It has been more than 10 years since ASHRAE introduced Standard 62.2, “Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings,” which was developed in response to concerns about increasing levels of indoor contaminants and mold growth in residential buildings. The standard, which may be applied to new or existing homes, defines the minimum requirements for mechanical and natural ventilation systems and the building envelope so as to provide acceptable IAQ in low-rise residential buildings.
As a continuous maintenance standard, a new version is published every three years, with the latest version being released in March 2013. Some in the HVAC industry may be surprised to see that this version contains some significant changes, including a major difference in the way outside air is calculated. While contractors may not yet feel the effects of these changes, they will in the future, which is why they should familiarize themselves with the new version of Standard 62.2.
Changes in Store
The committee tasked with revising the standard, ASHRAE Standing Standard Project Committee (SSPC) 62.2, consists of approximately 20 people whose backgrounds range from research to engineering to manufacturing. The chairman of the committee, Paul Francisco, a research engineer and coordinator of the Indoor Climate Research & Training program at the Illinois Sustainable Technology Center at the University of Illinois at Urbana-Champaign, noted there were a number of major changes made to the 2013 version of the standard, but two are particularly significant.
The first change impacts how natural infiltration is calculated and accounted for. In the 2010 version of the standard, every house was assumed to have at least 2 cfm of natural infiltration per 100 square feet of floor area, Francisco explained. If an airtightness measurement was performed, it was possible to get half credit for estimated infiltration above that default level.
The new version takes into account more weather data, including the impact of wind, which resulted in lower calculated infiltration rates. “However, because the wind assumptions were more conservative, the committee felt comfortable giving full credit for infiltration above the default level rather than the half credit that had been provided previously,” he said.
The second change involves the removal of the default infiltration of 2 cfm per 100 square feet, which has been in the standard since its inception. “Newer homes are often much tighter, and the committee felt that assuming every home had that much infiltration, at a minimum, was no longer valid,” said Francisco. “Therefore, the decision was made to remove the default credit and require that any credit for infiltration be based on measured home airtightness.”
Paul H. Raymer, chief investigator, Heyoka Solutions LLC, Falmouth, Massachusetts, and a member of the SSPC 62.2 committee, added that by applying the infiltration credit calculation, the whole-building ventilation rate (which is calculated using the area of the building and the number of people in the house, represented by the number of bedrooms) can be adjusted to match the actual performance of a specific house in a specific location. “Ventilation for the number of occupants did not change in this version, but the ventilation based on the area of the building did change from 1 cfm per 100 square feet to 3 cfm per 100 square feet.” So, in the new version, mechanical ventilation rates are increased to 7.5 cfm per person plus 3 cfm per 100 square feet.
Another significant change made to the standard is the requirement that a carbon monoxide (CO) alarm be installed in every home — not just those with combustion appliances or attached garages. The rationale for this, explained Francisco, is that the most rapidly increasing cause of CO poisoning is the indoor use of combustion equipment that was not meant for indoor use, such as generators, power tools, and heaters.
The new version of the standard also includes the removal of climate-based restrictions, so, essentially, supply fans can now be used in cold climates, and exhaust whole-building ventilation can be used in hot humid climates. As Francisco noted, it was discovered that problems such as mold in humid climates and dryness in cold climates were caused by other factors (e.g., vinyl wallpaper, leaky buildings) rather than the type of ventilation system installed.
Lastly, a new section on multifamily buildings was added, clarifying that the ventilation rate for each individual dwelling unit must be calculated as if that unit was a single-family home, except there is no allowance for an infiltration credit since unit air leakage could be due to adjacent units, said Francisco.
The new version of Standard 62.2 hasn’t yet affected Sonoran Air in Phoenix, which specializes in the installation of HVAC systems in new construction and custom homes in the Southwest, said Greg Cobb, president and CEO. “The majority of our installs are part of the Energy Star program, which still follows the 2010 version of Standard 62.2. Non-Energy-Star installs fall to code levels of ventilation, which are similar to the 2010 version of 62.2 as well.”
Cobb has some issues with the new version of 62.2, noting the standard has become increasingly complex, but still does not address key issues. “Fresh-air ventilation rates are a semi-educated guess at best because homeowner lifestyles and occupant densities vary significantly. Opinions on the proper levels of fresh air vary widely as well. While I understand the reasoning for the change — because homes today no longer have the same infiltration levels that were assumed acceptable a few years ago — it is extra complexity that is not helpful.”
As a result of this complexity, Cobb believes many installers will not take the time to measure and calculate the infiltration offset specified in the new version of the standard. He assumes they will just use the basic formula, which will lead to over-ventilation. “Over-ventilation will lead to more noise and higher utility bills, which will cause many homeowners to simply disable their ventilation systems out of frustration, leading to poor IAQ.”
Francisco noted he has received similar feedback from contractors who are concerned the procedure for calculating infiltration is more complicated; however, he does not believe this to be the case. “In previous versions, the calculation procedures were not included in the standard, but rather referred to in other documents. Now, instead of having to go to three other documents, all of the calculations are in 62.2. It looks messier, but there are tools available that cut through the complicated math.”
The biggest concern Francisco has heard from contractors involves the removal of the default infiltration credit. “A lot of people are concerned the change is causing required ventilation rates to skyrocket. I agree, this is the case if an estimate of infiltration is not made, but if people do blower door tests, the impact is not going to be that big for many homes. However, I understand people don’t want to do blower door tests, and they also don’t want to put in more mechanical ventilation. This change means people don’t get both.”
Raymer also acknowledges there have been concerns about the change in airflow rates in the new version of the standard, but he maintains the issue is more fundamental. “Until recently, mechanical ventilation issues have been generally ignored, but it’s pretty simple, acknowledged Raymer. “Homes are being made tighter to save energy and reduce the impact on the environment; people still need air to breathe; tighter homes trap pollutants, which need to be removed or diluted; and mechanical ventilation is an element of that removal and dilution process.
“Contractors need to recognize that mechanical ventilation is a critical component to keeping people healthy in tight homes. Once they accept the fact that mechanical ventilation is necessary, they will find the new version of the standard to be a great resource generated by a group of very dedicated people who are experts in residential ventilation.”
Still, there is no question that transitioning to the 2013 version of Standard 62.2 will require a change in business practices, said Cobb. “In the markets we serve, most homes are tested by energy inspectors after HVAC startup and commissioning of the ventilation system. Thus, the blower door test to measure infiltration is not known at the time the ventilation controller is programmed. With the new version of 62.2, either the HVAC contractor will be responsible for measuring infiltration rates at startup, or else the energy inspector will be responsible for programming the ventilation controller.”
Cobb believes there are better ways to achieve reasonable IAQ rather than having the standard mandate that outside air be introduced at a set rate, whether or not it is needed. He would rather see the committee set IAQ targets and allow for intelligent controls and sensors to determine when and how much outdoor air is needed. “This would simplify the task for contractors and encourage homeowners to actually use ventilation systems that are installed and not just view them as wasting energy and money.”
SIDEBAR: More Changes Coming
ASHRAE recently proposed another change to Standard 62.2: Dwelling units of multifamily buildings of any height would fall under Standard 62.2, rather than Standard 62.1-2013, “Ventilation for Acceptable Indoor Air Quality,” which currently has responsibility for multifamily residential buildings that are four-stories tall or taller.
According to Paul Francisco, chair of the Standard 62.2 committee: “This will provide consistency of ventilation requirements for dwelling units regardless of building height. For new construction, this will result in a change of requirements for dwelling units in four-plus-story buildings. For the retrofit market, this change will result in coverage by ASHRAE ventilation standards for the first time in four-plus-story buildings.”
Other changes to Standard 62.2 are currently underway, as well, including one that has already been approved but has not yet been published. “This would bring unvented combustion into the scope of the standard, and users should expect to see something about that in the 2016 edition,” said Francisco.
There is also an interest in focusing on specific contaminants because particles — particularly in kitchens — have been identified as a major health risk, said Francisco. “We also would like to provide more explicit guidance in the standard on options that may reduce costs without impacting health. For example, maybe lowering ventilation rates when outdoor temperatures are more extreme, and natural infiltration is higher, with rates being increased when it is mild outside to compensate. This would better account for infiltration rates and increase ventilation when conditioning costs are low.”
Francisco expects other issues will be considered as well, such as differences due to ventilation system type, filtration, etc. “We also would like to simplify the flow of the standard to make it more user-friendly. When changes are made on a consistent basis, it is bound to get messy, and it can be helpful to reorganize the flow, even if no changes to substance are made. This also would have the potential to address some of the concerns that are raised by users.”
Publication date: 8/4/2014