Making Breakfast and Indoor Air Quality
Recently, I made bacon for breakfast. Noteworthy, I know. But, it got me thinking about indoor air quality and the massive impact that I can have as a designer on the long term health of homeowners. For the sake of brevity in this article I will not go over why indoor air quality is important, but if this is your introduction to the idea and you want to learn more about specific effects that bad air can have, please refer to one of these resources:
https://www.epa.gov/indoor-air-quality-iaq/introduction-indoor-air-quality
https://www.lung.org/clean-air/indoor-air
https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health
Returning to my morning bacon, I recently picked up an Indoor Air Quality monitor because I have been curious how well my mechanical system has been keeping up with the demands of my household. In the space of 10 minutes my air went from ‘green’ to ‘red’ from the single source of contamination! In particular, particulate matter of 1.0, 2.5, and 10 microns exploded from safe single digits to 600-800 micrograms per cubic meter (µg/m³). The unhealthy range starts at only 65 µg/m³.
Yikes!
I specifically chose not to use my recirculating hood fan so that I could see what would happen, but I would not expect anything less than a hood fully vented to the exterior to make a significant difference. We opened the windows to create a cross breeze, and it took over an hour to stabilize back to safe levels. This experience underscores the importance of considering air quality early in the design process. While a recirculating hood is certainly better than nothing, if my home were outfitted with a vented hood we could have easily evacuated the contaminants while cooking and kept our air clean.
While the kitchen is one of the biggest potential contributors to indoor air contamination there are other long term contaminant sources that can pose health hazards and we have systems for mitigating each. These may include: a radon mitigation system, proper wall assembly selection and detailing/air sealing, avoiding use of Red List chemicals such as formaldehyde (common in adhesives, for full list: https://living-future.org/red-list/), selection of low VOC materials, a balanced mechanical system including a make-up air system and HEPA air filters, and even to the design of the kitchen hood itself. All of these are an important part of ensuring that homeowners will breathe fresh air for many years to come.
Some owners may opt for an active air cleaning system such as a purifier. These can be included in the mechanical system to increase confidence that all contaminants are being removed. However, these systems require electricity and regular maintenance to function long term. Instead, I prefer to invest time and attention during the design process to ensure an indoor air environment where a purifier is simply not necessary.
One area where early planning can have an outsized impact is the garage. Your garage has many air pollutants that you do not want to infiltrate into your home. Gasoline, solvents like mineral spirits, insect killer, paints, etc. are all common inhabitants of a garage space and all of these may affect air quality if vapors are allowed into the living space. There are two main strategies for ensuring these items are isolated. The first is to separate the garage into a standalone building. This would be the method that would give the most confidence, however not all designs would benefit from this method, and personally I like being able to get out of my car and step in the main house without entering the cold/hot outside air. The other method to ensure isolation is to place the main mechanical room for the home system in a place other than the garage. While the building code does not allow a system to serve both simultaneously, it does allow the system to be placed in the garage, and if not properly sealed can easily intake contaminated air to circulate around the home. The reliability of the air sealing falls to how attentive the technician is on the day your system in installed. Something as simple as not pressing hard enough into a tape seam or the presence of dust will result in a poor seal. It is far better to place the equipment in a room within the home so that all return air comes only from the interior space and remains free of contamination.
In the end, if cooking contaminants are evacuated in a short time, it is likely no more damaging to your health than sitting around a campfire roasting marshmallows, but my concern grows when considering long term or frequently occurring contaminants. These will build up, leading to decreased health and quality of life over time. Considering the possible sources of contamination and the different ways to mitigate them during the design process is well worth the effort. Bacon has so much to teach us.