Knowledge Center
Guides that explain the ideas behind the calculators. Every article is reviewed for factual, technical and editorial accuracy before it is published.
- Airflow & Ducts
400 CFM per ton: when to use more or less
400 CFM per ton is a starting point, not a target. See how airflow trades temperature drop against moisture removal and when to go lower or higher. - Psychrometrics
Dew point vs relative humidity explained
Relative humidity changes whenever the temperature does; dew point doesn't. Learn what each one means and how to predict condensation on windows and ducts. - Energy & Operating Cost
Heat pump vs gas furnace running costs
Compare heating fuels on one scale: cost per million BTU of delivered heat. Worked examples, the break-even electricity price, and what changes the answer. - Energy & Operating Cost
SEER vs SEER2: what changed and how to convert
SEER2 replaced SEER in 2023. See why the numbers are lower, how to convert between them, and the federal minimums by region. - Sizing & Loads
Why square feet per ton fails for AC sizing
The 400–600 sq ft per ton rule of thumb ignores what really drives cooling load. See why it oversizes systems and what to use instead.