How Much Fresh Air is Enough and Who Decides?

My assessment of adequate indoor air quality is when you can move from indoors to outdoors, or outdoors to indoors, and air inside feels as fresh as it does outside. My recommendation for assessing your home’s indoor air quality is to NOT do the math and rate to standards, but to take a deep breath inside your home. Before you forget how it feels, walk outdoors and take another deep breath of fresh outdoor air. Does it feel different? Does the outdoor air make you feel better? The air you prefer to breathe is the air you should be breathing.

Why Does Indoor Air Quality Matter?
Familiarize yourself with problems caused by poor indoor air quality. There is a good article by James Hamblin that appeared in “The Atlantic” in March of 2014 titled “The Toxins That Threaten Our Brains.” We also have a lot of great resources at our website.

If there is one idea I would like to be able convey to readers it is that like temperature, fresh air introduction and indoor air quality exists as a range. That range can be from bad to good, and it can be changed to suit the occupants’ preference, comfort, and health needs.

Below are two standards for indoor air quality.One standard strives toward “A High Level of Comfort,” the other to not dissatisfy the majority of occupants. One strives to not cause or aggravate illness, the other recommends reducing the likelihood of health risk.

Standard 1
“Acceptable indoor air quality: air toward which a substantial majority of occupants express no dissatisfaction with respect to odor and sensory irritation and in which there are not likely to be contaminants at concentrations that are known to pose a health risk.”

Standard 1 is part of the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) standard “62.2-2013 Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings”. This is the guiding standard for home indoor air quality in the US and is likely the standard that was used for your home if it was built in the last few years. It states, “While acceptable IAQ is the goal of this standard, it will not necessarily be achieved even if all requirements are met.” This doesn't exude confidence in a standard that is not very demanding to begin with.

ASHRAE has calculations and tables for calculating the ventilation rate for a given residential configuration, but they are not available to the general public (at least not for free). Remember that installed equipment and systems often do not deliver at their intended capacity. For example, it is not unusual for a fan rated to move 100 cubic feet per minute of air to only deliver a small percentage of this volume.

If it were easier to assess health risks from long term exposure to indoor pollution I believe that ASHRAE would have a whole different set of recommendations. Energy savings are pretty easy to assess, while the correlation of health problems to long term exposure to indoor pollutants has so far been impossible to prove.

Standard 2
Indoor Air Quality (IAQ) can be defined as: the physical, chemical and biological properties that indoor air must have, in order:

• not to cause or aggravate illnesses in the building occupants, and
• to secure a high level of comfort to the building occupants in the performance of the designated activities for which the building has been intended and designed.

Standard 2 is from the International Society of Indoor Air Quality and Climate (ISIAQ). It is from the ISIAQ’s, “Performance Criteria of Buildings for Health and Comfort.” I like this standard better because it strives for a healthier environment.

While my recommendation will not likely end up being the new standard for building code, I do have my own ideas on the topic. I like the 0.5 air exchanges per hour that is the standard in a number of European countries. I like this number because I believe it is a good starting place for fresh air introduction. From the 0.5 air exchanges per hour, the homeowner can regulate fresh air introduction to a level that makes sense both in comfort and in utility cost (there is a cost to heating and cooling fresh air).

When I first started working in my present office, the indoor air quality was lousy. My office is now ventilated at the 0.5 air exchanges per hour rate. When I walk out of the building at the end of the day the difference in breathing outdoors is negligible. In case you missed it, my assessment of adequate indoor air quality is when you can move from indoors to outdoors, or outdoors to indoors, and the difference in air quality is negligible.

In my home the difference is negligible during temperate and warmer months, but more noticeable in the middle of the winter. We sacrifice some indoor air quality for lower heating bills during the winter, and boost our fresh air intake as much as possible when it is more affordable.

My recommendation for assessing your home’s indoor air quality is to NOT do the math, and to remember that even if you knew how much fresh air was being introduced into your home, the design amount was to meet building code, which is the minimum. Instead, take a deep breath inside your home. Before you forget how it feels, walk outdoors and take another deep breath of fresh outdoor air. Does it feel different? Does the outdoor air make you feel better? The air you prefer to breathe is the air you should be breathing.

About the author
David Davis is a Certified Energy Manager, and product designer for the Fresh Air Manufacturing Company. Among experience leading to this role was five years as a utility efficiency expert, five years as an HVAC instructor for Boise State University, and a number of earlier years as an Engineering Specialist for Siemens and Honeywell. Learn more about fresh air here.