OK Bushy here goes ............. I've just re-read Part F of the Building Regs ( I know .......... sad ).
Three types of ventilation needed ............
1 Rapid (windows doors etc)
2 Background (trickle vents, hole in wall etc)
3 Extract (kitchens, bathrooms, utilities, rooms with no window)
Background: 6000sq.mm average per room .............. minimum for room: 4000
e.g. one room has 8000, next room has 4000 etc, therefore average = 6000
I know, I know, but stay with me anyway ..................
In simple terms ......... you gotta have background ....... either trickles or hole in the wall with slider which you can keep closed thus defeating the object completely. Welcome to my world lol
New windows come under Building regs ....... UNLESS fitted by a FENSA registered company (similar to the old CORGI thing)
Your contractor is obliged to comply with the Regs. In order for him to "break the rules" you sign the disclaimer .......... putting the responsibility on you to make other arrangements to make it comply. You've worked that out for yourself.
I can't think of any alternative other than a through the wall vent I'm afraid.
There are more complicated alternatives though ............ Google "Passive Stack Ventilation" .................. but I don't think you would want to go there :o)))