William and Matt, Roof absorptivity is the key (that is radiation absorptivity). You can select some seemingly darker colors that have a lower absorptivity. However, some lighter color roofings can have absorptivities has high as dark roofs. The only way to know is to get the information from the roofing manufacturer.
Bill. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Matt Lafferty Sent: Wednesday, September 24, 2008 4:22 PM To: 'RE-wrenches' Subject: Re: [RE-wrenches] Personal project: roofing colors Hi William, I'm interpreting your question to be mostly aimed at finding out how roof color affects the temperature inside your house. It makes a heckuva difference. Conventional wisdom holds true... Lighter colors absorb less heat than darker ones. If you are going to stick with comp, from a thermal point of view, go with the lightest color you and your family can tolerate looking at... Remembering that one day the whole house will be covered in that same color. Roof color is only one factor that affects thermal performance of your roof & attic system. Using a "white" shingle will reduce the heat that is absorbed by the roof covering, which reduces the amount of heat that transfers into the sheathing and attic space. Adequate attic ventilation is a larger issue. Same principle that Matt Tritt mentioned... Do NOT skimp on attic ventilation! Lotsa eave (low-side) and ridge (hi-side) venting is a must. The most effective ventilation scheme is one where convection draws the air across the bottom surfaces of the roof sheathing. A radiant barrier is also worth considering. There are various methods and products available, depending on the framing configuration of your project. Some of these can perform dual-duty by creating ventilation paths at the bottom side of the roof. And don't forget adequate and properly installed insulation. (Don't block your ventilation pathways with your insulation...) All these things together are a system that will affect livability (comfort & aesthetics) as well as energy use. The neat thing is that these are passive... Once they are installed, they don't require maintenance (other than roof replacement) or energy to operate. It's worth it to do it right up front. Enjoy the remodel! Matt Lafferty -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of William Miller Sent: Wednesday, September 24, 2008 9:06 AM To: RE-wrenches Subject: [RE-wrenches] Personal project: roofing colors Friends: I have an energy question on a personal project. We are adding two rooms to our house and it is time to select roofing colors. Nothing will match the weird comp shingles already on our roof, so we are going to not match and re-roof the rest of the house later. In the meantime, I need to pick a shingle color. How much difference does a lighter roof color make here in our inland California (Mediterranean) climate? We get over 100F frequently in the summer. Thanks for your insight. William Miller _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org _______________________________________________ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
