The Importance of Relative Humidity in your Home


This time of year always warrants a revisit and reminder about humidity, more specifically relative humidity, and wood flooring. We are here to break it down and explain what this actually means to you.

Relative humidity is the ratio of the actual amount of water vapour contained in the air at any given temperature to the maximum amount of water vapour in the air at any given temperature can hold, which is typically expressed as a percent.


Wood is a hygroscopic material. Always containing water, it constantly exchanges water vapour with the air, picking it up when atmospheric relative humidity is high, and giving it off when relative humidity is low. Since wood swells as it absorbs water, and shrinks as it releases water, both its moisture content and its dimensions are controlled by the relative humidity of the surrounding environment; air and subfloor. Wood moisture content is equal to the weight of the water contained in the wood divided by the total weight of the wood, also expressed as a percent.


The relative humidity (RH) of outdoor air drawn inside your home is drastically altered by heating and cooling controls and wide seasonal swings in relative humidity. Since warm air can hold more water vapour than cold air, the relative humidity of the air with a certain absolute humidity can be changed by simply changing its temperature.

For example, if in the winter the outside air is -6C and 65% RH is drawn inside and warmed to 20C without humidification, its relative humidity drops to about 10%. Alternatively, in the summer, if the outside air is 20C and 60% RH that flows into the basement at 15C, the final RH will end up at 82%. In order to minimize this movement, the relative humidity must be maintained according to product specifications for all flooring products. We reccomend all of our wood flooring collections maintain a RH between 40-60%.


Engineered flooring can help mitigate significant movement and is built to outperform solid hardwood on a wider scale in these circumstances. That being said, it is still a natural product and will move should the RH not be maintained. Our recommendation is always to make sure your humidification system is operational and on throughout the fall winter and early spring months (dependant on where you live). We love a steam or mist humidifier that doesn’t only work when heating in the winter months, but adds moisture into the air when needed. This is not only good for your flooring, but also provides moisture for other millwork in your home and most importantly you and your family. Minimizing shrinking in your baseboards, kitchen cabinets and getting rid of static and those pesky nose bleeds by simply making the decision to follow the optimal RH for your home is a no brainer.


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