An interesting insight into the sausage making of mechancial ventilation standards...

Indiana's Weatherization program has been incorporating ASHRAE 62.2-2010 for just over a year and a half now with some pushing from DOE.  As can be expected of any change, there were some CAPs that wanted to learn how to do it, and do it well.  Others were skeptical and a little resistant to change. 

Nothing new or outrageous about any of that. 

This article at Green Building Advisor gives some insight between the difference of lowly anti-poverty energy conservation program's abilities compared to those of the New Home Construction industry. 

I'm not surprised if anyone is a little confused reading the article.  I was the first time I read it as well.  "Oh great, now we've got to put in even bigger fans!" ran through my head.  "After all, Lstiburek wouldn't throw a fit unless it is a fit worth throwing..."

But the clarification comes a little further down:

Defenders of the new ASHRAE formula point out that the newest version of the standard provides an alternate method of calculating the minimum ventilation rate — a method that may restore at least some of the infiltration credit.

The alternate calculation method requires that the home must be tested with a blower door. Once that’s done, and you have a cfm50 result from the blower-door test, you can get an infiltration credit that may reduce the need for mechanical ventilation. You have to use the following formula:
Infiltration credit = 0.052 • cfm50 • (story factor) • (weather factor)

The story factor is the number of stories raised to the 0.4 power. So, for a one-story building, the story factor is 1; for a 1 1/2 story building, the story factor is 1.18; for a 2-story building, the story factor is 1.32; for a 2 1/2 story building, the story factor is 1.44; and for a 3-story building, the story factor is 1.55.

What’s that you say? You’re not sure what your weather factor is? You'll have to look it up from a list of 1,100 locations.

Now,  this should look a little more familiar (but not totally).  Or maybe not if you don't look at the back end math of the current 62.2 calculator we've been using in Indiana.  The formula above is from the 2013 version of ASHRAE 62.2.  Indiana is currently using the 2010 version of ASHRAE 62.2. 

The nuance of the difference between 2010 and 2013 aren't the point.  Bottom line, Indiana's rag-tag group of Weatherization techs are able to maneuver this fan sizing process day in, day out.  While sophisticated new home Builders can't seem to be able to put a blower door in a new home, do some multiplication, and turn a dial in a fan housing. 

I do enjoy these little situations where the weatherization 'industry' here in Indiana has its act together better than what could be found in almost any new home.  It is a little sad for the state of new homes.  But it is something for our weatherization program to be a little proud about. 

If anyone is a little skeptical about the impacts a properly sized whole house ventilation system can have, try installing one in your home.  The difference isn't big, but it is the little things that aren't there any more.  Leaving for a day or two and the house doesn't smell like stuffy house is my personal favorite...