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. […]

We all learned how to read the tonnage off of a model number within a few weeks of beginning in the trade. What you may (or may not) have learned is that just because something has an 036 in the model number, that does NOT mean it actually produces 36,000 BTU/hr. It doesn't reach the […]

Take a look at the screenshots above. The one on the left is for Death Valley at 282′ below sea level, and the one on the right is Denver, CO, at 5,280′ above sea level. Notice the barometric pressure values; they are almost the same. That means that barometric pressure is corrected or “normalized” to […]