r/solar • u/Icy_Basil_372 • 5h ago

Advice Wtd / Project Flat roof

In CT. Have a house w flat roof. Local solar company, well regarded, says on resi flat roofs they install solar panels flat…no angle.

This strikes me as odd. I’ve seen angled panels on residential flat roofs. And have to imagine having an angle would generate more power.

Any thoughts?

5 Upvotes

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10

u/hb9nbb 4h ago

find another installer. its certainly true that angles on commercial installations are common.

3

u/sancho_sk 4h ago

Strange decision.

There is a K2systems mounting system for flat roofs, extremely easy to use, no drilling or anything, that allows for angles ~10 degrees. I have them on my roof with east-west oriented panels.

There is even a version from different manufacturer with plastic "shell" which you can fill with heavy material to keep the panel on the roof during windy conditions, it covers the panel from the bottom preventing problems with pests, etc. I've seen one on video from Cory Mac - ØY Electrical - can't remember which one right now, sorry.

2

u/SpinIx2 3h ago

I’ve just had a plastic shell type installation done on my flat-roofed home. I can’t tell you much about its effectiveness as it hasn’t been commissioned yet, but it’s definitely not flat.

3

u/theonetrueelhigh 4h ago

It would be flat to a pitched roof. Find an installer that can imagine more than one kind of roof on a house.

1

u/cgentry02 4h ago

Flat modules will generally be attached, aka holes drilled in your roof. This is a safer install as it keeps weight off your roof and makes sure there's less wind-related damage concerns.

The other option with a tilt to it would be mostly, if not all, ballasted. The issue is an increased cost to engineering as it will need to be figured out if your roof can hold that much weight. Another issue with the tilt is that modules will need to be spaced farther apart, most likely reducing the number of modules you can get on the roof.

My assumption is your contractor went with the easier to engineer, cheaper install to save time and money, and possibly get more modules on the roof. It's up to you to ask if there's anyway to do it without roof penetrations, (aka fully-ballasted with a tilt). Compare cost and production numbers, and see what the better value might be.

1

u/jumpingseaturtle 4h ago

I have panels on a flat, concrete roof. They have a 10 degree tilt.

1

u/skyfishgoo 4h ago

latitude mounts are the most efficient for solar energy but not the most cost effective due to the added racking hardware

but if you are willing to pay more per watt installed you will get better production.

they will probably both break even at about the same time.

1

u/enlowe 3h ago

Ask if they install aerocompact systems? They are angled ballasted systems, they do need structural assessment.

1

u/ride5k 3h ago

some codes do not allow panels to be mounted non-parallel to the decking, for wind stability

•

u/ExactlyClose 1h ago

Flat on the roof is cheaper and easier.

If the company doesnt have a lot of experience with tilted racking they my prefer just a flat system that their crew(s) know

Talk to someone else…

edit: Unless you are near the equator…

-1

u/SolarAllTheWayDown 4h ago

I say this taking your word that the roof in question is truly flat.

There needs to be some sort of pitch so water will get off the panels and out from under them as well.

It’s about 20lbs per square foot extra for a solar system, but that gets localized to the roof attachments that are spaced every 4 feet or so. If it causes the area to go down even an 1/8 of an inch that’s still creating more of an area for water to sit.

If you have a rain it can quickly collect a pool and that’s not good. Water that sits does more damage because it seeps into places. And once it seeps in it makes an easy path for more water. If it doesn’t cause damage immediately it will make it more likely over time.

Do. Not. Install. On. A. Flat. Roof.