Re: [Phys-l] paint your roof?

[Roger Haar <haar@physics.arizona.edu>]

Hi,

	Does the mansard roof have a raised edge so that the cool air can pool? 
 Here in Tucson, my Santa Fe style house with its parapet wall does. 
One morning when it was 45 out, I needed to check the roof and found a 
1/4 inch of ice on some water that had ponded on the roof.  The roof was 
a fairly bright white, but who knows what it is in the infrared.

Thanks
 Roger Haar  UA Physics

Michael Edmiston wrote:
> Highly-reflective roofing materials can actually receive an Energy Star 
> rating if their solar reflectivity is higher than 65%.  There is also a CRRC 
> (Cool Roof Rating Council) certification for products meeting the Title 24 

> [2]  I was up on the roof late one afternoon to paint some trim around the 
> hatch and around the edge of the roof.  The roof felt only a little above 
> ambient temperature when the sun was on it.  It absolutely was not hot.  The 
> amazing thing was when the sun went down.  The roof got cold.  Not ambient 
> temperature... but cold.  That white roof was radiating like crazy.  I 
> thought maybe I was imagining it, so I got a digital thermometer and placed 
> it in contact with the roof and it was about 60 F when the ambient air 
> temperature was about 72 F.  This made me rethink my thoughts about 
> blackbody radiators.