Illinois Sustainable Technology Center, University of Illinois at Urbana-Champaign

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1 Topic B14: Policy, standards, and regulations ASHRAE STANDARD 62.2: WHAT S NEW AND WHY Paul W FRANCISCO,* Illinois Sustainable Technology Center, University of Illinois at Urbana-Champaign *Corresponding pwf@illinois.edu Keywords: Ventilation, Standards, Residential SUMMARY ASHRAE Standard , Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings, incorporates 17 new addenda compared to the 2010 edition. About half of these are major changes to the requirements of the standard. Most of the changes were adopted to better ensure that the intent of the standard would be met in all residential buildings covered by this standard. These changes covered a range of issues, including the elimination of an assumed minimum amount of natural infiltration, how the effectiveness of intermittent ventilation is calculated, the basis on which alternate ventilation options shall be deemed equivalent to the prescriptive requirements, and a major new section on multifamily buildings. Other major changes included increasing flexibility of ventilation options through the removal of climate-specific restrictions and protecting residents from life-threatening carbon monoxide. This paper explores these changes with background on why they were adopted and implications for users. INTRODUCTION ASHRAE Standard 62.2 is the consensus standard for ventilation and acceptable indoor air quality in residential buildings. This standard adheres to American National Standards Institute (ANSI) requirements regarding consensus and committee balance, meaning that there must be members from each of several stakeholder categories and that super-majorities are required to pass any changes. Standard 62.2 is referenced by a number of residential programs in the United States, both for new construction and for the retrofit market. This standard, which is under continuous maintenance, recently came out with its 2013 edition (ASHRAE, 2013a). This edition includes 17 changes from the 2010 edition. While some of these changes are relatively minor, many of them are significant. This paper reviews the more major changes in this latest edition. The review includes a discussion of what each change was, the author s view of the rationale behind the change, and a discussion of the implications. The most significant changes to Standard 62.2 since the 2010 edition relate to the treatment of natural infiltration, which is ventilation through leaks in the building envelope that results from natural environmental conditions. Additional major changes include calculations for flow rates of fans that run intermittently, climate restrictions, the requirement for carbon monoxide alarms, equivalent ventilation, and multifamily buildings. RESULTS AND DISCUSSION

2 Treatment of Natural Infiltration There were two changes to ASHRAE Standard 62.2 which greatly impacted how natural infiltration was treated. These were designated addendum n and addendum r. Historically, 62.2 assumed that homes had at least 2 cubic feet per minute (cfm) of natural infiltration for every 100 square feet of floor area (10 L/s per 100 m 2 ). If a leakage test was done on the home with a blower door and the estimated infiltration from this test (including adjustments for climate) was greater than the assumed level, a credit toward the fan flow could be taken equal to half of the excess. If the blower door test estimated lower infiltration than assumed, however, no increase to the fan flow rate was required. This can be represented by the following equation (based on I-P units): Q fan = 0.01 A NP 1 2 (Q inf 0.02 A) (1) where Q fan is the required fan flow rate, A is the floor area, NP is the number of people, and Q inf is the estimated natural infiltration rate. Addendum n had three significant impacts. The first was to bring the entire calculation procedure for natural infiltration into 62.2 rather than referencing multiple other standards. While this did not by itself change the requirements it did make users of the standard more aware of the assumptions in the calculation. The second significant impact of addendum n was to recalculate the weather factors used to estimate the natural infiltration based on climate. This was prompted by the expansion of the number of weather stations for which factors could be calculated, from under 300 to over Previously, these weather factors had been calculated using moderate wind shielding and terrain factors. The prior use of moderate factors had been a major justification for allowing only half credit of excess infiltration to be taken, since many homes would have greater protection from wind. In the new calculation much more sheltering from wind was assumed. This resulted in lower weather factors. However, it also provided justification for allowing full credit to be taken for natural infiltration. For many homes that received leakage tests there has been little change to the final required mechanical flow rate. The third significant impact of addendum n was to split the fan flow calculation into two paths: the first path used the default infiltration and did not allow an additional infiltration credit, and the second path assumed no default infiltration but allowed for the full estimated infiltration credit. These two paths can be represented as: Option 1: Q fan = 0.01 A NP (2) Option 2: Q fan = 0.03 A NP Q inf (3) These equations show that in option 2 the coefficient for area has been increased by the default infiltration. However, the default natural infiltration became a concern because many homes are now being built tighter than this assumed rate, suggesting underventilated homes. This fact also helped to stymie efforts to provide credits for systems that were designed to provide

3 distributed ventilation rather than ventilation at a single point, in part because there were concerns about giving tight homes that were already underventilated even less ventilation air. These concerns prompted addendum r. Addendum r removed Option 1 from the parallel paths provided by addendum n. The result is that there is no longer any default infiltration in For homes that do not get a leakage test this means that the entire target flow rate must be delivered by mechanical means. This has a bigger impact on new construction, which often has not gotten leakage tests, than on existing buildings undergoing retrofits which typically do get tested for leakage. Intermittently Operating Fans ASHRAE Standard 62.2 has always allowed for intermittently operating fans. These are fans which are scheduled to come on periodically without occupant intervention, but do not run continuously. Fans that come on only with an occupant-controlled switch do not count as intermittently operating fans. Two changes of significance were made related to intermittently operating fans. One of these, addendum u, explicitly made it clear that if the ventilation system ran at least once every three hours the flow rate required when the fan was on was simply the flow required to make the average flow (including off times) equal to the continuous flow rate required by the standard. In other words, if the fan was on for half the time, it had to have twice the flow rate as the continuous requirement, and if it ran one-third of the time it had to have three times the flow rate as the continuous requirement. The other change, in addendum i, modified how the ventilation effectiveness was calculated. The ventilation effectiveness accounts for buildup of contaminants during the time when the fan is off. Modeling studies found that, with cycle times of three hours or less, this buildup was not sufficient to warrant any further flow rate increases. However, for cycle times over three hours it was necessary to increase flow rates beyond the simple calculation described in addendum u. Prior to addendum i, the ventilation effectiveness was calculated based on cycle time and fractional runtime of the fan within each cycle. In addendum i an additional term, turnover, was brought into the calculation of ventilation effectiveness. The motivation for this change was to make the intermittent calculation consistent with the default infiltration assumptions of the standard. An additional motivation was to update the calculation to account for improved understanding of how intermittent operation interacted with contaminant emission rates. This resulted in the inclusion of the turnover term. Turnover is calculated as a function of the required continuous flow rate, the cycle time of the intermittent ventilation fan, and the floor area of the home. Addendum i replaced cycle time with turnover in the format of the table used to find ventilation effectiveness. Unfortunately, the determination of the values in addendum i is dependent on the assumed infiltration rate, and the addendum was approved prior to the approval of addendum r. Therefore the values in addendum i are based on 2 cfm of natural infiltration per 100 ft 2 of floor area. While this decision brought the intermittent ventilation calculation into consistency with the standard at the time, the values are again inconsistent with the default infiltration assumptions of the standard.

4 The primary implication of the changes regarding intermittent ventilation is that the actual fan flow rates will be different than they had been with previous versions of the intermittent ventilation effectiveness calculation. In general, the resulting intermittent ventilation rates will be lower than previously. Climate Restrictions Addendum g removed climate-based restrictions on ventilation strategies. Prior to this addendum there were limits to the amount of net exhaust that was allowed in hot humid climates and to the amount of net supply that was allowed in cold climates. More recent field experience convinced the committee that the problems that these limitations were intended to prevent were not caused by the ventilation systems but rather by problems with the building envelope that could not be solved by these limitations. Since the limitations were neither the cause of nor a solution to the problems, these restrictions were simply deleted such that any ventilation system strategy may be implemented in any location. This does not mean, of course, that there cannot be problems in these climates but it does mean that with appropriate envelope design no systems are precluded. Carbon Monoxide Alarms There had been multiple attempts to get a carbon monoxide alarm into Standard This was successful with addendum l. There were two differences between addendum l and previous attempts. One was that a number of states had begun to require installation of these alarms in homes. The second was that addendum l required these alarms for all homes, regardless of whether there were any combustion appliances in the home or whether there was a garage attached to the home. Most requirements for carbon monoxide alarms have centered on homes with combustion appliances or attached garages. However, data were brought to the committee showing that a large source of carbon monoxide poisonings is portable combustion devices such as generators and tools. These can be found in any home, and in the case of generators may be used specifically in all-electric homes when there is a power outage. These data convinced the committee to support the requirement for carbon monoxide alarm installation in all homes. There was some disagreement surrounding whether the standard should be including life safety devices rather than focusing on more persistent indoor air quality concerns, but in the end addendum l was approved. Equivalent Ventilation Standard 62.2 has always allowed for ventilation designs that meet the intent of the standard. However, the language had previously stated that alternative options could be used if approved by a licensed design professional. There was no guidance as to what the basis for equivalence should be. The committee decided that this provided too little information to be useful and could lead to alternative options that did not follow the intent of the standard. Therefore, addendum m was developed, which specified the basis on which equivalence should be determined. The core of this basis was annual dose, such that any alternative option must keep the annual dose of a contaminant to which an occupant was exposed no higher than that which would occur using

5 the continuous fan flow rate specified by the standard. Addendum m also requires that supporting documentation of this equivalence be provided. This addendum allows for innovation or the use of other solutions such as designed passive ventilation, while ensuring that such options provide the same or better protection for occupants as with the prescriptive ventilation options specified in the standard. Multifamily Buildings Multifamily buildings three stories and less are a part of the ASHRAE 62.2 scope. However, historically there has been little in the standard that specifically addresses multifamily buildings. There was a statement that doors between dwelling units or to common hallways should be gasketed except when the ventilation system required the use of the hallway for transfer air. There was also a statement that exhaust fans should not share a common duct and that a single exhaust fan could be used for multiple units if it ran continuously or if there were backdraft dampers for each inlet. Otherwise, no accounting for multifamily building characteristics was done in the standard. Addendum j added a new section to the standard expressly for multifamily buildings. This addendum made it clear that the ventilation requirements for dwelling units were the same as for single-family homes, and that this ventilation must be delivered to each unit, not as an average of all units. The committee was concerned about cross-contamination between units, which is perhaps the most significant difference between these low-rise multifamily buildings and single-family homes from an indoor air quality perspective. Because of this concern, coupled with the fact that a leakage test does not distinguish between leaks to outside and leaks between units, addendum j does not allow multifamily dwelling units to get an infiltration credit. Additionally, a major portion of addendum j was to put in a requirement to minimize transfer air. There is guidance regarding air sealing and gasketing, but the most significant portion of addendum j regarding transfer air was to put in a metric to demonstrate compliance, 0.2 cubic feet per minute per square foot (100 L/s per 100 m 2 ) of the dwelling unit envelope area (meaning all six sides, not just floor area). This was the first time that a quantitative target for limiting transfer air had appeared in the standard. Two other areas were included in this addendum. The first was ventilation for common areas, specifically corridors and garages. These spaces are required by addendum j to have the same ventilation as appears for larger multifamily buildings in ASHRAE Standard 62.1 (ASHRAE, 2013b). The final area of attention was ventilation system design. The previous language regarding exhaust fans was retained by addendum j, and in addition supply fans are allowed to serve multiple units as long as the fan runs continuously or there are backdraft dampers for each supply outlet to prevent cross-contamination when the fan is off. This change has major implications for multifamily buildings, since it is the first time that most of these requirements have been explicitly stated for these buildings. The restriction that natural infiltration credits cannot be used in multifamily buildings is a significant change. The target for limiting transfer air also, for the first time, provides a quantitative target rather than the unenforceable qualitative intent of sealing and gasketing.

6 CONCLUSIONS ASHRAE Standard 62.2 has a number of important changes since the 2010 edition. These changes have mostly been incorporated in an effort to ensure that all buildings covered by ASHRAE Standard 62.2 have systems that meet the minimum intent of the standard to provide acceptable indoor air quality. The elimination of the default infiltration credit means that tight homes cannot assume more leakage than they actually have, but instead all natural infiltration credits must be determined through actual leakage tests. This ensures that all homes will have at least the minimum target ventilation rate regardless of tightness. The changes to the intermittent ventilation effectiveness values account for improved understanding of the relationship between contaminant buildup and intermittent operation. The clarification on what the basis is by which equivalent ventilation options are judged (annual dose) means that this metric is the basis for all systems. The new multifamily section means that it is clearer to those who work with that sector of buildings what is needed to meet the objectives of the standard in more complex residential buildings. The two addenda discussed above that were not adopted in order to better ensure that all buildings would meet the minimum intent of the standard were those that removed climate restrictions on ventilation strategy and required carbon monoxide alarms. The former of these allows greater flexibility in the climates that previously had restrictions, and was done because it has been determined that the problems that prompted the restrictions were neither caused by nor could be solved by the ventilation strategy adopted. The latter of these was done because the majority of the committee deemed carbon monoxide alarms a reasonable protection against hazardous conditions and therefore were covered by the intent of the standard to provide acceptable indoor air quality. REFERENCES ASHRAE. 2013a. ANSI/ASHRAE Standard : Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA. ASHRAE. 2013b. ANSI/ASHRAE Standard : Ventilation for Acceptable Indoor Air Quality. American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta, GA.