Solar panels on a flat roof - tilt or no tilt?

[ncs55]

A lot of roofers like that seal in the picture. The jury is still out for me on that type. I have not had much experience with them. It seems like they consume a lot more sealant than is necessary to make a flat roof leak proof.

[jetsurgn]

First Flat roofs seem more difficult from pitched roof.
Flat roof good idea to have a roofer involved
Their seems to be two schools of thought with sealing the attach points, Chemlink like in the photo and Flashed.
Which one is preferred?

[ncs55]

The best way to seal roof mounts is however your licensed roofer is willing to do it so that his guarantee (and your homeowners insurance) is in effect.

True, Let the roofer decide the best way to seal them, because the roofer is the one with the liabilities. If it leaks it will be up to the roofer to fix it and if there is any substantial damage hope that his insurance company is decent enough to handle it. Usually leaks are small and cause damage over a period of time, from what I have seen. Slight leaks can lead to mold which is the worst kind of damage as that affects your health, especially black mold. I am not sure if you would want to make a claim with your home owner policy as your rates will go up because of his mistake. Any good roofer will give you a 10 year warranty. If they offer less than ten years I would be looking for a different roofer.

[solarix]

The best way to seal roof mounts is however your licensed roofer is willing to do it so that his guarantee (and your homeowners insurance) is in effect.

[ncs55]

So what the best mount method for a flat torch down paper roof? Chemlink E-Curb??

We seal the stanchion with Chemlink at the base, (don't skimp here), and then have a roofer seal the flashing down with torch down. If you cannot do it that way then you can seal the stanchion the same way, then use mastic all around the bottom edges of the flashing, place the flashing down in place, push it down firmly then run another bead around the edges of the flashing at least 2" on each side of the edge all of the way around, then a layer of yellow resin coated glass fabric, or equivalent around and on top of the mastic and then one more layer of mastic overlapping the first layer of mastic. Make sense?

[jetsurgn]

So what the best mount method for a flat torch down paper roof? Chemlink E-Curb??

[ncs55]

If you have a composition type of roof make sure they used approved flashings at every standoff. If you have a tile roof make sure they double flash each standoff. Also make sure that they are not mix matching the racking system. IE say using one manufacturers standoff with another manufacturers rails. Mix matching these components voids any warranty from either manufacturer.

[ncs55]

Yes SW, agreed. Tilting does limit the total wattage installed, however it will increase the amount of harvest. So tilting can actually shave a few modules off of the system and still have the production needed to meet the demand. The total wattage installed can be drastically different from the total harvest and system production, especially when tilting is concerned. It is not about the total wattage installed, unless you are a sales person on commission. It is about how can you get the most harvest in the space / orientation allotted for your installation. It really depends on the location and what you have to work with. It is a good sign to see that at least the one company bidding is willing to use tilts.

[DanKegel]

I'm advising our church on a very similar system (9-11kw, southwest orientation, 10 degree tilted roof, also in Santa Monica).
Would love to hear how yours turned out!

[dominic213]

I would also suggest an SW tilt as it will give you more power in the afternoon. The usage will be very high on the afternoon and so SW tilt will be ideal. What I did was, I changed the orientation of my flat roof by hiring a commercial roofing contractor of Empire Roofing Corporation and made an ideal slope for the roof which will help in water shedding and keep them much safe and clean.

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[dusterbuster]

Hi guys, just another update. I went back to the installer and asked if he could incorporate a 15 degree tilt and relocate a few panels, which they did. I think all things considered for our situation, this is a decent compromise. Thanks everyone for your helpful input.

[J.P.M.]

Hey guys, the installer came back with a proposed plan that incorporates a 10-degree SW tilt. The designer said he didn't want to go too high because we have a short parapet around the roof of our 1 story home (so hopefully the panels remain unseen from ground level) and to reduce spacing between the panels. Do you think a 10-degree tilt will be sufficient to help keep the panels clean?

Also, to provide the tilt, the installer has switched the mounts to Ironridge Tilt Leg and Foot w/Chemlink E-Curb (rather than Quick Mount PV QMNC Q Base Comp for a flush mount). In comparing the diagram of the tilt versus flush mount, it looks like there is a bit more waterproofing required with the tilt leg mount (although maybe that is just manufacturer specific to Ironridge). Should I have any concerns that a tilt leg mount may increase the likelihood of water intrusion?

Often, solar is a trade off of many requirements, but if one (aesthetics) impairs performance in one or more ways, like lousy tilt angle, that's when compromises may be warranted. Simply put, horizontal orientation of solar arrays almost always impairs performance due to less than optimum tilt/azimuth and more frequent cleaning, and there is not much to be done about it in a practical sense. If you are willing to accept those limitations and the penalties imposed, so be it.

Tilted racking has been around as long as flat plate collector technology ( > 100 years or more) and is pretty well developed. Well designed tilted systems can easily be as leak tight as arrays parallel to a mounting surface if done in a competent and professional manner. That's one more reason why an established vendor is worth a (slight) premium.

[inetdog]

I... (And that doesn't even take into account afternoon load peaks.)

Nor does it consider potential Time Of Use (TOU) rate advantages for any overproduction.

[jflorey2]

I would strongly suggest a SW tilt. Southwest orientation will give you more power in the afternoon, when you would be using it.

In addition, "June gloom" is a big factor in Socal installations, and often there isn't much sun before 11am in May/June. A recent study here determined that the best azimuth for coastal installations near LA and San Diego was about 195 degrees to account for the loss of sun during prime months due to morning clouds. (And that doesn't even take into account afternoon load peaks.)

[Ian S]

Hey guys, the installer came back with a proposed plan that incorporates a 10-degree SW tilt. The designer said he didn't want to go too high because we have a short parapet around the roof of our 1 story home (so hopefully the panels remain unseen from ground level) and to reduce spacing between the panels. Do you think a 10-degree tilt will be sufficient to help keep the panels clean?

Also, to provide the tilt, the installer has switched the mounts to Ironridge Tilt Leg and Foot w/Chemlink E-Curb (rather than Quick Mount PV QMNC Q Base Comp for a flush mount). In comparing the diagram of the tilt versus flush mount, it looks like there is a bit more waterproofing required with the tilt leg mount (although maybe that is just manufacturer specific to Ironridge). Should I have any concerns that a tilt leg mount may increase the likelihood of water intrusion?

My foam flat roof solar installation here in Phoenix has a 15 degree tilt. The 15 degree tilt results in slightly reduced annual production but that's offset by the higher production during the expensive summer months. In the future, you can expect many utilities to follow the lead of SRP in Arizona to make late afternoon production far more valuable than production at other times. A southwest orientation works best for that.

A flat roof installation that's tilted looks OK from the front but the back view leaves a lot to be desired IMHO but I would not have wanted a flat install due to the dirt issue. Make sure you have your roof inspected before installation so that any flaws can be corrected. There should be no issue of water leaks if your roof is sound and the installation is done properly.