flex duct

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The Joy of Flex

A recap of my Building Science Summer Camp presentation

Posted on Aug 16 2017 by Allison A. Bailes III, PhD
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I recently spoke at the Westford Symposium on Building Science. You may know it better as Building Science Summer Camp, since that's what everyone calls it. I'll fill you in on what you missed if you weren't there.


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Image Credits:

  1. Energy Vanguard
  2. Texas A&M, Professor Charles Culp
  3. Thomas Battoe
  4. Mike MacFarland

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The Uniform Mechanical Code Looks to Limit Flex Duct

A current proposal recommends limiting length to 5 feet and requiring rigid elbows

Posted on Dec 21 2016 by Allison A. Bailes III, PhD
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Some people love flex duct. Some people hate it. Some of us are OK with it if it's done right.

As I've documented here numerous times, many flex duct installations leave a lot to be desired. They sag. They're kinked. They're twisted around pipes.

If there's something bad that can be done with flex duct, someone has done it. And the result of all those mangled flex duct installs is poor air flow, which creates comfort problems, uses more energy, and is one reason systems get oversized.


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Image Credits:

  1. Energy Vanguard

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The Science of Air Flow in Flex Duct

A Texas A&M study shows how much of a hit you take when you let flex duct sag

Posted on Sep 16 2015 by Allison A. Bailes III, PhD
prime

Sagging flex duct is bad for air flow. We all know it. We all talk about it. It turns out there's research data to prove it, too. Texas A&M did a study a few years ago to look at the pressure drop that occurs for different levels of compression. If you're not familiar with this study, the results may astound you.


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Image Credits:

  1. Energy Vanguard
  2. Kevin Weaver and Charles Culp, PhD, PE

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The Difficulty of Stopping Air Leakage Between the House and Garage

I-Joists and open-web floor trusses, especially with flex duct running across the garage wall, can be troublesome

Posted on Jun 10 2015 by Allison A. Bailes III, PhD
prime

A home with an attached garage is usually a home in which people breathe more carbon monoxide (CO). Of course, having an open carport or detached garage is better for air quality (and a feature that usually gets points for you in green building programs like LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. and EarthCraft House), but what if you don't want to give up that attached garage?


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Image Credits:

  1. Energy Vanguard

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The Two Main Reasons Your Ducts Don’t Move Enough Air

Understanding the physics of air movement can lead to better duct systems

Posted on Jun 11 2014 by Allison A. Bailes III, PhD

Two things. Just two things in your ducts are responsible for giving the blower in your furnace or air handler a hard time. They make the blower push against more pressure, thus reducing air flow or increasing energy use, depending on blower type. They cut the amount of air that gets delivered to the rooms. And they can be reduced but not eliminated. Do you know what they are?


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Image Credits:

  1. Energy Vanguard
  2. ACCA

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The Lipstick-on-a-Pig Million-Dollar Home Syndrome

Despite spending large sums of money, owners of expensive homes often get cheapo HVAC systems

Posted on Oct 16 2013 by Allison A. Bailes III, PhD

I wonder about a lot of things. I wonder what life would be like if gravity were stronger. I wonder why Americans don't dance more. I wonder why so many people who can afford million-dollar homes get cheapo HVAC(Heating, ventilation, and air conditioning). Collectively, the mechanical systems that heat, ventilate, and cool a building. systems. That last one bugs me more more than the first two, by the way. It weighs on my mind because cheapo HVAC seems so out of step with the rest of a million-dollar home.


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Image Credits:

  1. Martin Holladay
  2. Energy Vanguard
  3. Bob O'Connor - Wall Street Journal
  4. Jamie Clark, Climate Control, Lexington, Kentucky

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How to Install Flex Duct Properly

Following the Air Diffusion Council's standards would lead to better installations

Posted on Mar 13 2013 by Allison A. Bailes III, PhD

I've written a lot about duct problems (especially those in flex duct) because they're so abundant. A couple of years ago, I even wrote an article in the Energy Vanguard Blog about whether or not flex duct should be banned. My answer was no — but that we need better quality control.


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Image Credits:

  1. Energy Vanguard
  2. Air Diffusion Council
  3. Robert Bean

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Should Flex Duct Be Banned?

Like fiberglass batt insulation, this product is rarely installed properly

Posted on Nov 28 2012 by Allison A. Bailes III, PhD

Ah, flex duct. That bane of home performance contractors and green builders everywhere. If you’ve seen only one forced-air duct system that uses flex, you’ve most likely seen a bad installation.


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Image Credits:

  1. Energy Vanguard

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