Q. We rent a duplex less than five years old, and there are considerable problems with condensation and mildew, especially around the windows. In the wintertime, we must use towels to absorb all the water. I realize an air exchanger would remedy the problem, but our landlord does not. He says the problem is due to the fact that a family of four live in the house. However, only one person lives in the other half of the duplex and condensation problems are there also. Our landlord suggested leaving the bathroom fan on all the time, which we tried to no avail. Can you help us convince our landlord there really is a problem? H.T.

A. Obviously, Mr. Landlord is not familiar with the National Building Code. Since 1990, all new houses require an air exchanger. During the energy crisis of the 1980’s, the Code introduced the requirement for a vapor barrier, to reduce air leakage and thus conserve energy. But, the relationship of air tightness to condensation was not immediately foreseen. By 1990, numerous condensation problems developed and air exchangers became mandatory.

Older houses were naturally leaky. So much, in fact, that the area of all the cracks in an older house, if added together, would be equivalent to a two-foot square hole in the side of the house. Although older houses wasted energy, condensation problems were minimal, and mechanical ventilation was not necessary.

A common misconception about a vapor barrier is that it keeps moisture out. This is quite contrary to its true purpose – to keep moisture generated inside the house from reaching into the exterior walls and rotting the wood structure. Moisture is created inside a house by cooking, washing and even breathing.

It is absolutely essential to install the vapor barrier on the warm side of the insulation. Inside every wall and roof is a place called the “dew point”. The dew point is the temperature at which water vapor carried in the air condenses to a liquid or, in colder weather, frost. If the vapor barrier is installed incorrectly on the cold side of the insulation, the condensing moisture becomes trapped inside the wall as it cannot evaporate to the outside air.

Sounds like your landlord is a short term economist. Installing an air exchanger is much cheaper than replacing exterior walls, windows and finishes. A family generates more moisture than a single person, but any unremoved moisture eventually damages the building components. Organisms grow inside the walls with even minimal amounts of moisture – in places unseen until it’s too late – and wood is one of their favourite foods.

While it is easier to install an air exchanger during construction, experienced technicians have ingenious ways of installing air exchangers in existing houses with minimal tear-up. Ductwork is concealed in the walls, floors or attic, and only openings for grilles are cut in the gyprock.

From a health standpoint, breathing in a poorly ventilated house is not recommended. It causes headaches, dizziness, drowsiness and aggravates allergies. A bathroom fan, running continuously, only removes five percent of the air in a house. It is simply not powerful enough to ventilate the whole house. An air exchanger is needed for complete ventilation and healthy breathing.

If your family has health problems related to air quality, and your landlord remains adamant about “cost control” in the short term, find another place to live. It will be difficult for the landlord to find another tenant if the interior damage is that apparent. You could also seek a doctor’s opinion about the poor air quality.

In any case, a landlord should listen to their tenants’ concerns about health and safety. The tenants live in the building and are acutely aware of the apparently minor problems which a landlord may prefer to ignore. If listened to, tenants can actually save a landlord money in the long run, by sounding early warning about potentially serious problems, especially those related to moisture.

NATIONAL BUILDING CODE

The National Building Code is published by the National Research Council of Canada (NRC). It is prepared as a model code to permit adoption for legal use by a provincial or municipal authority. Once adopted by an authority, the code carries the force of law. The code has been adopted by the smaller provinces in Canada, while larger provinces such as Ontario, Alberta and British Columbia have developed their own provincial codes based on the national code.

The primary purpose of any building code is public health and safety. The code establishes minimum construction standards for new or renovated buildings, but is not a textbook of building design regarding workmanship or aesthetics, for which design professionals must be consulted.

The code is continually upgraded by the NRC to reflect the latest developments in technology and safety through committees of architects, engineers, contractors and building authorities. The code is published every five years, with interim amendments issued as required.

One section of the code, Part 9, deals exclusively with houses and small buildings. When hiring a contractor, stipulate that work be done to all applicable codes, including the National Building Code, National Fire Code, National Plumbing Code and Canadian Electrical Code.