Mounting (on shingle) roof options???

I've got a south (yeah!) facing back 6/12 (i.e. 26 degree) roof in Salt Lake City (~41 degrees) with about a 14 H x 40 W clear area (actual roof is 60x20).

I'm leaning towards CS6P-230-P (64.50" x 38.70"). Landscape fits 4 rows of 7 (which I prefer to get the most out of the space), while portrait only holds 2 row of 12 (but seems to have a mounting to rafters advantage - 4 rows perpendicular to the rafters).

I priced out the iSolar mount (~$4K) and Iron Ridge (~$3K) and hoped I (with your help) could come up with a cheaper DIY solution. I've decided against adjustable tilt or tracking (we have quite the rust problem from the salt air and therefore avoid as much mechanicals as possible).

My first design includes lots of angle (and/or T) aluminum in a bunch of support triangles and along the edges of the panels (sort of like a tray). I have since read that panels 'ought' to be supported 1/4 to 1/3 of the way in - any comments on this?

My second design is strictly galvanized pipe (with the appropriate T's, elbow, roof flanges and ubolts) - any comments on this?

For either design a concern is whether increasing the angle from 26 degrees to 41 degrees is worth the extra price/work. Has anyone regretted leaving their panels at roof angle (or conversely regretted angling their panels above roof level)? I understand that angling decreases snow load concern (as long as there is enough clearance), but increases wind concerns - I don't think it is a good idea to angle so much so that the panels are above the ridge-line.

Anyone have advice as to how frequent (4'? 8'?) the roof penetrations ought to be (as opposed to the thickness of the angle aluminum or galvanized pipe)?

Also it appears that in some cases the panels are held in place to the support strictly by pressure (top clamps) is this sufficient or should I design some type bottom attachment?

Thanks in advance for any advice (and/or things I've overlooked).

Comments

  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Mounting (on shingle) roof options???
    I've got a south (yeah!) facing back 6/12 (i.e. 26 degree) roof in Salt Lake City (~41 degrees) with about a 14 H x 40 W clear area (actual roof is 60x20).

    I'm leaning towards CS6P-230-P (64.50" x 38.70"). Landscape fits 4 rows of 7 (which I prefer to get the most out of the space), while portrait only holds 2 row of 12 (but seems to have a mounting to rafters advantage - 4 rows perpendicular to the rafters).

    I priced out the iSolar mount (~$4K) and Iron Ridge (~$3K) and hoped I (with your help) could come up with a cheaper DIY solution. I've decided against adjustable tilt or tracking (we have quite the rust problem from the salt air and therefore avoid as much mechanicals as possible).

    My first design includes lots of angle (and/or T) aluminum in a bunch of support triangles and along the edges of the panels (sort of like a tray). I have since read that panels 'ought' to be supported 1/4 to 1/3 of the way in - any comments on this?

    My second design is strictly galvanized pipe (with the appropriate T's, elbow, roof flanges and ubolts) - any comments on this?

    For either design a concern is whether increasing the angle from 26 degrees to 41 degrees is worth the extra price/work. Has anyone regretted leaving their panels at roof angle (or conversely regretted angling their panels above roof level)? I understand that angling decreases snow load concern (as long as there is enough clearance), but increases wind concerns - I don't think it is a good idea to angle so much so that the panels are above the ridge-line.

    Anyone have advice as to how frequent (4'? 8'?) the roof penetrations ought to be (as opposed to the thickness of the angle aluminum or galvanized pipe)?

    Also it appears that in some cases the panels are held in place to the support strictly by pressure (top clamps) is this sufficient or should I design some type bottom attachment?

    Thanks in advance for any advice (and/or things I've overlooked).
    If you go to Unirac's site, there is a calculator where you enter the rafter spacing and array size and it will tell you how much rail and how many penetrations you will need. Racking companies will give you assistance in designing your array and will help you preserve the integrity of your roof. If you go with a DIY solution you will incur more risk of damaging your roof and/or voiding your roof warranty. Something to consider.

    As to the tilt angle, you can estimate the difference in production using PVWatts (http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/), but understand that if you mount your array at a different tilt than your roof, your mounting will get a lot more expensive, and it will introduce more dead load and wind loading stresses to your roof that you should not ignore.
  • newenergy
    newenergy Solar Expert Posts: 291 ✭✭✭✭✭✭
    Re: Mounting (on shingle) roof options???

    If the salt air is a problem I wouldn't put anything up there but stainless steel and aluminum. I know your layout is not very efficient for racking, but $.46/watt is really high. Keep shopping. Prosolar is cheaper (not really any more than just buying stock alum angle), but I don't know if it's available there. I think you can find a better price on Iron Ridge too.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Mounting (on shingle) roof options???

    Well if you have a grid that is 4x7
    with dimensions of 14x40' that is going to be 40x5 = 200 linear feet of metal

    You can get aluminum mill stock 2x4's for around $2.5 a foot or $500 woth of metal plus a top and bottom "U" channel and a bunch of bolts and washers to tap into the aluminum metal.

    I'd just buy the roof stand offs from the manufacturer unless you are realy good at working with metal. I've never been able to source the hollow round pipe they use in the aluminum extrusions.

    Of course I dont' know what your codes people are like. In the country where I live as long as it looks pretty solid it would probably pass. Where my sister lives in Florida you need a engineer's stamp on the drawings.

    You can private message me for exact metal you would need, but obviously if you need it certified by an engineer figgure an extra few hundred to get that done.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Mounting (on shingle) roof options???

    also there are special taps called sprial taps you can buy them for $7 or so from
    mcmastercarr.

    I dont' know why places like home depot or lowes do not carry them, but you can litterally use a power drill and tap aluminum very very easily.

    don't even think about trying to machine all the metal without a chop saw with aluminum blade. you can get 10" off ebay for $30 or so

    it's a lot more work, but it is a lot cheaper to do it yourself.
  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    Re: Mounting (on shingle) roof options???

    if you want someone else to design it call your local 8020.net distributor
    they do design work for free. that being said the aluminum extrusion is around $3 a foot and they pad their profit margin with a bunch of high priced connection hardware. The trick is to just buy the metal and then put it together with low priced nuts and bolts from the local hardware store, by cutting and tappign the metal yourself the price will be about half what 8020 might quote you to begin with.
  • real3d
    real3d Registered Users Posts: 2
    Re: Mounting (on shingle) roof options???

    Hi all - My first post!

    DaylanDarby - I live just south of you in Highland, and I've just ordered all my system parts and spent a little time the last two days at the city office talking to the inspector and the building department. Unless you plan to do your install on the sly, you are going to be much better of in teh long run, (cost/headache/time) ifyou just go with a manufacturered rail system. I spent months researching resellers/dealers/wholesalers of PV system parts, and by far I love Ironridge. Their website (like unirack) has a great calculator that can calculate your roof loading and specify minimum allowable spans for the railing/supports. You will need this information to get a building permit for your installation. The city will want to know the point loads at each support (dead load), PSF for the roof, and how you will attach it to your roof structure (some form of lag bolt and the length). If it is an older home, will will have to show that the roof can carry the load; if it is of modern code construction, it will be much easier to show.

    I considered building my own racking - don't do it. Civicsolar and simpleray have some of the best prices I have found anywhere (civics prices are lower than listed once you get a quote), but simpleray has the best shipping (flat rate) anywhere. I went with 250w siliken panels from civic for $375 ea, and ordered all else from simpleray.

    Your angle is not optimum, but like others have said, if you angle it, the wind loading (up and down forces) will go up quickly. You will get a good summer sun angle, but less efficient in the winter. Is shading going to be any issue? I have an 8/12 roof and am planning for 5.5' spans, which is still a safety factor for 60 psf snow load and 150 mph wind. I will have two lag bolts per standoff (4"), to hold it all down. With the snow here in utah, and summer heat, I went with the 4" standoffs for better summer cooling and more clearance over the snow pack buildup in the winter. I'll use standard oatley flashings for the standoffs (don't consider just L feet brackets here in utah - it will eventually leak). Remember to predrill and fill the holes with roof sealant before putting in lags.

    Ready made rails will also make grounding much more simple and fast with WEEB clips. I went through the entire grounding plan with the inspector to make sure it would fly, and he is good with it and becoming more educated everyday.

    Lastly, you might want to consider (if you are using enphase m215) designing your system to clip a little. It won't hurt the inverters, and as teh panels degrade each year, you will have higher output over the life of the system. Obviously this only works if you can get a higher output panel at the same cost (or not much more). At $375 for 250W silikens, it is hard to go wrong!

    Cheers,
    real3d
  • real3d
    real3d Registered Users Posts: 2
    Re: Mounting (on shingle) roof options???

    One last thought...

    Any manufacturer you are considering, for hardware, panels, etc, be sure to read all the install manuals/notes, tech briefs, guide, etc you can find at their sites. I learned tons of great things about similarities and differences between manufacturers, and answered many many questions I had and didn't know where to look for the answer. And when you find great info, be sure to save the .pdf for easy reference later (it is often hard to find specific info again on the web, even with a bookmark/favorite).

    If you want a full list of materials I'm using for cost reference, just let me know.

    real3d
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Mounting (on shingle) roof options???

    I've been using the mounting feet sold by Unirac. I'm in hurricane prone FL, and I wanted to keep the panels low profile.

    I'm moving next week, and I removed all the panels. They'll be put on the new house. I was very impressed by how well they've been doing up there. No leaks, and were very secure.

    dscn6176.jpg

    dscn6175.jpg

    dscn6049.jpg

    dscn3437.jpg

    http://www.altestore.com/store/Solar-Panel-Mounts-Trackers/RV-Specialty-Solar-Panel-Mounting/Unirac-990009-RV-Mounting-Feet-Set-4-U-MF-4/p3931/?gclid=CLKa2dSy1asCFQ1b7Aod6QzDMg

    I pre-drill the holes through the shingles into the plywood below, apply a decent amount of 100% silicone caulk, then use a stainless steel lag bolt with a washer to secure the bracket to the roof.

    This method worked so well, I'll be using it again shortly...
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Mounting (on shingle) roof options???

    If you or any buddies have access to a IR thermometer, see how hot those panels run in the sun, vs ambient. Looks like there is little air circulation, and decent mounts hold up to hurricanes OK - longer than the shingles will. It's the flying resin chairs that will bork your panels.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Mounting (on shingle) roof options???

    too late mike he said he removed them.
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Mounting (on shingle) roof options???

    They'll be installed on the new roof in a few weeks. However, the peak of Summer is over, so won't be able to measure worst case.

    The panels sit up a couple of inches off the roof, so not completely flush. Z-brackets raise the frames up an inch, and the frames are ~2" thick. The new roof is a steeper pitch, which might help airflow under the panels.

    As mentioned in another thread, I'm in hurricane prone FL. Things like shingles don't do well here. I didn't want anything standing up from the roof as it'll become a sail during a storm. I'd rather lose some efficiency, rather than the panels themselves!

    Ref: http://forum.solar-electric.com/showthread.php?p=93494
  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: Mounting (on shingle) roof options???
    2manytoyz wrote: »
    I've been using the mounting feet sold by Unirac. I'm in hurricane prone FL, and I wanted to keep the panels low profile.

    I'm moving next week, and I removed all the panels. They'll be put on the new house. I was very impressed by how well they've been doing up there. No leaks, and were very secure.

    I pre-drill the holes through the shingles into the plywood below, apply a decent amount of 100% silicone caulk, then use a stainless steel lag bolt with a washer to secure the bracket to the roof.

    This method worked so well, I'll be using it again shortly...

    What do the lag bolts screw into? Not just into the plywood decking, I hope.
  • topper
    topper Solar Expert Posts: 113 ✭✭
    Re: Mounting (on shingle) roof options???

    Thanks for asking all these questions as I am in the same boat. Same size house with less tilt.4/12 pitch. Axiouse to see more info.
  • HTG PVinPA
    HTG PVinPA Registered Users Posts: 16
    Re: Mounting (on shingle) roof options???

    The key to long term success of non-leaking bolt/screw penetrations is the water cutoff mastic on the screw. We use Firestone Water Block Seal S-20.

    I wouldn't trust silicone sealant spread around the plate & bolt head.

    Kim
  • 2manytoyz
    2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Mounting (on shingle) roof options???
    ggunn wrote: »
    What do the lag bolts screw into? Not just into the plywood decking, I hope.

    Why not? Solar pool heaters are attached to shingle roofs in this fashion, have been for years. They hold up to storms here in FL. They use #10 screws for the hangers. I'm using 1/4" lag bolts. 16 per panel. These panels are using the low profile Z-brackets. If the panels sat up higher, I'd want them into the rafters. As they are, the wind really can't get under them, and since each panel is individually secured, the low pressure across each one is minimal, compared to an entire array tied together on a frame. If the plywood decking isn't secured to the rafters properly, chances are the plywood would lift off during a storm anyway. The house I just bought is a 1990 vintage, and survived the hurricanes of 2004.

    A lot of things may not hold up well to water, but silicone isn't one of them. The product I'm using is rated at 50 years. And having removed my panels from the roof recently for the move to the new house, I can assure you this stuff sealed tightly against the screws, the wood, and on the shingles where it oozed out during installation. It will tear the shingles before it lets go. I have yet to carve the washers off the mounting feet. Still stuck in place.

    I stopped using petroluem based roofing products as they break down in a matter of a year or two here if the sun hits it. If I was concerned with the sealant I'm using, my next choice would be 3M 5200. Used on boats below the waterline.

    My panels held up to Tropical Storm Fay. Lots of wind/rain for several days. Not a drop leaking in.