Fluffy cavity-wall insulation...do we need ventilation?

[WabbitPoo]

Sorry if this has been asked and answered before but our 50's built house has cavity wall insulation in the form of wooly pellets. Can I in some way block the vents in the outside walls and block the cavity at the top of the walls in the loft so we dont get strong cold draughts blowing thru all plug sockets, rad pipe entries, etc? these strong winds makes it very clear where the cold air is coming in!

We have only one suspended wooden floor, so would not block the vents under that.

 

[noseall]

This is one of the main reasons I dab plasterboards to walls the way I do, i.e. to prevent 'chimneying' behind the boards. I discovered this on a windy day also!

How is your house plastered? Air can move through the floor cavity and up behind dabbed boards etc.

The answer to your questions is yes, block up any cavity vents and prevent the movement of air within the cavity. It will do you no favours now that you have CWI. However, if it hade been done properly there should be little air movement.

 

[JohnD]

Also, electrical sockets and radiator pipes should not have openings into the wall cavity, so it does sound strange. I would have expected a house if that age to have plaster onto the inner skin of brick or block. Has it been altered or extended?

 

[WabbitPoo]

All "solid" walls with plaster over brick. No dabbed PB.

I might have been exagerating a little about the plug sockets!, but we do get strong draughts up thru the floorboards upstairs.

I'll get to work sealing wall vents when the wind drops!

 

[JohnD]

if you ever have the floorboards up, it may help to stuff mineral wool between the joists against the outside wall.

 

[ree]

If you are referring to sub-floor air bricks then you must not block them, even for the one suspended floor.

Air bricks that provide make-up air in the upper walls must also be left open - extensions can be used to meet the D&D finished surface. This can be a safety issue eg. make up air for gas appliances.

Cavity brushes are available to form cavity barriers around any air bricks - they, of course, prevent particle insulation from filling the air brick.

 

[noseall]

If you are referring to sub-floor air bricks then you must not block them, even for the one suspended floor.

WP is on about redundant cavity ventilators that are no longer of any use.

 

[ree]

I dont know what you mean noseall? Do you perhaps mean:

Way back i heard old brickies referring to single skin air bricks with no cross cavity connection sleeve as being useful for "venting the cavity" as well as supplying make up air to the inner skin wall vent, below in the sub-floor area some inner skin bricks were simply left out.

Its probably just me but i'm not familiar with any vent whose only purpose is to air vent the cavity.