The Latest from the Energy Vanguard Blog

Duct design schematic diagram showing vents and air flow
Posted by Allison Bailes on June 9, 2017
To this point in our little series on duct design, we've been calculating intermediate quantitites: available static pressure, total effective length, and friction rate. Today we use all that to find out how big the ducts need to be. We're following the Manual D protocol for duct design, a standard...
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UL and Intertek partner with home builders in new home energy rating program for Florida
Posted by Allison Bailes on June 8, 2017
In case you didn't see the announcement out of Florida, two big well-known names have entered the market for home energy ratings and energy code compliance. Underwriters Laboratories (UL) and Intertek are working with the Florida Home Builders Association (FHBA) certify home energy ratings, blower...
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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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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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Home energy quiz from the US Dept. of Energy
Posted by Allison Bailes on May 4, 2017
I found this little quiz on Twitter the other day. I got 9 correct out of 12, but I'd like to dispute one of my wrong answers. One of the answers surprised me. And I was glad to see one of them support an article I wrote in 2014. If you want to take the quiz before reading my quick take on it, go...
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Condensation on the insulation jacket of a duct running through a crawl space
Posted by Allison Bailes on February 14, 2017
Water vapor from the air condenses on air conditioning ducts in humid climates. It's as normal as poorly insulated bonus rooms making occupants uncomfortable or cigarettes causing lung cancer†. Condensation on ducts is most common in crawl spaces and basements, where the air is more likely to have...
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This heat recovery ventilator is inside the building enclosure
Posted by Allison Bailes on February 10, 2017
If you've been hanging around here for a while, you know I encourage architects and builders to find a way to get the ductwork and heating and cooling systems inside the conditioned space of a home. In cold climates, this usually happens without much argument. In hot and warm climates, we're not...
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