Photovoltaic roof mixed with concrete tiles, opinions sought


#1

In a few weeks I hope to have installed a photovoltaic roof (electric solar power). The design is basically that of a concrete tile roof, because the solar cells are mounted in a tile (see at www.openenergycorp.com).

I live on Long Island, NY, USA. In this area just about everything is asphalt shingles, so expert advice is hard to find. The roof is to be installed by both a roofer and solar installer. This will be the first such install in this area.

Here is the design:
35 degree pitch (about 8 in 12 I think).
600 sqft rectangle.
The underlay will be 100% Grace Ice and Water Shield.
The tiles will be mounted to battens.
Battens will be 1x4 pressure treated wood, with all fixings made from stainless steel.
2 layers of Ice and Water Shield will be at eves and gabels, with metal gabel end flashing and eve drip edge sandwitched between the two layers.

Any repairs to the roof would be complex because of the mixture of concrete tile and solar tile, so it is important to get it right first time.

My questions:

  1. Is it worth using 2 layers of Ice and Water Shield across the whole roof surface?

  2. I am having a hard time deciding between using elevated battens or counter battens. Both will give me the air flow that I need under the tiles and allow water shed. What are the pros and cons of counter battens vs elevated battens. As I see it:
    Counter battens might protect from water penetration a little more, but allow a little less air flow and use more matterial.
    If I use elevated battens the elevators will be made from small sections of 1x4 pressure treated lumber, with a nail driven through the batten elevator deck and into the beams.

  3. Grace advise to use smooth shank hand driven nails with Ice and Water Shield to get the best sealing. But ring shank nails have greater wind resistence (higher pull out force) and a nail gun is so much faster! What are peoples’ experiences?

  4. Is it good to use a liquid sealer even when using Ice and Water Shield?

  5. There will be a ridge vent cut in the attic. I want the air from under to tiles to vent. If I rely on natural convection (no fans) is there a risk of hot air from under the tiles getting into the attic, or vice versa. The plan is for hot air from the attic and hot air from under the tiles to both vent to the atomosphere.

  6. There will be a parameter of concrete tiles around the solar tiles. One area of concrete tiles will be a natural place to walk. The tiles are standard weight. I plan to fill the void under two columns of concrete tiles with Great Stuff expanding foam (probably the pro version since it has lower application temperature). Any comments?

If you have good advice on only one of these issues please post a reply.

thanks in advance.


#2

it all sounds a little to complicated.

gweedo.


#3

are you nuts?


#4

Interesting

I think two layers of I&W is overkill.

If you use elevated battens I don’t think using ring shanks to hold the battens will be a problem. The water ( if it gets under the tile )will flow parallel to the vertical battens.

No need for liquid sealer.

Venting should work fine if you have proper soffit venting.

hmmmm, Great Stuff will be tricky to work with. I think there are other foams made just for holding and supporting tile.


#5

Well maybe, I’ll let you judge.

If I have $xx,xxx dollars to spend, am I nuts for spending it on a solar system that will likely generate enough power to negate my total electricity usage for the next 20 years, or would I be more nuts for buying something like an Escalade (for non US board readers – gas guzzling SUV) that will burn fosil fuels and tie the US to questionable foreign policies?

I am also an engineer and relish an engineering challege.

:slight_smile:


#6

[quote=“dennis”]Interesting

I think two layers of I&W is overkill.

If you use elevated battens I don’t think using ring shanks to hold the battens will be a problem. The water ( if it gets under the tile )will flow parallel to the vertical battens.

No need for liquid sealer.

Venting should work fine if you have proper soffit venting.

hmmmm, Great Stuff will be tricky to work with. I think there are other foams made just for holding and supporting tile.[/quote]

I got a reply from Gace tech support today regarding Ice and Water Shield.

I was told: Ring shank nails are not a great idea unless the ringed part is also at the same depth as the Ice and Water Shield. However, wood screws are okay, IF the tip cuts and does not drill a hole. There are many different tips for wood screws so one has to be careful. The install manual could be read to imply that only nails should be used, but that is not the intent, screws can be used too.

Techie also said that: Liquid sealers are generally okay, but not likely needed. So nice to hear two voices say this. Indeed the top of Ice and Water Shield is a plastic and compatible with all but liquids with strongest solvents, just don’t get any on the underside.

Two layers are okay, but it is more cost effective to apply a second layer in strips (maybe 6" wide). Again Techie agreed with you - over kill, this gives me more confidence.

QUESTION:
Do you know the names of any of these alternatives to Great Stuff for supporting the tiles in a semi-walkable region. I only need it for about 36 tiles. I saw one alternative on Dow Chemical’s web site, but it was only sold in large quantity. Something in a can like Great Stuff would only require a few cans at a sensible price. I only need it for support since the tiles will be secured with two #12 screws plus a rain channel wind clip. No risk of wind uplift there, only cracking from walking.


#7

[quote=“gweedo”]it all sounds a little to complicated.

gweedo.[/quote]

I’ll try and remember to post a picture when done :slight_smile: