Are your wall vents ducted?

By The Helpful Engineer / On / In Existing Building Issues

Vent with cover on
Vent with cover on

There is greater interest at this time of the year in reducing heat loss from our homes and reducing fuel bills. Most home-owners correctly concentrate on the areas of biggest heat loss by upgrading the insulation to their roof, walls or windows. However a quick check will reveal whether your home is losing unnecessary heat from unlined wall vents.

My own house, and my neighbours, all have this problem. As a result the cold air is able to spread out behind the walls, and insulation, and cool the house. The heat loss is worse during windy conditions. I cannot understand why the builder did not line the vents properly, but the houses are about 16 years old and attitudes to insulation and heat loss were looser then.

It is part of the building regulations that vent ducts should be composed of rigid continuous insulated pipework.

The first step to check whether this problem affects your own home is by simply removing the vent cover to investigate. If the vents are unlined the easiest solution is to install a continuous insulated duct between the internal and external vents. This is straight forward enough unless the external and internal vents are not in line, in which case more work is required to line them up, usually this means adjusting the inner wall to suit. See pictures below of this work being carried out in my neighbours house. Thanks for the photographs Ronan.

Wall vent without lining
Wall vent without lining
Wall vent with lining installed
Wall vent with lining installed
Vent with cover on
Vent with cover on

9 thoughts on “Are your wall vents ducted?

  1. You are very welcome! Another neighbour had previously recommended that my wife and I do this to stop the draughts entering the house in the Winter. This October just gone I really noticed a big difference in the house after sealing these vents. There was a big reduction in condensation levels where the ceiling and the outer walls met and thus less humidity.

  2. I am getting a lot of condensation in our rather small bedroom. Would fitting a ducted vent in the wall cure this or would i be better venting into the loft?

    1. Hi Ed,

      Yes better ventilation, and insulation, will help. But don’t vent the room into the loft, vent it to outside to avoid problems with moisture in the loft.

  3. Condensation is a tricky business. It’s down to how much moisture the air can hold at a given temperature. So the warmer the room, the greater the condensation on any cold surfaces. To avoid condensation occuring, you need to ensure that the temperature variation through the wall is such that the dew point never occurs. That is why we insulate the outside face of the inner leaf of a cavity wall, to keep the inside warm so condensation doesn’t occur on the walls. However, condensation will still occur in areas of high humidity, on your windows even on double glazing, if the room is poorly vented (kitchen/bathrooms/laundry rooms etc).

  4. just remembered this article recently. We need to line our vents as we wake up every morning to condensation on the windows and there is no clothes being dried or dryer in use, etc. What is the best material to line a vent? house is 40 yrs old with some walls cavity block and some cavity walls.

  5. Hi Ronan, this situation exists on my timber framed 3-bed house built in 2007. I reckon it’s having a large effect on heat loss, basically negating much of the installed wall insulation. Could you recommend someone in North County Dublin to retro fit? Could I do it myself? Many thanks Paddy

  6. We have external insulation on a house we bought. We now want to put in a vent for a tumble dryer and have been told it’s not advisable . They say it will cause the render to bubble….. we hope there is some method of doing this as we’re also planning a new shower room which will need ventilation on the same wall. Would appreciate your advise. Thank you. Mary

  7. Thank you for a very helpful article.
    I’m planning to do this, though I too have the problem grant the holes are not aligned.

    Can you please tell me how, once you introduce the rigid ducting, you managed to seal the gap between the ducting and the ‘outer’ wall leaf.

    Also, was the ducting not visible though the grill from the exterior?

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