Concerning duct testing in crawlspaces (this is for new houses for Energy Star, but will be the same for existing houses):

I have a house on a conditioned crawl with ducts in that crawl.  There is an exterior hatchway into the crawl, and no intentional connection between the house and the crawl.  When performing a total duct leakage test, no problem, just open the hatch before the test.  When performing a duct leakage to outside test, the crawlspace ducts never experience the effect of the blower door, so the test is inaccurate, with leakage to outside numbers that are too high.

We know the numbers are too high in a case like this, and we have been able to simulate the problem in a house with a basement by taping the basement door while doing the leakage to outside test.  Just today, we tested 2 identical houses that we had sealed while under construction.  The 2 identical houses - 1400 ft2 on a basement making them 2800 ft2 of conditioned space - had building leakage of 620 CFM50 and 650 CFM 50.  Duct systems are entirely within the shell.  Both had a leakage to outside numbers of 20 and 26 CFM25 range.  We then taped the doors to the basements and got numbers of 82 and 92 CFM25 as leakage to the outside.  In these cases, off by a large factor from the real 20-25 number.

Without cutting a hole in the floor or installing a second blower door in the crawlspace, do you have any ideas?

Ed Minch

Tags: conditioned, crawl, duct, testing

Views: 669

Reply to This

Replies to This Discussion

It does, but even though:

"According to the RESNET Formal Interpretation mentioned above: The measured outside leakage shall be deemed to be 0  CFM25 for each system the meets the following criteria: 100% of ducts and air handler located in conditioned space boundary, 100% visible, and not located in an enclosed space such as a chaseway, interior or exterior wall or roof cavity or in an enclosed floor cavity."

EStar says you have to test BOTH total leakage and leakage-to-outside on every house, with a few exceptions some of which you mentioned.  I think V 3 has overreached on a lot of topics, this total leakage number being one of them.  

Here is another topic:  Next time you do a duct-leakage-to-outside test, when the test is done, leave the equipment running with the leakage number showing on your manometer.  Then pull the tape off the registers one at a time.  Check the leakage number on the gauge.  If the house is reasonably tight  (let's say 4 ACH50), the number won't change even with all registers open - you didn't have to tape!

Ed Minch

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

Maria Lacey replied to Linda Wigington's discussion Low-cost electricity monitoring: Accuracy & Applications in the group 1000 Home Challenge
"I attempted to use an AZTech device. I have used the Watt Stopper, Watts Up Pro, Kill-A-Watt…"
1 hour ago
Maria Lacey joined David Eggleton's group
Thumbnail

1000 Home Challenge

Linda Wigington distinguished between deep retrofits & deep energy reductions, thus expanding…See More
1 hour ago
Profile IconCynthia Sandherr, James Skeldon, Mathew Castel and 3 more joined Home Energy Pros
3 hours ago
Andy Li replied to David Parker's discussion Energy auditor equipment for sale- blower door, duct tester,combustion analyzer in the group Energy Auditing Equipment for Sale, Trade or to Purchase
"Is Minneapolis Duct Blaster still available? send some photos and how much do you ask for? my…"
6 hours ago
Andy Li joined allen p tanner's group
Thumbnail

Energy Auditing Equipment for Sale, Trade or to Purchase

Discuss the pros and cons of the equipment you are interested in prior to purchase. Post equipment…See More
6 hours ago
Tom White posted a video

Nexus eWater System

Unlocking the Power of Grey Water: Nexus eWater System
7 hours ago
Hal Skinner replied to Richard Beyer's discussion What's your opinion on the best insulation option for your GREEN attic space?
"Mornin Richard, Maybe 'Options' might be more appropriate here?  We take the path…"
8 hours ago
Richard Beyer posted a discussion
9 hours ago

© 2014   Created by Lawrence Berkeley National Laboratory.

Badges  |  Report an Issue  |  Terms of Service