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Airvents and blocking them up

Discussion in 'Building' started by rob_j20, 14 Jan 2017.

  1. rob_j20

    rob_j20

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    Im decorating a room and removed an air vent, the plan is to brick it up is this okay. The airvent never seemed to have any airflow and on removal it turns out the house has cavity insulation.

    [​IMG]

    I removed the "fluff" from in front of the air brick, and reaching up it appears to be clear into the loft and i think there called soffits (the bit along the roof that sticks out and has air vents in.
    So can i brick this up internally. If it makes any difference the vent is in a back bedroom.
     
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  3. John D v2.0

    John D v2.0

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    It's fine to brick it up with the usual caveats about making sure you open windows a short time every day etc etc, but in your case it might be worth bricking the inside and outside separately and putting some more insulation in top avoid a cold area. Or you could wait and see if you get black mould there before you decide.
    Ideally the cavity should be closed at the top, but I'm guessing that's how they built them, plenty of ventilation!
     
  4. amigo

    amigo

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    rob_j20 I hope your not going to mind me jumping in as this thread is very similar to what I'm going to ask.

    Basically, we live on a hill and my 1930s semi-detached house's elevation is around 650ft above sea level so it is very cold. Our home's ground floor is extremely cold. I have found the reason is because we have lots of external vents with lots of gushing wind. There are a total of 8 vents running around the house and they look similar to this:-

    [​IMG]

    Some are to ventilate the suspended floors and kitchen and 2 are there to ventilate an old coal cellar.

    Now I know that I must not block these vents as it can cause damp and rot and I don't plan to.

    But my question is that can I replace the standard stone/concrete vents with an adjustable/open-close vent similar to this? :-

    [​IMG]


    Please correct me if I'm wrong, but my reason is simple. Most houses of 1930s have similar old stone vents, but it seems like when these houses were built, the builders didn't take into consideration the elevation of the property where there is a lot more wind/air circulation and had these stone vents with large holes. I'm thinking that so long as some air is circulating, I can put on the adjustable air vents, but closing them slightly during winter period to have smaller holes and for the air circulation to slow down. This should still allow enough draught without being so windy and cold.

    What do you think? Is this a bad idea?
     
  5. securitynewbie

    securitynewbie

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    I'm BUMPING this thread because I'm also interested in Amigo's questions as I'm in a similar situation too.
     
  6. JohnD

    JohnD

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    you are fitting closable vents so you can close them.

    If your ground floor is cold and draughty underneath, that's correct. If it is cold and draughty above the floor, it suggests you have either got holes in the floor, or have no carpets and the wind is coming up between the boards. You can insulate between the joists for a better solution.
     
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  7. amigo

    amigo

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    Thanks JohnD. Actually to be honest, the floor isn't that cold as it's fully carpeted in every room. The only exception is the hallway which is directly above the cellar. I plan to insulation the cellar ceiling with rock wool to counter this draught.

    However wherever these vents are located, the external wall is extremely cold. So please correct me if I'm wrong, but my suspicion is that because my house is located on a hill, fast winds are entering these vents and travelling up the cavity, thus cooling down the walls a lot more than one would normally expect.

    I actually had a company out to insulate the cavity to resolve this, but it's been denied because their survey revealed that there is rubble within the cavity and also some of the stones are almost bridging the cavity, so unfortunately I can't go down this route. This is why I'm thinking it should be okay to reduce the speed without causing serious damage. Of course as soon as winter is over, I'll open all vents again during the warmer weather.

    If you think this is wrong or have any other suggestions, then please let me know.

    Thank you.
     
  8. JohnD

    JohnD

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    the hole through the wall should not be open to the cavity, it should be sleeved. If you have access under the floor, you might be able to find or make a sleeve. Sometimes slates were used, mortared into the wall. You can also use loft insulation wood, poked into the gap tightly enough that it will not come loose and fall out. Rake out any of the rubble that you can reach first.

    I have had some success with a powerful builder's canister vac, poking the suction hose along the bottom of the cavity. It is easier if you can take out a brick at each corner.

    Prefab rectangular sleeves probably exist, but I have not seen them on sale.
     
  9. amigo

    amigo

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    Your right....I now remember when one of the vents was taken out a while ago, it was totally sealed around it. So now I'm left in a bit of a pickle, because all this time I thought that air is escaping from the gaps in the vent/cavity and cooling parts of the wall down, so what could it be?

    Even if I could vacuum the rubble from the cavity, what do I do about the stones/bricks bridging the cavities?
     
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  11. JohnD

    JohnD

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    just get out as much as you can.

    If air is not blowing into the cavity from the airbrick, it could be blowing up, for example, holes where the timbers of a porch or bay window are built into the wall, or a doorframe, or maybe just bad pointing or bricklaying. With luck they might be accessible under the floorboards, and you can inject expanding foam round the joist ends which might also reduce squeaking. I had a house once with such big gaps over a bay window that the cat climbed in when I took the floor up and wouldn't come out. I had to push an inspection lamp in for her to see how to escape.
     
  12. amigo

    amigo

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    I think your spot-on with regarding to air coming through the bay-window, because I can feel it through the wooden sill. I'm sure there is no way of accessing this without either taking brickwork out or ripping up the sill to fill the cavity.
     
  13. JohnD

    JohnD

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    you might find there is a gap, partly filled with cracked plaster, around the frame where it fits into the wall. Depending where you live, it might be set into the inner or the outer leaf.

    The wooden "sill" or windowboard might also come off, with a bit of levering or hammering. Once it starts to move you will see where the nails are (paint will pop off their heads). I have pushed mineral wool down one of mine like that.

    You might be able to get your arm, or an invalid's "helping hand" in to remove any fallen mortar or bits of brick.
     
  14. securitynewbie

    securitynewbie

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    Hi John. Regarding the sill. Would OP need to actually take the whole sill off totally or would he be able to simply lever it up an inch or so to push mineral wool in?

    Also wouldn't lifting the sill damage any wallpaper or the windows?
     
  15. JohnD

    JohnD

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    I'm sure you would take it right off, then replace it neatly when finished. You would expect to repair the wall where plaster was dislodged, and repaint the sill.

    it may fit into a groove in the bottom of the frame.
     
  16. rob_j20

    rob_j20

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    Any more ideas with the original post? I plan on leaving the external air brick there, it only adds to the loft ventilation.
     
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