Air Quality Control – The Key to Healthy Buildings

October 14, 2022

Many have experienced burning eyes and dry throats while working at an office or at home. In heavily-populated offices, good ventilation is not always a luxury. This causes high levels of CO2 in the air, which can cause fatigue, headaches, and dizziness, and lessen your productivity and general feeling of well-being. This creates a challenge in maintaining healthy buildings and who wants to work in an office while not feeling their best?

While CO2 in the office is bad enough, there’s also the problem of particle pollution such as dust, dirt, soot, pollen, or smoke flowing into office spaces. According to the EPA,[1] extended exposure to that pollution can lead to many negative effects such as, coughing or difficulty breathing, decreased lung function, and in extreme cases, nonfatal-heart attacks, to name a few. To make matters worse, the solution to reducing indoor CO2 levels is to bring in more outdoor air, which increases the particle pollution (assuming the same air filter).

Pairing the effects of CO2 with particle pollution makes the office sound like a place you would rather avoid. Office spaces are supposed to be a welcoming area where employees can apply their skills to work as efficiently as possible. Building owners and managers grapple with this issue of occupant health to create healthy buildings while trying to stay within an operations budget. Luckily, the Energy Management Research Center has created a tool that can estimate the indoor air quality based on specific inputs.

Indoor air quality tool for healthy buildings

Introducing the Large Office Building Indoor Air Quality Calculator, Schneider Electric’s tool to easily estimate the trade-off between CO2, particle pollution, energy, and carbon emissions within a commercial office. A big thanks to Slipstream for allowing us to use their “Back-of-the-Envelope” calculator as the basis for the energy calculations in our air quality calculator.

The Indoor Air Quality (IAQ) calculator is meant to be used by facility managers to assist in managing building finances while addressing feedback from the building’s occupants. This calculator is broken down into two main sections: inputs and results. The input section itself is broken into two subsections: building location & attributes and scenario variables.

Building location & attributes

Location: Consisting of 10 programmed locations, like Hong Kong, New York, Singapore, etc. The idea is to choose the location that best represents the climate in your own building.

Electric Cost: Cost of electricity for your location

Natural Gas Cost: Cost of natural gas for your location

Electricity CO2 Factor: The average amount of CO2 produced per kWh of electricity generated. You can change this value based on the emissions factor in your region.

Annual Avg Outdoor PM 2.5: This is the annual average concentration of particles 2.5 micrometers in diameter or smaller. A good level is 5 μg/m3 and below and is considered unhealthy when it rises above 35.5 μg/m3.[2]

Annual Avg Outdoor PM 10: A good level is 54 and below and is considered unhealthy when it rises above 155.

Annual Avg Outdoor CO2: A normal outdoor level is 350-450 parts per million (ppm). Acceptable indoor levels are less than 600 ppm and complaints of stuffiness come at around 600-1000 ppm.

Scenario variables

Air Filtration Level: This rating describes how well the filter removes different sized particles in the air. A MERV rating of 13 or higher (MERV 13+) means that the filter gets rid of at least 90% of the particles.

Occupant Density: This is the ratio between the number of occupants in a building and the total building’s total floor area.

Ventilation: A benchmark for good ventilation is CO2 readings 1000 parts per million (ppm) and below. If the benchmark readings are above this level, reevaluate the outdoor ventilation rate.[3]

Infiltration Level: Infiltration is ingress of outdoor air into a building through openings like cracks in the building shell. Choices are “leaky”, “average”, or “tight” corresponding to 0.5, 0.3, and 0.0 air changes per hour (ACH) respectively. This is based on infiltration due to the natural pressure difference between indoor and outdoor.

Minimum Return Air: Return air is the portion of the supply that is recirculated back through the vents. Increasing the minimum return air causes the indoor air to go through the air filters more frequently and increases fan energy.

Heat Recovery Ventilation System: Energy saving system that uses a heat exchanger to pre-heat the incoming cold ventilation air when heating energy decreases.

Each one of these sections have a more in-depth explanation when you click the question mark at the top right corner.

The “Results” section makes it clear as to how the specific inputs affect the calculated result. This section is designed to show the difference in the changes that were added in the “Alternative” subsection of the “Scenario Variables” inputs. As you change different inputs, you will see the “Baseline” and the “Alternative” values compared. This is the case for the “Annual Indoor Air Quality when Occupied” section as well as the “Annual Energy & Carbon” section. When evaluating the first section of the results, you’ll see that the meter will move and the results will give you a rating of “Good”, “Moderate”, and “Unhealthy”. This will allow you to see which inputs produce the best air quality for your building.

Cost efficiency vs indoor air quality

In the “Results” section, the “Annual Energy & Carbon” subsection includes the percentage increase or decrease in energy, emissions, and energy cost. If the percentage in the “Reduction” column is 0%, no change has occurred. If the percentage is negative, as shown in the image (e.g., “Other Energy” shows -37%), the annual energy, emissions, or cost has increased as a result of changes to the “Alternative” scenario. Positive percentages indicate a decrease or savings in the annual energy, emissions, or cost. The more positive percentages you see, the better your financial and emissions situation. However, you need to balance this with CO2 and particulate levels. With that in mind, use the IAQ calculator to find the sweet spot between your financial situation and building air quality.