Blocking external sub floor vents ?

iMax

Hi there,

I live in a 30 odd year old house that has a chipboard floor downstairs upon which we have those green fibreboard insullation boards & then real wood floor layed over it.

In two rooms in the house there's sub floor vents on the outside. These are plain old (rusting beneath the paint) steel slatted vents. In recent evenings the tempreture has dropped considerably & I can feel a draught coming up through the floor/skirting. The floor is actually very cold to touch near where these vents are placed.

Can I block them up using sprayfoam or something else to cut down on the draught coming in them ?

Have I any other options ?

TIA

gsxr1

No.

they are part of the venting system in your home. Closing them could lead to mold and condensation problems under your floor.

You may be able to reduce the amount of venting depending on the size of the area and the amount of vents

Do you have wall vents?

iMax

Thanks for the reply gsxr1, yes there are wall vents in every room, I've cut these down from approx 7" square to a 2" letterbox ( also stuffed them with a block of cut foam - not closed entirely but not an open hole to the street either). That did improve things somewhat but the cold is really noticeable now.

The vents are about 5" high & there's three around the house - Front, side & back. The one on the back has some sort of tight mesh on it which has been painted over before we bought the house, resulting in a much warmer room there.

willbur

it is not a good idea to block any air vents in a house as the prevent damp/ and mildue etc, however you can put a wire mesh with small holes
on the underfloor vents to stop mice and insects/bees getting in , regarding cold wind on the outside you could place alarge board against the wall at a angle to stop direct wind put still allowing air to circulate ,doing this just during the winter months:cool:

iMax

Thanks wilbur

RKQ

I agree with above advice. Mould and damp might sound a small price to pay but if you do block the vents you will create stagnant air under your timber floor - ideal conditions for Dry Rot.

The dry rot spores can quickly spread throughtout your house, stretching behind the plastic up to the roof.

Metal vent covers with loovers, might help prevent direct wind in stormy conditions while maintaining critical cross-ventilation.

Clean mastic or decorator chalk could be used to seal gaps in skirting boards or between the floorboards & shirting boards.

bibibobo

willbur wrote: »

it is not a good idea to block any air vents in a house as the prevent damp/ and mildue etc, however you can put a wire mesh with small holes
on the underfloor vents to stop mice and insects/bees getting in , regarding cold wind on the outside you could place alarge board against the wall at a angle to stop direct wind put still allowing air to circulate ,doing this just during the winter months:cool:

just wondering if there are any commercially available metal mesh vent covers or should i just fashion some outa some expanded metal. i am mainly trying to prevent mice and rats having an easy entry point.

Heatherview

Hi hMax
Floor vents are an essential part of the construction (They can be a draughty pain I know been there ) I had much the same as yourself. I got length of 110mm perforated sewer pipe about 2 mts long blocked the ends under the floor with a bit of strong aeroboard and cemented it into the old 9" x 6" vent. I now have a warmer room and controlled ventilation under the floor. See sketch might help ???

Seem to be working alright
Heatherview

Heatherview

Hi iMax

Vent details attached
Heatherview

iMax

Thanks for the detail heatherview !

blackbox

Depending on where you live, blocking vents could lead to a build-up of radon gas.

Mainly an issue in granite or basalt areas.