Formed in 1996, the ASHRAE 62.2 committee developed and maintains a residential ventilation standard for buildings three stories and less which is titled Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings. It is reviewed and revised every three years. The first version of Standard 62.2 was published in 2003, the second in 2007, and the most current version is ANSI/ASHRAE Standard 62.2-2010. (ANSI stands for the American National Standards Institute. ANSI certification of a standard means that a specific consensus process was used to develop and maintain the standard and is required for adoption of a standard into codes.)
Is ASHRAE Standard 62.2 current best practice for ventilation? In a word, no. ASHRAE 62.2 is a standard that national experts could agree upon that sets a minimum standard for ventilation — not best practice, which would further customize ventilation rates based on factors such as number of occupants in a dwelling and strength of pollutant sources. Using air quality testing equipment in conjunction with improving ventilation procedures is highly recommended.
Meeting the ventilation requirements for ASHRAE Standard 62.2 will not always provide enough ventilation for a home. In these circumstances, ventilation rates need to be increased beyond the Standard.
DOE issued revised Health and Safety Guidance WPN 11-6 in response to concerns with clarity and consistency in how health and safety issues are approached by grantees. To draft this guidance, DOE reconvened its Health and Safety Committee to review trends and practices of the WAP network. The result was a compilation of past guidance, with minor changes and clarifications, into a comprehensive user- friendly table. However, since addressing health and safety measures is not always straight forward, as seen in several examples below, and sometimes leaves much interpretation to the grantee, DOE decided to respond to several direct questions from the Weatherization network and offer additional clarification on ASHRAE 62.2 as required by WPN 11-6 in this collection of frequently asked questions.
The answers below may vary for subgrantees due to requirements set by the grantee’s Health and Safety Plan. ASHRAE 62.2 is a minimum standard so grantees may have incorporated additional guidelines based on local conditions. Be sure to consult your DOE-approved Health and Safety Plan for specific direction that is applicable for your state, territory, or tribe. DOE will continue this dialogue and add questions and answers that come up. Grantees should contact their respective Project Officer if a question is not answered below or if additional clarification around health and safety is needed.
“Grantee” refers to the state, tribe, or territory who directly receives WAP funds.
“Program” refers to all of the activity being conducted under the grantee for the DOE WAP.
1. What ASHRAE documents will help me understand the requirements and background of residential ventilation?
The core document is ASHRAE 62.2-2010, Ventilation and Acceptable Indoor Air Quality in Low-RiseResidential Building. This is one of the ASHRAE standards that are continuously maintained, meaning they are often improved/changed. The volunteer committee members meet for two days of meetings twice each year to discuss and improve the Standard. A new version of the Standard is published every three years.
Another is the 62.2 User’s Manual for ASHRAE Standard 62.2-2010. This includes a discussion of the Standard, background material, and many good examples for proper application of the Standard.
Finally, ASHRAE Guideline 24: Ventilation and Indoor Air Quality in Low-Rise Residential Buildings. Thisdocument provides information aimed at helping to achieve good indoor air quality that may go beyond the minimum standards. ASHRAE 62.2 is limited to providing minimum requirements. All of these documents can be purchased from ASHRAE at www.ashrae.org.
2. How much ventilation is required in bathrooms?
In each bathroom, room with a shower, tub, or spa, the Standard requires at least a 50 Cubic Feet per Minute (CFM) exhaust fan that the occupant can turn on when needed, or a 20 CFM exhaust fan that operates continuously. For existing dwellings, this requirement does not have to be met if the Alternative Compliance Path is used (see question 9 below and Appendix A of ASHRAE 62.2-2010).
3. How much ventilation is required in kitchens?
For kitchens the Standard requires at least a 100 CFM exhaust fan – a range hood is best – that the occupant can turn on and off when necessary, or an exhaust fan that runs continuously and is sized to provide 5 air changes per hour (ACH) based on the kitchen volume. For existing dwellings, this requirement does not have to be met if the Alternative Compliance Path is used (see question 9 below and Appendix A of ASHRAE 62.2-2010).
4. Somebody told me a bathroom or kitchen fan can also serve as the whole-building fan. Is this correct?
Yes, this is correct. The Standard allows a local bathroom or kitchen exhaust fan to also serve as the whole-building ventilation fan, as long as the fan satisfies the minimum requirements for both the local and whole-building ventilation. Using a bathroom as an example, the fan operates continuously at the required minimum whole-building ventilation rate. When the occupant uses the bathroom, they activate the local ventilation which increases the CFM flow of the fan enough to satisfy the requirement for local bathroom ventilation (50 CFM). Alternatively, as long as this continuous CFM flow rate of the whole-building ventilation is at least 20 CFM, it will also satisfy the local ventilation requirement without a boost to 50 CFM when the occupant enters the bathroom.
Note 1: the local ventilation requirement in the Standard is 50 CFM if the fan is operated when needed, or 20 CFM if the fan is operated continuously.
Note 2: For a fan that operates when needed, Standard 62.2 requires the fan be no louder than 3 sones. However, if this fan is also to be used for whole-building ventilation, it must be no louder than 1 sone in order to meet the whole-building fan minimum requirements. Existing fans that are being left in place are exempt from these sound requirements.
5. When must I comply with ASHRAE 62.2?
The Department of Energy is requiring that low-income weatherization programs implement the Standard in weatherized dwellings during the 2012 Program Year. Full grantee implementation must be complete by the beginning of the 2013 Program Year. Check your state/grantee Health and Safety Plan for a timeline for local implementation.
6. How do the Building Tightness Limit (BTL) and the Minimum Ventilation Rate (MVR) relate to ASHRAE 62.2?
The BTL, MVR, and some other existing dwelling CFM50 threshold values are all based on the older, and now obsolete, ASHRAE 62-1989 ventilation standard. As weatherization programs implement the current ASHRAE 62.2-2010 Standard, the use of the BTL, MVR, or other thresholds to limit the air sealing activities on a dwelling based on ventilation requirements will cease. There is no comparable threshold to use with the current ASHRAE 62.2-2010 Standard. Since there is no set limitation for building tightness, homes can be tightened as much as is cost effective through the Savings-to- Investment ratio (SIR) as determined by the audit. The minimum ventilation rate as used in the Standard defines the required CFM of ventilation, and is unrelated to the MVR or BTL used previously as a CFM50 threshold.
7. Why doesn’t the volume of the dwelling make a difference to the required whole-building minimum ventilation rate?
Standard 62.2-2010 uses square footage to determine the ventilation rate. This was in large part because floor area is easier to determine and is often available in public records. Because many ceiling heights are close to 8 feet, the volume and floor area scale. Also, the determination of the infiltration credit does account for height of the building so the volume indirectly comes into play there. It is important to accurately reflect the volume based on the entire square footage included in the envelope. For example, if a basement or attic is brought into the envelope, that square footage should also be considered in the ventilation rate calculation.
8. What is the difference between local ventilation and whole-building ventilation?
Local ventilation is intended to remove pollutants near their source, such as water vapor and odors in a bathroom or cooking odors in a kitchen. Generally, local ventilation is controlled by the occupant on an as-needed basis. Local ventilation must always be exhaust ventilation.
On the other hand, whole-building ventilation is intended to dilute the indoor air with fresh outdoor air, thereby reducing concentrations of pollutants already in the air. Whole-building ventilation usually runs constantly. If it is designed to run intermittently, it must be automatically controlled and have a higher flow rate than if it ran continuously. Whole-building ventilation may be provided with exhaust, supply, or balanced ventilation.
9. What is the purpose of the Alternative Compliance Path for existing dwellings?
The Alternative Compliance Path was added to the 2010 version of the Standard to make the Standard easier to comply with in existing dwellings (this Alternative appears in Appendix A of the 2010 version). This compliance path allows one to increase the CFM flow rate of the whole-building fan to compensate for deficits in local ventilation (less than 50 CFM in bathrooms and 100 CFM in kitchens).
a. May I leave existing local fans in place?
Yes, you may leave existing bathroom and kitchen fans in place, but they must be correctly ducted to the outside to count toward the flow rate CFM calculation. If you are using the Alternative Compliance Path, these left-in-place fans do not have to comply with the requirements of 50 CFM for bathroom and 100 CFM for a kitchen.
For existing fans that will remain in place, the alternative compliance path requires either the measurement of the flow rate CFM or using the airflow rating from the fan specifications. Fan flow testing and post retrofit compliance verification are required by WPN 11-6. See Section A4.2 of ASHRAE 62.2-2010 on page 12 for more information.
b. If I replace an existing fan with a new one, should I match the size of the existing fan, or should I comply with the Standard’s requirements?
If replacing a local fan, the new fan must meet the minimum CFM flow and sound requirements of the Standard.
10. I am weatherizing a four-story or more multifamily building. How do I apply ASHRAE 62.2 to this building?
The building you refer to is not covered by the ASHRAE 62.2 Standard. ASHRAE 62.2 addresses residential buildings of three stories of fewer, single-family, and multifamily. ASHRAE Standard 62.1 addresses multifamily buildings greater than three stories but is not required by DOE and would rarely come into play with the type of work the WAP performs. Multifamily buildings of four stories or more must have a ventilation strategy developed for the particular needs of that building based on ASHRAE standards. But most importantly, occupants of the building must not be left in conditions that may be worsened by any work to be performed on the building. If the conditions are such that they cannot be corrected with WAP funds, the building must be deferred. Kitchens and baths without adequate ventilation are likely worsened when performing shell measures on the buildings. Balancing or repairing existing systems may be sufficient to address the condition; however, where ventilation is lacking, a determination will have to be made on installing ventilation or deferring the building because of unreasonable costs depending on allowable health and safety activity for the particular state/grantee.
11. When determining the number of occupants when using the Standard for our weatherization program, should we use the number of bedrooms plus one, or can we use the actual number of occupants?
The Standard specifies the use of the number of bedrooms, plus one, to estimate the number of occupants if occupancy is not known. If occupancy is known to be higher, the Standard specifies that this higher occupancy be used. Using the number of bedrooms, plus one, works pretty well for new homes where the number of bedrooms is known, but the actual number of occupants might not be. This method is based on the assumption is that the master bedroom will house two people and all other bedrooms will house one. This assumption does not necessarily work for weatherized homes where the actual number of occupants in known.
12. Implementing ASHRAE 62.2 is not required where acceptable indoor air quality already exists as defined by ASHRAE 62.2. When and how can I determine if acceptable indoor air quality already exists?
ASHRAE 62.2-2010 defines acceptable indoor air quality (IAQ) as: “air toward which a substantial majority of occupants express no dissatisfaction with respect to odor and sensory irritation and in which there are not likely to be contaminants at concentrations that are known to pose a health risk. (p.3)
Determining unacceptable indoor air quality can occasionally be quite simple, but it is usually challenging. If the air in a home is reeking of cat urine, it is unacceptable. If the water heater is spilling, causing 200 ppm of carbon monoxide to enter the home, it is unacceptable. If a waste pipe has broken in the basement, it is unacceptable. High polluting events are usually pretty easy to detect (not in the case of carbon monoxide or radon) and fix. Our health and safety protocols are set up to find and correct such issues or defer the unit depending on allowable costs. ASHRAE 62.2 is not intended to address these high-polluting events.
The challenges are the more typical cases that might include small areas of mold and mildew, formaldehyde emitted from kitchen cabinets, or volatile organic compounds (VOCs) from carpets, paint, and household cleaners. Weatherization personnel do not typically have the equipment or protocols to detect these problems. ASHRAE 62.2 is intended to mitigate these types of pollution by diluting the indoor air with fresh outdoor air (whole-building ventilation) and eliminating some pollution at its source (local bathroom and kitchen ventilation).
Grantees may develop protocols as part of their Health and Safety Plan that can adequately demonstrate acceptable IAQ on a performance basis, and may not be required to install a fan as specified in the prescriptive requirements. However, this demonstration is not fulfilled by a subjective assessment by an auditor. Rather, it must be an objective assessment that holds up to questioning and must be approved as part of the State Plan review process. Essentially, if you do not want to install a fan, prove why it is not needed. Otherwise, do not try to subjectively assess whether each home meets the definition of acceptable IAQ, but instead implement the prescriptive ASHRAE 62.2 ventilation.
Interviews with the client should not solely be used to assess whether a home has acceptable indoor air quality. One reason is that expressed dissatisfaction is only a part of the definition of acceptable IAQ, and there are pollutants that clients cannot sense which are likely to increase in concentration following weatherization if ventilation is not added. A second reason is that the responses from clients will be based on pre-weatherization, rather than post-weatherization, conditions.
If the audit identifies only baseload measures, and acceptable IAQ already exists as defined by ASHRAE 62.2 and demonstrated by results of the initial assessment including diagnostic testing, ASHRAE may not be required. The grantee health and safety plan must incorporate similar language to utilize such an assessment in the field. The assessment results and method for determining acceptable IAQ must be documented in the client file and revealed to and signed by the client.
Some examples of assessing for acceptable IAQ – When installing baseload measures only, or measures that have no bearing on the air exchange rates from pre- to post-weatherization.
Radon – Zone 1 and Zone 2 areas are considered to have unacceptable air quality and therefore ASHRAE 62.2 is required. Zone 3 areas can be considered to not have radon that creates unacceptable air quality. Pets – Homes with indoor pets can be assumed to have unacceptable air quality. Smoking – If an occupant of the home is a smoker, the home is considered to have unacceptable air quality. Gas range – If the home has a gas-fired range (oven, range-top burners, or both) without an operable range hood vented to the outdoors, it is considered to have unacceptable air quality. Moisture – If a visual and sensory moisture assessment for historical and existing evidence of moisture problems demonstrates moisture concerns, including but not limited to condensation on windows, rotting sills, musty odors, suspected mold, water stains, etc., the home is considered to have unacceptable air quality. Carbon monoxide – It is required to correct CO at the source for higher levels, but even lower level CO poses problems with long-term exposure. Conduct ambient test of CO upon entry, prior to performing blower door tests. If there are detectable CO levels in the dwelling, which are higher than levels outside the home, the home is considered to have unacceptable air quality. Carbon Dioxide – Prior to performing blower door tests, measure CO2 in the living space and the master bedroom – if the levels are above 1000 ppm (the level that occupants begin experiencing CO2 related symptoms), the home is considered to have unacceptable air quality. VOCs/formaldehyde – If furnishings or materials known to emit VOCs/formaldehyde have been installed within the past year, the home is considered to have unacceptable air quality. Materials include cabinets or other furnishings made of sheet goods (MDF, plywood), new flooring (includes carpeting and other flooring installed with adhesives), and any other materials know to contain and off-gas VOCs and/or formaldehyde. Odors – If there are objectionable odors, the home is considered to have unacceptable air quality. Ozone – If any ozone producing equipment such as an electronic air cleaner is present, the home is considered to have unacceptable air quality.
Note: Since most weatherization activity changes the air quality and envelope of the home, an historical assessment is not appropriate to determine acceptable IAQ. Additional scientific assessment is required when changing the envelope in any way or affecting indoor air quality through insulating, installed combustion appliances, etc. VOC/formaldehyde, moisture assessments, and other technical determinations must be used for determining acceptable IAQ in these cases; otherwise, ASHRAE 62.2 must be performed. Again, any assessment protocol must be included in the grantee Health and Safety Plan and approved by DOE.
13. May I terminate the ductwork for my ventilation fans in the attic?
No, you may not; this is substandard practice. Moisture from exhaust fan air contacts surfaces in a cold attic, leading to condensation and possible mold and mildew problems. All ventilation fan terminations, both local and whole-building, must be outdoors. If you discover existing fans that are vented to an attic (this is pretty common), they must be extended to the outdoors (or the fan removed completely, patching the hole left in the envelope) if the unit is to be weatherized.
14. May I operate the whole-building ventilation intermittently?
Yes, whole-building ventilation may be operated intermittently, however it must be automatically controlled and the flow rate must be higher than if it were running continuously. For example, if the required whole-building ventilation rate is 35 CFM, but it is decided to operate the fan on a one-hour cycle time of 30 minutes on (0.5 hours) and 30 minutes off, the ventilation rate during the on time must be doubled to 70 CFM. If the choice is to operate the fan for 20 minutes on (0.33 hours) and 40 minutes off, the on-time fan flow rate must be 105 CFM. To find the intermittent flow rate for these examples, simply divide the continuously operated flow rate – 35 CFM for this example – by the ontime- per-hour decimal – 0.5 and 0.33 for the two examples – to find the intermittent flow rate CFM. If a whole-building fan operates less than once every four hours, the intermittent flow rate calculation becomes more complex; see Section 4.5, page 5, of the Standard for detailed information.
If you decide to operate a whole-building fan intermittently, keep in mind that the higher flow rate might adversely affect the safe operation of combustion appliances as compared to the lower continuous flow rate of the same fan.
15. What factors determine the minimum required CFM airflow for the whole-building ventilation?
The basic factors that determine the minimum required whole-building ventilation are area and occupancy.When using the Alternative Compliance Path, existing ventilation, location of operable windows, andhome air-tightness (post-weatherization) also come into play.
Whole Building Minimum Airflow Requirement Calculation
CFM 1. Infiltration whole-building rate from equation352. Alternative compliance supplement+203. Infiltration credit-15Final Whole Building minimum requirement40
For existing dwellings, the initial whole-building ventilation rate is calculated using the simple equation: QFan = 0.01AFloor + 7.5(Bedrooms + 1). Let’s assume the initial rate is 35 CFM. Then add the alternative compliance supplement that results from deficits for local ventilation requirements in bathrooms and the kitchen. Say this is 20 CFM; so we are now up to 55 CFM. Finally, subtract the infiltration credit to get the final whole-building ventilation requirement. Let’s assume the infiltration credit is 15 CFM. So for this example, our final requirement is 35 + 20 – 15 = 40 CFM for continuously operating ventilation. This is a minimum requirement for this example.
16. Now that the Standard is required by my program, I am afraid I will have to install ventilation in every dwelling we weatherize. Is this true?
Chances are you will have to install local ventilation and whole-building ventilation in most of the dwellings you weatherize, but not all.
17. As I air seal a dwelling to a tighter and tighter level, what happens to the requirement for local ventilation? What happens to the requirement for whole-building ventilation?
As you make a dwelling tighter, the requirement for local bathroom and kitchen ventilation does not change; it is independent of the tightness level.
On the other hand, as a dwelling becomes tighter, the requirement for whole-building ventilation becomes greater. This is because the “infiltration credit” is reduced as the dwelling becomes tighter. Of course, your air sealing efforts should not be limited by the requirement for whole-building ventilation, but by the cost effectiveness of your air sealing; you should keep tightening the home as long as it continues to be cost effective. Agencies should not use this as a rationale to reduce the amount of air sealing they will perform.
18. Why should we put time and money into air sealing a home and then spend more time and money putting in ventilation?
The answer to this question has to do with the way you think about the issue. It is helpful to think of the process as “controlling airflow”. This process requires two basic tasks. The first task is reducing uncontrolled air leakage in the dwelling; something we are all familiar with. The second task of controlling airflow is installing ventilation to ensure a minimum amount of fresh air is available to the occupants. These two tasks go hand-in-hand as the two parts of controlling airflow; one is not appropriate without the other. The ability to provide additional air sealing could also have a net benefit in energy savings.
The chart below, based on a single-story 1,500 square foot home, shows that leaving a home leaky does not ensure good indoor air quality at all times. In fact, as the chart shows, during the coldest times, when heating costs are likely at their highest, air leakage is far above that required to maintain good IAQ due to the stack effect.
The story told by this chart:A single story 1,500 sq ft home without a fan:
Left at 4,000 CFM50 leaks 225 CFM at 0°F but still gets inadequate fresh air whenever the
exterior temperature exceeds 60°F.
Brought to a rather loose 2,000 CFM50 doesn’t get enough fresh air any time the exterior
temperature is over 35°F.
Sealed to 1,000 CFM50 never gets adequate fresh air!
Leaving the home at 2000 CFM50 and adding a fan provides proper ventilation from 35° and up but, because the home is still relatively loose, too much air enters whenever the exterior temperature drops below 35°F.
We do our clients a real disservice when we rely on looseness and natural ventilation for IAQ.