This review of my blower door experience is in challenge of numbers near 30 ACH50, found in example Home Energy Score Reports, issued by US Department Of Energy, Better Buildings Program in years 2015 and 2016. The reports are both for fictitious homes in Arkansas, built 1970, perhaps with little consciousness of energy efficiency.
2015 Example:
v2015_HEScore_BB_example_12-15-15.pdf , a two-story home 1800 sf with 8-ft ceilings, testing in at 4200 CFM50, 17.5 ACH50. I did not remember confronting so large a number, before.
2016 Example:
Home Energy Score Report Example.pdf , of about November 2016, a single story home with ten-ft ceilings, 1500 sf, testing in at 6500 CFM50, 26 ACH50.
If such large numbers are not fictional in lax construction for milder-weather Arkansas, it does not suggest that huge savings from air sealing justify blower door madness, in Portland, Oregon. Few weatherization contractors in this area will accomplish real tightening of more than 3 ACH50, and some with their building scientist pedigree as blower door believers, will charge more than $2000 for the deed. Yes, at such unjustified cost, it is not worth doing. For a 1000 sf Portland home with an inefficient gas furnace, even with $2 per therm applied cost of natural gas heat, the savings per ACH50 reduction, in preheat cost of fresh air, are only $10 per year. Please see my Insulation Math . Annual savings of 3*$10 = $30 per year at cost of $2000 are a poor investment. At best, the present value of savings through a twenty year horizon are 44*$30 = $1320. Please find that *44 payback multiplier (vs. *20) in this blog post .
At fair sealing cost of $300, the return is excellent. Abhor a blower door and test-in, test-out , with this. A blower door is almost never employed as the guide of important sealing measures. The value in tightening a home is in just acting in a permanent way, upon every sealing opportunity one sees, in dealing with evident drafts, and in the course of preparation to add insulation. Preparation must include all treatment of home integrity including plumbing, wiring and roofing deficiencies, that would be obstructed by the added insulation. Wiring includes anticipated communications wires and upgrades to permit most-efficient LED lighting.
Where I have spoken out as an Energy Trust Trade Ally, I have asserted that blower door testing with public support should be done rarely, for a stated purpose. Results should then be freely shared, so that we can accelerate consensus on further testing investments. This narrowing of test practice and sharing of paid-for results, never happened. My own sharing here, from my own investment, is a start.
My Test Results
I owned a Minneapolis blower door from 8/15/2008 to 5/16/2009, to dutifully employ it for air sealing test-in and test out in qualification of customer rebates. Finding no other resource, I trained myself with measurements in my 1955 single-story ranch home, 986 sf. I quickly found a stable, repeatable 1330 CFM50 Baseline result. This is 10.1 ACH50, a bit more drafty than the 7 ACH50 target for a healthy home. Tightening my home would take more than three years of staged effort, never to need or to again employ a blower door.
Higashi, October 2008:
The first test in a customer home was done 10/17/2008, a larger single story home, testing in at 1625 CFM50, 14.4 ACH50. The home tested out 11/10/2008 at 1410 CFM50, 12.5 ACH50, with $27 per year saving of cost to heat makeup air. This was in sealing and insulating of poor solid-steel HVAC ducts of both attic (return) and crawl space (heated), with no other evident opportunities. An air sealing rebate of $215 was paid at a foolishly-offered $1 per CFM50 reduction. The work did not include any discovery under blower door conditions. The crazy ducts block crawl space access and are likely to be detached and again to leak, soon. I did not feel good about this, but always seek the maximum offered rebate for a customer.
Bronner, November 2008:
The second test was done 11/24/2008, testing in to check work of one notorious HPwES crew. who failed to do any apparent sealing, missing quite-large opportunities including a garage wall holed by long-ago car impact of a wood pile. The test-in was 3740 CFM50 in a complex 1937 two-story home, 11.8 ACH50. The test out 1/19/2009 was 3050 CFM50, 9.6 ACH50, but this large improvement, not earned, is thought to be due to closing the door to a conditioned basement, not likely the condition in other tests. I became fatally disenchanted with my blower door here. A blower door show would never be of any use to me in finding anything, and only wasted a half day of progress. I immediately sensed that prior testers in a home always used their blower door only as a marketing scam, not understanding readings at all and doing nothing useful by the testing; always spending more time in testing than in crude and unguided “sealing.”
Costello, December 2008:
The third test in a customer home was done 12/12/2008, testing in at 760 CFM50 in a small single story ranch home, a tight 7.0 ACH50. There were no sealing opportunities and no test-out, where the attic was insulated and the crawl space was sealed and conditioned.
Levine, February 2009:
This is a typical bungalow home with top half-story weirdness, with result 2300 CFM50, 12.0 ACH50. There were no sealing opportunities in my attic access and insulation work, and no test-out.
Three jobs have shed light on other contractor’s misuse of a blower door, and the magnitude of home leakage that might be found in the majority of existing homes, which were built before 1990.
Wheeler: (January 2010)
This is a 914 sf single-story home built in 1951. It was evaluated as one of 200 homes in a 2008 pilot program of assigning Energy Performance Scores, EPS, in existing homes. The assigned EPS score of 80, was done with PTCS duct sealing and with R30 insulation of the crawl space by an independent contractor. A blower door test-in of 3670 CFM50 was reported. Extremely large 30 ACH50 was not computed, and was not attributed to a fallen-down duct in the crawl space. That duct was simply reattached by the CS insulation contractor, who may have needed to remove and then reset, all ducts. At May, 2010 and no longer owning a blower door, I just thoroughly fixed things in the attic of this home. Fixes included replacing broken HVAC solid steel ducts much in the way and frequently stepped-upon, that had been gauze-wrapped and gooped as evident teaching of PTCS that goop fixes anything; the goal is cheapness independent of durability and safety against traffic hazards. I would hereafter have complete disdain for PTCS and EPS.
Weigand: (May, 2010)
This is a 1400 sf single-story home built about 1970. It was my second confrontation with one notorious HPwES crew, which reported 4220 CFM50, 22.6 ACH50. This extremely large infiltration, not flagged for concern, is in part the result of construction with exterior walls open to the attic. I thoroughly insulated the attic of this home, with preparation including replacement of many poor solid-steel HVAC ducts, sealed air tight. I was not allowed to cap the exterior walls.
Chamberlain: (October 2011)
This is a 1590 sf single-story home built in 1973. This was my third confrontation with one notorious HPwES crew. The home tested in at 3392 CFM50 (20 ACH50), and tested out at 2248 CFM50 (13.2 ACH50). The very large CFM50 change, 1144 CFM50, at paid cost $450, might have qualified an air sealing rebate of more than $1000, but in the end this home owner did not get any air sealing rebate. The achievement not rewarded, was fraudulent, with perhaps-deliberate misuse of a door to generate most of the reduction. Negligible sealing was achieved in the attic, leaving test-in of about 20 ACH50. My very thorough and imaginative sealing surely reduced leakage by more than half, less than 10 ACH50, but in this Energy Trust did not care. I could not engage a volunteer to do the test out as a learning exercise.
More than 30 ACH50 is possible then in pre-1990 existing homes, where testing is with detached HVAC ducts. Absent detached ducts, numbers much more than 12 ACH50, are not in my experience. I did try to employ my blower door just before it was sold, in a 3500 sf three-story home in Northeast Portland, and found I would have needed several blowers to generate minus fifty pascals test conditions. The evident problem was balloon frame construction, and my interest in testing was over. I can ony suggest that this home with hydronic heat, no heat ducts, was well under 30 ACH50 test-in.
In the course of this exercise I discovered writing by Allison Bailes III PhD, Energy Vanguard, upon discoveries in his Atlanta condominium, built around 1970. Higher infiltration numbers are to be expected in multi-family homes, but his blower door numbers surprise me.
(At July 18, 2016)
http://www.energyvanguard.com/blog/how-i-achieved-a-21-increase-in-airtightness
Here find test-in at 29.6 ACH50, where part of a bathroom ceiling is missing. Ceiling patched, and with some air tight sealing of exterior walls, the number is down to still-large 20.8 ACH50. Despite advocacy for and practice of blower door testing, Mr. Bailes seems to despair of further reducing his condo fresh air supply.
He had previously found that Celotex exterior sheathing under a brick exterior of the complex was severely buckled.
(At April 26, 2016)
http://www.energyvanguard.com/blog/air-flow-pathways-in-a-leaky-bathroom-wall
Here is the report of fixing the exterior sheathing leakage, at a bathroom wall only.
(At May 23, 2016)
http://www.energyvanguard.com/blog/how-to-fix-a-leaky-underinsulated-exterior-wall
Also in the course of this exercise I found that homes built from 1994 to 2004 are notoriously leaky, due to cheapening of exterior sheathing, at least in New Zealand . The leakiness refers first to rot problems. We in USA too have cheapened exterior sheathing in reliance upon house wrap, and have had lapses in provisions to screen and drain falling water. Where this is thought the concern of building science, a blower door operator will not be depended upon for solutions.
No comments:
Post a Comment