Why 50 Watts per Square Foot?

Why 50 Watts per Square Foot?

Many companies that design and sell snow melt systems specify 50 Watts (170.6 Btu’s) per Square Foot for the heating area. Delivering 50 Watts per Square Foot often times requires a very large source of energy (electricity, gas, oil, etc.), and costs a great deal to operate. Why are they designing snow melt systems that deliver 50 Watts (170 Btu’s) per Square Foot over the entire area to be snow melted? Surprisingly there are many reasons given but, only one of them stands up under scrutiny and, as a result, is justified from “in the best interests of the end user” perspective.

The only correct reason is: Given the geographic location of the project and the annual snow fall rates for that location, combined with the needs and desires of the customer, 50 Watts per Square Foot are required to satisfactorily melt snow.
Below are some of the most common, yet incorrect, reasons for designing 50 Watts (170.6 Btu’s) per Square Foot or some other equally subjective number into a snow melt system design.
Reason #1: Because 50 Watts per Square Foot is always necessary! – Maybe, if your project is a Helipad, or other critical area that must under any and all circumstances be clear of snow and ice, then that amount of heat may be correct, provided; the project is located in Vancouver, BC or Salt Lake City, Utah. In nearly all other snowy areas of the U.S. and Canada 50 Watts per Square Foot is not enough heat.  What about a non-critical driveway or sidewalk? While there is no definitive answer that is geographically neutral, most of the time residential and non-critical commercial/industrial snow melt projects require less than 50 Watts per Square Foot to satisfactorily melt snow, any more is a waste of energy, money and expensive service upgrades.

Reason #2: 50 Watts per Square Foot is What My Product Delivers! – Seldom spoken but frequently the real reason is simply that the project has been designed to meet the needs of the specific product that the party submitting the proposal represents. Designing the project to fit the product is problematic for many reasons including: it forces the designer to overdesign the materials necessary to satisfy the requirements of the project; it costs more both up front in materials, labor, and energy supply size; and, it costs more in operating expense.

Reason #3: It is Better to Over Perform When it Comes to Snow Melting! – Don’t fall for it; designing a snow melting system to “over perform” is code for “hang onto your wallet” not only up front but over the life of the system, which should be many years.

The Bottom Line! How much heat is required to melt snow in a given geographic area depends not only upon location but also upon the annual snow fall hours experienced and the needs and desires of the end user or customer. Heatizon Systems determines the correct amount of heat for its snow melt projects by relying upon information available from the American Society of Heating, Refrigeration, and Air Conditioning Engineers, Inc. (“ASHRAE”) and understanding the expectations of its customers.

Is 50 Watts per Square Foot needed to melt snow? Sometimes!

Steven Bench is the Managing Member of Heatizon Systems a leading manufacturer and marketer of electric radiant heating and snow melting products located in Murray, Utah.