Invest in a fan with a timer switch. Your bathroom fan should run 15 minutes (minimum) after you've turned off the water, showering or bathing. This will reduce condensation and significantly increase the lifespan of your bathroom. The BC building code requires bathrooms without a window must have a fan. Keep this in mind if you plan on renovating your basement or building a legal suite!!
If you are renovating and your existing bathroom does have a window, it would be a good idea to get a fan installed regardless. Make sure your fan consists the right CFM (Cubic Feet per Minute of air exchange) to fit the bathroom.
Ventilation efficiency is a 'must have' and will prevent spores of mould from growing, paint bubbling, and sealant breakdown.