I’ve heard from a couple of people lately, when we were discussing the importance of indoor fresh air, twelve months of the year, that “of course, it’s winter now so we won’t open any windows”. (And the same response is perhaps even more common when air conditioning is running.)
Readers of this blog know the universal call for better fresh air ventilation from numerous public health and even energy/environmental authorities. For example:
"the easiest and the most 'painless' way of avoiding future infections is by upgrading indoor air quality systems in every building. It works! There are studies that show children that go to schools with good ventilation are 75 percent less likely to get sick.”
https://news.yahoo.com/covid-19-emergency-over-who-statement-reaction-doctors-205917048.html
Environmentalists Recommend More Fresh Air
The environmental aspect is perhaps unexpected, because most of the time in most climates, increasing the fresh air means increasing the energy consumption and cost.
The bottom line? Those recommending it have determined that better fresh air is worth it. For example, the leading global authority on “high performance” energy/environmental buildings, the U.S. Green Building Council, has published detailed sets of design guidelines for a quarter century. These are called Leadership in Energy and Environmental Design, or LEED, and there are now more than 100,000 LEED-certified buildings worldwide. (Note 1)
Indoor Air Quality (IAQ) is one of LEED’s seven core strategies. One commenter explained: "IAQ is critical for human health, comfort, performance, and productivity. Poor IAQ can lead to a range of health issues, including respiratory problems and allergies, and massively impact cognitive performance. A high-performing building should not only be environmentally sustainable but also serve and promote the health and well-being of its occupants.”
The latest version of LEED promotes the same fresh air standard that we selected in the summer of 2020, as measured by a carbon dioxide (CO2) concentration of 800 ppm or less.
Practical Aspects
It is unfortunate but true that accurate and sustainable measurement of CO2 is tricky. A CO2 sensor is much more complicated than a temperature or humidity sensor, tends to drift out of calibration, and the marketplace is flooded with very poor-quality devices, most made in China. To view our current recommended models, see How To Buy an Air Quality Meter (Hint - It’s Tricky)
But you can improve your ventilation even if you don’t have a meter. Here is how to assess your present level of fresh air in your house, workplace, or building:
- If you move your hand around the lower edges and the bottom of your windows and doors, you might feel air wafting in. If this effect is consistent at most of the windows, then you probably have adequate fresh air. You will feel this air mostly in the lower floors of a multi-story building.
- If you find a noticeable smell when first entering a building (think walking into a hardware or ag store and smelling all the chemicals!) then you probably do NOT have adequate fresh air.
What To Do About It
In a commercial building, and in some homes, the furnace/AC system introduces a small amount of outside air and distributes it around the building through the ductwork. If this is the case, and if your thermostat cycles on the heating/cooling when it is needed, then shuts it off for a while, then repeats this cycle, you may have a simple way to increase the fresh air. Most thermostats for these systems will have a switch that says “Fan” and then has two positions, “AUTO” and “ON”. (You may have to lift the thermostat cover to find this switch.) If your equipment is cycling on and off, you should find the switch in the AUTO position. Move it to ON and the fan will circulate the air continuously, doubling or tripling the amount of fresh air in the building.
In buildings without such a system, strategically opening a window or two will usually be enough. Many windows are positioned right above a source of heat, so you can open one of these an inch or so, and the cool air will be heated somewhat as it falls toward the floor. To avoid big differences in the amount of incoming air due to wind speed and direction, open just one window in a given room. How many windows? Maybe one per 500 square feet—of course this will vary widely!
If you have a heating system with ductwork, it is also easy to have a contractor install a small duct to bring in fresh air and mix it into the recirculated air duct, and then the system will send it throughout the building. The amount of this fresh air can then be adjusted to suit your needs.
Background Information
See the following blog posts for much more information:
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Note 1: Kohler and Lewis was the mechanical engineer for New Hampshire’s first LEED-certified commercial building in 2003, the Society for the Protection of New Hampshire Forests – French Wing Addition in Concord, and has since designed more than a dozen similar projects.
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