no problems and I hope that continues.

Craig Payne
www.eco-panels.com

Craig;

after 15 years we probably would have heard something,
Can you post the link to the specific ORNL recommendation?

EPS is 'closed cell'. Somebody needs to get their facts straight before spouting out misinformation that not only is inaccurate but also confusing to people who are trying to do research on a specific product. A building science course might help too; just to learn a little about sol-air temperatures and the maximum temperature a roof surface can acheive. The temperature of the roof would have to be between 160 and 176 farenheit for the EPS to melt. Do you really think the roof is getting that hot?

It's obvious you are trying to sell the urethane panels, and that is fine. But next time stick to the merits of your own product instead of disparaging others with misinformation.

Dave

Dave, In Southern California asphalt roofing in the summer time reaches temps of 165F in the heat of the day. Not sure what happens with metal roofs.

I will be heading back to Oak Ridge next month and will follow up with Bill Miller (Building Technologies Center roofing expert) to get more specific clarification. For Mr. Stevenson, I do work in building science, support the entire SIP industry and once again, ORNL specificially said EPS (including closed cell EPS used on SIPS) could be affected by temperature build up using metal roofing. As with any other product, understanding the advantages and disadvantages helps everyone make (hopefully) a better informed decision. Both of the studies below show temperatures above 160 degrees using metal roofing. And, as Dick Mills points out, apparantly the same is true for asphalt shingles. It may be disparaging, but not misinformation.

http://www.ornl.gov/sci/roofs+walls/staff/papers/18.pdf

http://www.ornl.gov/sci/roofs+walls/staff/papers/19.pdf

Mr Miller's e-mail is: millerwa1@ornl.gov

Craig Payne
Eco-Panels

CTP;

Thanks for the postings, however you need to re-read yourself  -  the report states that the surface temp of roofing reached 160, OSB deck reached 140, and I could not find any mention of EPS in the report.

Please point it out if I missed it

Thanks

Chris,

You are correct that the study does not mention EPS and that the surface temp of the OSB under the metal is around 140 degrees. The reason I posted these studies was to make sure Mr. Stevenson understands that roof temps can get that high using metal materials. As for the comment by Mr. Miller at ORNL, I can't find a specific paper/study to back up his concerns at this time. I will be looking into this further and reporting back on this topic.

Regards,

Craig Payne
Eco-Panels

CTP;

 written documentation is appreciated instead of word of mouth, I am sure Mr. Stevenson  is aware of the EPS melting point as I am, both being in the business.
None of your posts addressed the original concern from "CathyK"of the standing metal seam roof over sips, your study was about stone coated metal roofing?

FYI ............I have installed 3 dark brown stone coated metal roofs directly to SIPs in Florida, the oldest being 6 years old, none have shown any ill effects from the direct application.

I found nothing disparging in your reports

Chris,

The ORNL study, (I did not do the study) as I mentioned previously, was provided (albeit stone coated metal) for Mr. Stevenson as he specifically questioned whether a roof could get that hot. As for Cathy's original question, yes I do understand she was asking about standing seam. I also mentioned that I am working on getting that info and will be more specific with documentation as it relates to other metal roofing materials.

What specifically have you done to check the integrity of your roof sips under the brown stone coated metal roofs? Do you have specific documentation or studies that challenges Mr. Miller's comments?

Craig Payne
Eco-Panels