Building Science & Load Calculation

This photo is of a blower door test we performed at my own house using a Retrotec blower door. You will notice the 15-passenger van outside the window, which is a dead giveaway. A blower door is used to measure the tightness of a building and is often discussed in terms of an ACH50 number. […]

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 […]

I didn’t install this unit. First off, attic installations are among my least favorite applications from the standpoints of serviceability, system longevity, and a laundry list of other items. Here in Florida, it’s just a bad idea due to the high humidity and temperature in a vented attic and the condensation issues that can and […]

You are probably all familiar with radiant barriers. Sometimes, it’s thin foil draped under the roof deck. Other times, it’s used on the inside of stud walls or over furring strips before the drywall goes up, and there is even plywood with a radiant barrier attached to one side that is used for roof decking. […]

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 […]