Metro Shingle Install & Venting

Joe G
6/7/2014
Hi all, I know similar questions are being asked on this forum (and others), but I’m finding so much conflicting information and things not specific to my situation that I wanted to just layout my details and get a more direct response. Also, I have a roofing and solar company that I’m working with and while I trust them, I want multiple expert opinions. House Details: -Los Angeles Area -Built in 1975 -Current venting: 2 Gable vents on each side with an intake and exhaust fan respectively -There are no soffit vents. -There are no ridge vents. -Front half of the house has 8 foot ceilings with attic space, including the Kitchen on the rear half on the right (attached pic section A), rear half of the house has 16 foot Cathedral ceilings (attached pic section B). -There is insulation on attic floor where ever there is attic space. -There is spotty insulation on the attic wall that is between the Cathedral Ceilings and attic space. -In the attic, there is a large empty space between the Master Bedroom and the Living Room (these rooms are in the rear half of the house, both have the Cathedral Ceilings) that has no insulation, probably a few feet wide. Below this space are the Master Bedroom closets. There is no insulation above the closets, or on the master bedroom wall on the left, or living room wall on the right (again, in the attic). -I can’t tell if there is insulation above Cathedral Ceilings / beneath roof deck. -Exhaust fans from 2 Bathrooms exhaust air out the gable vent. -Existing roof is Asphalt - we will be tearing off the existing roof as I am the new owner of the home and have no idea what’s underneath. -All AC Ducting is in the attic, along with the air handler / furnace. Metal Roof: -Metro Shingle in Charcoal is our currently selected roof. -This is a direct to deck install -They offer ‘SmartVents’ that install in place of a few shingles More Info: -I wanted to install the roof on Battens with a radiant barrier but this is a flat metal shingle, and Metro does not support a Batten install for Metro Shingle. From my research, none of the ‘flat’ metal shingles are batten installed. Metro does support battens for it’s ‘raised’ shingles like Shake and Cottage. Questions: I want to be certain that the install is done ‘correctly’ for my home and want to avoid any condensation issues etc. I was hoping that someone could give me their expert install advice for this project; What type of venting, underlayment recommendations - to prevent condensation, etc. I am dead set on a metal roof but I am just not feeling very confident because is so much information out there and seemingly many different ways to do the install; correctly and otherwise. Thanks in advance. Joe
Todd Miller
Isaiah Industries, Inc.
6/7/2014
It does not sounds like your home has the venting that is required by code. And, when you're dealing with gable vents and cathedral ceilings, it's hard telling if the venting is doing anything at all. Now, that said, if you have not had condensation issues in the past, it is unlikely you will after the metal is installed but there have been some rare instances when the thermal dynamics of metal roofing were enough to be the straw that broke the camel's back. Of course, you're in a dry climate where condensation is not frequently a problem. So, your concern is more about trying to keep heat out of the home. You could install vertical battens over the existing roof, followed by another layer of decking and underlayment before the metal shingles. Then you could vent the resulting chamber. For extra assurance, I would consider consulting with an insulation and ventilation expert ... also, Metro's corporate offices are not far from you. You could ask them to come take a closer look at your house and I am sure they would. I hope this helps.
Joe G
6/14/2014
Hi Todd, Thanks so much for the reply. Until your comment regarding adding a 2nd layer of decking I had not even considered this to be an option. It's now looking like this is the best option for many reasons; we'd have adequate ventilation throughout the entire roof for the metal, and from all my research with a radiant barrier this method would basically cut off almost all heat transfer. We have a large attic and are thinking of converting it in the future and a double roof deck install would allow us to keep the attic unvented. Our roofing company would be using SharkSkin for the lower deck underlayment and radiant barrier and then use TechShield for the 2nd / upper roof deck to act as a 2nd radiant barrier. We're installing a dark charcoal metal shingle and so I think every little bit will help. Here's the deal, I simply don't want to install asphalt because I don't want to replace the roof anytime in the near future. Whether the asphalt warranty is lifetime, 50, 30 years or not, it WILL breakdown and need to be repaired. So, that's step 1, I want a metal roof, but a flat shingle metal roof, not a raised shake or tile. Well, a metal roof does need some ventilation and so I either vent my attic and therefore lose the ability to convert the attic later, or we install a 2nd deck. Anyhow, could you comment on the weight that the extra deck will add? From my calculations, our current roof (~40 squares) composite / laminate shingle roof most likely weights anywhere from 8,000 - 10,000 lbs. The Metro Shingle will weigh around 4,480 lbs (that's unbelievable). The 5/8" OSB decking around 8,400 lbs. The solar system we'll be adding is 820+ lbs, but will be on one area of the roof. So, the new weight on the roof will be around 13,700 lbs. (that doesn't include the batten weight). Remember, we're in Earthquake country here. I did some searching and there was an article written regarding this very thing (http://www.metroroofproducts.com/pr/061404_safest.pdf) and Tom Black commented on the use of lighter steel roofs. What would your recommendation be in my case? Obviously we're using steel, but the extra deck is going to add some weight. And granted, it's not going to weigh as much as concrete tile, which I can't believe would be maybe 70 tons for our roof, but it's still a concern. Thanks again for your input Joe
Todd Miller
Isaiah Industries, Inc.
6/14/2014
I feel like you're okay on weight. If you really wanted, you could engage a structural engineer. The only lighter weight roofing options would be a painted steel shingle roof rather than stone-coated, which might save you about 1200 pounds total, or a painted aluminum shingle roof which could save about 2400 pounds. Thanks for visiting the site again. We do appreciate your interest and research. Contact me anytime.

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