Two things are undersized in almost every bathroom: the fan and the light at the mirror. Both are cheap to get right during a renovation and expensive to fix afterwards, because both live behind finished surfaces.
A fan ducted into the attic is not ventilation. It is a humidifier pointed at your roof structure. Warm, saturated air discharged into a cold attic condenses on the underside of the sheathing, and on this coast — where attics stay cool and the air is already humid for much of the year — that moisture does not evaporate away quickly. The result is staining, then mould on the sheathing, then in bad cases compressed and ineffective insulation below it. It is one of the most common findings when a ceiling is opened in an older Nanaimo home, along with a duct that stops short of a soffit vent, or a flexible duct that sags where condensate pools. Ventilation means ducted outside, through a wall or roof cap with a functioning damper, insulated where it crosses unconditioned space, and as short and straight as the layout allows.
Sizing is arithmetic, not guesswork. The working rule for a bathroom under about 100 square feet is one CFM per square foot with a floor of 50 CFM, and for larger rooms the calculation is done by fixture — allowing for the toilet, the basin, the shower and, in particular, a jetted tub, which requires far more than people expect. But the rated CFM on the box is measured at a specific static pressure, and every metre of duct, every elbow and every metre of flexible rather than rigid duct reduces what the fan actually moves. A 110 CFM fan on a long, kinked flexible run can deliver less than half its rating. Sizing therefore accounts for the duct run, not just the room. Make-up air matters too: a fan can only exhaust what the room can replace, which is why an undercut on the door of around 20mm is part of the system rather than a detail.
Run time is what actually clears the room. A fan switched off as someone leaves the bathroom has not finished the job — the moisture is still in the air and in the surfaces. A timer switch running the fan for twenty to thirty minutes after use, or a humidity-sensing switch that runs until the room returns to ambient, is the single most effective moisture control measure available in a bathroom, and it costs less than the tile trim. In a climate where rooms dry slowly, it is close to essential.
Lighting at the mirror is a different job from lighting the room. A single ceiling fixture behind you throws your own shadow onto your face and puts deep shadow under the eyes, nose and chin — which is why bathroom mirrors have a reputation for being unflattering. The fix is cross-illumination: light from both sides of the face at roughly face height. Vertical sconces flanking the mirror at around 1,650mm to centre, a backlit mirror with a diffused perimeter, or an illuminated cabinet all do it. Colour temperature belongs in the same conversation — somewhere in the 2,700K to 3,000K range reads warm and domestic, while 4,000K reads clinical, and a high colour rendering index matters disproportionately here because this is the room where people judge skin tone. Layering the rest is straightforward once the mirror is solved: general ceiling light, a damp or wet rated fixture over the shower, and a low-level or night circuit that makes a two-in-the-morning trip bearable without waking anyone.
Electrical work in a bathroom is governed by where water is. Receptacles serving a bathroom require GFCI protection, and current Canadian Electrical Code practice requires a dedicated circuit for bathroom receptacles. Fixtures within the zone above and around a tub or shower must be rated for damp or wet locations, and there are clearances from the tub rim within which switches and receptacles cannot be placed. A heated floor needs its own circuit and a GFCI device. Any of this requires an electrical permit and inspection, and it is coordinated with the plumbing rough-in so the walls are only closed once.
Heated features worth roughing in. A heated towel rail is the other upgrade people rarely regret — a warm, dry towel in a coastal winter, and one less damp object hanging in a humid room. Hardwired is tidier than a plug-in version and requires a cable at a set height decided during rough-in. A heated floor, an in-mirror demister pad, a fan-heater combination unit for a room that struggles to warm up: all of them are trivial to include while the walls are open and disruptive to add afterwards.