Health problems associated with poor indoor air quality cost businesses and building owners billions of dollars each year. At the same time, any amount of air moved or conditioned by associated equipment will necessarily reduce the energy efficiency of a building, so it’s a delicate balance that your utility’s customers need to be aware of.
The use of well-monitored and often complex ventilation systems can ease the friction between these two seemingly incompatible issues and allow catering to each set of overall variables.
Indoor air quality (IAQ) is a more significant concern to most occupants of commercial buildings than in previous decades. Honeywell conducted a recent Building Occupant Survey Report which polled 3,000 office building workers across the United States and other countries. Results of those surveyed show that:
- 82% are more concerned about IAQ because of COVID-19
- 77% agree that indoor air is less healthy to breathe than outdoor air
- 65% are ready to leave their job if their employer doesn't take steps to create a healthier indoor environment
- 55% said it's important that they be kept informed about the air quality in their building
With these concerns in mind, the balance between IAQ and energy efficiency shifts towards more airflow, and for good reason. Everything from viruses and bacteria, building materials and furnishings, cleaning agents, copy machines and pesticides need to be carefully monitored and accounted for. Any of these pollutants contribute to building-related illnesses, including Sick Building Syndrome (SBS).
Symptoms of SBS include dry mucous membranes, as well as eye, nose, and throat irritation. The World Health Organization estimates that up to 30% of new or remodeled buildings may have unusually high rates of health complaints. The National Institute for Occupational Safety and Health identifies poor ventilation as an important contributing factor in many sick building cases.
So how do we address all these concerns while still achieving good overall building efficiency (lower kWh per square foot)? The obvious answer would be to simply increase the supply of outdoor air, but depending on the temperature differential between indoor and outdoor, that air needs to be conditioned, which would result in increased energy use.
Listed below are some effective methods of minimizing that impact:
Dedicated Outdoor Air Systems (DOASs) are the most effective at just circulating air through a building and reducing concentration of contaminants. But DOASs often require conditioning of the air entering the building, so they are usually paired with other technologies to meet ventilation requirements while still achieving reasonable efficiency.
A study conducted by Energy 360 and the Northeast Energy Efficiency Alliance presented at the ACEEE Summer Study this year paired DOASs with high efficiency heat/energy recovery ventilators (HRV/ERV) and high-performance electric heat pumps that demonstrated a 69% improvement in HVAC energy usage (48% of building energy).
Heat pumps, which replace furnaces and air conditioners can deliver up to three times the amount of heat per the amount of energy consumed. They use an energy source that is much less volatile in price than comparable natural gas furnaces, usually resulting in lower overall energy prices per season in mild to moderate winter climates. High efficiency heat pumps are defined as those meeting or exceeding the Energy Star minimum rating for those systems. Pairing heat pumps with dual or multispeed motors can also reduce energy use (saving up to 85% of the energy used by a single speed motor when maximum operation is not necessary most of the time).
Variable air volume and variable refrigerant flow are also methods of conditioning outdoor air in a more efficient manner. Variable air volume systems work by varying a building’s airflow at a constant temperature, compared to a continuous air volume (CAV) system that delivers constant air flow at variable temperatures. Variable refrigerant flow systems improve on both by zoning sections of a building (such as sun on one side, not on the other) so that variable levels of refrigerant are used in each zone, and since they are paired with variable speed drives, they are customizable to each zone, and when paired with a heat recovery system, can allow both heating and cooling simultaneously in different parts of the system.
Another option is to install a system that transfers the energy from the exhaust air to the incoming air without allowing the two streams to touch in an energy recovery ventilator.
Some other methods of balancing good IAQ with energy efficiency include the following:
Air Supply and return air vents should be located a reasonable distance away from each other to allow for balanced air distribution, as well as locating all outdoor air supply vents away from sources of pollution, such as exhaust vents, heavy traffic areas and trash dumpsters.
Air filtration is also an option where ideal airflow is not possible. Charged plasma ionizers induce particulates to coagulate or stick together, making them bigger and easier for your filter to catch. Upper-Room Ultraviolet Germicidal Irradiation (UVGI) light sources can help eliminate many types of fungi, bacteria, germs, viruses and pathogens. Filters of many different materials can also be utilized, but maintenance is an important component of their installation. There are two types of filter ratings, MERV and HEPA; look for MERV ratings equal to or greater than 13 to filter COVID viruses, whereas HEPA is equal to MERV 17 or higher.
It’s also critical that the building be commissioned properly to make sure things like controls and monitors are properly configured for operation based upon occupancy levels or building hours. Carbon dioxide sensors are also invaluable in helping determine startup and ongoing demand-controlled ventilation and air quality affecting occupants.
Building energy codes, such as the International Energy Conservation Code and ASHRAE 90.1, require a commissioning plan for most large HVAC systems. Commissioning is mandatory for some green building certifications. An excellent tool is the ASHRAE Commissioning Essentials for more information and resources that provide details on the commissioning process.
If you design and operate your system with the recommendations above, you should be able to strike a nice balance between IAQ and energy efficiency.