Per Standard 62.2, the required modification to the ventilation air requirement.

Just over six years ago, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) published Standard 62.2, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings. The standard defines the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope in order to provide acceptable IAQ in low-rise residential buildings.

The standard applies to spaces that are intended for human occupancy within new and existing single-family houses and multifamily structures of three stories or fewer, including manufactured and modular houses. According to ASHRAE, the standard helps ensure air inside homes is clean and safe by limiting sources of pollutants and requiring enough mechanical ventilation (45 to 75 cfm for an average-size house) to provide dilution for unavoidable contaminants.

While initially considered somewhat controversial, Standard 62.2 is now widely accepted and used by numerous green building programs and state and local entities around the country. Indeed, the Centers for Disease Control (CDC) and the U.S. Dept. of Housing and Urban Development (HUD) recently recommended Standard 62.2 as an effective way to reduce indoor air pollution through ventilation.

The widespread acceptance of Standard 62.2 throughout the industry means that all HVAC contractors need to become familiar with its guidelines. That is especially the case for those looking to tap into the lucrative green market, as most building programs touting energy efficiency require mechanical ventilation based on the standard.


Some industry experts have noted that Standard 62.2 is the most important standard that contractors know the least about, and to some degree, Steven Emmerich, chairman, ASHRAE SSPC 62.2, agrees with that statement. “That was certainly true up until recently, but I think that is changing now. The standard is being more widely applied, and some people have to deal with it whether they want to or not. Other people want to learn about it, so they’re taking advantage of the materials and classes we offer to find out how to apply it. We probably have a ways to go in getting everyone familiar with 62.2, but we are getting the word out.”

Even if contractors do not work with any green building programs, they should take the steps necessary to learn about Standard 62.2 in order to provide the best possible service for their customers, said Emmerich. “It is incumbent upon contractors to provide their customers with the mechanical systems needed for the best available protection for their comfort and health. Standard 62.2 is the best standard we have - the only national standard we have - on how to do that.”

Per Standard 62.2, typical composite curves of various MERV levels.

In order to make Standard 62.2 as easy to use as possible, ASHRAE published a user’s manual that explains how to comply with all the requirements of the standard. It also provides examples illustrating specific methods of complying with sections of the standard and includes background material explaining why many of the requirements of the standard exist.

Emmerich noted that even though the current user’s manual is based on the 2004 version of the standard - the current version of the standard came out in 2007 - all the important information is included. “The user’s manual was designed to be easy to use by contractors. We wanted to make it a very useful tool. If contractors would like to see something different, we would definitely like to hear about that,” he said. A new user’s manual, which will be created based on the 2010 version of the standard, is currently in the works.

When Standard 62.2 was first published, ASHRAE came up with a list of ways homeowners could ensure they had proper IAQ in their houses.


Since its original publication in December 2003, many changes have been made to the standard but none of them alter its basic principles, said Emmerich. The standard still requires whole-building ventilation, local exhaust (e.g., fans in kitchens and bathrooms), limited source control, and quiet, effective air-moving equipment.

“For the most part, we are just trying to clarify some of the information. As more people have applied the standard and more bodies have adopted it, questions have been raised in terms of making things clearer, so we’re trying to make it easier for people to apply the standard. For example, the original standard did not make it clear as to which systems required airflow measurements in order to verify the standard was met. We added an addendum to clarify that because we want to make sure the whole-house system actually provides the airflow required by its design.”

The overall amount of ventilation that is required by the standard has not changed since it was first published; however, a table has been added that clarifies the ventilation rates based on whether an intermittent or continuous system is being utilized. There have also been a few changes made in terms of limiting duct leakage when ducts are located in garages.

One of the more significant changes made recently involves how the standard should be applied to existing buildings. “When we first wrote the standard, we were thinking more in terms of new construction,” said Emmerich.

“Obviously, some things that are easy for a contractor to do in a new building are a lot harder to do in a renovation. For example, it might be difficult to run ducts to a certain place, or a house might have an existing fan that meets the airflow required but is not one of the quiet fans needed to meet 62.2. Does it make sense to replace that fan with a quiet one just for that reason? Maybe not. So we created a new appendix to make it easier to use 62.2 in existing structures.”

ASHRAE SSPC 62.2 is currently considering a laundry list of minor changes that have been proposed for the 2010 version of the standard. Also being considered for future inclusion are several significant changes, including a requirement for CO alarms. This requirement was considered for the original version of the standard but was removed before final publication, due to concerns by some that this standard is not the place for such a requirement. The committee already approved a proposed change adding CO alarms to the standard, and the proposal went through the public review process. The committee is considering the comments received prior to deciding on a final action.

Another addendum that has been proposed will consider treating ventilation systems differently based on details of the system design. “Right now it doesn’t matter if you have an exhaust system or a supply system, a single point or a multipoint, we treat them all the same, and they all have to provide the same airflow,” said Emmerich.

“We have proposed an addendum that would give ventilation credits for different types of systems because they physically act differently. Exhaust systems and supply systems are not equal, so we are trying to come up with a system of credits that is fair based on physics, yet keep it simple so that people can apply it.”

That last point is the biggest concern because if the standard becomes too complex, there will be resistance in the marketplace from code bodies, builders, and contractors. ASHRAE SSPC 62.2 strives to keep it simple, as Emmerich said, in order to make the standard more appealing and easier to use for everyone involved in the industry.

To view ASHRAE Standard 62.2, visit

Publication date:03/22/2010