They had filled all the air brick holes with silicon! Which has led to condensation build-up throughout the house. Why oh why would anyone think it’s a good thing to try and hermetically seal a house? Word of warning – check your air vents!

Surely your survey picked up on that ??

So did mine (can imagine it was the original occupant who was a well known DIY idiot), someone must have unblocked them at some point as the cement had been chipped out. Lots of nice soft black floor boards on the top, oddly underneath is fine and dry. Debating whether to just rip them up and replace with T&G chipboard as it would allow me to insulate underneath (properly!) and get rid of the multiple acess hatches cut in at various points in time.

I think this is standard practice for wall air bricks if cavity wall insulation has been installed. This may be the reason. Air bricks to ventilate under a suspended floor are not sealed, but do get sleeved to stop cavity filler going under the floor.

Tooms

I think this is standard practice for wall air bricks if cavity wall insulation has been installed

this happened at my place. It seems to be common practice but not sure whether it’s a good thing or just a bodgers way of getting round a problem.

My air bricks never got jammed up. Given they have a clay pipe behind to channel air across the cavity there’s no reason to (what was ridiculous was the 150mm hole they drilled in the wall to provide air for the gas boiler, way to go guys, cosy as)

my air vents were all isolated from the cavity by wire brushes before the cavity was filled not hard to do and leaves functioning ventilation.

I cover one of mine up in the winter as it causes a mega-draft but that comes off in Spring.
Am I a bad man?

I keep wondering about the airbricks in our kitchen wall. Either it’s (a) for ventilating the kitchen because the gas boiler used to be in there but isn’t any more, or (b) it’s for the cavity wall which is now full of insulation anyway. It seems redundant now; it either can’t ventilate the cavity or it makes the kitchen cold for no benefit. I keep pondering about stuffing all the holes with newspaper and seeing if the house falls down.

I cover one of mine up in the winter as it causes a mega-draft but that comes off in Spring.
Am I a bad man?

Depends how damp your house gets and how much ventilation there is elsewhere. In general you need that draft to replace the warm damp air in the house with cold dry air from outside (which you then heat up leaving the house warm and dry).

And if you’ve any kind of gas/oil/wood burning appliance unblock them now before you kill yourself with CO.

The air bricks are for ventilating under the floor where the cavity drains to and damp accumulates.

Given they have a clay pipe behind to channel air across the cavity there’s no reason to

except they don’t always have the pipe behind. Hence crankboy’s use of wire brushes. Anyone know if I can retrofit this sort of thing to reinstate the ventilation? (NB it was not me who sealed up the airbricks)

Easy to retrofit, chisel a brick out, fit a plastic vent pipe across the cavity, put back a new air brick.

You will find the reason that some air bricks do not bridge the cavity with either a clay or plastic duct, is because they are ventilating the cavity and not providing a source of fresh air for a heating appliance.

Which is also why cavity wall insulation is a very bad idea, irrespective of what material it is comprised of. It effectively stops the cavity doing what it is and was designed to do. Eventually, even polystyrene balls will absorb enough moisture to transfer any damp from the outer skin to the supporting inner skin.

Personally, I wouldn’t even consider buying taking out a cracking huge loan and all the liability for a property with retro-fitted cavity insulation.

For those of you who have, look to remove as much of it as you can, or sell the house and move to one that will be healthier for you and your family.

Also depends very much on how old the house is. My 1930’s house has solid brick walls,so there are large air bricks in all rooms and also under the suspended floor. Necessary for ventilation to prevent damp and mould.

So of course, the previous owner spec’d uPVC double glazing with no trickle vents, and papered over all the air bricks. Muppet.

Which is also why cavity wall insulation is a very bad idea, irrespective of what material it is comprised of.

You do realise that about 90% of new build houses are cavity wall design with closed cell style insulation filling the cavity…

Yes I do! The insulation, typically Rockwool, although Cellotex or Kingspan closed cell panels are also used and are fastened to the inner skin, leaving an air gap between it and the outer skin.

Our previous owners added double glazing without trickle vents, cavity wall insulation and blocked up the air bricks – damp/condensation nightmare!

Thankfully it has been solved by the addition of a positive pressure ventilator mounted in the loft, which was cheap to install and very efficient to run.

IIRR, early cavity walls (Thirties, say) can have rain penetration that runs down the outer face of the cavity. Something to do with the mortar in the vertical joints in the brickwork. I trust the Nation’s brickies have got it right since.

IIRR, early cavity walls (Thirties, say) can have rain penetration that runs down the outer face of the cavity. Somethin

I found that out when it rained in my living room through my bay window (with wooden lintel!), though I think that was more to do with the fact it was probably 70 years old.

That is the point of cavity walls in general. It still happens on modern builds hence cavity trays. Bricks are pourus!