Building Science & Load Calculation

Windows might seem like the builder's problem, but they play a big role in what we do every day. Poorly designed windows can spike heat gain in summer or loss in winter, messing with load calculations and forcing HVAC systems to work overtime. That leads to uneven comfort, higher bills, and more service calls. Getting […]

This tech tip was heavily inspired by one aspect of Rick Sims’s 2021 HVACR Training Symposium session titled “Conductsation.” The entire presentation is worth a watch, but the advice in “Conductsation” and this tech tip are tailored to hot, humid climates. The contents of this tech tip may NOT work for colder climates. Dr. Allison […]

Equipment selection may seem like a pretty straightforward process: look at the data plate, find the tonnage that’s close to your Manual J calculation’s total load, and you’re good to go, right? The problem with that approach is that a 3-ton unit won’t deliver 36,000 BTUs per hour like it says on the data tag. […]

Fenestration is a fancy architectural term that means “openings in the outside of the building.” You will see this word a lot when you read ACCA Manual J or when you are doing a Manual J load calculation. Fenestration loads include heat losses and gains through windows, doors, skylights, etc., and they can make up […]

I’ve been designing a system for a home here in Dallas and noticed a couple of interesting (and disturbing!) things about the equipment’s advertised capacity vs. the actual capacity at design conditions.  Equipment is rated at AHRI conditions (95 degrees outside and 80-degree dry bulb, 67-degree wet bulb inside). These conditions make equipment performance LOOK […]

This tech tip was heavily informed by Ed Janowiak’s past symposium presentations. You can watch his presentation about setting proper airflow HERE. You can also now purchase your tickets for the 6th Annual HVACR Training Symposium HERE. HVAC School was founded by a Floridian—representing Climate Zone 2, to be exact. So, it’s no surprise that […]

This tech tip was written by Luke Peterson, the president of The Maintenance Department in Louisville, KY. Luke was a speaker at the 5th Annual HVAC Training Symposium in 2024 and has been on HVAC business panels at the symposium in 2023 and 2024. Thanks, Luke! As an HVAC technician, your primary goal is not […]

A few weeks back, I wrote an article called “5 Takeaways from Manual T.” That was a nice article, but I sense there was some disappointment. Some of you still want to know how to “do” a Manual T. Well, this article is for you! We are going to go through the process of selecting […]

“Did you do a Manual J?” “Did you run a Manual S on that?” “What does Manual D say?” If you’ve asked any design-related questions on the internet in the last several years, you’re probably familiar with these questions. But how does one “do” a Manual T? I bought Manual T last year and gave […]