Many contractors in northern climates stick to inside work during winter because digging and pouring a foundation can be hopeless if large areas of ground are frozen. In addition, pouring concrete over frozen ground can lead to structural issues when the ground thaws.

That’s where a ground heater, also known as a ground thaw machine, ground frost heater or ground thaw system, can come in handy.

What is a ground heater?

These portable units heat surfaces and thaw frozen earth, allowing contractors to carry out excavation and foundation work when the temperature drops. In addition to extending the working season, ground heaters decrease stress on equipment and make in-the-dirt tasks less labor intensive by softening the soil.

Ground heater types and how they work

How do ground heaters work? To answer that question, it helps to walk through the two main types of ground heaters.

Hydronic heaters

A hydronic ground heater or glycol heater consists of a boiler, a pump, a blower fan and a long hose filled with a propylene glycol mixture.

The heating hose is laid out in evenly spaced loops on the surface that needs heating. The fuel-fed boiler heats the propylene glycol mixture, which is pumped through the hose, heating the ground or other surface. The blower fan blows heated air across the area, and a vapor barrier is placed over the hose to keep moisture in. An insulated blanket can be laid over the hose to prevent heat from escaping.

Hydronic ground heaters can cover a large area efficiently, with little heat loss. This model with a 3,000-foot hose can cover 6,000 square feet, for example.

Ground thawing blankets

Ground thawing blankets are essentially electric blankets used to warm frozen earth and other surfaces. Easy to throw over any surface, or even a piece of heavy equipment to keep the engine warm, the blankets are conveniently moved from one area of a worksite to another as long as a power outlet is available.

Common uses of ground heaters

There are several uses for ground heaters that keep construction sites humming during the colder months.

Prevent and remove ground frost

To remove ground frost, the hose of a ground heater is placed directly on the soil, covered by a vapor barrier and then covered once more by an insulating blanket if desired. This method can thaw about 6 inches of frost every 24 hours, which eliminates 3.5 feet of frost over seven days. It's not an overnight fix, but it beats waiting for spring.

Cure concrete

After a pour, concrete must be allowed to cure. If the concrete freezes, the curing process may take longer or result in uneven curing or cracks. Freezing can reduce concrete strength by up to 50%.

A hydronic ground heater such as this diesel model capable of thawing 10,000 square feet is used at the pour location to warm the ground to between 85 and 90 degrees. After the pour, the heater can be used to maintain the concrete's temperature until it has reached the required strength.

Warm the air for workers

In cold weather, worker productivity often suffers. Ground heating systems can be used to create warm ambient air for workers in small enclosures or well-insulated and dried-in areas. The hoses that would typically be laid on the ground or on top of concrete are connected to a portable heat exchanger or fan coil. Air is then blown across the heated coil and into a space or, using a setup of several heat exchangers, multiple spaces.

De-ice surfaces

Ground thawing blankets can be used to de-ice sidewalks, worksite walkways and other surfaces as well as to thaw frozen pipes and melt snow from roofs.

Visit our online marketplace to view our selection of ground heaters.

Kim Slowey is a writer who has been active in the construction industry for 25 years and is licensed as a certified general contractor in Florida. She received her BA in Mass Communications/Journalism from the University of South Florida and has experience in both commercial and residential construction.