mounting solar panels on R-panel roof

[ionized]

Whew, I have a hard time deciding which forum to post this in. How to mount panels on a roof is technical, but outside what is usually here.

I need to put new roofs on my garage and house before I install panels for hot water and photovoltaic. For some time, I have been considering installing a white metal roof to cut cooling costs. (Most probably, I am also going to foam insulate my roof deck and seal my attic as well.) Until a week ago, the only kind of metal roof I knew about was standing-seam. After some dialog with a roofer, I now understand that there are much more economical ways to clad a roof with metal panels. He is talking R-panels. He says it is cheaper than shingles and, in fact, another roofer was much higher with shingles.

Some time ago I started exploring solar installation and got some estimates from a couple of solar installers. I contacted (e-mail) them about mounting solar panels on R-panels. I am waiting for a response, but I thought I would throw it out to you guys. Does anyone know how this is done typically?

I have more roof than I need to net zero with electricity and I don

[Mike90250]

What do you say solar gods? Do any of you have experience with this kind of roof?

Never seen one. I know there are good clamps for standing seam roofs, no idea about R-panel.

[solar_dave]

Here is a page with PDF for R-panels

http://www.metalroofingsource.com/gov_R_panel.htm

looks like direct attach to sheathing with gasket screws, and I suspect you could mount and seal accordingly.

You might ask your local building inspection department what they know about R-panels.

[russ]

Standard profile metal roofing. Excellent life and installed well will last for long. Several different profiles available.

Your solar installer should help you pick the profile so you can be positive the feet he has access to will fit the profile.

Tell him if he damages the profile to set his panels on the roof that you get to do the same thing to his head. There is zero reason to damage the roof as we have seen some examples of.

[silverhorsefarm]

I have an installation on an Ondura roof:

http://www.ondura.com/

Unirac makes a hangar bolt for installations on roofs that are not flat for the L-feet. I would imagine that it would work with these panels as well.

[ionized]

Thanks for your thoughts. I got a little back from one installer. He is mostly concerned that the gasket on the mounting hardware matches the roof life. With good metal and installation, that would be a very long time barring catastrophe.

I have a couple of additional thoughts. First, I see some info on web pages that indicates that there are some solutions for existing R-panel roofing, especially associated with covered parking. There is not enough information to determine if this is an practical way to use new R-panel with photovoltaic systems. That would be keeping in mind that the LA and Fed programs for PV systems might make adding a "retrofit" right away might be less expensive than "upgrading" to standing-seam from the get-go. The retro-fit would essentially be the mounting system.

There is no info about wind rating, or any way to begin guessing what effect this might have on my attic temperatures when installed over a white
Roof.

http://www.solarenergyandpower.com/retro-fit-to-solar-covered-parking/

http://www.solarsealed.com/gpage4.html

Second, and I like this better, is the possibility that the increased price of standing-seam over R-panel could be part of the solar installation cost. Look at it this way. I am going to have a metal roof. Peel-n-stick will cost a lot less than racks. In fact, the added cost of the standing-seem could be considered to be the cost of a mounting system. I don't know how the tax officials will feel about that.

[russ]

I have yet to read anything about the stick on type panels being successful.

Dow is coming out with their version of solar PV roofing in the near future - at least then you would know the company would be around to service the guarantee.

To invest in a new type of panel/material that does not have a minimum of 5 years track record is looking for trouble.

Are they certified by CA for example? If they are not certified by state then you have to ask why.

[ionized]

Yes, russ, being on the bleeding edge of technology is unnerving. You are right to advise caution with an investment as big as this.

I don

[russ]

I would suggest looking carefully at the insulation scheme for the roof/attic.

You can easily add a closed cell foam on top of the rafters and drop the attic temp drastically. I used 150mm of Dow XPS foam over the rafters and even on the hottest days the attic stays comfortable.

Consider a radiant barrier as well.

[ionized]

Foam at the roofline and sealing the attic are part of the plan. In this humid climate open cell foam is recommended by most. The foam and the white roof should individually lower attic temp rise by 30%. That will be 50% if they are both installed since the marginal improvement will be less. The house was built in 1949. Since then a lot of holes have been added between the ceiling and roof. So many that it is going to be a lot easier to cut air infiltration at the roof than at the ceiling.


Radiant barrier would be good if I stick with shingles.

Joseph Lstiburek wrote:

> Venting attics in the South was dreamed up by some disgruntled
> Yankee pissed about the Civil War and wanting to get even.

[paul_wood]

The use of PV panels in large numbers within the country in increasing numbers and the state patronage has developed the industry itself and today one finds hundreds of manufacturers there.
The end result has been the dropping down of the price of PV panels considerably in the world market.
If you are looking for PV panels, made in China, one word of caution! All Chinese PV products are not of high quality though there are a few.
In fact many are not! Look for the appropriate (and valid) certifications for compliance with British, Irish or EU quality standards.

[russ]

Hello Paul Wood, Welcome to Solar Panel Talk!

We welcome posts that inform members and guests but not for anyone to just stop by and drop an advertising link. The object of Solar Panel Talk is to help fill in the gaps in knowledge we have on the topic.

Regarding Chinese products - some are good and some not - similar to European or American products. It has more to do with the individual companies reputation and desire to stay in the market than where they come from.

[hannamand]

Any follow up on this? I'm looking to put solar on my (already existing) R-Panel roof. So far what I've seen is "Pull out one of the screws that's already holding it down, and put a neoprene gasket under an aluminum L-Bracket"

[solarix]

We use a device called a straddle block which stands across the corrugation hump on the roofing so that your solar mount screws goes through the high part of the roofing. Actually is just a piece of aluminum C-channel large enough to work. Still need to seal the hole but so much less water getting to that spot. Only works when there are horizontal purlins that allow putting the screws where needed. Of course, R-panel roofing has hundreds of gasketed screws going through it already, so I am also good with using a gasketed L-foot right in the field.