Airflow - chimney

[Dylan123]

Hi,

I have a boarded over chimney. This has a vent in it to allow airflow.

I wish to put a fireplace over this. It’s an electric flat pack one which sits on the wall. How would I ensure that I can get that airflow up the chimney?

another point is: I am insulating my floor which is suspended timber. There is great cross airflow below.

when I insulate, this will cut the airflow from the room and I’m concerned how this affects the chimney - even if I can solve the issue of the vent, it has nowhere it can draw air from.

given I am going below the floor, could I make a vent to draw air up under the skirting to the chimney so it kind of bypasses the room? Ie a vent from the (well ventilated) crawl space, direct behind the new fireplace so I don’t have an issue with the vent in the wall?

If so, anyone know how this is done, what the vent is (pericopic?)

There is a big concrete hearth in front so i have no idea how this would be done without literally cutting a Chanel in the concrete.

must be an easier way, or can I just find a way to vent from the existing vent through the new fireplace, but then with the insulation, will it get airflow? I guess this would only happen if a window or door was open.

really confused how to best tackle this.

thanks

 

[cdbe]

It only requires passive ventilation - not sucking litres of air up the chimney, if anything you want to limit what it takes from the room as the heat goes with it. If you can't re-jig it so the electric fire doesn't cover it you could fit a new one on the side of the breast, or see if you can pipe or duct to below floor as you suggest which is probably the best option. Also consider fitting a chimney balloon.

 

[Dylan123]

It only requires passive ventilation - not sucking litres of air up the chimney, if anything you want to limit what it takes from the room as the heat goes with it. If you can't re-jig it so the electric fire doesn't cover it you could fit a new one on the side of the breast, or see if you can pipe or duct to below floor as you suggest which is probably the best option. Also consider fitting a chimney balloon.

Ok, so when I fit the new one on, if I just find a way to leave a few tiny cracks for air then should be ok? I could just not seal the skirting, there is a recess behind the skirting and plasterboard (I boarded it so know the layout), so it’s just making sure it’s not airtight as opposed to having to allow an open duct

 

[Harry Bloomfield]

Often the concrete slab is laid on two brick walls, one at each side. Could you perhaps drill several holes through the concrete, at the very back of where the grate would normally go, to allow that essential ventilation?

 

[Dylan123]

Often the concrete slab is laid on two brick walls, one at each side. Could you perhaps drill several holes through the concrete, at the very back of where the grate would normally go, to allow that essential ventilation?

the concrete slab is indeed on brick, it’s actually 3 walls surrounding it with slate on top.

I have an SDS drill but never used it on concrete. The issue is the actual fireplace is plasterboard over. I have plasterboard wall in between which I don’t want to have to re do.

I can’t back to the actual fireplace.