painting roof white &/or radiant barrier insulation & insulating AC attic cooling ducts?

Re: painting roof white &/or radiant barrier insulation & insulating AC attic cooling du

reflective insulation usually requires and air gap of between 1/2in and 1in and is usually facing the side to reflect the heat back into. this is almost always facing the interior to keep heat into the home as this deals with the radiant aspect of home heat loss. it would work in reverse i suppose, but to lay it on top of the present insulation won't do allot of good because of the air gap requirement.

i don't think a standard paint will work on roofing shingles, but in theory it would work to help cool the attic area by reflecting some of the heat away rather than absorbing it.

Re: painting roof white &/or radiant barrier insulation & insulating AC attic cooling du

I did a bunch of research on this last fall and we installed radiant barriers as rollandelliott describes (directly to the rafters) in one section of our attic this winter. We had to wait until the dead of winter because any other time of year our attic was so hot we couldn't even enter it. This part of our attic is now much cooler, not cool by any streatch, but we can now enter it. The upper parts of our house don't heat up nearly as quickly as they used to. We are planning to do the rest of the attic starting this winter. We used those cheap space blankets for our radient barrier. Most of the expensive radiant barriers sold in hardware stores have that same reflective mylar on them as the space blankets. The expensive barriers usually also have some sort of backing, but I think it is the mylar part that does the biggest part of the job. We saved a lot of money using space blankets and are getting good results.

From what I've read the radiant barriers reflect radiant heat back up toward the outside of the house instead of allowing it to penetrate the rest of the house. The amount of air that gets hot between the radient barrier and the rafters should vent out through the roof vents.

From what I understood while researching radient barriers of this sort were not worth the effort in cooler climates in the north. This is primarily for radient sun energy that enters the house right through the roof. The radient barriers work much the same as those shiny mylar sun shields people put in their car windows in the summer time. And those can really do wonders to keep out the heat as well. I read a bit about the special paints as well, and seem to recall that they did help but were not as effective as the barriers.

You can also think of it as a radient space heater. Put a space blanket between you and one of those heaters and you won't get hot.

Re: painting roof white &/or radiant barrier insulation & insulating AC attic cooling du

to be sure we are on the same page here i was saying of placing the reflective material on top of the ceiling area rafters is not good because of the long span to the roof itself. standard insulation should not go on the ceiling rafters as another barrier could trap moisture and lead to all sorts of problems. it may work to a small degree in the roof rafters if the air gap is proper. 10 and 12in gaps are not proper. as was said already, this needs vented for each rafter space when its the roof rafters. if one is to go to that much trouble then throwing a small amount of insulation there with the vapor barrier facing up may work better, but one would still need to vent the attic space below due to humidity considerations. go get some advice from a professional if you can for your circumstance. ask him for an estimate too, but odds are it won't be acceptable for you to pay it and at least you would know what the best way is for you.

Re: painting roof white &/or radiant barrier insulation & insulating AC attic cooling du

From what I can tell, the map mostly relates to the information given in the first paragraph where it says: "Radiant barriers and interior radiation control coatings are designed to work in your attic to keep some of the heat from the sun away from your living space. For homes with air-conditioning duct work in the attic in the deep south (such as in Miami in Zone 1 or Austin in Zone 2), radiant barriers could reduce your utility bills by as much as $150 per year using average residential electricity prices. If you’re able to participate in one of the Time of Day rate plans, your savings can be even greater (almost $200 per year under the current Miami Time of Day rate plan). For milder climates, like those in Atlanta and Baltimore, annual energy savings will be about half those of their southern neighbors. In the northern climate zones, the savings drops further, going from about $40 to $10 per year as you go from Chicago to Fairbanks."

You are in the same zone as Atlanta (as am I), and according to the statement the cost savings will be about half that of zone 1 and 2, so as much as $75 a year or up to $100 a year if you participate in a time of day rate plan. The radiant barrier materials I am using will total about $60-$80 (space blankets, duct tape, and construction staples, and I think installing the barriers was worth it for me. If you want to use something more official than space blankets it may cost around $300-$600 for the install, depending on what material you use and how big your attic is, and may not be as worth it. Depends on if you think saving $75 or so a year is worth it. If you decide to use it, I would love to hear what you decide to use and if you get good results since we are in the same zone.

Kelly