Rough in solar on new roof
ktim
| Posted in Mechanicals on
We will be building this year and are including resilience as part of the design. One piece of that is being solar ready and EV ready.
We are in Ontario, Canada 🇨🇦. Can anyone tell us what conduits/equipment/space we should be including in the construction of our home?
We hope for subsidies to be implemented in the future to facilitate the actual PV install and the EV charger install and wish to be ahead of that eventuality. Air sealing the penetrations in the air barrier now is the goal here. That and not having to run new wires on the outside of the house or open anything up for access.
Thanks!
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Replies
KTim,
I am not a PV installer, or an electrician. So take my post with a grain of salt that I don't know everything.
I'm a big fan of futureproofing in design and have spent a lot of time thinking about the singularity of pv's (when the cost vs energy produced becomes worth it to install) and how that's going to affect dwelling design and how we can optimise for pv systems.
A few major question for you though, low slope roof or typical peaked? Renovation or a new build? Metro or rural?
For instance, if I was outside of the Darth Vader grasp of Toronto zoning, I would design for a mechanical penthouse on a flat roof. And have my electrical service go into there, and all PV components and batteries also there so wiring for the PV's is straight an simple. And everything is somewhat isolated. I'd rather have a fire on my roof than in the basement. This also frees up space in the basement, leaving more room for functional living space. However most normal people on thinking of dwellings intend to have their functional things (mechanical, electrical, washers, cleanouts etc) in the basement, it sounds like you expect to do that based on the question of conduits.
From the roof.
On my last build I placed a 12x12 PVC Junction box on the low slope roof with three 1" conduits going down to the electrical room. In hindsight I wish I did four conduits. BUT, I also have three outdoor minisplit units on the roof, rough in for a NG generator, and expect to do a rooftop patio (with electrical) in the future. So consider what you're going to need for conduits and for of good practice/avoiding future frustrations, add a spare. Your conduits cant have bends more than a total of 360 degrees. But with bigger wires it's a pain in the ass to pull, so try to have as straight a shot as possible. You should place 2 or 4 pull strings in the conduits, so you can pull wires later. If you have more than 180 degrees of bends I'd suggest placing webbing in there to save some future hassle. It's not that much more expensive, just less available (I'm sure Bill will contribute more to this)
Based on your roof pitch and thus you're roofing material will dictate your roof system and can play a role in your construction costs. For instance, if it's a high slope roof, I'd suggest a standing seem metal roof so you can clip the pv panels to the seems and don't have any roof penetrations to mount the panels. If it's a low slope roof, you can consider getting bifacial panels (which are a little more energy efficient) to which you can either screw brackets to the deck and use a polyurethane roof membrane. Or consider doing a live vegetative roof to protect the poly membrane and still contribute to the bifacial panels (not as efficient for the PV's but more efficient in maintenance). Green roof suppliers have brackets where theyre held by the weight of the greenroof so that could be something easier implemented in the future.
The electrical room
This should obviously be near your service entrance so it's beside your panel. You need to consider how much space you will need for battery storage. I don't think Ontario will have the microfit program forever, I foresee future houses will soon be semi-self reliant, and maybe one day totally self-reliant from the grid, while still tied to the grid as a backup. So for example, look at Tesla powerwall setups as they have diagrams that show the components needed. you'll need to have a main switch at your incoming electrical service, before your main electrical panel. This will allow you to work your system later without having to pay for hydro to come disconnect and reconnect your service. You will need wall space to mount your panels, and I suggest wall mounting the battery packs on the walls to free up more ground space. When dealing with batteries, I'm of the opinion that you should have well sealed double 5/8" drywall and a fire door for that room, and should also have its own ventilation in the event of offgassing or fire.
Hopefully that didn't just ruin day.
Jamie
Thanks Jamie. Lots to consider. We're 3/12 metal roof, new build rural with a flexible building department. Mechanicals in the conditioned attic. If I ever did get batteries that is where they would have to go too but I agree about the fire safety.
KTim,
If the mechanicals/electricals are all going in the attic, and you're already doing a metal roof (hopefully standing seam) I don't think you need to do anything at this point.
Other than have your electrician install a master shut off before the main panel. And maybe have a seperate meter if you want to do the microfit, but that might be it.
I agree with calling an installer out for a consult.
But since theres no basement, and the only thing separating the PV's and the equipment is the roof, were not talking about conduits and architectural and interior preplanning. The day you install PV's you can drill a hole through the roof and sleeve it at that point. Just leave enough room near the electricals for extra equipment.
Most new residential solar will be micro inverters. This means all you need is a 1 1/2" PVC conduit and junction box on the roof for connection as all the wiring is AC.
With micro FIT, you want to install a two meter base. This is easy now but expensive later. Make sure to talk to your local utility as it will require some explaining that only one meter will be installed and the 2nd one blanked off. If you are looking to add an ADU to the basement go for a 3 meter base.
Thanks Akos. I will check with our utility on the meter bases. No basement so no adu.
I'd be surprised if financed solar isn't already cheaper (or close) than grid electricity without subsidies. In the US, unsubsidized residential solar is about $3/w which gets you a levelized cost of electricity of $.14/kWh if you finance it over 30 years at 4% and produce 1200 kWh/year per kW installed. That's an annual production typical of northern US states and results in a LCOE that's about the national average electricity price with no future increases.
Problem here is winter and snow. We actually get a fair bit of sun in the winter but snow cover and drifting are issues for dependability.
I require my roof design loads to increase by 10%-25% depending of where the house is located. Here is some good info I've put together in my website: https://cobodesigner.com/solar-pv-systems/
I remember a similar thread here from a couple of years ago. One of the solar installers chimed in and said that you should have the trusses and roof system designed for the extra loads, including wind loads, and get an engineering stamp on the designs up front. This will save $ and time later. He had some other specific recommendations, but I think some of the other advice you've received here covers most of it.
Thanks Armando. I'm probably already at that as I went with the next higher snow load numbers.
What happens when they put panels on existing houses? My 1892 house has just 2x6 rafters that are 24' long. I don't think an installer around here would even balk at slapping some panels on that.
Do what AKOS recommends. You will waste the least amount of money. Technology changes so fast it makes you head spin. First off, the Utility company is not going away. The way you are billed will change. A substantial fixed infrastructer charge will be implemented. Everyone connected to the net will pay without regard to electric use. It is about the cost to distribute the electric and not the power it self. Were you planning on going totally off grid. All the new equipment for off grid changes the economics. Oh, what are you going to do when we get cheap electric from small scale nuclear? Don't you need a substantial system to charge your EV in the evening after the sun goes down?
Small scale nuclear! Any day now :).
Not planning to go off grid at this point but who knows? Depends on $ and effort required. I plan to rough in conduit for an EV charger but until there's a more robust charging network I have no plans to get any fancier than a hybrid around here.
I am in the same position with my house build starting on Monday. I got my roof trusses design to be solar ready and I will be installing a 2" conduit (schedule 40 PVC) from the utility room straight up into the attic.
Arnold
I just had a system pre-wired and there was just a piece of conduit to get through the roof, then Romex from the top floor ceiling to the meter.
Perfect.
Thanks for all the great info. The roof is designed above the regular snow load. We will be rural with a 3/12 roof for the solar field. Plan to be tied to the grid as I am too lazy to maintain a complex battery system but I do have space for it if that is what the future holds. The conditioned attic is where all the mechanicals are going as we are on a slab. Easy, straight shot from roof to panel. Good advice on the dual metres. Not likely to do the more involved stuff...once again, I'm lazy and would rather be fishing. Really appreciate the input and will research the suggestions.
There's lots of advantages in going with a microinverter system. It's a relatively low voltage system (240 volts in the USA) compared to string inverter architecture. A string inverter system will always have very high voltage on the roof and even a DC disconnect on the roof (which a microinverter system doesn't need) will ALWAYS have high voltage during daylight on the input of that DC disconnect box. Microinverters systems are just safer in an emergency situation. Standard plain romex wiring without conduit is possible on microinverter systems in most places, except on roof where wiring is not covered by solar panels.
If you install low profile (3 inch high) Soladecks on the roof and locate them beneath solar panels that are grouped together you don't even need conduit on the roof. All wiring will be covered by solar panels with a Soladeck located underneath them. Romex will span from soladeck through roof to where it terminates in a combiner box.
Don't use the soladeck as a combiner box but instead pass separate romex for each grouping of solar panels (up to the maximum current permissible) to a combiner box located at an accessible point near the main panel and AC disconnect box. This maintains redundancy and allows for easier troubleshooting if it's necessary later. Individual circuit breakers on the combiner box associated with each individual romex allows for quick isolation if a fault develops. Most important an electrical fault won't bring down the whole system, just the one at fault.
Finally, parallel the outputs of the C.B.s in the combiner box and connect that output to an AC disconnect. Technically you don't need even a AC disconnect box because the microinverters are designed to shut down if they don't see voltage from the grid side. But it's probably code to include it and is just good practice. That easily visible and placarded AC disconnect switch gives people working on your house in an emergency peace of mind that they aren't going to get electrocuted.
You might also consider reaching out to a local-to-you solar installer that has a good reputation and offer to pay them a modest consulting fee to have them provide you with locale-specific information regarding the prep they'd like to see in place for a future installation. They might even do that for free in hopes of getting your future business. It's quite possible there are specific requirements and/or practices in your locale of which we are not aware, and it would be good to have that in hand to complement the useful information shared by others in this topic.
Good point. Thanks!
I have seen some pretty large conduits recommended coming thorough the roof on this thread. In my experience a 3/4" conduit through the roof will cover most systems unless you are going pretty big(10KW+). No need to make things hard by working with waaaayy oversized conduit.