FAQ · Insulation & solar panels · SE Queensland
Can you insulate a roof that already has solar panels?
Yes. Easily. Your panels sit outside on the roof; ceiling insulation goes inside, down on the plasterboard. We pump cellulose in from the roof cavity without lifting a panel, and just work around the solar wiring like any other cable.
I get asked this a lot, usually by people who reckon their solar has somehow ruled out insulation, or that the two do the same job. Neither’s true. Here’s how we insulate a ceiling under an existing solar setup, and why solar and insulation are a team, not a choice.
Your panels are outside. Your insulation is inside.
The first thing to understand is that solar panels and ceiling insulation live in two completely different places, and they never meet. Your panels sit up on the outside of the roof, bolted to the tiles or the metal sheet. Ceiling insulation goes the other way entirely, down on the inside, lying on top of the plasterboard in the roof cavity. There’s a whole roof between them.
That’s why having solar makes no difference to how we do the job. We pump the cellulose in from inside the roof space, so we never climb onto the array, lift a panel, or touch a bracket. There’s zero risk to your solar, because we’re working in a different part of the roof altogether. If you’ve been told you can’t insulate because of your panels, that simply isn’t right — a house with solar is no harder for us to insulate than one without.
We work around the solar wiring, same as any other cable.
The only bit of your solar system that’s actually up in the roof cavity is the cabling, the conduit running from the panels down to your inverter. We treat that exactly the way we treat your house wiring, your plumbing and your air-con ducting: we work around it. A bit of cellulose laid over a conduit-run cable doesn’t harm it; that’s the same situation as the ordinary electrical wiring that’s sat under ceiling insulation in millions of homes for decades.
What we don’t do is smother anything that’s meant to stay clear. If there’s an isolator, a junction box or a fitting in the roof space that needs to be accessible or kept ventilated, we keep cellulose away from it. The same way we shroud the manhole, keep clear of downlights and stay off the flues. Every Comfort Zone owner-operator is trained to spot that gear and work around it, and because the job is photographed and the photos are checked before you’re invoiced, you can see the finished coverage with those fittings left clear.
“Solar wiring in the roof is just another cable to us. We pump around it the same way we’ve worked around house wiring for forty years, and we leave clear whatever’s meant to stay clear.”
Why you want both
Insulation cuts the load. Solar powers what’s left.
Here’s the part people get muddled. Solar and insulation aren’t rivals. They do two different jobs, and they work best as a pair. Solar panels make electricity. They do nothing to stop the heat pouring down through your ceiling on a 38-degree afternoon. Insulation is what stops that heat, so your air-conditioner isn’t fighting a roof cavity sitting well over 60°C all day long.
Think of it as two halves of the same bill. Insulation lowers how much energy your house needs in the first place, it cuts the cooling load. Solar lowers the cost of the energy you do use, it powers what’s left. Bolting solar onto a hot, uninsulated house is like pouring water into a bucket with a hole in it: you’re generating power just to dump it back out through the ceiling. The Australian Government’s yourhome guide estimates roof and ceiling insulation can cut heating and cooling costs by up to 45% , so insulation makes every solar kilowatt go further.
If you’re doing both, insulate first so you size your cooling and solar to a house that already runs cooler. If your solar’s already up, no problem. We’ll insulate around it and you’ll feel the difference the next hot day.
Insulation & solar panels: the related questions.
Can you insulate a roof that already has solar panels on it?+
Yes, and it's one of the easiest jobs we do. Your solar panels sit up on the outside of the roof, while ceiling insulation goes down on the inside, sitting on the plasterboard in the roof cavity. The two never touch. Because we pump cellulose in from inside the roof space, we don't lift a single panel, touch a bracket, or go anywhere near the array on the roof. There's no risk to your solar at all. The only solar gear that's actually up in the roof cavity is the wiring and conduit running from the panels down to your inverter, and we simply work around it the same way we work around your electrical wiring, plumbing and air-con ducting. Having solar doesn't make your house any harder to insulate.
Won't the insulation cover or damage my solar wiring in the roof?+
No. The cabling from a rooftop solar array runs in conduit through the roof cavity down to the inverter, and a bit of pump-in cellulose laid over a properly-installed, conduit-run cable doesn't harm it. It's the same situation as your ordinary house wiring, which has sat under insulation for decades. What we don't do is bury or smother anything that's meant to be left clear. If there's an isolator, a junction or any fitting in the roof space that needs to stay accessible or ventilated, we keep cellulose away from it, the same way we shroud the manhole and keep clear of downlights and flues. Our installers are trained to spot that gear and work around it, and the job photos show the finished coverage with those fittings left clear.
Do I still need ceiling insulation if I've already got solar panels?+
Absolutely, they do two completely different jobs, and they work best together. Solar panels make electricity; they do nothing to stop heat pouring down through your ceiling on a 38-degree afternoon. Insulation is what stops that heat, so your air-conditioner doesn't have to fight the roof all day. The smart order is to insulate first: a properly insulated ceiling cuts how hard your cooling has to work, and then your solar powers the smaller load that's left. Insulating after the solar is fine too, you haven't missed the boat. The Australian Government's yourhome guide estimates roof and ceiling insulation can cut heating and cooling costs by up to 45%, so it's still the cheapest comfort upgrade you can make, solar or not.
Should I insulate before or after getting solar installed?+
If you're doing both, I'd insulate first, but either order works, so don't let it stop you. Insulation cuts the load your house puts on the air-conditioner; solar then powers whatever's left, plus everything else. If you insulate first you size your cooling (and therefore your solar) to a house that already runs cooler, which can mean a smaller bill all round. But plenty of my customers already have solar up when they call me, and that changes nothing about how we do the ceiling, we pump the cellulose in from inside and work around the cabling in the cavity. The one thing I'd say is don't skip the insulation because you've got solar. Solar lowers the cost of the energy; insulation lowers how much energy you need in the first place.
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Or call Peter on 0414 586 315 , happy to talk through insulating under your panels, no pressure.
Peter Johnson
Owner / installer · Comfort Zone Insulation Team® · Since 1986