FAQ · Air-con & insulation · SE Queensland
Should I get air-conditioning before or after I insulate?
Insulate first. Insulation does the heat-control heavy lifting, so a properly insulated home often needs a smaller air-con unit, and whatever you fit runs less. Maybe you don’t need a bigger air-con; maybe you just need insulation.
I get this one most when the weather turns. Someone’s upstairs is an oven, they’re about to ring an air-con bloke, and they want to know whether to sort the insulation first or last. My honest answer is the same every time: insulate the ceiling first, then buy the air-con. Here’s why the order matters more than people think.
An air-conditioner doesn’t stop heat getting into your house. It just fights the heat that’s already in. Insulation does the opposite: it stops the heat at the door. In summer your roof cavity can sit well above the outside temperature, and all that heat presses down through the plasterboard all afternoon. If you size and buy your air-con while that’s still happening, you’re buying a bigger machine to fight a problem a blanket of cellulose would have solved for a fraction of the cost, and then paying to run that bigger machine every quarter for the life of it. Fix the roof first, and you size the air-con for the cool, sealed house you’ll actually be living in.
“Maybe you don’t need a bigger air-conditioner. Maybe you just need insulation. Get the ceiling sorted first, then size the air-con for the house you’ll have, not the oven you’ve got.”
Insulate first
Why insulating before the air-con saves you twice.
Insulation cuts the heat load your air-con is built to fight. Do it first and you spend less on the unit and less on running it. Here's how it stacks up.
Insulation does the heavy lifting
A proper ceiling blanket slows the heat pouring in through your roof all day. That's the bulk of the summer load your air-con is built to fight.
You can size the air-con smaller
Installers size a unit to the room's heat load. Cut the load with insulation first and a smaller unit holds the room, or one unit covers what used to need two.
Whatever you fit runs less
In an insulated home the air-con reaches temperature, cycles off, and the room stays cool for longer. Less run-time, lower bills, a unit that lasts.
It works in winter too
The same blanket that keeps roof heat out in summer keeps your heating in through winter, so the order helps your reverse-cycle running costs both ways.
None of this is a hard sell on a bigger insulation job. It’s the opposite. Insulating first usually shrinks the air-con job. The Australian Government’s yourhome guide estimates roof and ceiling insulation can cut heating and cooling costs by up to 45%, money that comes off every power bill, on top of a smaller air-con to buy in the first place.
The line worth remembering
Maybe you don’t need a bigger air-con. Maybe you just need insulation.
Here’s the part people get wrong. When a room won’t cool down, the instinct is to throw a bigger air-conditioner at it. But if the ceiling above it is letting roof heat pour in all day, even a big unit is running flat out just to keep up, and you’re paying for that fight every quarter. Put a proper blanket of cellulose up there and you cut the heat load right down, so a smaller unit holds the room, or one unit covers an area that used to need two.
The same yourhome guide notes ceiling insulation can cut heating and cooling costs by up to 45%, and that it works both ways. Heat out in summer, heat in through winter. Done right, insulation is the cheapest air-con and the cheapest heater you’ll ever buy, because it works for the life of the house with no power going into it. So before you upsize the machine, sort the roof.
Already got the air-con in?
It’s never too late to insulate after the fact.
Plenty of people ring me having already put the air-con in, with the upstairs still cooking. That isn’t a fault in the unit. It’s a missing blanket above the ceiling, and the air-con is losing the fight against a roof that pours heat in faster than the machine can pull it out. You don’t have to rip anything out to fix it. We pump cellulose into the ceiling cavity above your existing setup, and from that day the unit you already own runs less, cycles off sooner, and holds temperature for longer after it stops.
So whether the air-con’s already in or you’re still shopping, the insulation is the bit that keeps paying you back. On every power bill, summer and winter. Every job is photographed and the photos are checked before you’re invoiced. That’s our system, the same on every job, run by Comfort Zone franchise owner-operators trained to one standard, so you can see the roof was done right, even the bits you’d never climb up to look at.
Honest answers
Air-con & insulation. The questions I get asked most.
Should I get air-conditioning before or after I insulate?+
Insulate first. Insulation does the heat-control heavy lifting; it slows the heat pouring in through your ceiling, so a properly insulated home often needs a smaller air-con unit, or fewer of them, to hold the same temperature. Sizing an air-conditioner for a hot, leaky, uninsulated house means buying a bigger machine than you'll ever need once the roof is fixed, then running it harder and longer to fight a problem insulation would have solved for a fraction of the cost. The Australian Government's yourhome guide notes ceiling insulation can cut heating and cooling costs by up to 45%. So the honest order is: insulate the ceiling, then size and buy the air-con for the cooler house you'll actually be living in.
Will insulating mean I can buy a smaller air-conditioner?+
Often, yes. Air-con installers size a unit to the heat load of the room, and an uninsulated ceiling is a huge part of that load, because in summer your roof cavity can sit well above the outside temperature and that heat presses down through the plasterboard all afternoon. Put a proper blanket of cellulose in the ceiling and you cut that load right down, so a smaller unit can hold the room cool, or one unit can cover an area that used to need two. I've had plenty of customers tell me the same thing: maybe you don't need a bigger air-conditioner; maybe you just need insulation. Insulate first, then get the air-con quote, and let the installer size it for the insulated house, not the oven you have today.
I already have air-conditioning. Is it too late to insulate?+
Not at all, and it's still one of the best things you can do. If your air-con is already in and the upstairs still cooks, the unit is fighting a roof that's pouring heat in faster than the machine can pull it out. That's not a fault in the air-con; it's a missing blanket above the ceiling. Adding ceiling insulation now means the unit you already own runs less, cycles off sooner, holds temperature for longer after it stops, and covers more of the house. You don't have to rip anything out: we pump cellulose into the ceiling cavity above your existing setup. The Australian Government's yourhome guide estimates roof and ceiling insulation can cut heating and cooling costs by up to 45%, so it keeps paying you back on every power bill, air-con or not.
Is insulation really cheaper than just running a bigger air-conditioner?+
In the long run, almost always. A bigger air-conditioner costs more to buy, more to install, and then more to run every single quarter, and it's treating the symptom, not the cause. Insulation is a one-off cost that keeps working silently for the life of the house, with no power going into it. Done right it's the cheapest air-con and the cheapest heater you'll ever buy, because it keeps the heat out in summer and in during winter without you flicking a switch. The honest sum is simple: a properly insulated home holds its temperature, so the air-con you fit can be smaller, run less and last longer. That's why I tell people to spend on the insulation first and let it shrink the air-con job, rather than the other way around.
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Not sure whether to insulate or upsize the air-con? Call Peter on 0414 586 315 , I’ll give you an honest answer for your roof, not a sales pitch.