The short answer
Light a stick of incense or a candle and move it slowly around the frame on a windy day. The smoke shows air movement long before your hand can feel it.
- Pick a windy day and close all the internal doors.
- Move a lit incense stick slowly around window and door frames, letterboxes, loft hatches, floorboards at the skirting and around pipe entries.
- Watch the smoke, which will pull sideways where air is moving.
- Mark the spots and deal with them: brush strips, draught tape, silicone, a chimney balloon for an unused fireplace.
What will ruin it
Do not seal a house completely. Air bricks, trickle vents and extractor outlets are there on purpose, and blocking them causes condensation and, where there is a fuel-burning appliance, a genuine carbon monoxide risk.
Why it works
You feel a draught as moving air on your skin, and you stop feeling it well above the rate at which heat is actually leaving. Smoke follows air movement that is far too slow for a hand to detect.
Gas work requires Gas Safe registration by law and most electrical work is notifiable. Where a tip says to call somebody, that is the advice. Full disclaimer.
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