Springbok Home Inspections

Short note on humidity in basements.
I have a number of customers buying dehumidifiers to deal with excess humidity in basements. I’ll list a few causes and make recommendations.
New homes tend to have humid basements that may be due to the curing of the foundation. A recommendation is to wait two years before finishing the basement. This allows the cement to cure and faster.
Leaks are a question of “when” and not “if” in Ottawa. Most basements will develop some leaking. This needs to be addressed by an expert. Even though it may be minor, the damage can be substantial. Water has no smell, so the “damp smell” is mold. Finished basements makes it more difficult to monitor. Check baseboards every few months to see for discolouration as an indicator of moisture.
Poor cold air return. Ottawa has a wide temperature swing between winter and summer. Vent adjustment is different for the two seasons. Ideally a hot air return would be used for summer and cold air for winter. It’s not often done. However for basements the ideal location for the cold air return would be 6” off the floor. This would ensure that the cold air is circulated through the AC system and dehumidified. In many basement the cold air return is on the plenum 7’ or more off the ground. It is really pulling in the warm air. If this is the case it can be an easy fix with good results.

Hope this helps. Feel free to ask questions.

Humidity management in Canadian homes.

Humidity in this regard refers to the amount of water vapour present in the air. Relative Humidity (RH) is a measure of the percentage of water vapour compared to the saturation point or maximum amount of water vapour for the temperature and pressure at a given time.
Why is humidity important?
The amount of water vapour in the air is important for both human health and the health of our houses. Current guidelines recommend 40-60% RH for optimal health.
Advantages of optimal humidity:
Reduces transmission of airborne bacteria and viruses. Especially Canadian winters make us more susceptible for colds and flu.
Our respiratory systems function better leading to fever infections, especially during the dry winter months. Optimal humidity will help to reduce the dry mouth and sinus in the morning.
Winter dry skin is alleviated. Especially skin on the lower legs is prone to drying out in winter. In a well humidified house the skin will have an opportunity to recover.
Allergies and asthma is reduced. Increasing air moisture reduces the amount of dust, fur, etc. floating around reducing the triggers of asthma and allergies.
Less static electricity in the house. Not serious but it is unpleasant and can damage sensitive electronic equipment.
Musicians are well aware of the impact of humidity on the tuning and sound quality of some music instruments for example guitars, pianos and woodwind instruments. The human vocal cords also perform better with correct humidification.
What are the consequences of too high humidity in a house?
One example would be basements of newly constructed houses where caution is required to prevent humidity from exceeding 60% over a prolonged period. The number one concern of humidity in excess of 60% would be mold and rot. Mold and rot can damage the structure as well as having a negative impact on respiratory health.
What are the consequences of low humidity in a house?
Low humidity impact both human and structural health. Advantages of correct humidity for humans is discussed above. However the structures we live in are constructed with materials that absorb water. Low humidity can have the effect of drying out the structure leading to shrinkage and cracking. Examples would be wood floors creaking and drywall cracking.
How can we manage humidity in the house?
High humidity can be reduced by using a dehumidifier. Caution is required to avoid the area around the dehumidifier from becoming too dry. In general humidity migrates slowly through living spaces and localized areas can be more or less humid.
In summer air conditioners are a good dehumidifier. If the humidity in a basement remains high check for proper cold air return installed 6 - 8” above the floor level. Also check for leaks and wet floors. A dehumidifier might not be required or ineffective.
Low humidity especially during the winter months can be remedied with the installation of a humidifier. Various technologies are available including ultrasonic(cool mist), steam and evaporative. Humidifiers can be stand alone or installed on the central heating system. Furnace installs give the best results. A professional installer will make sure the installation is correct and safe.
Practical note regarding humidity control during Canadian winters.
During cold spells it will be very difficult to maintain even 30% RH. It’s also advisable to reduce the humidity settings during cold spells to prevent condensation for example on interior window panes.
Conclusion
Correct humidity is essential in our living and work spaces for the health of both the occupants and the structure. Canada poses a unique challenge due to the difference between summer and winter weather. However it is possible to provide good control and improve health and comfort.

Springbok Home Inspection is an Ottawa based company, dedicated to providing professional services, putting the client first. I am a member of Ontario Association of Home Inspectors (OAHI) and adhere to their Code of Conduct and Standards of Practice.

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