Roofing Materials?

[bjbTay]

Hotinhawaii,

Are you using the TPO membrane on a flat roof or pitched?

Hawaii Dreaming

[Charles Moore]

With as much rain as Puna gets, it might be possible to just use the surface area of the water tank to catch the rain. There is an excellent book, Water Storage by Art Ludwig, that shows a ferrocement water tank with wings that funnel the water into the tank.

http://www.amazon.com/Water-Storage-Emer...0964343363

I recently attended a workshop in Mexico (http://www.flyingconcrete.com) whose instructor builds ferrocement houses. The roofs are cement. In some cases the water is funneled from the roof to a tank located under the foundation. I have seen a few of these under the house water tanks in Hawaii as well although the roofs were the standard metal ones.

A cementitious waterproofing (Thoroseal, Tegraproof etc.) can be applied to the ferrocement roof that is NSF (National Sanitation Foundation) approved for drinking water.

I have 25 minutes of video of the workshop I'd like to post to the web but my connection is so slow. Maybe when I get to a faster connection.

[hotinhawaii]

Regarding TPO on flat roof:
I have used it on pitches as low as 1/12.


Responding to Charles:
If you were to just use your water catchment for catching rain, in lower Puna, you would catch about 10000 gallons in one year. But, because you would have to leave the top off to catch the rain, you would lose a lot by evaporation and you would also collect anything that fell into it. Bad idea.

[bjbTay]

Hotinhawaii,

Thank you for your reply regarding TPO membrane used on roofs as low as 1:12.

Barbara Taylor

[Charles Moore]

In the tanks I am referring to virtually no water is lost to evaporation. There is a single small screened entry point for water. Screen small enough to keep out critters and mosquitos. The filtration and resulting water quality could be similar to any standard roof catchment if done properly. Creating a first flush for rat and bird ****e etc., might be a challenge however.

[MarkP]

Any house is going to have a roof. Any roof should have gutters/downspouts, etc. You would have to go out of your way not to use the roof of the house. Tail wagging the dog, reinventing the wheel, cart before the horse, etc. I am not seeing the benefit of not using the house roof. True, there is no official food grade roofing but the modern roofing is close enough. Filtration will do the rest. I have no qualms about drinking water from a well made and maintained catchment system. Also I have seen at least one nifty setup where the top of a ferrocement tank is made into a beautiful covered lanai which I think is a better use for it. The actual catchment system should have as little texture as possible. If I were a bird or a rat I would find it less comfortable to hang out on a steeply sloped blazing white, sterile, and slippery painted metal roof than on a rough gray flat concrete roof.