In short, the role of an existing infiltration credit is being tossed about in proposed addendum j. This proposal would eliminate the section describing the infiltration assumptions that are present in the standard.
"This proposed addendum illustrates why public comment is so important to the standards development process," said David Grimsrud, chair of the Standard 62.2 committee. "We have strong opinions on both sides of the fence regarding this addendum. Working to reach a common ground will help build a stronger standard."
Some committee members feel that code officials, who apparently use it to require more mechanical ventilation than is currently required in the standard for new housing, often misinterpret the section. Also, the requirement could imply that new houses are as tight as they ever will be and that new housing should be leaky enough to provide the amount of infiltration suggested, according to Grimsrud.
On the flip side, removing the credit would significantly reduce the recommended ventilation rate in new housing, thereby increasing steady-state pollutant concentrations, according to Grimsrud.
Still others suggest that weatherization agencies that use the standard in assessing strategies for tightening existing homes and/or adding mechanical ventilation will be left without guidance, he said.
Fellow committee member Max Sherman had some observations, too. And, he is not alone in his viewpoint. "Those who support this addendum believe - not necessarily correctly - that deleting this section deletes infiltration," said Sherman. "There are a variety of disparate reasons various people do not like infiltration.
"The mechanically focused sort wants to â€˜build tight; ventilate right' and therefore wants full-size mechanical ventilation systems. Some people do not like infiltration because they view it as poor quality air, undependable, or energy inefficient. Some view this addendum as a way to lower total rates.
"My own view is that this addendum is not well thought out and that the committee does not really have a consistent view of what they are doing. In fact, this addendum could lead to the opposite of what some of the committee wants."
So window opening, which is assumed to provide the ventilation required in the exception, should not be an acceptable alternative to the ventilation requirements, according to Grimsrud. The proposed addendum would remove the exception that whole-building mechanical systems are not required in that specific region.
"Exception â€˜a' to section 4.1 currently allows homes in mild climates to use operable windows instead of mechanical ventilation to meet the whole-house ventilation requirement," explained Sherman. "The original thought was that people in â€˜paradise' commonly open their windows for ventilation because it is not an energy or thermal comfort burden to do so and should not be required to have redundant mechanical systems."
According to Sherman, the state of California is the most populated area that would potentially qualify under this exception. The state is planning to adopt 62.2 in its next code cycle, but wanted to know if the state should allow windows or whether to require mechanical systems. The state funded a study, of which Sherman was a part of, to survey window opening behavior of people who lived in homes built since 2001 to see how people use windows. The survey showed, according to Sherman, that only a very small fraction of people in recently built new homes use their windows enough to matter.
"Accordingly, California is not going to allow window opening to meet their whole-house requirement in the proposed new code. The 62.2 committee was also persuaded by the study, and feels there is no longer any justification for allowing these climates to have an exception."
Although people will use windows to provide extra ventilation for unusual events - possibly parties, cleaning, and painting, for instance - Sherman believes very few people appear to use their windows to provide minimum whole house rates on a regular basis.
But, don't hold your breath, contractors. "Other design options, however, would become more confusing if the addendum passes," suggested Sherman. "For the contractor trying to make sure adequate ventilation is truly being provided, the addendum makes it tougher."
Turning to addendum k, this impacts only those mild southwest climates for which Exception "a" applied.
"Those climates were treated differently than other climates," said Sherman. "That difference is removed and now the same solutions are required. Regardless of climate, operable windows are not an acceptable compliance option for meeting the whole-house ventilation rates."
In the end, there is a lot at stake for contractors, as well as system designers and system installers.
To read the proposed addenda or to comment, visit www.ashrae.org/publicreviews. Public review and comments are welcomed through Nov. 6.
Publication date: 10/30/2006