DCV vents for renovation and extension

ravendude

Wondering if DCV vents are worthwhile in my case...

Adding an extension and renovating some rooms in our house. Existing house was built in the late 90s, dormer, obviously will never be properly airtight but we will do all we can, walls pumped, attic and crawl spaces filled and we will be putting good quality triple glazing throughout and low u-value sealed doors etc.

Wondering if I should be asking to have DCV vents specced to affected rooms? I know very little about them to be honest. Are they worth the extra cost? They seem to average 100 euro a unit. I'm thinking maybe to ask for them in bathroom, and 2 affected bedrooms.
Would they be worth the exra money over just trickle vents in the windows? Will they help with warmth much?
Do they need to be wired etc?
Can you install separate DCV units, not ducted as a system? Ie. Something just like smart vents? Ie. This way I could fit a couple of vents at a time, over time.

ravendude

Maybe this is a stupid question,... are all rooms supposed to have vents (where no mvhr)? Or just bedrooms, bathrooms and rooms like that?
Is there a difference between what regulations say you must have, and what you should have?