please help? we have recently bought our first house and have discovered 1 or 2 vents in every single room. they are about 20cm x 20cm and not very attractive. a friend said something about them being necessary becasue of the chimney stack. the chimney stack is still inplace up through to the attic but the fireplace is not in use, we would really like to fill in the cavities behind the vents ( the cavities are large) but wanted tp make sure it was safe first and if it is , how do we fill them in? thanks very much.
If you have other ventilation in the house and they are not there because of gas fires you can block them up. Do not put anything in the cavity as if you bridge this you could be asking for water to travel across the cavity. See our project on condensation to see about ventilation.