Add a second roof to block the sun

[STOMPS]

I have add on to my house that is similar to a sun room. I would like to keep it cooler since it is open to the living room and kitchen. It has a shallow roof just big enough for r 19 insulation. What I would like to do is build a second roof on top of the original and about 12 inches high for air flow. I may combine it with a radient barrier.

Has anyone out there done this before? Could I make it with some sort of removable (for winters) awning material or build it strong with wood and shingle. I am worried about the second roofs load on the sun room room.

For the record I live in Austin TX

[Joseph Meehan]

Off the top of my head, I would suggest reflective or very light colored metal slats with space between each one to allow free air flow mounted just a few inches above the existing roof.

[willshak]

on 8/8/2007 11:04 PM STOMPS said the following:

You could do that but you would have to leave the ridge area open or install a ridge vent on your new roof so the hot air between your new roof and old can escape. I think 12" is a little overkill, though. What color is the roof now? I have a 4 Seasons room on the back of the house that gets sun all afternoon. When it was built, I made the mistake of matching the shingle color to the existing house roof, which was black. It was too hot in the sunroom in summer, sometimes 10º F more than the outside temp, even with all windows open and ceiling fans going. Leaving all the windows closed, most times resulted in a 20º greater temp difference. I figured I would go for a lighter shingle color, but wanted to test whether it would make a difference before I spent all that money, so I bought some Henry's asphalt roof coating in White ($35 for 5 gallons at HD). I painted the roof with it and the difference was astounding. Now the interior temp never gets above the outside temp with the windows open. If I leave the french doors open between the CAC house and sunroom, the temp inside is about 10º cooler than outside.

[gfretwell]

This is very common in Florida. It is called a "roof over". There is an aluminum pan roof product for doing this with 3" of styrofoam between the top and bottom sections. It knocked about 15 degrees off the peak heat in my sunroom. I think Home Depot sells it but usually the contractors and aluminum dealers make the retail price, just about what the wholesale price plus installation, is.

[Darrel]

Ever since I had my sunroom added over 10 years ago, the structural insulated panels on the roof pop like crazy when it gets warm. I wonder how something like that roof over would work on there. I've tried every thing else I can think of.

[DanG]

It is called a cold roof. It is a fairly normal thing to do in a cold climate to create a thermal barrier. They should provide a similar dead air insulator for heat load.

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