Moisture Generated in the House – Moisture can come from many sources – people, pets, cooking, showering, fish tanks, drying cloths etc. etc. were air born moisture can be produced. All this moisture which is captured in the air as humidity should be directed outside, if not, then there is a real possibility that this high level of humidity can condense on cold surfaces such as windows, behind cold toilet tanks, on cold water pipes or cold surfaces such as exterior facing walls and possibly produce condensation or water and in the long term it may produce mold and damage building components. Here are two detailed publications which help explain in more detail NRC Moisture Problems and – CMHC Moisture and Air a Householder’s Guide.

Controlling the Humidity – If Humidity Generated in the House, is too high you may produce moisture related problems like mold, musty smells and or water damage, too low and you may feel dry throat, breathing problems, static shocks etc. In New Construction – Homes are even more susceptible to moisture, due to the amount of water used in construction materials which will evaporate over the first few years – can damage wood floors, cabinets and produce very high levels of moisture in basements behind insulation and on cold water pipes. HRV’s Heat Recovery Ventilators are also being installed in many of the newer homes to help reduce the humidity/moisture levels. In some cases Dehumidifiers may be required in basements.

Where do you Ventilate:

1. Washrooms – Fans in washrooms should always be left on for approx 25-30 minutes especially after showers or the very least a window should be left open to help draw that moist air outside. You may want to provide a timer for the fan. I find timers to be more useful since it’s easy to push a button and walk away. Some people feel connecting the fan switch to the light switch is an option. Personally I don’t like this since most people will turn off the light switch when they finish in the washroom, however you may still need more time to reduce the humidity level in the washroom. For more info click the following links; HVI Washroom Fan Guide, CMHC Bath and Kitchen Fan Guide and Choosing an Energy Efficient Fan.
2. Kitchens – Range Hoods should also be used during and after cooking. Some earlier construction used flow through range hoods which only captures the grease and not the humidity. Ideally range hoods should vent DIRECTLY outside. For more info click the following links; HVI Kitchen Range Hood Guide and Choosing an Energy Efficient Fan.
3. Laundry Rooms/Dryers – If you have a laundry room with a ceiling fan, you should be running this fan during the drying cycles. Also, make sure your dryer vent hose is connected directly to the outside and the hose itself is not damaged, leaking moist air into the house. I would also make sure the dryer vent hose is of the flexible metal type, see image to the right. And make sure you have the hose cleaned regularly of lint, lint can be combustible (catches on fire).
4. Cold Cellars (Cantina) – Basement cold cellars will typically have a window or a vent hole – this is used to allow fresh air into the cold cellar to help reduce the humidity level, which can condense to free flowing water/moisture when the temperature starts to drop. Don’t block these holes or you may get musty smells and or water damage, such as mold.
5. Basements – May require a Dehumidifier which can help reduce the moisture levels. You may also want to insulate any exposed cold water pipes, warm moist air can condense on the pipes and drip water, see picture to the right.
6. Attic – Most attic’s will have roof venting and or soffit venting, some will have turbines and some will have fan’s inside the attic which will have either a manual switch or controlled by humidity levels. Attic ventilation or venting is required to reduce the possibility of humidity condensing on the attic walls causing water related damages such as Attic Mold. Ventilating the attic can also have other benefits read further…HVI Attic Ventilation.