Building Science & Load Calculation

This tech tip features a diagnostic flowchart by Genry Garcia. Thanks, Genry! The name of this document, “The MAD Room,” was chosen as a nod to the MAD-AIR study completed by John Tooley and Neil Moyer, presented in 1989. The teachings from that document played an instrumental role in creating the following diagnostic workflow. Disclaimer […]

There has been a lot of advice being tossed around by contractors and builders about the best time to use the emergency heat feature on an all-electric heat pump system. The answer is never! That was easy. Next article… In all seriousness, “Emergency Heat” should be used as described, ONLY during an emergency. I guess I should […]

Understanding the relationships between ductwork, home comfort, and the load on a house is a complicated and dynamic problem. There are a large number of variables. Some of the data is fairly straightforward, like the other elements of field data collection we have covered so far in this series. Ductwork has different levels of insulation […]

This tech tip recaps the livestream by the same name, featuring HVAC School contributors Matt Bruner and Adam Mufich and special guests Michael Housh, Chris Hughes, and Dustin Cole. You can watch that livestream on our YouTube channel HERE. “High-performance HVAC” is a term we hear quite a bit these days, but it’s not easy […]

A manual J load calculation will require you to input the U-value for the windows or “fenestrations” on the house. Fenestration is a fancy construction word for window. Figuring out the U-value and SHGC of a window on an existing home is very difficult. But first, let’s dive into what the terms U-value and SHGC […]

There are three types of floors: slab-on-grade, crawlspace, and basement. It should be fairly obvious when you are collecting field data as to what type of floor you are working with. Here is a brief overview of how each type affects a load calculation. Much of the information for this article comes from Allison Bailes’s […]

This article will cover how to collect field data for walls on an existing home for an ACCA Manual J calculation. In full disclosure, I had never collected any field data for a Manual J before I wrote this article. Many of the methods discussed were suggested by HVAC technicians and contractors in an online […]

Starting to work on a Manual J load calculation can feel extremely overwhelming. How do we know what to focus on? What does normal look like? What if I’m way off on something and install way too big or small of a unit? On a practical level, what is the payback or value of spending […]

This tech tip was a collaborative effort between Matt Bruner, Adam Mufich, Ed Janowiak, and Genry Garcia. Thank you to everybody who gave their input! The next time you come across a homeowner who wants a bigger HVAC system, or you simply want to set expectations for a customer, share this tech tip with them. […]