Utility room with window - does it need an extractor too?

This is a personal choice as there is no regulation to say you have to or don’t have to. I would advise you if I was doing it to have one.

To the best of my knowledge it is now a requirement that all new bathrooms, toilets and kitchens have suitable ventilation. A window does not meet this requirement

Guidance from HM Planning Portal: "Any new kitchen; bathroom (or shower room); utility room; or toilet should be provided with a means of extract ventilation to reduce condensation and remove smells." The specification can be found in Approved Document F - Ventilation. When changing a bedroom to utility, "the installation of the fitting or fittings will involve alterations to, or new connections to, a drainage stack or an underground drain, the above ground wastes and drains are controllable (Part H Building Regulations)", but the plumber who did it will be deemed a 'competent person' for self-certification purposes. Responsibility for compliance: "It is important to remember that if you are the person (e.g. designer, builder, installer) carrying out building work to which any requirement of Building Regulations applies you have a responsibility to ensure that the work complies with any such requirement. The building owner may also have a responsibility for ensuring compliance with Building Regulation requirements and could be served with an enforcement notice in cases of non-compliance." Lack of regs compliance will always bite you on the backside when you come to sell or remortgage, but the regs are actually straightforward and not onerous to comply with, so there's no need to stress too much. I've developed several properties for sale / rental (in which I was the person responsible for complying with Building Regs) and always fit an external vent for tumble dryers and an additional humidistat controlled extractor for the utility room to take care of moisture introduced by the washing machine. This is particularly important for older buildings where condensation problems are more prevalent. Hope this helps!

Our local building regulations officer insists that there is an extractor fitted in any utility room that has a washing machine or tumble dryer in it so I’d bite the bullet and put one in or you may not get it approved by the council