Humidity – The worst enemy of your wood trim
Why should you worry about air moisture in your home?
If you have temperature and humidity problems in your home, you will also have never-ending problems with all the wood trim and doors. Do you want to know why? This article describes the problem and tells you what you need to do about it to solve the problem.
Water vapour is naturally present in the air we breathe. The amount of water vapour the air contains is called relative humidity. In the desert the relative humidity will be very low, like 15%, whereas in damp climates such as the rain-forest the relative humidity can be very high, like 80% or more. Heat and cold are transmitted through wet air much more effectively than with dry air. High humidity effects the comfort of humans because it prevents them from cooling their bodies through sweat. Heat feel hotter and cold feels colder in a damp climate. High humidity in the air will effect human comfort, health and safety. It can also effect everything contained in your home.
Damp air will effect wood as well as humans because both plants and animals contain a very high percentage of water. Wood constantly exchanges water vapour with the air, picking it up when atmospheric relative humidity is high, and giving it off when relative air humidity is low. When the amount of moisture fluctuates, wood will either grow or shrink. This natural reaction of wood to temperature and humidity is sometimes what is responsible for the structural problems encountered by home owners. Gaps in wood trim suddenly appear that was installed perfectly. Doors close improperly, flooring begins to squeak, wainscoting boards separate, cornice, casings and baseboards come away from the walls. If you have any one of these symptoms then you might have a temperature and humidity problem with your home.
It can can become a real problem in the cold winter months if you have high humidity in your warm home but poorly insulated windows and doors. Windows will sweat with moisture, doors will not close properly and wood trim on cold walls or ceilings can shrink causing unsightly gaps to appear. Wet air also feeds mold and mildew which will cause natural wood products to rot.
Older houses built before the 70’s are naturally leaky and will allow cold air to seep into the home during winter and hot air into the home during summer. This makes the home difficult and costly to heat or cool. Building with air leakage also expose the home to humidity and outside air pollution. However, modern homes are sealed so efficiently that mechanical ventilation is required to get any air circulation. They have evolved into controlled versions of the old “naturally leaky” houses that were designed to exchange inside with outside air without the need for high-tech control systems that monitor and control humidity and temperature in the home. This intelligent environmental control system is called “heat recovery ventilation” or HRV.
During the winter, the HRV system removes stale wet air and introduces fresh, dry outside air into the home by using a “smart” forced-air ventilation system. In the winter, air becomes extremely dry – and can drop the relative humidity in your house to the point where it can damage the wood finishes and furniture in your home. Under extreme conditions even do structural damage as wooden joists and beams bend and shrink. Radiant floor heating, because of its high efficiency, is becoming increasingly popular in older homes for winter heating. This technology is creating another problem with baseboard mouldings and wood flooring because it creates a hot dry environment only at floor level.
Without a smart environmental control system in your home, indoor relative humidity can drop to desert-like conditions of only 15% during cold winter months and rise above 75% during the hot, humid summer months. Moisture content of wood casings swing from 4% to 16% and 6″ wide casings can grow more than 5/32″. Everything made of wood is affected by extreme fluctuations in temperature and humidity in your home regardless of who manufactures them.
So what can you do about the problem, if anything?
Install high quality wood trim products that have no more than 8-12% moisture content. At Decor Mouldings, we use only lumber that has been kiln-dried to 6-8%. It will pick up a small amount of moisture again after the drying process but we monitor it to ensure that it does not exceed the 8 -12 % moisture content before it leaves our factory . Use products like finger – joint pine that have a mix of grain orientations within a single piece so one part constrains the movement of the other.
If you are building a new home there are many sources of humidity – curing concrete, curing drywall cement and drying paint just to mention a few. If possible, you should wait a few weeks or more before installing the new wood trim in your home to allow air humidity levels to dissipate. When you take delivery of your wood trim and doors you should store them inside your home for 2-3 days to allow them to acclimatize. This is especially important during the cold, dry winter months or the hot, humid summer months. DO NOT store your wood trim on a concrete floor. Newly poured concrete holds a large amount of moisture and cures for several weeks. A cold, damp concrete floor is a bad place to store wood trim. Choose a location that is warm and dry. Do not leave your wood trim exposed to direct sunlight. All these conditions will cause wooden trim and doors to warp.
If you have a “smart” environmental control system in you home DO NOT set it to keep your house too dry in the winter. Your wood trim and flooring will be damaged as a result and gaps may appear due to shrinkage. Maintain a relative humidity of 35-50% and a temperature of approximately 68 to 75 degrees Fahrenheit, or 20-25 degrees Celsius.
This temperature and humidity range is healthy for you and will help keep the wood products inside your home looking good. We recommend that you invest in a smart humidifier/dehumidifier system if possible. You should also invest in a digital hygrometer, an inexpensive device available at most hardware or building supply stores. This device will allow you to measures humidity and temperature levels in your home. Remember that the investment that you make in purchasing a hygrometer, humidifier, and dehumidifier are relatively small compared to the investment you will make in your home and furnishings.
What do I do about windows that have winter condensation?
Condensation in the winter will only be a problem if you do not have winterized double pane windows in your home.
Whenever the temperature outside your home drops to -20 C, the inside of the single pane of glass in a window becomes cold enough to cause condensation to form as moisture from the warm, damp air touches it. Water will accumulate on the inside pane and eventually start running down the window onto your wooden trim. This will damge and eventually destroy your wood window trim and may eventually cause the wood to rot. The colder it gets outside, the worse the problem will become. If you have an smart heating and ventilating system in your home you will be strongly tempted to drastically reduce the relative humidity of your house until there is no more condensation. Doing this for even the short period of a week will cause serious problems with the wood products in your home.
What other ideas and recommendations do you have to control home humidity?
Keep indoor plants – they will improve air quality and absorb moisture, especially during the winter months.
Make sure you read the technical manuals that come with your home heating and ventilation system. Make certain you are familiar with the routine maintenance procedures required, such as air filter cleaning and replacement. Make sure your system is working properly before experiencing the extremes of the hot wet summer and cold dry winter.
What do I need to know about my Heat Recovery Ventilation System (HRV)?
The primary purpose of a HRV system is to bring fresh air into the home during the cold winter months or hot summer months when windows must be kept closed. Modern buildings are designed to be almost air-tight, so it is very important to circulate fresh air in the ventilation system rather than simply recirculating stale air. The HRV system uses something called a “heat exchanger” on the air to keep warmth inside the building in winter, and cool air inside it during the summer.
In the summer, warm, moist, stale air is taken from inside your house in areas such as kitchens, bathrooms and laundry rooms. It is exhausted outside the house while fresh air brouht into the heat exchanger and cooled through a heat exchanger. During the winter months exhaust air passes through the heat exchanger to remove the heat and keep it inside your home. HRV systems do not control indoor air humidity, only heat.
Energy Recovery Ventilation (ERV) systems control and monitor both heat and humidity level in your home. They use an advanced heat and humidity sensor system. A combination humidifier / dehumidifer built directly into your home ventilation system to add or remove moisture from the air and maintain a pre-set temperature humidity level.
If your are using an HRV system, turn the dial on the thermostat to the lowest speed setting available during the winter heating season. The fan on the HRV will run full time, ensuring a continuous supply of fresh air into your house. Running at a higher speed may lead to high humidity conditions that are hard to control. Watch your hygrometer carefully during the winter – maintain 45% RH. Bathrooms and kitchen exhaust ventilation fans override the main fan on the HRV so that they can exhaust humid air & offensive odors quickly.
During the cooler days of the summer months you can turn your HRV to the off position to save energy. Open windows in your home can supply all the fresh air required. You can turn it on again during the hot, humid summer days, when it will cool your home and only run for brief periods of specified time.
The controller device used for an HRV to set air moisture levels is called a dehumidistat, because it removes water from the air. It is usually found on the wall beside the heating system thermostat, which controls the heating system in the winter. If the relative humidity in the home rises above a pre-programmed minimum setting (usually 45%RH), the fan on the HRV system will turn on automatically and run at high speed until the level drops to the appropriate level. Your home ventilation system may also be setup to add moisture into the air during the dry winter months using a humidifier. The controller for this system, called a humidistat, is also normally located beside the thermostat for the heating system.
If you have both a humidistat & a dehumidistat as controllers, make certain you use the following settings for your ventilation system so that the HRV & humidifier do not conflict with one another:
- Humidistat (humidifier) – 45%RH (ideal – 35% min.)
- Dehumidistat (HRV) – 5% higher or 50 %
In conclusion, by controlling humidity and temperature in your home, you can make certain your wood doors and trim and mouldings will look as good 50 years from now as they do today.
