This post is to inform building owners of the meaning behind the termHVAC.”

“HVAC” is pronounced: “H” “VAC” – this is not understood by most, and for good reasons, given the complex breadth of the mechanical contracting trade.

A building may, or may not include Heating, Ventilating, or Air Conditioning (HVAC) systems. Of course, most buildings – residential and commercial – do include a heating system, which is essential in most of these United States. But most owners of heating systems do not know what type of heating system theirs is. So, here is a brief categorical breakdown.

H-V-A-C is broken down, as follows…


Heating System Types Include:

Gravity Hot Water (GHW) – Rare

Forced Hot Water (FHW)

Gravity Hot Air (GHA) (no fan/blower) – Rare

Forced Hot Air (FHA) (with fan/blower)


Heat-Generating Equipment (equipment that converts fuel/energy to heat)


Space Heaters


Water Heaters

Heat Pumps

Resistive Heaters



The Sun – Passive Solar – Glass Thermal Units

Terminal Units (equipment that emits heat that is generated by types of heating systems described above)

Steel & Cast Iron Radiators

Baseboard Convectors – Copper Fin Tube

Baseboard Convectors (Radiant) – Cast Iron

Panel Radiators (Convectors) – Steel

Fan Convectors (Hot water coil & Fan)

Air Handlers (Hot water coil and blower)

Radiant Panels (floor; ceiling; wall)

Burners (associated with heating)

Rotary-Type – (rare)



Pot-Type (rare)

Electric Resistive

Fuels (associated with heating)

#2 Fuel Oil

#6 Bunker Fuel

Waste Oils (typically, automotive and cooking oil)


Propane (LPG)

Natural Gas (NG)


Methane (fossil fuel-based and “other”)

Chord Wood

Wood Pellets

Bio Fuel (manufactured and derived from plants)



Here in New Hampshire, every building – intended to be occupied by humans in winter – has some type of heating system, but not all are “central heat” systems.

If/when you have a heating “emergency,” it will be helpful when you call an HVAC contractor/service company (in New Hampshire) to explain to them:

  1. What type of heating system you have.
  2. What type of fuel/gas your heating system utilizes.
  3. What the nature of your heating service issue is.

Happy heating!

A Radiant Heating System - designed and installed by John Rocheleau, in 1996


Ventilation Systems Types Include:

Heat Recovery Ventilators (HRV)

Energy Recovery Ventilators (ERV)

Non-Heat Exchange Ventilators

Carrier HRV Ventilator

Air Conditioning

Air Conditioning Systems Types Include:

  1. Central
  2. Ductless – “Mini Split”
  3. Swamp Coolers


Carrier 5-Ton Infinity Condensers

What is “Indoor Climate Control?

Indoor Climate Control (ICC) includes all equipment and systems that affect the Temperature; Air Quality; and Humidity of a space, and includes “HVAC” systems, as previously described. HVAC and ICC are often grouped together under the heading, “Mechanical Contracting.”  Mechanical Systems also include Fuel Tanks & Piping; Ducting; Fossil Fuel Venting; Kitchen Exhaust & Make-up Air (MUA); Combustion Air Supply (CAS); Snow- & Ice-Melting Systems; Pool Heating and Potable Water Heating; Fire Sprinkler/Suppression Systems… and this list is not even complete!

No wonder building owners are generally ill-informed about the meaning of HVAC; I can’t even recite it completely, and I have 37 years in the trade!


ERV, Make-up Air, Kitchen Exhaust & Packaged Heat/Cool RTU installed by John Rocheleau