TOPIC: Energy Efficiency
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I have an awkward little house in Phoenix, AZ. Imagine an A frame then cut it in half and add a little room above it. The 80's were a strange time. The majority of the roof is one big south facing plane. Brilliant, I know, lol. To make matters worse, the whole house has vaulted ceilings, very little insulation and no attic on the south side. It has a single layer of shingles from 1983. My dad and I would like to get supplies for a metal roof and DIY it. He is a contractor and Journeyman. What would be the best way to insulated it? We are thinking white tin on purlins and battens with spray in foam. Should we remove the shingles or put it all on top. I saw hard foam metal panels online, but it looks like they are only for commercial buildings. I work for a solar company now and we are planning on putting solar panels on top. Having a large south face works to my advantage for solar, but it is at 45 degrees. Weight isn't really a concern with solar, the panels are so light. But the lag bolts for the racking that holds the panels is a concern. We were thinking of an air pocket, but with bees and rats in Phoenix, it would be hard, even with netting to keep them out. The highest peak is where the air handler is, which is terrible, lol. It has no insulation or drywall in there. I am planning on adding radiant foil to the inside where the air handler is.
Pitch of course is a big factor here as you know all too well. Some good things though include that there does not appear to be any hip or valley.
I think that adding a vented airgap along with insulation and a reflective metal roof would be good. On pitches like this, insulation needs to be blocked to keep it from sliding.
If you built a roof over this roof with, say, 2x6 sleepers along the existing rafters followed by nominal 1/2" decking, you could fill the cavity partially with insulation (perhaps poly iso) and then leave an air gap and vent it. Then your decking, underlayment, and reflective metal roofing.
Yes, the airgap would have to be closed off with mesh or screening or other filter. A thermal break though, especially if vented, is just very effective for such situations.
That said, there are many ways to skin this cat. Always happy to talk through options if you wish to call me. 1-800-543-8938 ext 201
I have a similar home in Texas also with a shingled roof, and a vaulted ceiling leading to a small attic over two small upstairs bedrooms.
The long front roof faces east with partial shade from an oak tree, and opposite short roof faces west with partial shade. Both sides of the roof still get a fair amount of sun in the summer.
The attic has gable vents, but no ridge vent, and there are no soffits or roof vents. It gets quite hot upstairs during the summer, and you can feel the heat pushing in through an unsealed attic. Window units upstairs are a must.
Altogether with a freestanding carport and a storage building, there is about 1650sf of roof that needs replacing.
I’m in the middle of a claim and am researching metal roofs. My current plan is below, and I wonder if I would be going too far with the radiant barrier plans:
Replace decking with LP Techshield, shiny side down.
Use a peal and stick underlayment, probably Sharkskin Ultra SA.
Then Sharkskin ventilated deck mat, nodules up.
Sharkskin Ultra Radiant underlayment over deck mat, shiny side down.
24 gauge standing seam metal roofing (we get hail).
I’m wondering do I really need two radiant barriers and should I skip the LP Techshield. Or, if two barriers are better than one, then the Techshield would keep me from having to get up in the small attic and staple foil to the rafters.
Any thoughts? Have I been drinking too much of the radiant barrier coolaid with this plan?
Have you talked to the SharkSkin folks about your plan? I feel like the extra radiant barrier will not gain you much. I am also a bit concerned about full ice and watershield over a relatively unvented space. My concern is that, as you go through seasons where it drops down cool at night outside, warm moist air driving out of the home will end up trapped in the attic where it will condense on cool surfaces, if not the underside of the roof deck then the gable end walls.
Thanks for your response. I will reach out to SharkSkin. Poor attic ventilation has been a concern. I'm thinking a ridge vent and/or low powered gable fan would help. I could have soffits cut under the west side eave but am not sure how to balance that on the east/long roof side.
If I opted to replace the shingles instead, GAF has a product called Cobra Intake Pro that I'm told could be installed on both sides of the attic roof in lieu of soffits. It might not look great high up on the top third of the long side roof where the attic starts, but with a ridge vent it should help.
I'd much rather have a metal roof though, one and done plus the energy efficiency.
I do like much of your plan. I just question the ice and watershield on the entire roof plus I am not sure that there will be ROI with two radiant barriers. Good luck. Feel free to reach out to me anytime at [email protected]
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