Forced Hot Air:
In a forced-air system, fuel burned in the furnace releases heat energy to air circulating through it. The hot air is then blown by a fan that is timed to cycle on and off with the furnace.

Hot Water Systems:
  Gravity - Operates on the principle that warm water rises. Hot water circulates from the boiler through large supply pipes, to the radiators. Cool water returns to the boiler due to the weight difference between warm and cool water. The lowest radiator must be located above the top of the boiler.

  Forced - Hot water is distributed by a pump. Pipes that carry the water to the boiler can be located above or below the boiler.

Radiant Heat:
Radiant heaters use the same means of heating as does the sun

Radiant heating systems involve supplying heat directly to the floor or to panels in the wall or ceiling of a house via flexible tubing under the floor.

A/C:

Ductless Split Systems:

Ductless split-system air-conditioners combine the zoning flexibility of a conventional room unit (a single air-conditioner installed through a wall or a window frame) with the whole-house cooling potential of central systems.

The term, "split-system," also describes some central air-conditioners and heat pumps. If you ask about ductless, split-system air-conditioners, make sure the dealer understands which system you are talking about. Another common term for ductless split-systems is "mini-splits."

The Unico System:
Small duct high velocity central heating & air conditioning system

Hot Water Heaters:

Tanks:

A  water heater (either gas or electric) offers a ready reservoir—from 20 to 80 gallons—of hot water. It operates by releasing hot water from the top of the tank when you turn on the hot water tap.

Tankless:

Demand water heaters heat water directly without the use of a storage tank. Therefore, they avoid the standby heat losses associated with storage water heaters.

Whole House Humidification:

Clean steam humidifiers can be added to home as part of the HVAC system to boost whole house humidification. Controlling the amount of humidity is easy for homeowners, just a touch or the dial to the recommended moisture setting.