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Atlanta, GA
773.398.5288
corbett@buildingperformanceworkshop.com
Advanced residential construction and home improvement consulting and owner's advocacy in Atlanta, using the latest building performance diagnostic and modeling techniques and tools. Airtightness, insulation, HVAC, ventilation, moisture, and air quality and EMF consulting for homeowners and building professionals alike.
Home performance articles and stories from the field with internationally respected building forensics guru Corbett Lunsford at the Building Performance Workshop. Hear new episodes of the Building Performance Podcast, see new videos from the Home Performance YouTube channel, and learn all about how diagnostic testing (more than an 'Energy Audit') can make home improvement and new home construction a proven process!
One of my longtime clients found a pretty big problem in the build of his family's forever home, and wanted to share. Open cell foam used in place of closed cell, and then covered (accidentally or intentionally) so it might never have been discovered. A great example of why you want to visit your build every day, and test and verify everything possible.
Using just one page in a load calculation, we can start to uncover the mistakes used in the math. Thanks to Aaron T. for sharing!
There are TONS of checklists out there to help educate us and tune our construction and home improvement processes- here are four:
2:35 Quality HVAC Installation (https://www.acca.org/viewdocument/residential-quality-installation-checklist-english)
16:16 Quality Foundation Installation (https://readynevadacounty.org/DocumentCenter/View/15502/Foundation-Inspection-Checklist-PDF)
29:05 Quality Framing Installation (https://www.austintexas.gov/sites/default/files/files/Development_Services/RES_BuildingFramingInspectionChecklist.pdf)
38:40 Quality Spray Foam Installation (https://www.epa.gov/sites/default/files/2015-08/documents/checklist_spf_contractor_client_communications.pdf)
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Same hotel as last time, different room and systems (not sure why). Well ventilated, but one improvement vastly changed the shower steam situation.
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WHY and HOW I model encapsulated attics as actual conditioned space, which gets a Btu and CFM assigned to them. You can see the load difference starts to really stack up with the amount of variables that go into it. Using Wrightsoft load calculation and SketchUp 3D modeling softwares. Thanks to Alex Meany (https://MeanHVAC.com) for teaching me how to work this magic on Wrightsoft.
CHAPTER MARKERS:
13:58 Surface Area Impacts
15:30 How to Model Conditioned Attics in Wrightsoft
27:37 Blower Door Impacts
31:15 Windows in the Attic
34:00 Duct Leakage Impacts
39:20 Value Engineering Impacts
Energy modelers and HVAC designers have to input SOMETHING into their software to simulate window performance, and it’s better to be in the neighborhood at least. Here’s the quick tip, along with a following disclaimer from an awesome follower who put all the problems with this simple conversion very clearly before us:
IMPERIAL U-FACTOR (BTU / HR X FT2 X DEG F) = METRIC U-FACTOR (W / M2 X DEG K) / 5.678
Now the problem with this equation:
‘Perhaps I've misunderstood the intent of the blog post, but it seems to suggest that European and American window U values are directly comparable, which is questionable. For window performance standards, EU uses ISO 10077 and US uses NFRC 100/200 (Canada CSA A440.2‐09 incorporates NRFC by reference).
One of the big differences between the two standards is that NFRC ratings are calculated at 0°F and ISO at 0°C. Very cold temperatures (large temperature differences) drive stronger convection currents between panes. Of course, window manufacturers will design to optimize published rating over real world performance. If you are designing for very cold temperatures, the tendency is to favor convection reduction at the expense of conduction reduction. Smaller gaps suppress convection currents at the expense of higher conduction, so window gaps tend to be smaller for US windows (rated at 0°F) than for EU windows (rated at 0°C). For my area, Massachusetts, NFRC is good input to Manual J since the reference temp is around 0°F, but ISO is better as a measure of thermal performance, since half the heating degree days are above/below 32°F. I think ISO would also be a better standard for a cooling dominated climate.
In case you are unfamiliar, I found that International Window Standards - Final Report April 2014 to be a great resource on this subject. The report's bottom line is that there is no good general correlation between ISO and NFRC standards. However, fig 3.10 in the report shows that ISO and NFRC calculate about the same U values for uPVC triple-pane windows over 4 different profile (frame) designs and 2 different window gappings. When building my home a couple of years ago, I was considering an American window and a design from Poland (btw Poland encouraged the window industry as a matter of national policy, so lots of good cheap windows are made there). Since both were triple-paned PVC, I felt justified in comparing the U values directly, despite the different standards.
I've seen your friend Matt Risinger (and Steve Baczek) comparing EU and US window ratings as if it is an apples-to-apples comparison, and this seems to be not quite accurate. That said, I think it is true that EU windows have better thermal performance for the same profile material and glazing, since the ISO standard is better aligned to real world performance conditions.
Hope you find this helpful,
Craig S.’
THANKS SO MUCH CRAIG, everybody be warned, but better this than just using default library items in the software and getting it completely wrong.
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4-page ACCA Worksheet for Manual D: https://buildingperformanceworkshop.com/s/Manual-D-Duct-Design-Worksheet-39sl.pdf
Automated ACCA Manual D Spreadsheet: https://www.acca.org/HigherLogic/System/DownloadDocumentFile.ashx?DocumentFileKey=0a4c57a8-9943-17ae-a1e7-92f71109dc8a&forceDialog=1
Calculators of all kinds for home performance: https://buildingperformanceworkshop.com/calculator
Get 1-on-1 help with any home: https://buildingperformanceworkshop.com/video-consulting
Pawel Wargocki has been researching sleep and indoor air quality (IAQ) and has found some pretty fascinating things- chapters marked below.
10 Questions About Sleep and IAQ
Sat down with my buddy, the fantastic engineer and educator Ross Tre-THEW-ey (https://te2engineering.com/meet-the-team/) to make three videos- this being the first. We dive into how commercial mechanical engineers are trained and how they might approach, rightly or wrongly, your upcoming home project-- and how you can tease the right info into their designs.
Check out my deep dive courses on Ventilation Design and more: https://buildingperformanceworkshop.com/ventilation
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Here’s the current pressure drop chart for the Aprilaire lineup that I recommend most often. Hope you find it useful.
In modern air-sealed homes, any big one-way exhaust fans should be at least considered for their potential depressurization of the whole home. In MANY MANY cases, the building code requirement of make up air only for kitchen fans bigger than 400 cfm MAKES NO SENSE and is stupid and dangerous.
If you’re bringing in make up air, you don’t want it shooting through your home at high velocity- in my experience keeping it under 300 feet per minute (3.4 mph) is a good way to slow it down enough. Here’s a simple trick to size your make up air system for a home kitchen exhaust hood:
The toe-kick area under your kitchen cabinet is 4” high. However many 100’s of CFM you’re bringing in, you’ll need the same amount of feet of length for this toe kick grille.
For example:
300 cfm kitchen exhaust, 300 cfm make up air, 3 ft of length (36 in long x 4 in high)
400 cfm kitchen exhaust, 400 cfm make up air, 4 ft of length (48 in long x 4 in high)
500 cfm kitchen exhaust, 500 cfm make up air, 5 ft of length (60 in long x 4 in high)
600 cfm kitchen exhaust, 600 cfm make up air, 6 ft of length (72 in long x 4 in high)
Hear it from the people who manufacture fresh air systems, not just from me. ERVs are for very airtight homes (under 2ach50) to balance the exhaust air from pollution sources inside. Download our universal ventilation layout concept at: https://buildingperformanceworkshop.com/s/BPW-PerformanceVentilationLayout.pdf
Thanks to:
Nick Agopian, Renewaire (https://Renewaire.com)
Travis Rasch, Broan-Nutone (https://Broan.com)
Bruno Poitras, Fantech (https://Fantech.net)
Ken Nelson, Panasonic (https://Panasonic.com)
Szabi Fekete, Zehnder (https://ZehnderAmerica.com)
1:16 Continuity of Balanced Ventilation
2:23 Sizing Considerations
3:36 International Mechanical Code Minimum for Continuous Ventilation Airflow
5:04 Boost Mode
6:27 ERVs in Cold Climates
10:12 ERV vs. Dehumidifier
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