Hughes Views #6 Building Science, The Missing Component of HVAC School

Such a generic term “Building Science”. Tell that to a customer and watch the thousand-yard stare! Ladies and gentlemen, we are no longer living in the days of common builds. What is a common build you say, well for me that would be a traditional house on a slab with batt insulation in the walls and ceilings, toss in some 4 foot windows then and mix that with a standard shingled roof incorporated with whirly birds and voila! If you were to ask me where that good old rule of thumb came in stating that 500 square feet a ton was a perfect guess; this would be it! You know these houses; they are all the same as far as load calculations are concerned. Hell don’t build a bedroom in this house wider than 11’ or you are going to have to order special carpet to fit, and you know that isn’t happening. I cannot tell you why builders in this era would not embrace better materials and building practices. I would assume that energy was not much of a concern, so what was the point of spending more for better products. I also believe we did not have anywhere near the understanding about air quality that we do today. Have you ever been in a foamed house, talk about clean!
Fast forward to present day, it seems like every few months there is a new product from manufacturing that’s sole purpose is to increase energy savings. Well here is where things got interesting. Run a blower door and load calculation on two thousand square feet with batt insulation with a vented roof and no attention to air sealing, now run the same tests with foamed walls and a foamed encapsulated attic space. Yeah, two different animals! Not to mention, you also are diving into another dynamic of how to deal with this attic, and boy I will tell you, there are some opinions out there on that one!
Good news here! In 2020, I went to the first HVACR training Symposium. While mingling at the event with the underground experts from the field, one of the guest speakers was a man named Dr. Allison Bailes. Dr. Bailes spoke a great deal about “Building Science” and I was all ears. He has a new book coming out (“A House Needs to Breathe…Or Does It?”) that is supposed to clear up misconceptions for us contractors about how to address situations that are formerly misunderstood. I have yet to get my hands on the book as I he is finishing it up right now, but you bet I will have it as soon as it comes out.
You’re in luck! From what I gather not many of the country’s HVAC force has jumped on this bandwagon of knowledge. I see many of my constituents looking the other way. I totally understand why one would want too; I mean this trade is challenging enough without building science. So, here’s what I am going to encourage you to do if you want to play the game. BUY A BLOWER DOOR! This is where it all starts. If you are going to do load calculations, a large input factor for the Manual J load is a true blower door number. If you have not heard of this by now, listen up because I am about to lay down your resources. There are two manufacturers that I would recommend for blower doors (The Energy Conservatory (Minneapolis Blower Doors) and Retrotec). There is great dialog going on in social media if you care to peak in. This is great for you because that means these guys care a great deal about the success of their products and are your fingertips for advice, and that is something America is missing a great deal of these days! Now if you need some advice on what you can do with this blower door then I would say look no further than Mr. Nate Adams, he as well can be found on social media advocating the use of the blower door, and is full of tenacity.  
I wish I could say I was a “building Science” expert, but that would be a lie. Hell, I am going to level with you, one of the main reasons I started The HVAC Grapevine was to be able to put all of these guys in one spot so I could grab nuggets of knowledge. After being in this trade for some time, I don’t know if anyone should go around saying they are an expert.   With the new products coming out all the time and the dynamics changing daily, it’s almost impossible to be an expert. Here’s the beauty of social media, I can see a new product for the first time, take a snap shot and post it to social media, within the blink of an eye I have an army who will help get down to the bottom of it. So, if the idea of jumping into building science scares you, maybe it should that way you will take it seriously. Whether you know it or not, you are already involved! Remember that there is a whole team of people here to help you, and the best part is, it costs you nothing. Wait that is not exactly true… The true payment is the time you spend to get involved and join the conversation. Show us what you are learning and contribute, that is the real payment.  

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Chris Hughes of Madisonville, Louisiana is a mechanical contractor, writer, HVAC enthusiast, and founder of Hughes Mechanical Contractors and The HVAC Grapevine.  He also writes and hosts The HVAC Grapevine Podcast.  You can follow him by joining his Facebook group or by subscribing to The HVAC Grapevine Podcast.  For any questions, he may be reached at

25th Jul 2023 Guest Blogger- Christopher Hughes

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