EcoRenovator - View Single Post - above sheathing ventilation (ASV) in East TX

dablack · 06-14-13, 03:10 PM

I would say this is a pretty good link. (if it shows up)

Cool Roof Design for Hot Texas Climate | Houston Cool Metal Roofs

If that doesn't work, I will post some pictures.

Anyway, here in TX since we don't have basements, most of our AC equipment is in the attic under a black asphalt shingle roof. Yes, the attics are vented but the attic still absorb tons of heat and just pump that heat into the AC systems. Really not the best idea. So, the first thing to do to combat this is to bring the AC into the conditioned envelope. I really don't have much attic in my build since my 2nd floor is basically IN the attic. So my insulation (spray foam) is up against the roof deck. That alone is a huge help but the upstairs will still pick up lots of heat. One way to fight that is to put on a white metal roof. Well, that is fine and good but I like the darker colors and so does the little lady. So, ASV put your metal roof about 1.5" above the actual plywood roof deck. This gap allows cool air to cool the metal from under it and stop it from heating up the plywood deck. This keeps heat completely out of the structure. The roof rafters are no longer thermal bridges to the metal roof. Also, since i'm putting verticle 1x2s down first and then horizontal 1x4s, if any water gets below the metal roof, it can drain out.

Austin

06-14-13, 03:10 PM	#3
dablack Helper EcoRenovator Join Date: Jan 2010 Posts: 65 Thanks: 0 Thanked 13 Times in 6 Posts	I would say this is a pretty good link. (if it shows up) Cool Roof Design for Hot Texas Climate \| Houston Cool Metal Roofs If that doesn't work, I will post some pictures. Anyway, here in TX since we don't have basements, most of our AC equipment is in the attic under a black asphalt shingle roof. Yes, the attics are vented but the attic still absorb tons of heat and just pump that heat into the AC systems. Really not the best idea. So, the first thing to do to combat this is to bring the AC into the conditioned envelope. I really don't have much attic in my build since my 2nd floor is basically IN the attic. So my insulation (spray foam) is up against the roof deck. That alone is a huge help but the upstairs will still pick up lots of heat. One way to fight that is to put on a white metal roof. Well, that is fine and good but I like the darker colors and so does the little lady. So, ASV put your metal roof about 1.5" above the actual plywood roof deck. This gap allows cool air to cool the metal from under it and stop it from heating up the plywood deck. This keeps heat completely out of the structure. The roof rafters are no longer thermal bridges to the metal roof. Also, since i'm putting verticle 1x2s down first and then horizontal 1x4s, if any water gets below the metal roof, it can drain out. Austin