Venting subfloor up the chimney?

[R D S]

I'm thinking 2 birds one stone here.....

I've been told I need better underfloor ventilation (there's no ventilation at the back of the house, just the front).

We are doing some refurbishments so it's as good a time as any to rip the floor up and put a couple of snorkel vents in the back wall.

And i'm blocking up a fireplace and apparently supposed to vent the chimney. As it goes against the grain to send hard earned warm air up the chimney I thought of venting the space under the floor into the unused chimney instead.

It seems like a no brainer to me.

[newshound]

And to me.

[The Natural Philosopher]

only possible downside is that it increases sub floor heat loss which may be an issue if the floor is poorly insulated

[tabbypurr]

Just do it in a way that is practical to undo. A flat we blocked the chimney in became stuffy & damp, reopening the chimney solved it.

NT

[R D S]

We're in the process of covering it with 25mm polystyrene 'boards' and T&G Caberfloor, so should be OK.

[The Natural Philosopher]

Make that 65mm and its still nowere near enough...

[Andrew]

30% heat loss through the floor. If any air leaks between those inadequate insulation panels then you might as well not bother.

[R D S]

There's nothing there now. Except the floorboards.

[MSK]

Just read your post and I was thinking of doing the same thing. My floor is insulated but I have poor subfloor ventilation. Rather than use fans I thought I would use the redundant chimney to draw more air. How did this work out for you ?