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Air vent in suspended timber floor

Discussion in 'Building' started by Coffeegoon, 5 Nov 2020.

  1. Coffeegoon

    Coffeegoon

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    Hello,

    We have a suspended timber floor, and that suspended timber floor contains an air grill (see picture attached). The grill attaches to a plastic ventilation shaft below the floor which is about 20cm long. It's a bit odd, given that most guidance on ventilating suspended timber floors talks about using air bricks to ventilate the space below, rather than ventilating through the floor itself.

    We're wanting to insulate the suspended timber floor. We have previously had air bricks installed to ventilate the void beneath the floor - so it should be sufficiently insulated.

    As such, I presume there's no issue insulating the floor, and removing the ventilation shaft from the grill before we do (such that the insulation covers the grill, so that it effectively stops acting as a ventilation channel).

    Otherwise doing the insulation seems a bit pointless if there remains a big ventilation channel from below the floor!

    Many thanks in advance for any thoughts!
     

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  3. stem

    stem

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    It may have been installed to provide an air supply for something. Do you have (or had) a gas back boiler, stove, or open fire in the room?
     
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  4. Coffeegoon

    Coffeegoon

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    Thanks Stem.

    It doesn't look like it. The room is a living room and the grill/vent shaft basically just exit into the void 20cm or so below the grill - there doesn't appear to be any connection to anything.

    There is a fire in the room, but it is nowhere near the vent, and doesn't look like it was in any way connected with it at any stage.

    It purely looks like an air ventilation shaft.
     
  5. ^woody^

    ^woody^

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    This is sometimes done to try and get some cross-flow of air in the floor void.

    Normally there should be vents at the opposite external walls so air flows across the underfloor void. If there is not this cross-flow, there is risk of moist air not being moved, and this could lead to timber rot of the floor joists.

    Is this anything like the situation there? Check outside vents

    If so, can some under floor ducting be installed and linked to an external vent?

    If the underfloor is adequately vented, then that floor grill can be removed.
     
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  6. Coffeegoon

    Coffeegoon

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    Thanks Woody. Yes, I think it is probably a hangover from when there were no airbricks installed into the external walls in the sub-floor area. There were none when we moved in, and we have subsequently had some installed. As such, I think it should be ok to remove this vent, as the sub-floor space should still be adequately vented via the air bricks - but just thought it worth asking in case there was something I was missing.
     
  7. stem

    stem

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    If the vent is there because you have an open flued appliance, as you can see in diagram (a) it doesn't have to be connected or even near to the appliance. Air vents for this purpose are fitted as a requirement of Part J of the Building Regulations.

    Capture.JPG

    The vent is there to make sure that there is sufficient ventilation for the appliance to function properly and prevent carbon monoxide poisoning. Often they are at the opposite side of the room to the fire. If you don't have the instructions for your fire, there's a lot of information on line. An example can be found here.
     
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