get free books and rmh plans
Permies likes rainwater catchment and the farmer likes Metal roofing for raincatch permies
  Search | Permaculture Wiki | Recent Topics | Flagged Topics | Hot Topics | Zero Replies | World Domination!
Register / Login
permies » forums » building » rainwater catchment
Bookmark "Metal roofing for raincatch" Watch "Metal roofing for raincatch" New topic

Metal roofing for raincatch

Kay Bee

Joined: Oct 10, 2009
Posts: 471
Location: Jackson County, OR (Zone 7)
We're looking to order our metal roofing for the house this week and have run into a bit of a snag... my previous research on metal roofing had convinced me that pretty much all metal roofing with a baked enamel coating was ok for rainharvesting (our water will be used for household water and for the garden/orchard).

Now that we are looking to order the material, suppliers are telling us that "baked enamel" is an antiquated coating and not generally available. hmm. Most of the systems I'm seeing are PVDF coatings for materials other than aluminum (not what we want).

Anyone have any thoughts on currently available metal roofing (standing seam to make it easy for attaching the PV panels) that is a good fit for raincatch?

"Limitation is the mother of good management", Michael Evanari

Location: Southwestern Oregon (Jackson County), Zone 7
John Polk

Joined: Feb 20, 2011
Posts: 6898
Location: Currently in Lake Stevens, WA. Home in Spokane
Antiquated material? Jeez. They must have found a cheaper way to make it is my guess.
"Industry" is all about the 'bottom line'.

I will admit that I haven't looked at new roofing for many years, so I have no idea what the industry is trying to 'push' these days. You certainly want something that will last for decades, but not if it means contaminating your (or your plant's) drinking water.

What are the choices available to you?

In my opinion, PV panels should be elevated several inches above the actual roof. Without a good air flow under them, they will get excessively hot. That greatly lowers their efficiency, shortens their life, and makes the house unbearibly hot inside.

Hopefully, somebody here will have some updated info on available roofing materials.

Kay Bee

Joined: Oct 10, 2009
Posts: 471
Location: Jackson County, OR (Zone 7)
Thanks John - I agree. I think that marketing is playing a large role in the supplier's opinion. There are still many sites that advertise a "baked enamel" finish, but then use a name brand such as Kynar or other PVDF based paint systems used on the metal roofing. Galvanized steel (expensive apparently), Galvalume brand, and aluminum (anodized or other coatings/treatments) are the main options I have seen so far.

The PVDF may be fine, but some digging has popped up a few warning flags. I just don't know how much testing has been done or required on this type of use for the coatings. Durability is the main emphasis in the industry as best I can tell.

The elevation of the panels off the roof is one of the reasons I like the "standing seam" type material. There are brackets that are easy to attach the panels to the roof (providing some elevation along with attachment) and does not need a separate metal mounting rack. I will need to also make sure that I can adjust the angle for the solar inclination throughout the year.
Jeremy Laurin

Joined: Dec 14, 2012
Posts: 18
Michael Reynolds of Earthship fame stated that the only company in the US using safe materials for rain water harvesting is Pro Panel. It was in his the second DVD. You can watch here if you like:

and more info here:
Kay Bee

Joined: Oct 10, 2009
Posts: 471
Location: Jackson County, OR (Zone 7)
Thanks Jeremy. I looked through the link and it was earthship style construction info that I was prettly familiar with, but I have not seen the video. I'll take a closer look once I get a couple hours free.

Thanks for posting both pieces of info!

I did a quick search for the pro-panel material and it looks like the basic components are similar to other metal roofing (24, 26 or 29 ga steel or galvalume) with PVDF or acrylic coating.

We ended up going with 24 ga steel panels with the PVDF coating. Had to make the call to get the roof on before the bad weather hit. I'll be curious to hear what Reynolds has to say on why the Pro Panel material is the safest.
topher alan

Joined: Nov 02, 2012
Posts: 4
Location: Traverse City, MI
Paul Wheaton mentions in his gaia's garden Chapter 5 podcast that Toby Hemenway is using baked enamel steel roofing on one of his buildings. I watched Michael Reynolds video where he mentions that "Pro-Panel" is the only source of lead-free baked enamel roofing but I haven't been able to find documentation to support that claim, on the Pro-Panel website. Does anybody have a source for lead-free baked enamel roofing?
Jeanine Gurley

Joined: May 23, 2011
Posts: 1393
Location: Midlands, South Carolina Zone 7b/8a
I'm glad I saw this. It has never occurred to me that I should think about the type of metal roofing - I have always assumed that any new metal roof would be fine.

Is it possible to use a filtration system that would remove these contaminates? Just in case sourcing the 'safer' metal isn't possible?

Or, is there any coating that could be applied to mitigate the problem?

1. my projects
Su Ba

Joined: Apr 18, 2013
Posts: 526
Location: Big Island, Hawaii (2300' elevation, 60" avg. annual rainfall, temp range 55-80 degrees F)
Just another thing to think about......metal roof paint. Most folks paint their roof especially if it starts to show rust. I wonder if the paint contains fungicides or algaecides? Most exterior house paints do. I do know that one should not use those anti-fungus, anti-algae strips on the roof cap if you plan to use the rainwater. But what's in the paint nowadays?

...Su Ba

It's never too late to start! I retired to homestead on the slopes of Mauna Loa, an active volcano. I relate snippets of my endeavor on my blog :
subject: Metal roofing for raincatch