Posts: 8,464
Threads: 1,032
Joined: May 2003
[
Do these liquid ceramics pollute the rain water going into a catchment tank?
-Veritas odium parit”(Terence 195–159 BC))-"Truth begets hatred".
[/quote]
I can't speak for all the manufacturers but I am aware of some that were rated for potable water. You have do do your own research. I would expect these to be in stock on Oahu at least. Kinda a commercial grade material. Not a lot of commercial work on the Big Island.
Assume the best and ask questions.
Punaweb moderator
Posts: 50
Threads: 18
Joined: May 2005
quote:
Originally posted by EightFingers
Bugs don't like living under a hot roof!
I dont blame them! lol
Posts: 3,205
Threads: 108
Joined: Jun 2010
It does blow me away to see so many dark colored roofs, especially down in Hilo. That combined with plantation construction must make for some horrific AC bills. Or a house uninhabitable when it hits the 90.
Posts: 50
Threads: 18
Joined: May 2005
I just found this site on whole house fans. Based in Kona. looks very promising. island cooling.com fans and radiant barriers. I think those whole house fans are the way to go along with painting the roof. On a mission!
quote:
Originally posted by terracore
I installed a solar powered fan in our ceiling. It blows the air from the house into the attic where it displaces the hot air. This scheme is usually called a "whole house fan" because it brings outdoor air into the house and also displaces the hot air in the attic, so it performs two functions unlike an attic fan. Because I didn't want to cut a hole in my ceiling I cut a hole for the fan into a piece of wood that was cut to the same size as the drywall for the attic hatch and replaced the attic hatch with my homemade concoction. I used to be able to feel the heat coming off our ceiling, now I do not. It still gets really hot up there but not as bad. Since it is solar powered, when the roof is getting the most amount of sun is when the fan spins the fastest.
Hawaii is offering energy rebates on whole house fans and attic fans: https://hawaiienergy.com/for-homes/rebates/hvac
" Whole House Fan
Get a $75 rebate on a whole house fan that draws cooler, outside air through your living space by pushing the hot air out of the home and out of the attic vents, creating a cooling breeze."
ETA: I bought mine on eBay. I think it was a 30 watt solar panel and a 12v fan with the pair rated to move 1500 cubic feet of air per minute at full sun.
Posts: 8,464
Threads: 1,032
Joined: May 2003
Fans will boost your electric bill. It is better to keep the heat out than to push it around.
Assume the best and ask questions.
Punaweb moderator
Posts: 4,250
Threads: 96
Joined: Mar 2014
If you can access the attic, the radiant barrier approach works quite well and is a cheap solution.
Posts: 7,734
Threads: 686
Joined: Jun 2011
quote:
Originally posted by Rob Tucker
Fans will boost your electric bill. It is better to keep the heat out than to push it around.
These generally use smaller, rather inexpensive solar panels that last 25-30 years. No electric bill. When I priced the ceramic paints, I could probably only get a gallon for what I paid for the whole house fan system and now there is a rebate that pays for most of it.
ETA: They have solar powered attic fans at Costco and they seem to have been a regular product there over the last year or so. I'm just not a fan of them because they require cutting into the roof and praying the installer knows what they are doing. Also, they are over twice as expensive as my whole house fan, don't move as much air, and solve half as many problems. And because I'm not a roofing guy, not a DIY project. If I tried to install an attic fan into my roof, I might as well install a catchment tank into my living room because all of that leaking water needs to go somewhere.
Posts: 468
Threads: 46
Joined: Jan 2009
I'm with Rob on this. Keeping the radiant heat out is the best solution to cooling a house. Radiant heat coming in through a dark roof warms the entire house--walls, furniture, floors, etc. this heat then dissipates and warms the air, making it feel hot for a long time. Fans can remove this convective heat that is warm air. But more warm air will be given off by the warmed objects. This cycle will only stop when the sun goes down. And in the meantime the air in the house will still be warm. Don't let the cycle start by allowing the radiant heat in in the first place.
I have used an elastomeric coating on a dark green roof. Instantly, the house was about 15 degrees cooler during the day. Over a period of about two years, however, the roof developed a coating of red algae and green algae making the roof start to turn dark again and the house is now heating up again. Maybe the ceramic or silicone roof coating wouldn't do this. I'd like to find out.
I was a big proponent of the aluminum radiant barriers for a while. They were miraculous under a slate roof in Baltimore. Here, my experience is that after a few years, the salt air corrodes the 99% aluminum surface and the radiant effect stops. In all the literature for them, anything that covers the surface like dust, or a thin layer of corrosion, renders them ineffective.
A white roof is the best way to keep a house cool here. The DOE has begun a project to whiten many school roofs in the state to cool schools and/or reduce ac costs.
Posts: 7,734
Threads: 686
Joined: Jun 2011
I would love a solution to prevent the heat from getting into the roof in the first place.
But I can't afford it.
Under $200 for a whole house solar fan: problem solved. Installation time, about an hour. It's been effective for the last 5+ years, and nobody has ever stepped on the roof.
Posts: 252
Threads: 28
Joined: Apr 2007
I helped a friend of mine build a roof on his shed using a patchwork cutoff pieces of roofing that were all different colors. It turned out to be a great unplanned experiment in heat absorption. The pieces that were any color other than white or off white were much hotter in the sun. I was amazed that even a very light green and a light tan seemed many times hotter than the white ones. The darker ones were pretty much too hot to touch during mid-day. So it may not solve all the heat transfer problem but its worth noting that white or off white will probably conduct much less heat.
