Downlights & insulation · the R-value killer
Your halogen downlights are eating your insulation.
An old halogen downlight is a heat source, so the wiring rules force a 200mm bare gap of ceiling around every one of them. Sustainability Victoria's figures show that dropping an R4.0 ceiling to an effective R1.4. Multiply that by a houseful of downlights and a big slice of the insulation you paid for is doing nothing.
There is a safe, simple fix. I'm Peter Johnson, I've been on the tools since 1986, and here is exactly what is going on above your downlights and how to put it right without creating a fire risk.
R4.0 down to R1.4
around halogen downlights
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Fitzgibbon, 2023
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What it's costing you
A houseful of halogen downlights can halve your ceiling's R-value.
Because a halogen downlight needs a 200mm bare clearance around it, Sustainability Victoria's housing manual shows four halogen downlights in a 10m² area dropping R4.0 insulation to an effective R1.4. That is most of your insulation gone, just around the lights.
It adds up fast across a whole house. One worked example with 40 halogen downlights pulls a real R3.0 ceiling down to about R2.78, and switching those fittings to coverable LED restores it to around R3.2. You can have paid for a good R-value on paper and be living under a much lower one, and never know, because once the manhole is shut you cannot see it.
This is the same lesson as the rest of insulation: the number on the bag is not the number in your roof unless the ceiling is actually covered.
A halogen downlight in a roof space. The bare clearance the rules require around each one is where your R-value leaks away.
First, the safety bit
That gap is not optional. It is a fire clearance.
A halogen downlight runs extremely hot, hot enough that the AS/NZS 3000 wiring rules brought in mandatory clearances after a spate of ceiling-cavity fires. Sustainability Victoria and Fire and Rescue both warn that ceiling fires rose with the spread of downlights. Insulation packed against a hot, non-rated fitting is exactly how those fires start.
So this is the one place in your roof where covering everything is the wrong move. You must never lay insulation over, or breach the clearance around, a halogen, non-IC or unmarked downlight. Anyone who buries your old halogens to make the ceiling look finished is creating a fire risk, not doing you a favour. The right fix is to change the fitting, not smother it.
Read the fitting
IC, IC-4, CA or non-IC: what your downlight is allowed to have over it.
Every recessed downlight has a classification that tells you whether insulation can cover it, only touch the sides, or must be kept clear. It is stamped on the fitting. This is the whole game.
IC / IC-4
Cover it.
Insulation may abut AND cover the fitting. IC-4 is also sealed against air moving between the room and the roof space. These are the LED downlights you want, so the ceiling can be fully covered with no gap.
CA90
Abut only.
Insulation may touch the sides but must NOT be laid over the top. Better than non-IC, but you still lose the coverage directly above each light.
Non-IC / unmarked
Keep clear.
Must have a clearance maintained on all sides and above. Insulation may never cover or touch it. Any unmarked or old halogen fitting must be treated this way. This is the one that costs you the most R-value.
The classifications come from the AS/NZS 60598.2.2 luminaire standard and the AS/NZS 3000 wiring rules (see BRANZ Bulletin 647 for the full table). The short version: look for IC or IC-4. Anything else, or no marking at all, gets treated as keep-clear.
The fix
Replace the halogens with IC-4-rated LED, then cover the ceiling properly.
- 1
Get a sparky to swap the halogens for IC or IC-4 LED downlights
A licensed electrician changes the fittings. IC and IC-4 LEDs run cool and are certified to have insulation laid over them. LEDs also use a fraction of the power, so they pay for part of themselves over time. This is electrical work, so it is the electrician's job, not ours and not a DIY one.
- 2
Now the clearance disappears
Once the fittings are rated to be covered, there is no bare 200mm gap to leave. The ceiling can be insulated as one continuous blanket, the way it was meant to be.
- 3
We cover it the right way
We pump cellulose across the whole ceiling, over the top of the IC-4-rated lights, so you get the full R-value with no cold gaps. See how we do that neatly below.
How we do it
A neat cap, not "half a batt left aside".
Plenty of batt installers deal with downlights the lazy way: they leave half a batt aside and walk away, so there is a bare patch of ceiling around every light, even the ones that could have been covered. That is easy for them and expensive for you in lost R-value.
On an IC or IC-4 rated light, we do it properly. We lay a thin sliver of polyester batt, about 10mm, as a cap over the top of the fitting, then pump cellulose over the lot. Two things happen:
- The ceiling is fully covered, with no bare gap around the light, so you keep your R-value.
- If a sparky ever pulls the fitting down from below to work on it, that little cap holds the cellulose back, so they do not get a face full of it and your roof stays where it should.
On a halogen or non-IC fitting we will not do that, because covering it would be a fire risk. We keep the clearance and tell you straight that the real fix is to change the light.
Straight answers
Downlights and insulation, the questions I get.
Can you put insulation over downlights?+
Only over the right kind. If a downlight is marked IC or IC-4, it is tested and certified for insulation to be laid over the top, so we can cover it and keep your R-value. If it is a halogen, non-IC, or unmarked fitting, you must never cover it or breach its clearance, because it is a heat source and covering it is a documented fire risk. That is the whole reason the marking system and the clearances exist. The safe answer for an old halogen is to replace it with an IC-rated LED, then cover it.
How much R-value do downlights actually cost me?+
A lot, if they are halogen. Because a halogen downlight needs a 200mm bare clearance around it, Sustainability Victoria's housing manual shows four halogen downlights in a 10m² area dropping R4.0 ceiling insulation to an effective R1.4. A worked example with 40 halogen downlights across a ceiling pulls a real R3.0 down to about R2.78, and switching to coverable LED fittings restores it to around R3.2. So your downlights can quietly be undoing a big chunk of the insulation you paid for.
What clearance does a halogen downlight need from insulation?+
For a heat-source halogen, the guidance is a 200mm clearance above and to the side of timber (Sustainability Victoria; the clearances were brought into the AS/NZS 3000 wiring rules after a spate of ceiling fires). A 50mm gap is only the figure for a lighting transformer or a low-heat incandescent, not for a halogen lamp. The exact clearance is set by the fitting's classification and the manufacturer's instructions, and the work is a licensed electrician's job, not something to guess at.
Should I replace my halogen downlights before insulating?+
Yes, if you can. It is the single best thing you can do for both your power bill and your fire safety. An electrician swaps the halogens for IC or IC-4 rated LED downlights, which run cool and are certified to be covered. Then we can pump cellulose right across the ceiling with no bare gaps, and you get the full R-value working for you. LEDs also use a fraction of the power, so the lights pay for part of themselves.
Do you cover our downlights or leave a gap like other installers?+
It depends on the fitting, and we do it to the standard, not by guesswork. For IC and IC-4 rated lights, we lay a thin polyester cap over the top and then pump cellulose over that, so the ceiling is fully covered with no bare patch, and a sparky pulling the fitting down later does not get a face full of cellulose. For halogen or non-IC fittings, we keep the required clearance or recommend you replace them first. We will not bury a fire risk to make a ceiling look finished.
Clearance and classification details summarised from AS/NZS 3000 (Wiring Rules), AS/NZS 60598.2.2 (luminaires), Sustainability Victoria's Energy Smart Housing Manual, and BRANZ Bulletin 647. Changing downlights is electrical work for a licensed electrician. This page is general information, not electrical advice.
See how it's done
Watch: downlights handled correctly on real jobs.
Peter's footage of how Comfort Zone treats downlights before and during a cellulose install — the right cap, the right clearance, no guesswork.
Filmed on real jobs over the years. Subscribe to the channel for more.
Had your downlights done properly so the insulation actually works? Worth a mention.
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Sort the downlights, get your R-value back.
Get your halogens swapped for IC-4-rated LED by a sparky, and we'll pump cellulose across the whole ceiling, over the lights, with no cold gaps. Send us your address and roof type for a fixed-price quote within 48 hours for most houses. Servicing Brisbane, SE QLD and Northern NSW.
Peter Johnson
Owner / installer · Comfort Zone Insulation Team® · Since 1986