Blocking up air gap between floor & ceiling?

How is the air getting through under the eaves? Are there some soffit vents or just big gaps?

It’s a sixties house built to a budget, there are a few natural gaps.

I don't quite follow what's happening; a sketch would be useful. I'm guessing you have vents in the soffits under the eaves, and the wind is coming up through those. You need ventilation between the roof itself and the bedroom ceilings, but not between the bedroom floors and the downstairs ceilings, so I'd expect there should be a solid closer there. If there isn't, I'd expect the access to fix that would be by taking off the soffits, not by working from upstairs? If you're trying to stop airflow, why use insulation, don't you need something solid?

This sounds very similar to our house. I've had to go into the floor-ceiling gap due to a water leak and there was a strong wind blowing through. We have these vents running full length, both sides of the house.

[url= https://i.postimg.cc/6qpXvJz8/PXL-20221015-111024933.jp g" target="_blank">https://i.postimg.cc/6qpXvJz8/PXL-20221015-111024933.jp g"/> [/img][/url]

Seems like a pretty stupid design but I'd just assumed they had something to do with essential ventilation. I've been tempted just to replace them with something solid.

I’ve been tempted just to replace them with something solid.

They'll be necessary to ventilate the space under the roof, otherwise you'll get condensation that will rot the roof. Anywhere you have a big temperature difference between the air inside the house and the outside needs ventilation. Floor voids inside the house are the same temperature each side so can be sealed up.

Is the gap between the ceiling and roof ventilated somehow, or full of insulation? As above, there is no problem insulating between the floor and the ceiling below, but any open roof space will need a flow of air.

I’ve been tempted just to replace them with something solid.

As above don't block them up, I'm having trouble with damp in our loft because the vents are restricted (insect mesh has overtime got blocked up) need to get up on a ladder and clean them out to increase ventilation.

 

[img] [/img]

Same as scotroutes pic except we haven’t got any specific vent, just plenty of gaps.

Similar situation here. House circa 1990 with a chalet style roof. I've got the same type of vents. I don't think blocking them is the answer. Your roof and voids are cold spaces. Having air circulation up there is intentional. The answer is to stop the heat getting from the rooms into the voids. My house is definitely under-insulated & I'll have to cut access hatches to access the voids. Interested in hearing what the correct type of insulation might be.

Anyone thinking of blocking soffit vents do not.

The chalet style houses - yes you can block up between the floor and ceiling but you still need an air gap between the bedroom ceiling and the sarkin

If you are in a new build with the soffit vents and are in the belief that your getting a draft inside the building from this . Your insulation envelope is compromised either by poor building standards/no inspection or subsequent poor modifications. In new builds there should be a solid closure plate detail.

What I've done Phil to retrofit (I've same style house) is basically insulated into the gap as far as I can with glass wool Then fitted a solid closure plate in between the joists and then I have glass wool up against the plaster board and the next phase Is breathable superquilt stapled and taped beyond that to creat a breathable but draft proof barrier as even with the insulation the plasterboard on those walls is cold to touch.

What I’ve done Phil to retrofit (I’ve same style house) is basically insulated into the gap as far as I can with glass wool Then fitted a solid closure plate in between the joists and then I have glass wool up against the plaster board and the next phase Is breathable superquilt stapled and taped beyond that to creat a breathable but draft proof barrier as even with the insulation the plasterboard on those walls is cold to touch.

Cheers.

I’ll do similar I think. There is minimal insulation between internal plasterboard and roof unfortunately. When we first moved in we re-skimmed all the walls and I slightly regret not going the whole way and stripping the plasterboard and re-insulating properly with solid insulation.

I won’t block up under the eaves, I realise the roof space / loft needs to breathe.

Added to the never ending list of jobs! I’ve got to do under the ground floor at some stage too 😬

We have a related issue because it's a three storey house with patio doors on the first floor. Be ause the window sits on the outer wall the wind from the cavity gets through to the gap between floor and ceiling. I've just filled the gap with expanding foam, which has helped greatly, but I only had to do it around the door. The cavity is still open to the air via soffits.

And a related question: sometime in the future there will be a new roof, would it be feasible to insulate as part of the same job as there will be access to behind the walls? Is that a done thing?

to insulate as part of the same job as there will be access to behind the walls? Is that a done thing?

But when you say new roof what do you mean.

That being 1960s is probably sarkin felt and tile. You wouldn't generally remove the sarkinunless is knackered.

But when you say new roof what do you mean.

That being 1960s is probably sarkin felt and tile. You wouldn’t generally remove the sarkinunless is knackered.

Ah, probably not then. Sarkin = green(?) boards that are under the tiles? Now you say that I realise you don’t often see right into people’s lofts when they have a new roof!

I guess I’ll be doing it from the inside then.

I've not bit the bullet yet but I have 125mm joists

I have been looking for some 75mm rigid glass wool batts locally (delivery charges make it prohibitive to buy a pack for an experiment)

And making my self a couple of flat plate tools compress it to install it against the plasterboard between the rafters. Leave a regulation 50mm air gap between the outside of the glass wool and the sarkin.

The theory works. In practice it will be trying to do a water pump on a 2.5 banana engine transit with the engine in situ.

Sarkin = something to do with muscle chemistry

Sarking = windproof layer the tiles etc are fixed over. Could be felt or ply etc