above decking insulation

marlene steger
3/3/2012
Hi, I am awaiting an estimate to re-roof my old farm house with Midwest Manufacturing Premium Pro-Snap steel roofing. I would like them tear off old curled black asphalt shingles , add 3 inches polyiso , then plywood, underlayment , then steel panels. I have minimal insulation in the already converted attic in 1986( now two bedrooms,one bath and a loft space ) and no ventilation(cathedral -type ceilings). I am needing to keep as much heat out of the living space as I can( Hot summer and Fall here) . Is polyiso the best insulation to use, or would an extruded poystyrene be better ? Also, would something like Enkamat work under the panels to cool the roof down even more? The roofing is 28 gauge and is supposed to be applied over a rigid substrate. Any thoughts? Things are always so complicated with an older home! Thanks
Todd Miller
Isaiah Industries, Inc.
3/4/2012
I like your plan and believe that you are using the right insulation. I am not familiar with using Enkamat for this purpose though I have often wondered myself whether it would help. I am not sure that any studies have been done to verify it is cost effective for this use. If it would qualify as a rigid substrate meeting the roofing manufacturer's specification, I still rather doubt the payback would be real soon. I would suggest making sure that you use a roofing product either in a light color or a dark color that has reflective pgment. Also, the formed metal shake and shingle products have a small air gap between the metal and most of the roof deck which acts as a thermal break for energy efficiency, similar to what the Enkamat might accomplish. I hope this helps.
Eric Novotny
An informed customer is the Best Customer!
3/4/2012
Above deck insulation is great. Stripping the old shingles is a must. How much square footage of roof is there over this section as well? Please reply back with a picture if you can as well and I will give you a full break down on my recommendations. Eric
Guest User
3/5/2012
Hi, Here is a picture. I can send a few more that show other areas. ( I think I can only send one per reply). I believe the roof takes about 20 square of roofing and is about a 9:12. There is a portion I forgot to mention (about 10 x 14) that is flat with rubber roofing. We will replace that with new rubber and maybe polyiso (not sure what to do). Also we will not be putting insulation down on the porch roof. We do plan on choosing a color for the steel that is at least 29 SRI. Once we re roof we plan to revamp the exterior. We do not want to go too light with the roof maybe a medium gray. Picking the right color is hopefully the last difficult decision we have to make. I need everything to be right because we won't be re-roofing again I hope! Thanks, Marlene
Todd Miller
Isaiah Industries, Inc.
3/5/2012
Thanks Marlene. What a beautiful place! Not trying to steer you but I do feel like maybe a shingle style metal roof would be more in keeping with the home's character. Have you considered any of those? I still think that your plan sounds good.
Guest User
3/5/2012
Hi, Thanks, Yes, I have looked extensively into all metal shingles and even the Inspire and DaVinci type. I will be getting an estimate on the Tamko Metalworks along with the Pro-snap this Tuesday from the contractor. I have been going back and forth on the issue for over a year. There are a couple of Metalworks slate installations locally on a ~3:12 roof, and two in Nashville , Illinois on steep roofs that look good. I have samples of metal shingles from other companies also including the stone- coated steel from Metro. It is difficult to make decisions just from photos of homes with different types of roofing.( Most roofing websites charge a fee to download an actual photo of your home with their product. (Renoworks) The Inspire website does allow you to simulate with your own photo for free.) I have always liked the look of the standing seam type. My biggest concern aside from aesthetics has been the issue of what type of insulation, and if I should use a vented panel like Crossvent or just go with an insulated nailbase product. I guess I will know more when we get the estimate. The home is out in the country on 40 acres with pole barns and other outbuildings so steel panels may look ok. I really appreciate being able to discuss my concerns in this forum. Thanks Again! Marlene
Todd Miller
Isaiah Industries, Inc.
3/6/2012
Thanks so much. It does sound like you're doing your research and we are happy to help. I will be happy to run your photo through Renoworks to drop in a metal shingle style or two. Is the picture you sent earlier the one you would like us to work with? Thanks again.
Guest User
3/6/2012
Sure. That would be great! Slate look would be fine. Probably not green or red or copper color. I like shingle look too but most are 30 gauge which seems a lot thinner. Marlene
Eric Novotny
An informed customer is the Best Customer!
3/7/2012
Run sloped iso on the flat roof and build in some positive pitch to it. Have you taken a look that the Classic Products offerings? They are quite nice. In terms of our other questions, first and foremost you have to get the roof deck (more preferably the ceiling) air tight. This will prevent the bulk air loss and what is usually responsible for a bulk of the moisture movement from hitting the structure and possibly condensing (creating rot, mildew, mold, etc.). There are scenarios in which rigid foam combined with an overdeck type vent is ideal because it allows for venting while keeping the dew point surface temperature at bay. There are expenses (beyond just the foam) associated with this type of undertaking so be prepared for that as well. I would like to see a minimum of 3" of iso on the deck which would create close to an R-38 total assembly.

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