Recommendations for prepping 'new' roof for eventual solar.

[Dadnatron]

I am going to be refurbishing a 120x40' tobacco barn. The roof is old aluminum with some cross running boards with approximately a 4" gap. *(I'm around 30' away, looking up.)*

I'm going to have a ribbed steel roof put on, but given the southern exposure of an entire side with a good angle to the sun, I'd like to at least think about future potential for solar. I calculate that, if I covered the entire south side of the roof, I'd be producing approximately 52MW/yr or between 2MW in Jan to 6 in June, according to the PVWatts calculator.

If I was to eventually desire to add some or all of the panels, what should I do with the current roof renovation to prepare for adding panels in the future?

The barn infrastructure is a very sturdy hand hewn, pegged structure. It is set pretty well, but I am toying with pouring a footing around the entire thing and setting it. Now, it is on a mix of concrete pylons and driven large 12" 'posts' about 6" out of the ground.

I'm not positive I will ever add panels, but if prices come down enough or it begins to make sense, I'd certainly like the option without redoing the roof, if that is an option. I'm not even sure how much energy I would use/need for the farm. I am definitely a 'just pay the bill' kind of electric guy.

 

[barko1]

I'm not positive I will ever add panels, but if prices come down enough or it begins to make sense, I'd certainly like the option without redoing the roof, if that is an option. I'm not even sure how much energy I would use/need for the farm. I am definitely a 'just pay the bill' kind of electric guy.

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I'd try to keep it off the roof if at all possible. In the city there is no room but on the roof, if you have space make it ground based. Easier to install and service, no problems dealing with your roof in the future. A few steel beams in concrete and it is easier to adjust to the optimal sun angles/directions. Panels got a lot cheaper and now they are getting more efficient. The bad news is that more and more electric providers are charging a monthly fee to access and seems like states are rolling back on net metering. If, as predicted, cheap storage (think Tesla) comes then no need to hook to the system.

 

[dmccarty]

The roof should be at the optimum angle for your latitude to maximize solar production. When I designed our house I made sure our south facing roof was close to the optimum angle.

The roof structure needs to be able to support the panels. You can add up the weight of the panels, guestimate the weight for the panel support structure and calculate the weight per square foot. Then look up span tables to see if the current roof structure will hold the weight.

Later,
Dan

 

[RNeumann]

If you were to put solar on the roof their is a little prep to do beforehand. The panels mount with little standoffs that will mount on top of the metal. Then the wires will probably run through a weatherhead and that flashing will also be installed on top of the metal.

Because of the point loads on the standoffs I'd sheet that side of the roof with 5/8" plywood or OSB. This will aid the installation since all you have now is the skip sheathing.