Schaefer Ventilation Equipment manufacturer of the HotZone radiant heater.

Heating people, not air.

Human thermal comfort is a function of ambient air temperature and humidity, the cooling effect of air movement and the amount of infrared, or radiant, energy shining on and being absorbed by your skin and clothes.

When the sun emerges from behind a cloud, you immediately feel warmer due to the increase in radiant energy received from the sun, although there is little or no change in the surrounding ambient air temperature. This is because radiant energy, which travels at the speed of light, elevates the temperature of solid objects when it is absorbed, but does not heat the air through which it travels.

Humans at rest tend to be comfortable at around 70°F or 22°C. When the temperature drops, we put on more clothes, get more active or turn up the heat.

Turning up the heat often means heating the air that surrounds us with some sort of central or in-space (local) convective heater. Air passing or being forced over a warm element or a pipe filled with warm water or hot combustion products absorbs the element's heat and becomes warmer.

Turning up the heat can also mean increasing the amount of radiant energy shining on you and the objects around you. There is a broad range of surface radiant heaters (floor, ceiling and wall; electric, hot water and gas) and reflector focused radiant heaters (low intensity (temperature) tube gas heaters and high intensity (temperature) gas and electric heaters.)

In many situations radiant, in-space (local) heaters are dramatically more energy efficient than any other heating choice. The energy efficiency stems from several factors:

  • Central heating systems are designed to get the whole building to 70°F, even when much of the building may be unoccupied. In-space (local) heaters, of any type, equipped with proper controls only heat the parts of the building that need heat, allowing most of the building to operate at lower temperatures and with lower heat losses.
  • Because you feel warmer with radiant energy shining on you, you can feel warm despite ambient temperatures lower than 70°F by as much as 15°F to 20°F. As heat losses from a structure increase in proportion to the difference between inside and outside air temperature, heat losses are reduced by 50% when the inside temperature is lowered to 55°F. and the outside temperature is 40°F.

In situations where there is poor or no insulation (factories, warehouses, outside) and high air exchange (factories, warehouses, stores, outside) the heat losses are huge, and therefore so are the savings with radiant heat.


If it isn't a HotZone® heater, it isn't spot heat!

The amount of radiant energy transferred between 2 objects increases as function of the fourth power of the temperature difference of the emitting surface and the receiver. A 1500° difference transmits 16 times as much radiant energy as a 750° difference.

Low intensity infrared (radiant) heaters include tube heaters and other low temperature sources. As the amount of radiant energy being transferred is quite low, the heaters have to be quite large. Tube heaters and other low intensity heaters heat people and objects with radiant energy and the air around them with large convective losses.

High intensity infrared (radiant) heaters include ceramic gas burners, exposed and enclosed electric elements and quartz lamps. These high temperature sources produce a great deal of infrared radiation with greatly reduced convective losses. Unfortunately, most of these heaters have very simple, ineffective reflectors and therefore do not focus or direct the infrared radiation.

Schaefer's HotZone® heaters:

  • Are the highest intensity gas or electric heaters on the market today.
  • Have a patented, lobster eye inspired, compound reflective lens that focuses and directs the infrared energy into a beam (or a spot).


Delivering heat from a distance.

Because HotZone® heaters focus and direct the infrared energy into a beam:

  • Heaters can be installed out of the way of people and equipment.
  • The radiant intensity is much less sensitive to distance from the heater (your head doesn't cook while your feet freeze).
  • Heaters deliver between three and five times as much infrared energy to the spot, compared to a similar powered, unfocused high intensity heater.
  • Heaters will raise the apparent temperature of a 25 square foot area by 20° with a single 3kW heater mounted 10 feet above the target.

Thermal comfort solutions using Schaefer's HotZone® heaters and appropriate heater controls:

  • Can reduce the energy cost for the same thermal comfort level (apparent temperature) by 30% to 50%.
  • Earns points towards your building's LEED Certification.
  • Are easy and cost effective to implement in new or existing facilities.
  • Can compensate for the thermal comfort deficiencies of the central heating system when no other heating technology can.
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