IAQ Health for Cold Climate Homes

Apparently, people spend even more time indoors during the winter - including almost 97% of the time for Canadians during the cold season! This means that the quality of your indoor environment becomes even more important to maintain your health and well-being. It’s during this time of year when the air within heated homes and offices becomes dry and stale. If you live in a place with cold winters, you are likely depending on some indoor heating during this season. There are few challenges that can emerge with our overall health when we utilize mechanical heating systems. These challenges can be attributed to the low humidity levels resulting from the dryness when heating the air, the indoor air quality (IAQ) resulting from the heating source emissions, and the lack of fresh air exchange with energy efficient building design.

When we heat the indoor spaces of buildings, the relative humidity can drop quite drastically. The ideal relative humidity (RH) for the health of your respiratory system is around 40%, but most heated interior spaces can drop below 20%. Anything below 20% RH can be quite uncomfortable and begin to negatively impact the membrane lining your respiratory system. Pharyngeal dryness, eye dryness, and nasal dryness can become serious challenges during continuous low humidity conditions.

Some folks will seek out space humidifiers to amplify the relative humidity of occupied indoor spaces during winter. These might be placed in the bedroom and operated during nighttime while sleeping or placed near the daytime workspace. Introducing humidity in localized spaces can indeed improve the RH level for our respiratory comfort but may also introduce some new indoor health problems. There are different types of humidifiers – ones that produce humidity through evaporation by means of a mechanical fan or a heating element, and ones that produce humidity through diffusion of water molecules by means of vibrations between two ceramic plates (piezoelectric transducer).

The ultrasonic humidifiers have become the most popular model in the United States, likely because they run more quietly (no fan noise) and in theory require less maintenance (no filter change-out). However, the ultrasonic humidifiers should only be operated with deionized or distilled water because the system otherwise tends to produce high amounts of fine particulate matter (PM_2.5) that is unhealthy to breathe over long periods of time. In addition, the water reservoir of any humidifier should be changed out regularly to avoid the development of harmful microbes and pathogens. Ironically, some advertising for humidifiers on the market boast about the large size of the water reservoir and the length of time it can run without maintenance or change-out (i.e. up to one-week or more). This may seem appealing for those who have busy lives and don’t want to be hassled with constantly tending to the maintenance of an appliance.

However, it is not advisable to have water standing in the reservoir of a humidifier any longer than 72-hours or 3-days. I recommend changing out the water on a daily basis or every two-days at most. The risk, otherwise, is the development of pathogens and bacteria, such as Pseudomonas, Brevundimonas, Acinetobacter, and Legionella. Scientific research publications on this topic recommend changing water tanks at least once each week, but I take a precautionary approach since there are other contributing factors such as the temperature of the space and exposure to light or placement in darkness, etc., which can exacerbate or slow pathogen development. To avoid the risks of these unknowns, be pro-active with regular water reservoir change-outs.

Certain types of heating systems can also cause poor indoor air quality (IAQ), such as biomass, wood stoves, and propane or gas heaters. These types of heating units produce nitrogen oxides, carbon monoxides, and methane, which can affect human health and potentially cause lung cancer. Unfortunately, around 50% of the world’s population employs biomass as a primary home heating source, especially in developing countries. Exposure to carbon monoxide alone can cause daily health challenges, such as headache, nausea, shortness of breath, fatigue, and confusion. According to the Centers for Disease Control and Prevention, the small amounts of carbon monoxide that penetrate our respiratory system can dramatically reduce the ability of the hemoglobin in red blood cells to transport oxygen.

The United States Congress is recently arguing over the use of gas appliances inside of homes and whether or not there should be a ban on gas appliances due to the human health impacts as well as the environmental impacts from emissions. While this is a more complex topic to address as it involves economic disparities, health, and environment, it is clear that if we prioritize human health, the electric heating systems would prevail. Ideally, we could run the electric systems from clean energy sources. Integrating passive solar heating strategies into the design of your house will give the greatest benefit all around for long-term health, affordability, and minimal environmental impact. Wood burning stoves and fireplaces, however, are very enjoyable and comforting during a cold winter night. It is important to keep these to a minimum and not depend on biomass systems as the primary source of heating due to the high amounts of particulate matter (PM₁₀) and polycyclic aromatic hydrocarbons (PAHs) that are produced – both problematic for health and the environment.

Sometimes we are making our best effort to reduce environmental impacts with certain design strategies, but simultaneously might discover negative health impacts as a result. Energy efficient house design, which increases air-tightness and insulation in the building enclosure system and construction, reduces the overall fresh air exchange rate that is typically experienced in less energy efficient homes. This means that the quality of indoor air can suffer – in fact… higher concentrations of toxins accumulate inside air-tight homes, which may include terpenes (hexaldehyde, alpha-pinene, and limonene) that are emitted from wood-based building materials, furnishings, insulation, interior décor, and other discontinuous human activities.

While it may be counterintuitive to open a window on a cold day as we don’t want the heat inside the home to escape, it can be helpful to briefly ventilate regularly occupied spaces with natural ventilation and fresh air. This can be done fairly quickly, for just a few minutes each day, so as to minimize heat loss while facilitating a more rapid exchange of fresh air. Mechanical ventilation systems are designed to cycle through specific outdoor air or fresh air intake exchange rates, so in theory these should suffice for provide adequate fresh air delivery. But if you have other types of heating units inside the home, such as the propane or gas units, you will want to supplement air exchange with some fresh and natural ventilation each day.

Some of the best overall advice for maintaining health in the winter (and all year) is to spend time outdoors each day. Taking a twenty-minute walk, or biking or hiking, can greatly benefit your respiratory health and cardiovascular system. It is also great to take daily showers of at least 10-minutes to soothe the respiratory system with steam in otherwise dry times. When you are constrained to being indoors the majority of the time, let’s find the optimal solutions for designing your home and workspace for your health! I am an advocate for the benefits of nature in design, including house plants that improve the indoor air quality and humidity levels. A future blog article will provide some options and details on integrating the right type of plants for your health, well-being, and indoor environmental quality.

If you would like more specific information on how to improve the indoor air quality health of your home, reach out to AIDA, LLC today for a consultation. You can always find more information and healthy home resources at Aletheia Ida Design and Architecture, LLC (AIDA, LLC) at www.aletheiaida.com.