When it comes to heating and drying needs on construction sites, a fuel-efficient system can significantly affect operating costs. The major types of heating systems are direct-fired open flame, indirect air and circulating water (hydronic). Hydronic heaters offer good fuel efficiency and do so while minimizing fire risk.

In hydronic heating, a central heater is located outside and warms a heat transfer fluid (typically a propylene glycol). The heated fluid pumps through a fluid-circulation system loop to remote heat exchangers (also called fan coils) that remove heat from the fluid to the area to be heated. The heat transfer fluid returns via the closed loop to the central heater for reheating. Hydronic heating systems reheat ambient air rather than cold outside air, so they typically are more fuel efficient than open-flame systems.

Circulating-fluid heating systems can do more than provide heat during times of plant expansions and construction projects, however. They also can be used in conjunction with a boiler bypass to produce potable and nonpotable hot water for a building during boiler repair or replacement.

Selecting the appropriate capabilities in a heater system is crucial to a project’s success. Here are 10 items to consider when matching the plant’s heating and drying needs with an appropriate system.

1. Optimize Heat Distribution

If a traditional indirect heater is set up at a site, heat enters at one end of the plant, but the other end will be cold. Work-around options such as using fans to avoid temperature stratification do not always deliver good results and consistent ambient conditions. A lack of consistent temperature results in an inconsistent work environment.

A hydronic heater, however, offers even points of distribution for the heated air inside the construction site. The uniformity of heat distribution helps ensure the construction area being heated is of the highest quality.

Hydronic heaters can be scaled up to meet the heating needs of larger facilities.

heater system

Selecting a heater system with the output and capabilities needed to meet the project objectives is crucial to a project’s success.

2. Gain Energy Efficiency

The most efficient way to transfer heat is via fluid heat transfer, which reduces overall fuel consumption. Conventional methods of temporary heating typically call for indirect-air or direct-fired open-flame heaters. These methods are inefficient, however, because they must heat outside air. Reheating warm ambient interior air allows for fuel savings.

Hydronic heating systems can attain a fuel efficiency of around 83 percent and lower total operating costs. Such systems reduce the environmental impact and greenhouse gas emissions. As an added benefit, they are designed to vent directly to the atmosphere. Many other systems vent into the work environment. Venting directly to the atmosphere eliminates the need for ventilation of noxious fumes.

3. Defend Against Mold

If a 1 million BTU direct-fired open-flame heater is used to provide heat in a construction area, it can add substantial amounts of water to the air every 24 hours. All that moisture, at minimum, can delay projects. At worst, high levels of moisture can allow mold and mildew to grow.

A hydronic heating system removes moisture from the ambient conditions by introducing dry air. Using an efficient heater to decrease moisture in the air can improve worker comfort and accelerate some stages of construction.

flame and moisture

Designed to be free of fumes, flame and moisture, an indirect-fired tri-fuel heater such as this one is available in size to 3.8 million BTU/hr.

4. Seek a Proper Cure

Some construction projects begin with digging below ground. Curing the concrete requires exposure to a steady amount of heat for a certain period of time. Improperly cured concrete can wreck project economics and schedules if the concrete must be replaced.

A hydronic heating system can safely provide the temperatures required for proper curing of the concrete and prevent concrete carbonization. Hydronic heaters can be supplied with a mixer booster system to control the desired temperature and maintain the optimum curing environment.

Such heating systems make it possible to pour concrete year-round, which extends the window in which plant improvements can be completed, while avoiding the risk of poor concrete curing quality.

5. Sometimes It Is About Water

When it is necessary to carry out planned maintenance or provide emergency heat if a plant’s ambient heating system fails, a boiler bypass can provide interim heating. A boiler bypass, also a hydronic heating system, can cost-effectively heat nonpotable and potable water on a temporary basis.

The use of a boiler-bypass system should be included for all planned maintenance so there is no service interruption to ongoing operations. In the case of a heating emergency, a boiler-bypass system can be brought to the site rapidly to provide the needed heating services. In either case, a boiler-bypass system ensures the facility has access to hot water for both nonpotable and potable water applications.

6. Connect with Direct Interface

A temporary boiler-bypass system with a plate exchanger can tie directly into the plant’s water system. It also is possible to use one plate exchanger for nonpotable water and a separate plate exchanger for potable water.

Multiple units can safely be used at a site to meet the emergency heating requirements.


An indirect-fired gas heater can be used for industrial and construction applications where warm air is required.

7. Seek Open Ventilation

When response time is critical for providing heat while a boiler is down, opt for a boiler-bypass system. Boiler-bypass systems are inherently safe and, as such, do not require compliance steps like obtaining certification tickets and 24-hour, third-party certified boiler technicians that are necessary when using other boiler heating systems.

8. Reduce Fuel Consumption

Reducing fuel consumption and carbon emissions is good for the environment, but it is also one of the fastest ways to reduce operating costs on a project. A highly efficient fluid superheater can offer up to 90 percent fuel efficiency with 25 million BTUs when heating large volumes of fluids.

9. Continue Production

When interim heat is needed for turnarounds, maintenance or even full plant startups, temporary heating systems provide a ready heating source. High capacity temporary heating systems can keep large bodies of fluids heated.

fluid superheater

A fluid superheater such as this tri-fuel design can offer up to 90 percent fuel efficiency and 25 million BTUs when heating large volumes of fluids.

10. Reliability and Redundancy

For large-scale applications, larger capacities are necessary. The most reliable large-scale heaters make it easy to switch between different types of fuel while offering multiple ways to mitigate risk and provide redundancy. For example, a unit with two burners allows operations to continue even if one burner goes down. As well, if the fuel supply to a burner is interrupted, a system with an on-board backup fuel supply will allow continuous operation until the primary fuel is restored.

In conclusion, the choice of heating method can affect the success of any given project, as well as safety and operating costs. The hydronic heating system offers a sound choice for temporary heating during plant expansion and construction projects.