In old houses the draughts provide the ventilation- so when you seal the leaks you need to think about ventilation. The simplest form of ventilation is of course opening the window after a shower. It may seem odd to go to all that effort sealing gaps to then open the window, but the important thing is that a short while later you can close the window- ventilation is controlled air flow.
I discovered that what I had assumed was an extractor fan in the cooker hood was actually just circulating- merely filtering out grease and blasting out the air slightly higher up, straight back into the kitchen. It wasn’t dealing with the steam from the hob at all. So where the cooker hood met the ceiling I cut a hole and ran ducting through the roof space to a vent in the roof tiles. Now steam from cooking is extracted to the outside instead of condensing on the windows and walls.
In a new, air tight house you might provide whole house Mechanical Ventilation with Heat Recovery. This often sits in the loft and has ducting to every room, extracting stale, humid air from bathroom and kitchens, and supplying fresh air to living spaces and bedrooms. The outgoing air passes through a heat exchanger to warm the incoming air, so you get fresh air whilst keeping most of the heat.
Extractor Fan with Heat Recovery
We installed a single room extractor fan with heat recovery in the bathroom. It’s designed to run permanently on trickle, or kicks up to boost when humidity is high.
So during the day, with the bathroom door open, it gently removes stale air from upstairs. This, for example, deals with the moisture from clothes drying on the ceiling rack just outside the bathroom.
When you take a shower the humidity sensor automatically switches to boost until the air is dry again.
Single Room Extractor Fan with Heat Recovery
Pros: Very effective ventilation. We never open the window in winter. Virtually zero mould growth now.
Cons: Audible. Not ‘almost silent’ as claimed when running on trickle. Sounds like a hair drier on boost.
Heat recovery effectiveness? Difficult to measure.