Soffit advice

I have a single storey extension - bedroom over a living area. It has a conventional pitched roof and the bedroom is in the roof space.

I've realised very large amounts of cold air are entering the space between the downstairs ceiling and upstairs floor. The biggest problem resulting from this is a freezing floor upstairs but I am obviously concerned about heat loss. The extent of the airflow can be quickly assessed by removing a downlighter - the resulting force of cold air coming down is very, very strong.

It seems as if the draughts/cold air are entering via the soffits, which are of the continuously vented (continuous rows of holes) UPVC type.

On a normal two storey house this ingress of air would obviously go into the loft, but in the case of my building it seems strange that the air goes between floor and ceiling.

So my question is, to what extent can I close the soffits or what other options do I have to reduce the gale going through the ceiling/floor void? I don't have a loft to keep aired so I am thinking that it would be acceptable to drastically reduce the airflow into the space I have described. It certainly seems as if the existing YPVC soffits allow an almost unobstructed flow of cold air into the house!

There is no practical reason to have air moving between floors. However there is good reason to have air moving around a loft space.

Is it not possible to stuff fibreglass insulation within the floor void to prevent the air from moving?

Is the bedroom on the first floor? I can't get to grips with your description of a single story bedroom extension in the roof.

Think i geddit now.

You have a single story extension, that has the roof above converted to a bedroom?

chalet design.room in the roof.

noseall said:

There is no practical reason to have air moving between floors. However there is good reason to have air moving around a loft space.

Is it not possible to stuff fibreglass insulation within the floor void to prevent the air from moving?

Is the bedroom on the first floor? I can't get to grips with your description of a single story bedroom extension in the roof.

Think i geddit now.

You have a single story extension, that has the roof above converted to a bedroom?

Click to expand...

I think it was built that way - don't ask! If you imagine the top floor and roof of a standard house cut off and plonked on the ground as a unit, you should get the idea.

So yes, the bedroom is in what would normally be a loft/attic. It has a couple of dormers and the usual restricted spaces to each side behind the purlin wall.

I know that there is insulation in these areas - essentially all the areas outside of the living space are insulated. Access from the inside would involve way too much disruption. Probably the only way would be via the eaves/soffit which are easy enough to reach.

There just seems to be way too much airflow through the void between ceiling and floor and I'm sure this must result in unnecessary heat loss. Despite a large well heated room below (with cavity wall insulation, double glazing) the floor above is always cold. If I remove downlighters in the downstairs room, a veritable gale blows down!

At the moment I'm tempted to either remove the soffits, jam even more insulation up and then replace, or fit solid soffits. I completely get the need to ventilate a loft space, but of course I don't have one! I also see the need to get some air to those areas outside of the 'living compartment' at the angle of the roof - I just think I have way too much ventilation.

Thoughts?

Air that moves over a surface cools that surface.

You need to prevent airflow where it is not needed and encourage it where it is needed.

I kinda understand your layout, in that you need to allow air through the soffit but not under the floor. Or, where that moving air is hitting any 'warm' surfaces - insulate these surfaces thoroughly so that the air can do what it likes behind the insulation.

Warm - warm surfaces = zero air movement.

Warm - cold surfaces = air movement + insulation barrier.

I hope some of the above makes sense.

soloution is simple the soffit vents are not required so replace soffit with solid soffit and not vented no airflow (which is not required) no draft also insulate sofft when replacing it ths would almost certainly fix the prob
p.s silicone seal where soffit butts wall to stop drafts blowing up

why isnt airflow needed????.i just put soffitt vents in on a loft conversion as BC said so.

airflow which is being created is not going into roof space as as it should be so what i meant was airflow not required in floor joists and as it isnt going into roof space and creating no problems simply stop it going into floor joists using solid soffit would do this

Thanks all for the advice.

Everyone who has removed a downlighter and felt the draught has commented that it isn't right.

I am going to replace the vents with either solid timber or plastic as suggested.