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What Should The Relative Humidity Be Inside My Home?

Proper temperature and relative humidity levels inside your home are an important part of maintaining good indoor air quality and comfort levels. The term ‘relative humidity’ may sound familiar, but many homeowners don’t truly know what it means and what kind of effects it can have on your indoor environment.

Humidity is the term we use to measure of moisture in the air - ‘relative’ modifies this term to reflect the maximum amount of water the air can hold. That maximum is dependant on the temperature of the air. Warmer air always holds more water than colder air - which is why we never have humidex warnings in January!


What Should The Relative Humidity Be Inside My Home?

Proper temperature and relative humidity levels inside your home are an important part of maintaining good indoor air quality and comfort levels. The term ‘relative humidity’ may sound familiar, but many homeowners don’t truly know what it means and what kind of effects it can have on your indoor environment.

Humidity is the term we use to measure of moisture in the air - ‘relative’ modifies this term to reflect the maximum amount of water the air can hold. That maximum is dependant on the temperature of the air. Warmer air always holds more water than colder air - which is why we never have humidex warnings in January!

A relative humidity in your home that reads 100% means that your indoor air is containing the absolute most amount of water it can. A home with a relative humidity of 100% is going to be sticky and uncomfortable - but a home with 10% relative humidity can be equally as unlivable. Maintaining an even humidity in your home is essential for comfortable living.

Signs Your Home May Have High Relative Humidity

humidity levels in toronto home

Elevated humidity levels indoors can be an indicator of poor ventilation or exchange between the building and outdoors. Poorly vented bathrooms, laundry facilities, cooking facilities or improper use of humidifiers can cause the relative humidity to rise leading to a mould and bacteria problem. One of the major indicators is when your windows show excessive condensation. Should this be the case, you may want to have an indoor air quality assessment performed to determine the source of the condensation.
 
Knowing if you have a high relative humidity inside your home isn’t always easy to tell, but there are a number of signs that may point to too much moisture:
  • Condensation on windows and doors
  • Mold growth on the ceilings, walls, or inside cupboards
  • A musty smell
  • Stains on walls and ceilings
  • Wood rot
  • Blistering paint
  • Cupping wood floors

Sources of High Humidity

  • Kitchen: The heart of many homes is the kitchen, but those delicious meals may be introducing excess humidity into your home environment. Having a range hood with a vent that goes to the outdoors can help draw off moisture coming from simmering, boiling or sautéing food and prevent it from staying in your home. Cheaper vent hoods often just vent the air straight back into your kitchen - catching only grease and not water vapor. Interestingly, natural gas cooktops produce more water vapor than electric stoves due to a chemical reaction between methane and oxygen.
  • Laundry Room: Your washer and dryer are obvious culprits in high indoor humidity. Without adequate ventilation, that warm, humid air will build up and can result in a musty odor and cause drying to take much longer. In older homes, the laundry room is often located in the basement - which brings us to our next source of humidity.
  • Basement:  Damp and moldy basements are a huge contributor to high humidity around the home. Even when the mercury drops, the ground can still be wet below the frost line and that water may absorbed by your basement walls. Here is where a dehumidifier can be a great short term aid in preventing moisture build up, though if you have a consistently damp basement, it might be better to think about investing in waterproofing or insulating your basement.
  • Central Heating: As we mentioned above, some furnaces come with a built in humidifier, since it’s most likely you’re running it during the dry winter months when a little moisture is more welcome. Problems can arise with poor, non existent, or malfunctioning controls, which may be letting too much moisture into the heated air.
  • Bathroom: This room is an obvious place to install a fan to reduce the amount of hot, humid air created from taking a shower or a bath. That long hot shower may be great for sore muscles, but it can created a lot of unwanted excess humidity in your home.

Solutions to High Humidity

To help reduce the amount of humidity in your home, the following tips are a good place to start, finding a permanent solution is the only way to reduce your indoor humidity levels in the long term.

  • Air Sealing: Sealing up cracks and gaps that may be pulling conditioned air out of your rooms or letting outdoor air into spaces can help regulate the amount of humidity in your home.
  • Ventilate properly: Good ventilation is often the best medicine for a humid home. Install fans over your stove or in your bathroom to ventilate unwanted moist air out of your home.
  • Insulate: Making sure your home had adequate insulation will help reduce humidity but also bring you energy savings by increasing your energy efficiency.
  • Install vapor barriers: A vapor barrier is a requirement in most building codes, and is a thin membrane, like a skin, that is wrapped around the exterior or your home between the bricks and the framing. It prevents moisture from entering your home while allowing your building to breathe.
  • Dehumidifier: For emergencies and times when a little support is needed, a dehumidifier is a great tool for reducing relative humidity, but it shouldn’t be relied on in the long run to provide a lasting solution.
  • Set the thermostat: Controlling the temperature setting on your thermostat is one of the most important things you can do. Don’t overheat your home in the winter, and turn off your furnace’s humidifier - not only will your monthly energy bills be lower, but your indoor humidity level will stay at a more comfortable level too. 

The Health Effects of High Humidity in Your Home

Beyond the damage that high humidity can cause to your property, an elevated level of moisture in your indoor air quality can affect your health as well. Relative humidity that is too high can result in mold, whose spores can affect the respiratory system and aggravate conditions such as asthma, making life indoors very uncomfortable for some people. Dust mite infestations, bacteria, and some viruses also grow and multiply faster in humid environments.

Conversely, low relative humidity settings can also make life difficult. Dry air is proven to aid in the spread of respiratory infections, allergic rhinitis, and asthma. It can also cause dry skin, sore eyes, and painful sinusitis. Most experts agree that a relative humidity in your home of 40-60% is the ideal range. Low humidity levels are usually the result of low outdoor levels experienced in Canadian winters when the outdoor humidity levels can reach the low teens.

How Can Psychometric Charts Help Determine Humidity?

A psychometric chart won’t tell you your future - but it can tell you more about the temperature and humidity of your home. A psychometric chart plots data points that represent your indoor air humidity at certain times of the day and year to find your optimal comfort zone. Terms like dry bulb and wet bulb temperature are used to capture specific points in time and can help a qualified reader to offer solutions to high home humidity based in science.

Energy Savings for Proper Energy Usage

Humidity levels should be managed throughout the year at appropriate levels for the season. In general ASHRAE Standard 62-2001 for Indoor Air Quality states the following:

  • Winter: Maintain relative humidity levels in winter between 30-40% and temperatures between 19-23 degrees Celsius. If your windows show excessive condensation, then the relative humidity percentage will need to be closer to 30%. Never exceed 45% in winter.
  • Summer: In warmer seasons, keep the relative humidity between 50-55% with the temperature around 23-26 degrees Celsius. Outdoor humidity levels may temporarily increase these levels.

To achieve these guidelines, the best thing you can do is to find solutions for areas in your home that may be causing high humidity. Running a dehumidifier or your air conditioner (which can remove humidity from the air) are only stopgap measures that are wildly energy inefficient. Not only will they cost you in your monthly heating and cooling bills, but they’ll also result in increased maintenance costs for your air conditioner or humidifier, which will need to run constantly to keep up with demand.

Awareness is Key

The best solution to high indoor humidity is awareness. If you’re experiencing any of the problems associated with high humidity, such as condensation on your windows, mold growth, or soaring energy bills, give us a call at SafeAir. One of our staff would be happy to walk you through our indoor air quality assessment process, which looks closely at relative humidity and its effect on your indoor air quality. All homes have unique ecologies that require individualized attention to be the healthiest, safest place for your family to be.