Technical knowledge
HVAC Terminology Glossary
All the definitions you need to confidently discuss air conditioning, heating and dehumidification. No jargon, concise, in plain English.
Short, practical definitions. Each term has a permanent link (anchored URL) you can share with a client or installer. Missing a term? Email us and we'll add it.
COP
- Coefficient of Performance — the ratio of heating output to the electrical input drawn at a given moment. COP 4 means that for 1 kW of electricity you get 4 kW of heat. The value changes with outdoor temperature.
SCOP
- Seasonal Coefficient of Performance — averaged COP for the whole heating season in a given climate zone. For Warsaw the SCOP in the Average zone matters. The best heat-pump air conditioners reach SCOP 5.0–5.1.
Hyper Heating
- Air-to-air heat pump technology that holds full heating capacity down to -15°C and operation down to -25°C. Introduced by Mitsubishi Electric, also used in premium Daikin and LG models.
A2A (air-to-air)
- Air-to-air heat pump. The refrigerant collects heat from the outdoor air and releases it directly into the indoor air — no water, no radiators, no hydraulic installation.
DC inverter
- A compressor with stepless speed regulation driven by direct current. Instead of cycling on and off, it matches its output to current demand. Electricity consumption is 30–40% lower than in on/off models.
Dew point
- The temperature at which water vapour in the air starts to condense. When the surface temperature of a wall drops below the dew point, dew appears — and, in time, mould.
Relative humidity (RH)
- The ratio of water vapour in the air to the maximum the air can hold at that temperature. The healthy band for a flat is 45–55%.
Hygrometer
- An instrument for measuring air humidity. A good calibrated digital hygrometer costs 200–400 PLN and is the basic tool for every RH survey.
Hygroscopicity
- A material's ability to absorb moisture from its surroundings. Hygroscopic materials include wood, paper and gypsum plaster — anything that softens or swells in damp rooms.
Sorption
- The process where a porous substance (the sorbent) binds water molecules from the air. Used in desiccant dehumidifiers — most often silica gel or lithium chloride.
Adsorption
- The binding of water molecules onto the surface of a sorbent — without penetrating its structure. Reversible, which is why the rotor in a desiccant unit can be regenerated with heat.
Absorption
- The penetration of water molecules deep into the sorbent material — for example into a solution of a hygroscopic salt. More common in industrial use than in domestic units.
Hygrostat
- A humidity sensor that controls the dehumidifier. It starts the unit once RH crosses the threshold and stops it when the target is reached. The single most important component for comfortable operation.
Condensation
- The change of water vapour into liquid water. In a condensation dehumidifier, controlled condensation on a cooled evaporator is the core of how it works.
Evaporator
- The heat exchanger in a condensation dehumidifier where water vapour turns into droplets. Cooled below the dew point.
Refrigerant
- The gas circulating through the refrigeration circuit of a condensation dehumidifier — most often R290 (propane) or R32. It cools the evaporator.
Heat-recovery ventilation
- Mechanical ventilation with heat recovery. Exhaust air transfers its heat to the incoming supply air, and a dehumidification module can be integrated into the same unit.
BTU
- BTU (British Thermal Unit) — a unit of thermal energy. 1 BTU/h ≈ 0.293 W. Air conditioner capacity is often given in BTU/h; e.g. 12,000 BTU/h ≈ 3.5 kW. Standard in US and Asian catalogues.
kW
- kW (kilowatt) — a unit of power. In air conditioning it denotes the cooling or heating capacity of a unit. Typical values for flats: 2.5–7 kW. Not to be confused with kWh — the unit of energy consumed.
EER
- EER (Energy Efficiency Ratio) — the cooling efficiency ratio, the cooling-mode analogue of COP. The higher, the less electricity the unit uses. An instantaneous value; the seasonal equivalent is SEER.
Split
- Split — an air-conditioning system with two units (indoor in the room + outdoor on the wall or balcony), connected by a refrigerant line. The standard for houses and flats.
Multi-split
- Multi-split — a split variant with one outdoor unit serving 2–5 indoor units. It saves façade space in multi-room flats and reduces the number of wall penetrations.
Outdoor unit
- Outdoor unit (condenser) — the part of an air conditioner installed outside the building; it houses the compressor and a heat exchanger. It requires a spot with free airflow and proper vibration isolation.
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