Floor insulation - ventilation question

ChasingtheWelshdream

Hi folks, we will be insulating our suspended wooden floor with celotex soon.

I know to take care around the air bricks, but our floor also has two of these vents, on opposite sides of the room.

In a previous Victorian house, similar vents were either side of the fireplace to improve the draw. This house is Edwardian so I wondered if they are for a similar reason, but they are not near the chimney. The fireplace is redundant.

The room has one external wall with 2 air bricks. These vents are at the opposite end, next to internal walls. This floor is suspended timber, all other rooms are solid floor. I wondered if they increase airflow throughout the floor, rather than just the two air bricks?

Would  anyone know what purpose these serve, if they are still required, and if they can be blocked when insulating? The air bricks will remain clear.

stuart45

With underfloor ventilation, it's better to have a cross flow, so they could be for this purpose, as otherwise they would only be on one wall.

ChasingtheWelshdream

Thank you.

I’m wondering how that works with putting celotex in the rest and leaving them clear to draw air from the room. They are quite draughty. 

FreeBear

If the fireplace is not used, I'd remove those vents in the floor. Fill the hole left behind with a plank of wood - You may need to be creative about providing support if the joists underneath are not conveniently located.

stuart45

ChasingtheWelshdream said:

Thank you.

I’m wondering how that works with putting celotex in the rest and leaving them clear to draw air from the room. They are quite draughty. 

They could have been installed opposite the fireplace as dual purpose. 
If you get rid of them, the room will be warmer, but the underfloor ventilation probably won't be as good. 
You could swap them for hit and miss vents that could be opened and closed as required.

Eldi_Dos

You could let your nose guide you as to the best course of action to take, does the air coming out the floor vents smell dry and fresh or does it have a musty dampish smell.


If you do decide to do away or change to closable vents one option could be to place 100mm ducts from just behind air bricks to near opposite wall then any breeze coming through air brick would be funneled to rear of underfloor area and help with circulation.

When you go to do the work get a bucket and small shovel and give space a good clearout, it is surprising how much stoor will have blown through the air bricks over the decades.

ChasingtheWelshdream

Thank you.

The air is fresh and all timbers are sound/dry that we have seen this far. I replaced an air brick recently and things were good as far as the torch shine anyway.

This is the floor plan if that helps.

stuart45

If you remove the vents, you won't get as much ventilation. You might get enough, but it's up to you. You probably do lose a fair bit of heat. 

ChasingtheWelshdream

Thank you. If it can still be insulated I think I would rather keep the vents than risk damaging the joists through lack of ventilation.

Not shown in the floor plan but there is a front room on the other side of the house with suspended floor,  that has no vents. I wonder if they were never there or have been removed over the years.

ChasingtheWelshdream

Actually @stuart45 I meant to ask you (as one of the many knowledgeable ones here) who knows about old buildings.

I’ve wondered why houses were built with a mixture of solid and suspended floors.

We have a front and back room with suspended timber, and the kitchen/utility (original scullery possibly) and hallway are solid. Just curious why not either all solid or all suspended.

Would you know?

Eldi_Dos

The floor vents might not be a original feature but could have been added if say a gas fire with back boiler had been installed in fireplace at some time, could explain why other room does not have them.