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We have an on going problem with our bungalow with one wall in our bedroom we have renovated evrywhere but the same problem has remained with this wall, the carpet and chest of drawers has green mildew and the skirting and wall area develops black spores which i am forever cleaning with bleach solution. You can feel the cold draught coming up through new timbers, underlay, carpet! Where this is happening on the 2 spots ,outside are airbricks this property was built in 1935 and has no problems. We feel this problem is a cause from these bricks and i know you are told not to block them up ( my husband is a brickie ) but these seem to be doing nothing else but causing this problem. We have have a de-humidifier and have left gaps for ventilation around wall area. :( :(

IF THE WALL IN QUESTION IS AN EXTERIOR WALL, YOU WOULD BE BEST ADVISED TO HAVE CAVITY WALL INSULATION INSTALLED TO WARM UP THE INNER WALL SURFACE.

SEE REPLY I RECENTLY POSTED TO PETER & ALISON.

ALDA.

You are perfectly correct.
The air brick immediately under the floor boards is the problem.
This hole is bringing the cold from the outside right into the edge of the floor.
And of course the wall is cold just there. As cold as it is in the garden.

I expect the floor is cold as well?
While wood is a good insulator (compared with some other things)
18mm of wood plus underlay and carpet wont help much.

It seems to me that this winter has has some nasty cold snaps (not as bad as China or Saudi Arabia etc)

Putting blown insulation into the wall will no doubt improve the overall heat loss of the bungalow but, it will not do anything for this hole.

The solution is to cover the inside of the wall with at least one inch of polystyrene. This will reduce the heat loss by about 90% And plastered over will become invisible.

Keeping in mind my earlier comment regarding the floor, while you are dealing with the hole and its heat loss, why not either take up all the floor boards and line the floor with four inches of polystyrene, to save heat loss through the floor.

[quote="ALDA"]IF THE WALL IN QUESTION IS AN EXTERIOR WALL, YOU WOULD BE BEST ADVISED TO HAVE CAVITY WALL INSULATION INSTALLED TO WARM UP THE INNER WALL SURFACE.

SEE REPLY I RECENTLY POSTED TO PETER & ALISON.

ALDA.[/quote]
The walls are single brickwork and rendered. Cavity wall insulation is not an option, even if we took off the render and put anothe course of brick flush we cannot do this due to the window frame, are there any other insulation systems known?

You could dry line the walls with insulated plasterboard.
Dot and Dab or Batten Fix to interior walls.