This month you’ll find expert advice on heating a living swimming pool, when you do or don’t need air bricks, tool reviews and MVHR guidance

Q Air bricks in the wall: should I keep them or remove them?

There are typically three possible reasons for an air brick: to ventilate the space beneath a suspended timber floor, to ventilate the cavity in the wall, or to provide sufficient air to feed a fire or boiler.

Providing ventilation to the underside of a timber floor is essential as it allows that space to remain dry and prevents dry rot becoming established. In that case the air brick must be retained and it must be kept clean and clear of debris. If insulation is installed under the floor - always a good idea - it is important to ensure that it does not block the air bricks. It’s also key that the insulation leaves at least 50mm of the floor joist exposed to that circulating air.

Air bricks installed to ventilate the cavity in the wall are only useful if there is no insulation in the cavity. If insulation has been, or is to be, installed to the cavity then it would be wise (but not essential) to remove the air brick and fill the gap. Air bricks are generally only at low level - just above the damp proof course - but the cavity will also be vented at the top of the wall, usually by leaving the cavity open at the top. If insulation is being installed that will need to be closed first.

Air bricks above floor level and passing right through the wall are there to provide combustion air to a fireplace or boiler. If there is a fireplace or boiler in that room then they need to be left alone. If not then they are serving no useful function and can be, and should be, taken out and the hole blocked up.