The Latest from the Energy Vanguard Blog

An energy recovery ventilator (ERV) removes stale air from the house and brings in outdoor air
Posted by Allison Bailes on October 22, 2020
Let's talk about one of my favorite subjects:  air.  Because of the global COVID-19 pandemic and the novel coronavirus (SARS-COV-2) that spreads it, the indoor air quality (IAQ) community—researchers, mediators, manufacturers, bloggers, groupies—is having a moment.  This must be the first time in...
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A pair-of-pants tee fitting for the duct system for my new Mitsubishi ducted mini-split heat pump
Posted by Allison A Bailes III, PhD on June 29, 2020
I've written about the load calculation and equipment selection process I went through for the new Mitsubishi* ducted mini-split heat pump in my house.  Now let's take a look at the design and performance of the duct systems for the two air handlers. Laying out the ductsThe schematic diagram below...
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A MERV-13 filter in a return filter grille in my dining room ceiling
Posted by Allison Bailes on June 24, 2020
Filtration is on the minds of a lot of people lately.  Because of the coronavirus pandemic, most of us would prefer not to breathe in air that contains any hint of the SARS-COV-2 virus that's been spreading the illness known as COVID-19.  Wearing a mask when going out in public is standard.  Having...
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The outdoor unit for our new Mitsubishi inverter-driven mini-split heat pump system
Posted by Allison Bailes on June 11, 2020
Last year my wife and I bought a 1961 ranch-style house, and I've been having a lot of fun fixing it up.  I wrote about the problem with the spray foam in the attic not covering the top plates and how I fixed it when we had the soffits, fascias, and gutters replaced.  I've also had a lot more spray...
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Follow these tips for quieter ducts, better air delivery, and happier homeowners
Posted by Allison Bailes on February 11, 2020
If a 12 step program is good for helping people deal with addictive behaviors, then a 17 step program ought to be better, right?  Or maybe it's just a random number that fits the number of tips that popped into my head as I planned this article.  In either case, I've written a lot about ducts in...
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Is there a limit to the amount of ductwork you can put on a low-static pressure ducted mini-split heat pump?
Posted by Allison Bailes on December 9, 2019
I like mini-split heat pumps, especially of the ducted variety.  And because I don't like to pay for a lot of excess power, I prefer to use ducted mini-splits with smaller blower motors operating at a low total external static pressure.  The Mitsubishi* units we have in our office and that I have...
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What's the best velocity for moving air through ducts?
Posted by Allison Bailes on June 26, 2019
The first thing to know about the velocity of air moving through ducts is that the slower you get the air moving, the better it is for air flow.  That was the main point of my last article.  In fact, the title asked the question, "Is Low Velocity Bad for Air Flow in Ducts?”  And the answer was that...
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What is the best velocity for air moving in ducts?
Posted by Allison Bailes on June 12, 2019
It's obvious that moving air too quickly through ducts can be a problem.  Faster air means more turbulence, more resistance, and more noise.  But I run into people who think that low velocity also can be a problem in ducts.  Just recently I heard someone talking about how low velocity causes "...
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What happens to the air flow in ducts when the size changes?
Posted by Allison Bailes on October 29, 2018
As we continue our study of indoor air quality and filtration, we now come back to duct design.  Today's lesson is on an interesting bit of physics that applies to anything that flows.  It could be heat or particles or electromagnetic energy.  In our case, it's air, a fluid, and the physics we're...
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