Energy Codes and Indoor Air Quality — Idaho Energy Code

Energy codes are linked to indoor air quality

The current Idaho Energy Conservation Code affects the indoor air quality of homes and buildings by managing heat, air, and moisture transfer through the walls, roof, and floor (the “envelope”) using air sealing, proper insulation, and better windows to control condensation and reduce potential pollutants from entering an indoor space. 

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Ventilation

Ventilation, or fresh air flow, is especially important for improved indoor air quality.

  • Natural ventilation is the movement of air through open windows or other planned and controllable openings to the outside of the building. 

  • Controlled ventilation occurs when the amount of fresh air brought in and out of the building is managed. This is achieved by sealing leakage areas in the envelope so that controlled openings, such as windows and mechanical equipment, provide the majority of ventilated air to building occupants.  Air intakes on furnaces and energy recovery ventilators (ERVs) or heat recovery ventilators (HRVs) are a few options that provide additional filtration to remove contaminants from incoming ventilation air.

 
Air Intakes

A return air system such as an air intake on a furnace is linked to outside air that is introduced at specific quantities by a motorized damped programmed to maintain optimum air quality.

 
ERVs and HRVs

ERVs and HRVs draw clean, fresh air into a home and remove stale air. According to Architect Magazine, “ERVs are designed to provide energy savings in mechanical ventilation systems. They recycle energy from the building's exhaust air to pretreat the outside air/ventilation air.” According to ASHRAE, ERVs can reduce equipment capacity and improve indoor air quality, thereby reducing energy consumption.

  • Uncontrollable ventilation happens through envelope air leakage. The Idaho Energy Conservation Code requires air sealing penetrations in the envelope such as gaps around can lights, plumbing, or electrical outlets as well as around windows and doors.  Sealing is typically done with caulk or foam.  Click here for more detail on air sealing.

The use of exhaust fans without properly managed ventilation is a health concern in Idaho. Click to learn how.

When a bathroom exhaust fan is turned on*, the house must recover the exhausted air. If there are leaks between the floor and crawlspace, the air from the crawlspace can be sucked into the home. In Idaho, radon (a colorless, odorless, and invisible gas that comes from soil) is a common risk and there is potential for air from the crawlspace to contain radon. Long-term exposure to high radon levels can increase the risk of developing lung cancer. There are many areas throughout Idaho that have high levels of radon; about 2 out of 5 homes that have been tested in the state have high risk levels above 4.0 pCi/L. For more information on radon and how to get a free test kit, go to http://healthandwelfare.idaho.gov/health-wellness/environmental-health/radon.

Another health risk can occur when the outside air is heavy with smoke from wildfires in the heat of the summer. Click to learn how.

If you turn on the exhaust fan over your stove*, the house could draw makeup air through leaks in the window frames or plumbing penetrations if not properly sealed, which can draw smoke into the home even though all the doors and windows are closed. *Anytime there is negative pressure in a building, air and potential pollutants can be drawn in through leaks -- not just when exhaust fans are used. It is important to recognize the value of exhaust fans in removing excess moisture, which reduces the risk of mold. It is recommended to use exhaust fans every time a shower is on or water is boiling on the stove.

To measure air flow, consider testing the air changes per hour (ACH) that occur in your home or commercial building. The current Idaho Energy Conservation Code for residences mandates that if a blower door test shows less than 5 ACH (at 50 pascals), mechanical ventilation is required to bring fresh air into the home.  Learn more about how to evaluate a home for energy efficiency and blower door testing.

Filtration

Another factor to consider is filtration, which is the level at which a filter removes particles and pathogens from the ventilation air stream.  Many existing furnaces or other air handling units can accommodate a MERV (Minimum Efficiency Reporting Value) 8 or possibly a MERV 10 level of filter.  Replacing these filters with a higher efficiency MERV 13 or HEPA (high-efficiency particulate air) filter will most likely require a heating and cooling professional to evaluate the equipment to see if it can push air through that high of a filter rating. Be cautious -- using too high of a filter rating can damage equipment.  If you want to use a HEPA filter, consider a stand-alone air purifying unit.

Additional Factors

There are additional factors to consider that affect indoor air quality such as not smoking indoors and selecting low-emitting materials, although these are not directly related to energy codes.  Some building materials emit Volatile Organic Compounds (VOCs) that can be harmful.  For new homes, there is a national certification program called EPA ENERGY STAR Indoor airPlus, which provides a checklist of measures for improving the quality of indoor air.

For all homes, ASHRAE published a Residential Indoor Air Quality Guide on Best Practices for Home Design, Construction, Operation, and Maintenance, which is a comprehensive resource on this topic. 

Strategies to Control Pathogens

Recognizing the link between building codes and healthy indoor air quality is particularly relevant now due to the widespread novel coronavirus.  According to Dr. Kevin Van Den Wymelenberg, Director of the Institute for Health in the Built Environment at the University of Oregon, viruses can last in indoor environments for up to 11-14 days.  Dr. Van Den Wymelenberg has conducted extensive research on the best ways to control pathogens from spreading indoors and created a webinar to share the most effective strategies -- from common measures such as filters to cutting-edge ultraviolet technologies.  The focus is on commercial buildings but some of the strategies could apply to homes. Click on the following five strategies to control pathogens from spreading indoors, as highlighted in the webinar:

1. Masks

Wearing a mask indoors can help reduce the spread of pathogens such as COVID-19.

2. The percent of outside air (OSA) circulating – “the solution to pollution is dilution”

Outside air percentage is the amount of fresh air from the outdoors that is being drawn into your home or building. The Idaho Building Code for commercial buildings requires compliance with ASHRAE 62.1, which outlines minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimize adverse health effects. In addition, other states have started to put very high efficiency (VHE) dedicated outside air systems (DOAS) into code. DOAS separate heating and cooling from the ventilation system to allow for optimal control of each of these critical building functions. Building on the DOAS concept, a “very high efficiency” DOAS includes heat recovery ventilation and focuses on increased equipment efficiency and optimized system design. When compared to a code-minimum system upgrade, VHE DOAS can reduce commercial building energy use by an average of 36% and HVAC energy use by an average of 65%.

3. The air changes per hour (ACH)

ACH is the amount of air changes per hour that occur in your home or building. Energy codes require air sealing of the exterior walls, floor, and ceiling that results in controlled ventilation. Controlling ventilation helps control the flow of pathogens like COVID-19.

4. The level of filtration

Filtration is the level a filter blocks particles and pathogens.

5. Disinfection

Disinfection is the use of cleaners and other solutions such as ultraviolet (UV) light to help reduce the spread of pathogens such as COVID-19; however, the more times you use disinfectants the more resistance can build up.

View Dr. Van Den Wymelenberg’s webinar and bio.

The EPA is another resource for more information on coronavirus and indoor air.

To read more technical detail on the topic of indoor air for commercial buildings, ASHRAE published a paper in April 2020 called ASHRAE Position Document on Infectious Aerosols. A primary message from this paper is that “ventilation, filtration, and air distribution systems and disinfection technologies have the potential to limit airborne pathogen transmission through the air and thus break the chain of infection.”  This paper also explains the science behind the common recommendation of “6 feet” for social distancing.  Learn more by clicking on these two excerpts:

Key Recommendations +

“This position document provides recommendations on the following:

  • The design, installation, and operation of heating, ventilating, and air-conditioning (HVAC)
  • Systems, including air-cleaning, and local exhaust ventilation (LEV) systems, to decrease the risk of infection transmission.
  • Non-HVAC control strategies to decrease disease risk.
  • Strategies to support facilities management for both everyday operation and emergencies.

Infectious diseases can be controlled by interrupting the transmission routes used by a pathogen.”

Building Science and the Role of HVAC Professionals +

“HVAC professionals play an important role in protecting building occupants by interrupting the indoor dissemination of infectious aerosols with HVAC and LEV systems. Building science professionals must recognize the importance of facility operations and ventilation systems in interrupting disease transmission. Non-HVAC measures for breaking the chain of infection, such as effective surface cleaning, contact and isolation precautions mandated by employee and student policies, and vaccination regimens, are effective strategies that are beyond the scope of this document. Dilution and extraction ventilation, pressurization, airflow distribution and optimization, mechanical filtration, ultraviolet germicidal irradiation (UVGI), and humidity control are effective strategies for reducing the risk of dissemination of infectious aerosols in buildings and transportation environments.”

Economizers are a part of the Idaho Energy Conservation Code for certain types of commercial HVAC systems and allow the introduction of increased outdoor air into the building when the temperature and humidity conditions are favorable to do so. Buildings with economizers allow for more flexibility in how much outdoor air they are bringing in and might be able to meet some of the ASHRAE recommendations more easily than buildings without economizers.

Indoor air quality has always been an important consideration in buildings but is even more at the forefront during times like the current health crisis.  Following the Idaho Energy Conservation Code provisions for air sealing, proper insulation, and better windows is one way to protect against condensation and potential pollutants that can be drawn into the home.  Energy codes help manage conditions that can affect building integrity and occupant health such as moisture, temperature, and indoor air quality.