Vented vs. unvented, etc - help!

Elsa Haas
12/19/2009
I’m trying to find someone who can help me figure out what to do about our roof. I would prefer someone who could come here and look. We can pay for the advice, but not some exorbitant amount! We (my husband, son and I) live in Staten Island (which is part of New York City), in what would be the attic of my mother’s house, except that it has windows and cathedral ceilings, and an open staircase (not a hatch) leads to it. My mother is 84, I have cancer, and my husband has emphysema. I’m trying to put on a new roof that will last a LONG time. I just managed to get a refinancing for my mother (a new 30-year mortgage). So we can get the roof done now, but we have no idea what the future might hold in store for us (and what our credit scores and income will be like at that point). A federal law (the Garn-St. Germain Act) protects anyone who inherits a house because of the death of a relative. So my brother (who lives elsewhere) and I will be able to assume the mortgage eventually and work out matters between us, without the lender’s being able to examine our credit scores or renegotiate the rate. But we need to keep future repairs to a minimum. Right now we have 3 layers of asphalt shingles which are falling off in one area (about 30 square feet), plus some leaks at flashings. So I started looking into getting a metal roof, because metal roofs last a long time and because they cut down on summer heat. This house was built in the 1940’s. It’s an L-shape, so there are two valleys. The roof (16 squares) is steeply pitched. There is no soffit venting because there are no soffits. There is no ridge vent. The roof decking is tongue and groove. The house has a brick exterior, with a lath and plaster interior downstairs and sheetrock upstairs – the sheetrock is from an upstairs remodeling job ten years ago that included new insulation. An energy efficiency guy (who was able to see the insulation in an area where the sheet rock had apparently been removed to install the pipes for the upstairs half-bath) says that 6 inches of fiberglass insulation was crammed into the rafter bays (the rafters are 2x6’s), and with no baffles. At that same point ten years ago, a fan was installed in each of the two bedroom ceilings, theoretically to draw heat out (you have to flip switches to make them work). But we have to use the A/C (a window unit for one bedroom, and a unit installed in a hole-in-the-wall for the other bedroom and a little office/storeroom, with the landing and half-bath between the two bedrooms) in the summer because it gets very hot. The energy efficiency guy said (based on fuel oil bills) that we seem to be using a lot of heat (we don’t turn on the heat upstairs – we just use what comes up the stairs). He also said the old fiberglass insulation is likely to get moldy because of the inadequate insulation, and to lead to structural damage. Before the energy efficiency guy came here, I had gotten several estimates from a local metal roofing company. One of the estimates that included insulation went like this: * Tear off old shingles. * Supply dumpster and clean up. * Inspect roof decking for rotten wood, replace four areas, if major replacing is needed extra charge may apply. * Furnish and install old fashion looking profile Englert's 0.32 aluminum standing seam with seams metal roofing over Englert's synthetic underlayment including all flashings, fasteners and underlayment necessary for completion. (The roofing company later clarified that this metal roofing is Englert A1500, 0.32 Galvalume, and Englert told me that the specs for the A1500 series aren’t on the website because only a handful of companies use it now.) * Furnish and install 1.5" rigid foam insulation. (The roofing company later clarified that this would be ATLAS LTTR 9.0 FOAM 2 ISO/ BLACK 1-5 4X8. See this link: http://www.alliedbuilding.com/products/productDetail.aspx?ProductID=12221110) * Furnish and install new power fans, vents, pipe flashings and chimney flashings. * Wrap wood facial along gables and support post. * All work performed by certified installers with 10 year workmanship guarantee. $18,300.00 total (materials and labor) But the energy efficiency guy suggested we install an insulated “cold roof” (which has a built-in airspace). I found this article (“Retrofitting an Insulated Cold Roof” by Dan Perkins): http://danperkinsroof.com/1108_JCL_Perkins_A.pdf The energy efficiency guy recommended we do what the article says. I called the author of the article (who is in Michigan) and had a long conversation with him. I went back to the metal roofing company and asked how much for a cold roof like the one in the article, and was told $27,800. That would eat up almost all the money we got through the refinancing, and we still need to do some other pretty major repairs (we have basement water problems, too, among other things). I then got some advice from someone who also has a Cape Cod-style house (but in eastern Massachusetts), and who had attended a Building Science Corporation seminar – see http://www.buildingscience.com/ . He wrote me that he had been advised to do this (an unvented roof retrofit): 1. Strip the roof down to the sheathing 2. Insulate the junction between the roof and the walls with closed cell foam (this is probably most easily accomplished from the outside by removing some of the old sheathing/sub roof planking) 3. Apply a peel n stick type of air/vapor/water barrier across the entire roof, make sure it is continuous and tie it into other air barrier elements in the walls. This layer will prevent any water that may back up under shingles from making into the house. This barrier is located on the inside of the insulation layer and prevents condensation from forming in the winter. Do not put the vapor barrier on the cold side of the insulation. 4. Install 2x4 blocking around the perimeter of the roof to support future trim (do not put 2x4s in the main roof construction since this could keep the insulation 'sandwich' from compressing properly) 5. Install insulation in two layers with offset joints to minimize 3D airflow paths - you have to use two layers of insulation. 6. Add a new layer of sheathing (1/2" ply, for example) - screw this down into the rafters as tight as possible using long screws 7. Add a standard rain barrier such as roof felt (cheap and effective here) 8. 30-yr shingles or metal roof or whatever else you have handy He added, “I am planning to install two layers of 2" polyisocyanurate board, which will add R-24 to my already existing R-12 mineral wool infill, for an R-36 roof. I am also planning to strip the dormers and give the walls the same treatment as the roof. The windows in the dormers will get a 4" bump out and we will have nice and deep window sills. While the thermal resistance of the roof will improve, the majority of my energy savings will come from reduced infiltration. Air barriers are a must! However, the reduction in uncontrolled ventilation will require me to install an energy recovery ventilator to ensure that moisture is removed.” He also sent me a link to this Building Science Digest article (“Unvented Roof Assemblies for All Climates”) – it describes new construction (not a retrofit): http://www.buildingscience.com/documents/digests/bsd-149-unvented-roof-assemblies-for-all-climates?full_view=1 I’ve been trying to learn about ccSPF, injecting tripolymer foam, SIPs, ventilated nail base, etc. I’m utterly confused. I put the energy efficiency guy and the guy with the Cape Cod-style house in touch with each other, and they debated everything in a series of e-mails that left me dizzy. Meanwhile, the shingles are coming off more and more with each storm. I’ve started talking to spray and injection foam insulation companies because one possibility seems to be to get the roof put on now and then, from the inside, use spray insulation. I’m trying to figure out whether it makes sense to do this: 1.) have the roofing company use the rigid foam insulation on the outside to create a vapor barrier (as in the original estimate); 2.) have the old fiberglass insulation taken out from the inside (I’ve been told this can be done by making a foot-wide horizontal “strip” of an opening in the sheetrock, halfway up the ceiling slope, and pulling the insulation out – and maybe taking out the insulation that is lowest down by working inside the crawl space that is behind the knee walls); 3.) have a spray foam insulation company spray in open-cell foam (I think I understand that we can’t have vapor barriers both on the outside and on the inside, so that’s why the spray insulation would have to be open-cell – it would create an air seal, but not a vapor barrier). I think I understand that injected foam is for vertical wall cavities, not for a sloped ceiling. I think I understand that spray foam is best applied to the tongue and groove decking from the inside (even when the weather would permit spraying from the outside, which it doesn’t right now). Two spray foam companies have said that they can spray the foam without taking down all the sheet rock - they just need that same foot-wide opening that would be used for removing the old insulation. But all the videos I see online show the spraying done only into completely exposed rafter bays. See videos here: http://www.ezerosolutions.com/resources-video.aspx Meanwhile, I’m trying to come up with a temporary roof repair to the area with the missing shingles (to apply after the current snowfall melts off and the roof dries). I would very much appreciate hearing about anything I’m misunderstanding or overlooking. I feel like I have no idea what I’m doing. This is all new to me.
Todd Miller
Isaiah Industries, Inc.
12/25/2009
As I understand, either option (the spray foam or the cold roof) will work and help to avoid condensation issues.
Guest User
12/29/2009
i would like to help but i can seem to finish this novel
Guest User
12/30/2009
Yes, sorry it's long. I said that I could pay for advice on this - preferibly someone who could come here to Staten Island (NY) to look at the house. It would have to be someone whose advice is likely to trump the conflicting advice I've gotten so far. So I wanted to lay it all out there. (And thanks, Todd, for your reply. Maybe the answer is that there is more than one answer.)
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