It’s no surprise that the standard is still objectionable to members of the National Association of Home Builders (NAHB), who responded to last summer’s call for comment with gusto. Now, at least one member of the medical community seems to be saying that more options need to be given to meet individual choices and medical needs.
These views were presented at a seminar on “Perspectives on ASHRAE’s Residential Ventilation Standard,” part of the society’s recent annual meeting here in Cincinnati. The proposed standard might be easier for contractors to comply with, but will it have any meaningful benefits for homeowners?
It’s not a huge document, he commented. In fact, the appendices are larger than the document itself. Last summer’s comment period had a whopping 5,000 commenters with 3,000 comments, 90% of which came from an NAHB letter-writing campaign, Sherman said.
At ASHRAE’s Annual Meeting here, the committee approved some addenda for public review and approved others for 62-1999, Ventilation for Acceptable Indoor Air Quality. (See related article, page 14.)
Residential Standard 62.2P, Sherman said, “defines roles” of the ventilation system. The standard also spells out what it does not include:
The standard does require:
The revised standard has an allowance for natural ventilation (openable windows, doors) in mild climates and under special circumstances (such as in hobby rooms). And there are outdoor air targets: Natural ventilation is required in most rooms, to be used in the case of special events — since builders usually don’t know in advance the room(s) in which homeowners will assemble model airplanes, etc.
The standard requires 20 to 80 cfm in homes with from one to five bedrooms (20 cfm required in a home with one bedroom, up to 80 cfm in a home with five bedrooms). It also requires mechanical ventilation that runs a minimum of 1 hour out of 12. This requirement can be met with the use of an installed bathroom fan, Sherman said.
There is also an allowance for existing building infiltration (leakage), but it must be measured using a blower door test. Exhaust and supply systems need to be balanced.
Carbon monoxide alarms were not mandated. As for particle filtration, air-handling systems must have a MERV 6 filter. Air-moving equipment must also meet sound-level requirements.
Operations and maintenance requirements leave a bit to be desired. The system must be designed for proper operation, and maintenance instructions must be left with the owner.
Another myth is that unbalanced ventilation will rot walls. It will not, Sherman said, if indoor humidity is controlled through ventilation.
He was asked if the standard addresses fireplaces and radiant systems. It doesn’t address fireplace sizing, Sherman answered, but does include backdrafting. As for radiant systems, the standard doesn’t deal with recommending heating systems at all, he said. “The standard doesn’t require an air handler; the bathroom vent will cover that requirement.”
Making it clear that the proposed standard deals with ventilation, not air quality, Sherman explained that the required filtration is not meant to filter for IAQ; it’s for coil protection, “so they don’t get dirty and grow yuck on them.”
The standard is much more concerned about moisture than cat dander. In fact, under this standard’s definitions, “A cat is a high-polluting event,” said Sherman.
If one is to judge by the session’s next two speakers, it appears that the standard offers too little to satisfy some members of the medical community, and asks too much of the building community.
Dr. Bascom specializes in allergy and immunology, and is a member of ASHRAE’s Environmental Health Committee. Among her patients, she has observed that some people have “markers of susceptibility to allergens.”
Asthma in particular is receiving increased public attention, she said. The American Thoracic Society is studying the health effects of outdoor air. And some public school districts are being compelled to recognize the special needs of students with asthma.
She pointed out to the ASHRAE members that “Health is in your mission statement but not in your training.
“You’ve ducked ‘health’ in the standard’s definition,” she continued. “There wouldn’t be butts at stake if it weren’t an issue.”
She pointed out that the standard doesn’t address thermal comfort. Its strength, she said, is that it avoids a pollutant-by-pollutant approach. Its real weakness, she said, is that it has too many “hedges.” It ducks the issues of a person’s “range of susceptibility” to asthma, and a comparison of perception vs. acceptable conditions.
“In medicine, we measure real factors,” Dr. Bascom said. “Quality of life can be measured.”
She also told the engineers that a person’s home is their castle; one size does not fit all; health varies wildly among people; and susceptibility to health problems varies widely.
Another hedge phrase used in the standard that she took issue with is “as long as it’s used properly.”
That phrase “means that it probably won’t be,” Dr. Bascom said.
She then questioned whether the standard would provide guidance on non-ventilation conditions that can lead to IAQ problems — like the all-too-common practice of installing carpet on concrete slab, resulting in “dust mite heaven.”
“Will the standard address issues like this?” she asked. “They are very common causes of asthma.”
Dr. Bascom recommended that the standard take a systems approach; that it needs more specific descriptions of moisture; it needs more on potential sources; and that it acknowledge occupant susceptibility.
“Why has health been ‘unlinked’ in this document, compared to the first draft?” she asked.
However, “We cannot achieve a zero-risk situation.”
There has been little research on residential ventilation, he pointed out, although there have been many studies based on offices and other commercial settings. Homes have a wide variety of sources, strengths, control, and susceptibility.
The advantages of mechanical ventilation, he said, are that it is independent of weather, and it is controllable. Its disadvantages are that it uses power, it adds a cost in construction, and it can be noisy.
He questioned whether ASHRAE’s prescriptive measures for mechanical ventilation should be included in the standard, since it duplicates and could conflict with existing codes, particularly those from the American National Standards Institute (ANSI).
The builders were represented by Richard Morris of NAHB, a Washington, DC-based association with 200,000 member firms. He charged that 62.2 is “seriously flawed because of bad research and bias toward mechanical ventilation. NAHB opposes whole-house ventilation requirement until studies show a direct link to health and whole-house ventilation.
“Where are the broad-based studies?” he asked. “IAQ in new homes is far better than it has ever been.”
(Note: Morris’s microphone lost its connection about halfway through his talk. We still heard that the standard is “seriously flawed” and “biased” at least two more times.)
Mechanical ventilation with a dehumidification package costs about $300 more for a new home, Lstiburek pointed out. Savings on the design of the duct distribution system can pay for these extras.
He referred to one ventilating dehumidifier as “magnificent,” but noted that it’s probably too costly to add in standard new homes. (For more information on the product, visit http://www.building science.com.)
He also discussed the use of CO detectors in Las Vegas, NV homes; these alarms went off in one particular subdivision. On examination, it was found that the ventilation system was drawing in air from the garage. The systems were corrected.
Regarding the problems of achieving adequate ventilation while using radiant heating systems, Lstiburek said his own house has radiant heat and that he prefers it to forced air from a comfort point of view. However, he wound up installing a duct system, then ducted central air, to achieve the type of ventilation that was acceptable to him.
ANSI/ASHRAE Standard 62-1999, Ventilation for Acceptable Indoor Air Quality, sets minimum ventilation rates and other requirements for commercial and institutional buildings.
The addenda approved for review at the Society’s 2001 Annual Meeting, held here June 23-27, include:
To obtain electronic draft versions of the ASHRAE 62-1999 addenda during the comment period, visit ASHRAE Online at www.ashrae.org/STANDARDS/pubrevdft.htm.