Except in rare cases, the weather outside always gets more attention than the “indoor weather” in our homes—the exception being when the latter leads to discomfort or health problems.

So what are the environmental conditions needed to balance comfortable heating with healthy living? Is it better to have a uniform temperature throughout the house, or to set it to different levels in different zones, or even room by room?

The variance factors are... varied

Besides the actual temperature of the air in a house, there are several factors likely to influence the perceived temperature; i.e., how hot or cold it “feels” to the occupants:

  • the relative humidity;
  • whether there are cold-air drafts;
  • the extent of cold or hot surfaces (walls, floors, ceilings, window glass, etc.); and
  • individual factors regarding the home’s occupants, such as age, clothing, level of physical activity, state of health, degree of fatigue, etc.

There’s also the fact that comfort is relative: it’s a highly personal assessment. What one person considers to be a comfortable temperature may be quite uncomfortable to someone else. Not only that, but we may find a certain temperature appropriate at a certain time of day, but inadequate later on.

Looking at things more “scientifically,” people generally feel comfortable when the environmental conditions allow their bodies to maintain their normal temperature (i.e., about 37°C) while relying on as few biological compensation mechanisms—blood circulation, sweating—as possible. Put more simply, the ideal temperature for you is when you aren’t aware of the temperature!

Air temperature

You have to establish a setpoint temperature for your home. So what should that setting be to ensure a comfortable, healthy environment?

To date, few scientific studies in Quebec have investigated the impact of temperature level on the health of a home’s occupants, admits Dr. Stéphane Perron, a physician specialized in public health and preventive medicine. Based on preliminary data, however, he recommends:

  • Setting the temperature to between 20 and 22°C (up to 24°C for older people)

Keeping the temperature too low results in, among other things, higher blood pressure (the body’s defence against cold). That increase can lead to disorders, especially in elderly people and those living with chronic health issues. In addition, some viruses, including the flu virus, survive more easily in drier, colder air.

Lowering the room temperature to 19 or even 18°C, however, will not inconvenience a person in normal health.

  • Maintaining a uniform temperature throughout the house

This option is preferable to creating indoor microclimates leading to wide temperature variations (for example, warmer in an office or living room, where you tend to move less; temperate in living spaces like the dining room and kitchen; cooler in bedrooms).

Moving from a warm zone to a somewhat colder one is linked to physical stresses that are harmful to health, especially in older people.

Relative humidity

The relative-humidity level plays a determining role in the quality of an indoor environment and its health impacts.

If the humidity is below 30%, the air is too dry. This can cause irritation of the mucous membranes of the nose and throat, and breathing difficulties in at-risk individuals (e.g., people with asthma). Dry air is also harmful if you have a skin or eye condition.

Conversely, a humidity level of 60% or more creates an ideal environment for proliferation of mould and dust mites—powerful allergens and irritants that can lead to respiratory problems like asthma.

The right actions

Here are the key methods for adjusting and controlling your home’s “indoor weather” to ensure healthy conditions in different seasons:

Temperature control

In summer:

  • Use an air conditioner.
  • Use portable fans and ceiling fans (this lowers the perceived temperature).

In winter:

  • Adjust the temperature setpoints.
  • Improve the building’s airtightness / thermal insulation to cut down on air leakage.

Humidity control

In summer:

  • Use a properly calibrated air conditioner to lower the humidity in the house.
  • If you don’t have an air conditioner, use a portable dehumidifier to lower the humidity in a room.

Note that the ideal humidity reading is less than 50%—a level that is hard to reach with most portable dehumidifiers.

In winter:
Controlling humidity is trickier during the winter months. Normally, you spend more time trying to lower the humidity, by ventilation or aeration, to avoid condensation and guard against mould growth. If you need to increase the humidity, you can run a humidifier—but do so with caution, especially during periods of extreme cold. Here are the right actions:

  • Using a hygrometer, monitor the relative humidity: it must not exceed 50%.
  • When conditions warrant, use, in a controlled manner, a portable humidifier or one connected to a central heating system to achieve a healthier (i.e., more humid) environment.
  • If you use a portable unit, be sure to maintain it daily: standing water is conducive to proliferation of bacteria. If you neglect that maintenance, you’re likely to substitute one problem for another!

Our thanks to Dr. Stéphane Perron, a physician specialized in public health and preventive medicine, for his contribution to this instalment of Tips & Tricks.

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