A room that stays cold despite the heating, a feeling of air around your feet: before buying anything, you need to know where the air comes in. The candle test is the simplest way to find out. It needs no tools and no skills, just a little attention.
What is the candle test?
You slowly move a flame along suspect areas: the bottom of doors, around windows, sockets on outside walls, hatches. Where air comes through, the flame bends, flickers or smokes. It's visual, instant and free. An incense stick works too: the smoke shows the direction of the air very clearly.
When should you do the test?
A cold, windy evening is ideal: the difference in temperature and pressure between inside and outside makes leaks easier to see. Switch off the cooker hood and fans, close the windows and go round room by room.
How do you do it, step by step?
- 1. Get ready with a stable candle in a holder, or an incense stick. Keep a glass of water to hand.
- 2. Move curtains, nets and papers out of the way: the flame always stays well away from anything that could burn.
- 3. Slowly move the flame 5 to 10 cm from the bottom of each door, then along the sides and top.
- 4. Do the same around windows, roller-shutter boxes, hatches and sockets on outside walls.
- 5. Note every spot where the flame moves, with the room and the strength (slight, clear, strong).
How do you read the result?
- The flame bends clearly into the room: cold air is coming in there.
- It flickers slightly: a small leak, worth fixing in a living area or bedroom.
- It stays upright: no significant leak.
What next?
It depends on where the leak is. Under a door, an Abrilys double draught excluder slides on in ten seconds and stops the air on both sides. Around a door or window, an adhesive weather strip on the frame closes the gap. At sockets, there are insulating pads that go behind the faceplate, fitted with the power off. At a roller-shutter box, insulation kits exist, but they need a bit more DIY.
Should you repeat the test afterwards?
Yes, it's the best way to check that what you've fitted works. Repeat it in the same spot, in the same conditions. And write it down: next winter, you'll know where to check first.
Frequently asked questions
Is the candle test enough? To find the usual air leaks, yes. For a full assessment of your home, a professional can carry out an air-tightness test.
Where does air get in most often? Under doors, then around windows and roller-shutter boxes. Our 5 fixes for a draught under the door will help you choose.
A leak under the door? Discover the double draught excluder
Article written by the Abrilys team. This is general advice: for an assessment of your home, or if you are unsure about the ventilation of a room, ask a professional.