ICY · English
Building science essentials
Understand how heat, air and moisture affect a building. These essentials help you describe a problem and plan safe observations.
This essentials page is in English. Longer guides, diagrams, downloads and the community directory are also in English. This is education, not site-specific engineering or confirmation of local service.
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Temperature and heat are different
Temperature describes a thermal state; heat is energy transferred because of a temperature difference. Without active work, heat flows from warmer to cooler regions. A cooling system moves heat; it does not make it disappear.
Follow the paths of heat
Heat can pass through materials (conduction), travel with moving air or water (convection), and transfer by radiation. Sun, occupants, equipment and outdoor air can add to a building’s cooling load. Examine the load before choosing more capacity.
Moisture depends on conditions
Relative humidity depends on temperature. Condensation can form when a surface is at or below the dew point of the nearby air. Record air temperature, humidity and surface temperature together; one humidity reading does not identify the moisture source.
Ventilation is not recirculation
Ventilation replaces indoor air with outdoor air; recirculation moves air within a system. They are not the same. Airflow and pressure depend on fans, ducts, filters and openings. More outdoor air can also add heat or moisture.
Cooling needs a heat-rejection path
Cooling may lower temperature and remove moisture; these are different loads. Nameplate capacity is not a measurement of performance under current conditions. A portable air conditioner must reject heat somewhere; discharging that heat indoors can undermine the intended cooling.
Keep a useful measurement record
Record time and time zone, location, units, instrument, operating conditions and measurement limitations. Compare repeat observations under similar conditions. Keep observations separate from possible explanations. A single reading or a small difference within measurement uncertainty is not proof of a fault.
Observe safely
Observe only from safe, accessible places. Do not open electrical or refrigerant systems, bypass protections or enter dangerous areas. Stop if conditions appear unsafe and seek appropriate local help. This guide does not replace professional assessment or applicable local requirements.
Read the sources and limitations in the linked English guides.