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Ventilation & Indoor Air Quality
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Navigating Code and Compliance Pertaining to ERVs

  • Research & Reports

Author: Ken Nelson, Panasonic Eco Systems

Ken Nelson, Panasonic’s veteran indoor air quality expert, recently joined a Technical Advisory Group for Washington State Residential Building Codes, tackling upcoming code changes for whole-house ventilation. This article takes a deeper dive into that important discussion.

Understanding IRC and IECC Definitions, and Relevance to Energy Recovery Ventilators

Recently, I participated in a Technical Advisory Group discussion for the International Mechanical Code Committee for the State of Washington, reviewing upcoming code changes for the Washington State Residential Building Codes.  

Our conversation turned to what was required in whole-house ventilation and how it would best align with minimizing building costs and maximizing occupant health and welfare.  Specifically, when not using a ducted furnace system, a strategy that has become more popular with the improvements in Ductless Heat Pumps.   

It’s well documented that continuous, balanced ventilation is, by far, the best way to ensure proper ventilation throughout the home.  Balanced ventilation means we mechanically drive fresh air into the house and simultaneously pull old air from the house - thus using Energy Recovery Ventilators (ERVs). This way, there is very little chance of excessive particulate or chemistry saturation of the air in the home. 

From a design standpoint, this can lead to some challenges.  The “return air” is usually drawn from a single or dual location within the envelope.  All rooms within a house, by their very nature, are connected and have what is called in the air flow world, “communication.”  This means that if the room is accessible by a door from inside the house, the air in that space can move from one room to the next.   

               

IRC Definitions

  1. Habitable Space (IRC Definition) 
    According to the IRC, Habitable Space refers to areas within a building intended for living, sleeping, eating, or cooking. It excludes bathrooms, closets, halls, storage spaces, and utility rooms. 
  1. Occupied Space (IRC Definition) 
    Although not as clearly defined in the IRC as Habitable Space, Occupied Space generally refers to areas where people may be present during a building's use. This broader term may include spaces like bathrooms and mechanical or utility rooms that do not meet the criteria for habitable space but are still frequented by occupants. 

IECC Implications on Habitable and Occupied Spaces 

The IECC focuses on the energy efficiency of buildings, influencing how ventilation and HVAC systems are designed: 

  • Habitable Space: Ensures proper energy-efficient ventilation. Compliance with IECC standards means adequate heating, cooling, and airflow without excessive energy loss. 
  • Occupied Space: This impacts energy recovery systems, which maintain air quality while conserving energy, especially in semi-habitable or transitional zones. 

The difference between the two is that the IRC determines the “where” (which rooms), and the IECC determines the “how” (energy management).   

Supply Air Inlet Location Considerations

Of course, the proper placement of ERV supply air inlets is critical to maintaining both code compliance and indoor air quality, and the IRC states explicitly: 

“Inlets should be strategically positioned to deliver fresh air directly to habitable spaces, enhancing occupant comfort and air quality.” 

However, many code jurisdictions call for fresh air in “occupied spaces.” The confusion is that a ducted furnace would be required to provide heated airflow into a closet, mechanical, or utility room. However, this action, whether from an ERV or furnace, is contrary to good air quality. 

Why would we want contaminated kitchen air to go anywhere other than through the “code-required” kitchen ventilation system?  The same goes for bathroom air.  Bathrooms are required to have an intermittently operated exhaust fan.  Bathroom air should pull from within the house and be exhausted without obstruction.   

ERVs are designed, installed, and operated to provide and enhance indoor air quality.  They filter, temper, and deliver fresh air to where the occupants spend time.  Ducting to utility, mechanical, and mud rooms adds cost to the home.   

Generally, when discussing the placement of supply air ducting with architects and builders, I speak to fresh air being delivered anywhere the occupants are inclined to take a nap—living rooms, media rooms, and certainly bedrooms.  Let those be the priority and allow the other spaces to communicate through a transfer grill or jumper duct. 

 

Ken Nelson is a longtime building industry veteran and ventilation expert, frequent speaker on building sciences, in addition to a BPI Certified Building Analyst and Group Sales Manager with Panasonic Eco Systems. 

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