HVAC & Plumbing Tools
Trade constants that turn out to be derivations — and the denominators that decide what a number actually means.
Sensible Heat & Airflow Calculator
BTU, CFM and temperature rise — where the famous 1.08 is density times specific heat times sixty, and falls to 0.93 in Denver.
Air Changes Per Hour CalculatorACH from airflow and room size — a number whose whole content is its denominator, so one fan spans a fortyfold range of ventilation.
Duct Size & Air Velocity CalculatorDuct diameter against air velocity — an inverse-square law, so doubling the duct quarters the speed and one size up fixes a noisy run.