With Radiant Heating You Can Be Comfortable and Sustainable

By Steve Swanson

Everything comes with a price in this world it seems. If you’ve ever thought about what it takes to maintain a comfortable temperature at home—all that expended fuel and electricity—you might have reached the conclusion that human comfort is diametrically opposed to a sustainable energy solution.

In other words, comfort comes at the cost of sustainability and vice versa. But what if I told you that a middle way existed in indoor comfort where you can have your cake and eat it too; i.e., stay comfortable while acting sustainably.

Well, it does, and it’s lined with radiant heating, a climate control solution that works both more efficiently and sustainably than traditional, forced-air heating systems.

Renewable energy— water, wind, etc.—can be used almost infinitely without running out. Nonrenewable energy—fossil fuels, wood, etc.— has a finite amount that will eventually be depleted. Sustainability refers to the controlled consumption of this nonrenewable energy.

Deferring energy use, though, has almost always meant sacrificing comfort. Shutting off the heat and wearing extra layers of clothing certainly means greater sustainability, but it also means less comfort. What exactly is comfort? The human body measures temperature by sensing heat loss or gain. When it comes to temperature, comfort is affected by how quickly or slowly heat leaves the body. Each person produces 500 BTUs of energy per hour, 100 of which are needed for metabolization.

The remaining 400 BTUs represent the expended energy that determines whether you feel hot or cold. If that energy leaves quickly, you will feel cold; if slowly, you will feel warm. So, with these numbers in mind, the solution to being comfortably sustainable must involve somehow using less available energy while still limiting the heat escaping your body.

Radiant technology puts that theoretical idea into practice. Hydronic radiant technology consists of warm water flowing through a network of crosslinked polyethylene (PEX) tubing embedded in a serpentine fashion under the floor. As the invisible waves of thermal radiation rise from the floor surface, they warm people and all the surrounding furnishings.

Unlike forced air, which transfers heat through convection, radiant transfers heat through radiation. A heat source—the tubing in the floor— emits electromagnetic waves through a transparent space without losing energy until these waves hit a cooler object: in this case, your body.

As a result, you feel more concentrated warmth than through convection, which loses heat to the air. Furthermore, since water can hold as much as 3,500 times the amount of heat as the same volume of air, it takes significantly less energy to sustain the process, leading to a lower monthly utilities bill.

This money-saving effect is bolstered when you consider air changes in your home. In a forced-air home, letting cold air in through an open door, or even running the normal air circulation necessary to maintain indoor air quality, expels warm air, wasting all that time and energy needed to heat it in the first place. Conversely, the water in a radiant system remains warm throughout. Once the door closes, your home will take little time to feel comfortable again.

Another major weakness of forced air that inhibits comfort is its uneven heat diffusion. Since hot air rises, most of the heat from a forced-air system winds up near the ceiling and distributes unevenly throughout the house.

Forced air thus runs contrary to human comfort, as revealed by the “Ideal Heating Curve,” which indicates that people, on average, experience comfort when the floor surface temperature is about 75 degrees Fahrenheit and the area around their head is around 65 degrees Fahrenheit.

Contrariwise, radiant heating follows the ideal heating curve almost exactly. Heat from below ensures your feet feel warm. Additionally, since the tubing lines the entire floor, heat is distributed evenly across the house, meaning no warm or cold spots. Finally, the ceiling area remains coldest, and rightly so, because there’s no reason for it to be warm up there. Radiant heating is thus extremely efficient when it comes to comfort.

In summary, radiant heating answers the question, “Can we act sustainably while maintaining personal comfort?” with a resounding YES!

Steve Swanson is the customer trainer at Uponor Academy in Apple Valley, Minn. He may be reached at steve.swanson@uponor.com.