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Friction rate can be used in a duct calculator to size ducts
Posted by Allison Bailes on June 1, 2017
Today's installment in the duct design series is a simple one. It's just a straightforward calculation that gives us the design friction rate from the two quantities I discussed in my last two articles. In part 2, I told you about available static pressure (ASP). In part 3, I covered total...
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The majority of Passive House projects in North America are certified through PHIUS
Posted by Allison Bailes on May 31, 2017
The Pembina Institute published a report on Passive House last year. Titled Accelerating Market Transformation for High-Performance Building Enclosures, the report looks at the challenge of climate change, what Passive House has to offer, the market for high-performance buildings, and more. In the...
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Length and equivalent length in duct design
Posted by Allison Bailes on May 30, 2017
Today we move another step down the road of duct design. I started the series with a look at the basic physics of air moving through ducts. The short version is that friction and turbulence in ducts results in pressure drops. Then in part 2 I covered available static pressure. The blower gives us a...
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Static pressure measured with a magnehelic pressure gauge
Posted by Allison Bailes on May 26, 2017
In part 1 of this duct design series, I discussed the basic physics of moving air in ducts. Now we're going to take that and use it to figure out how to make all the parts work together properly. First we choose a blower that will give us the total air flow we need. Then we design a duct system...
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duct-fittings-pre-insulated-sealed-mastic.jpg
Posted by Allison Bailes on May 25, 2017
When it comes to heating and cooling homes, forced air distribution is king. Yeah, my Canadian friend Robert Bean of Healthy Heating pushes radiant for both heating and cooling, and my Texas friend Kristof Irwin drank that koolaid and installed what may be the first radiant cooling system in Texas...
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Women needed in the building trades, including HVAC design
Posted by Allison Bailes on May 24, 2017
The photo above is from one of the home energy rater classes we taught a few years ago. We had 13 students in that class. Only one was a woman. That ratio actually is comparable to what you see in construction as a whole. According to OSHA (see chart below), about 9% of all workers in construction...
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Leaking basement wall could use negative side waterproofing
Posted by Allison Bailes on May 19, 2017
Just a quick note for you this morning about some building science resources I found on the Web this week. As alluded to in the title, one relates to the top of the house (cathedral ceilings) and the other to the bottom (waterproofing basements). And actually, these resources that I'm referring you...
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Does compression of fiberglass insulation cause problems?
Posted by Allison Bailes on May 18, 2017
I've been guilty of perpetuating a myth. Last month I wrote an article in which I said installing insulation, "cavities are filled completely with as little compression as possible." But is compression really such a bad thing? When I posted that same article on Green Building Advisor, commenter...
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Blower door test during a home peformance assessment
Posted by Allison Bailes on May 17, 2017
Dick Kornbluth was an insulation contractor in Syracuse, New York back in the 1970s. Then he discovered home performance. It's really the logical place insulation contractors, HVAC contractors, and similar companies to end up. Rather than doing just one job to make a building better, he did several...
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Missed insulation and air barrier
Posted by Allison Bailes on May 16, 2017
The Atlanta housing market is booming again. I see renovations, infill, and tear-downs all over the place lately. There's a rebuild after tear-down happening now along one of my main walks. You saw a little about it already. Remember that house with the terrible joist blocking to the garage? Well,...
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