Building Airflow Standards and the Average Contractor

Im running into some common issues in NYS that seem to keep coming up, and I am looking for feedback from others.  It is often noticed in my travels that a contractor will identify a target CFM50, and then work only to achieve that goal.


BPI's thoughts are,"Get them as tight as possible, fiqure out what amount of air needs to be made up, and provide make up air for that."


Are contractors afraid of the consequences of getting a home too tight?  Mold, Poor Client Health, etc, etc..  Is this because they dont understand the simpleness of supplying make up air?  Do they feel as though it is too costly?  Is it because Government Programs usually stiff the contractor on that type of measure?  Is it laziness? After all they achieved thier goals.  Is it that we as Trainers don't emphasize the ideals enough?


I am really just looking for thoughts.  I want to eventually address the problem locally.



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In the report I provide the general terminology "recommended standard for airflow" and then quickly discuss it's components (i.e. occupancy, volume, mechanical ventilation). The first point I stress is "leakiness." Folks typically don't want a leaky home, agreed? I tie comfort and healthy air into the mix to try and drive the importance of airflow management home.
The specific part of the report addresses not the "average" house but the one they live in. For example, not "Homes are typically leaky and can introduce a host of issues." Rather, my approach for better or worse, is to say "Your home (which I just spent 3 hours evaluating) has ratty FG in the attic, nothing in the walls, and a few other shortcomings. There are a lot of opportunities for cost-effective improvements, with immediate and long-lasting benefits to each.

Once the HOs see the full range of benefits to accrue from tightening up and controlling air exchange, I find that most almost completely shed their unease with tight houses.

I wonder what the house would look like during an opposing season. Assuming you are in a 4 season environment, would such a home that appears to be poorly constructed, had been "caught on a good day" where expansion & contraction provided ideal conditions, and falsely optimistic test results.

This sounds the difference between Pressure Boundary and Thermal Boundary.  Anyone who has lived in a mobile home can attest.


If you take a shoe box (mobile home), and wrap it in plastic (what they do), you have an outstanding pressure barrier, but no thermal barrier. 


I'd liken it to wearing a rubber boot, but no socks.  When the foot works, it heats up, that moisture from sweat gets trapped in the rubber boot.  When the foot stops, the heat stops, the non-insulated rubber boot lets the heat dissipate quickly, and the foot gets cold, and damp.


As for the BAS it is based on ASHRAE 62

ANSI/ASHRAE Standard 62.2-2010, Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings, is the only nationally recognized indoor air quality standard developed solely for residences. It defines the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings.
The 2010 standard encourages home retrofits to improve indoor air quality through allowance of alternative methods for meeting the standard’s requirements regarding kitchen and bathroom exhaust fans. The standard currently requires fans in those rooms.


For the explaining part - I have to give props to Ben Stallings for the approach I use now which compares how the two types of houses "breething" equates to their living counterparts (Namely insects & humans)

You can find the three simple slides I used for a class to high school trade teachers on Energy Auditor Talk

Eric, can we do a little reconcilliation here?

What was:

blower door cfm50
Your calc of 100% bas
How do you get the number (software, spreadsheet, pencil)


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