Yes you could.. but if you’re venting WCs then possibly pumping smells into the other area wouldn’t be good – not sure how 100% effective a non return flap would be on something like this.

Why not put an inline fan on the external side of the Y.. pulling air from both? Switching would be a little more complicated, but not rocket science.

Jeff

Sounds like the recipe for an Internet phenomenon!

+1 for looking into an inline fan after the duct merge. I am guessing that with all the joins etc the duct length will be quite long? If so a bit of additional draw that is switched on when either are used could help and prevent any flow the wrong way. Would have to check the wiring though as it would need to be linked to the wiring in 2 special locations, both should just be the lighting circuit though (but you may have two of those).

Or am I right in thinking that the cooker hood will be a centrifugal fan as that might prevent flow back better than a crappy axial like you get in a bathroom ceiling.

look at whole house heat recovery units

@sharkbait

The internet, it is a race you know……

I got my Y piece from lindab…….. wasn’t expensive, I think, but we have an account with them