We are building a new house in a historic area which will have a flat roof pitched slightly to the south for drainage. Our plan is to mount pv solar panels. Our solar contractor is talking about using a ballasted system. This seems to involve a rack that holds the panel and then concrete blocks to hold the rack in place. There is no other attachment of the rack to the roof. Anyone have experience with this system? We don't want to lose all our panels during a high wind. Thanks, Mark

Mark,

Ballasted PV arrays are very common, especially in large commercial flat roof systems where minimizing penetrations through the roof membrane is important to the building owners. They can be engineered for just about any wind and exposure condition, though installation angles for the collector are typically limited to about 15-20 degrees to keep the wind load moderate and the ballast amount reasonable.

In some areas, a hybrid fastened and ballasted system is required due to seismic or other loads or occasionally due to the limitations of the underlying roof structure.

PanelClaw ( www.panelclaw.com) and Rapid Rac (from unirac www.unirac.com) are two of the most common systems. There is lots of literature available on their websites.

Make sure the roof is designed to handle the extra load from the ballast (which typically ends up somewhere between 4 and 10 psf).

Best of luck,

~Fortunat
www.revisionenergy.com

Fortunat,

Thanks, that's a very comprehensive reply. I will check out the resources you mentioned.

Excelllent help.

Cheers,
Mark

I have a National Historic Registered property, we are going with DHW first, biggest payback.

Being grid tied there is not the incentive currently with PV, if we go that way in the future I would not locate them on the building. I know in CA you can buy into PV farms, we do not have that so I would place them away from the building.

A couple things to keep in mind.

-Even 60 degrees is going to be a minor loss in winter at your location.

-The AL plate is going to be covered in snow, just like the PV would have been.

-The sugestion takes care of itself, like when you go to work while its snowing.

-Snow is going to be a good reflector, like the AL plate.







____________
roofing contractors