It came to my attention recently that there may be a widespread misinterpretation of a requirement of the BPI standards.  The bottom of page 13 of the BPI Technical Standards for the Building Analyst Professional states the following:

When CAZ depressurization limits are exceeded under worst-case conditions according to the CAZ Depressurization Limit table, make up air must be provided or other modifications to the building shell or exhaust appliances must be included in the work scope to bring the depressurization within acceptable limits.

I would assume that ‘building shell’ refers to the exterior building envelope or pressure boundary of the building.  And if ‘makeup air’ refers to adding a hole in the building shell, then ‘other modifications to the building shell’ could be interpreted as sealing holes in the building shell.  I would like feedback from BPI instructors and BPI students to find out if it is being taught that sealing up a building and lowering the Blower Door cfm50 is a remedial action recommended in the work scope to solve worst-case depressurization issues.

Views: 418

Replies to This Discussion

if it is being taught that sealing up a building and lowering the Blower Door cfm50 is a remedial action recommended in the work scope to solve worst-case depressurization issues

 

This is not at all what was taught in the class I took.


This has never been taught in my class. We teach that the ideal remedy is to upgrade to a sealed combustion appliance to eliminate the interaction of house pressure on the appliances. If this is not a reasonable upgrade then there are other test which would give us an ideal of the cause of depressurization, sometimes it maybe return duct leaks in the CAZ zone(seal the ducts), sometimes it maybe large fans in the area (can be reduced in size ), the area around the appliance could possibly be isolated from the house and add air from outside, and other times I have had to add makeup air for dryers in the CAZ. Every situation is different but I have never or have never taught my students that just sealing the house tighter would be a proper corrective action for bringing depressurization within acceptable limts.
What to you think the standard means by 'other modifications to the building shell to bring the depressurization within acceptable limits.'  It mentions makeup air earlier, so I do not think it is suggesting making the building shell leakier.  Are there other modifications to the building shell they might be referring to that could bring the depressurization within acceptable limits?

Paul,

 

In fact I do think the standard is suggesting making the building shell leakier.  Obviously this would be a last resort, but it would be preferable to make a house leakier than to have a combustion appliance that is backdrafting. 

 

But usually excessive depressurization problems can be solved with pass through grills between various zones of the house, or jump ducts, or undercutting doors so they maintain at least a 1" return air pathway on the bottom.  Next steps would be to mechancially disable the highest speed fan setting on the kitchen fan or other large fan that is causing worst case depressurization.  

 

Another option is to put natural drafting combustion appliances inside their own sealed off and insulated utility room with make up combustion air coming in directly from outside.   Either that or move them to the garage outside the conditioned space.  If all else fails, then you have to start replacing natural drafting combustion appliances with either electric or sealed combustion units. 

 

One big misinterpretation I have seen people make, is that they confuse or conflate make up air needed for combustion appliances and worst case CAZ depressurization, with mechancial ventilation needed if you get a house below 70% of the Building Airflow Standard. 

 

If you have a tight house where mechanical ventilation is required, and it also is failing the CAZ depressurization test, you cannot solve both issues with one fix - unless you literally just add a big hole to the house which makes the CAZ and the whole house a lot leakier.   Instead, the CAZ issue needs to be addressed with one of the options I outlined above, and the mechanical ventilation needs to be addressed with an exhaust or supply fan of some sort, or an HRV.  But adding mechanical ventilation can't and won't solve a CAZ depressurization problem. 

 

 

RSS

Home Energy Pros

Home Energy Pros was founded by the developers of Home Energy Saver Pro (sponsored by the U.S. Department of Energy,) and brought to you in partnership with Home Energy magazine.

Latest Activity

Hal Skinner replied to Richard Beyer's discussion Spontaneous Combustion and Flash Fire regarding Spray Foam Insulation
"Richard, here is something else that might be pertinent. In my hundreds of conversations with our…"
32 minutes ago
Trip posted a discussion

Starting a Home Weatherization Business. Considering it...

I am considering starting a home weatherization business. (I live in Southeast Alabama)  Currently…See More
1 hour ago
Jim Gunshinan commented on Jim Gunshinan's blog post My Energy Upgrade California—The Numbers Are In
"To all, one thing I don't lack is advice from the experts! Thanks for the input, challenges,…"
2 hours ago
tedkidd commented on Jim Gunshinan's blog post My Energy Upgrade California—The Numbers Are In
"Jim, I'm glad you are open, that's great!  We all learn best when we are open! The…"
2 hours ago
David Eakin commented on Jim Gunshinan's blog post My Energy Upgrade California—The Numbers Are In
"Jim, Well, as the editor of Home Energy you should already know that the order of remediation is…"
2 hours ago
Greg Labbe posted a blog post

Technical Tape Desecration

Lets face it – building science is pushing the performance of adhesive tapes to a new levels and…See More
4 hours ago
Stacy Hunt posted an event

High Performance Enclosure Strategies: Part II, New Construction at Online

August 13, 2014 from 1pm to 2:30pm
Please join the Building America Program for our free webinar: High Performance Enclosure…See More
6 hours ago
Richard Beyer replied to Howard Katzman's discussion UV lights on filters
"Howard, There are numerous manufacturer's who swear these systems work and then you have the…"
14 hours ago
Christopher Morin posted a blog post

How do You Test a TXV?

  Thermostatic Expansion Valves (TEV or TXV), one of the most popular metering devices for…See More
18 hours ago
Howard Katzman posted a discussion

UV lights on filters

I recently saw UV bulb installations in 2 HVAC systems in a home. Each system had the Lennox…See More
20 hours ago
Don Fitchett joined Michael Stuart's group
Thumbnail

INFRARED THERMOGRAPHY USERS

This group is dedicated to knowledge sharing and discussion of infrared thermography for building…See More
20 hours ago
Don Fitchett commented on Diane Chojnowski's group Pinterest
"While most of our (BIN95.com) energy post and boards are industrial related, there are crossovers…"
20 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service