# Calculating a proper heater loss and getting it right

April 1, 2023

What are the differences in how you calculate heat loss for Gas-fired Radiant infrared systems verses a forced air systems for a building?

There are a few key differences between a heat loss calculation for a forced air system and an infrared system.

1. Methodology: The methods used to calculate heat loss for a forced air system versus an infrared system are different. A forced air system typically uses a calculation based on the volume of the space, the desired temperature, and the thermal resistance of the building components (walls, windows, etc.). An infrared system, on the other hand, relies more on an analysis of the radiant surface temperature and the emissivity of the building components.

2. Emissivity: Emissivity is a key factor in calculating heat loss for an infrared system. It is a measure of how well a surface can emit radiant energy, or heat. Different materials have different emissivities, which can affect their ability to retain heat. For example, a low-e window has a lower emissivity than a standard window, which means it reflects more radiant heat back into the room and prevents it from escaping.

3. Radiant heat transfer: Infrared systems primarily rely on radiant heat transfer, whereas forced air systems rely on convective heat transfer. Radiant heat transfers heat directly from a warmer surface to a cooler surface without the need for air movement, while convective heat transfer requires air movement to distribute heat throughout a space. Because of this, infrared systems can be more efficient, since they don’t rely as much on air movement to distribute heat.

Overall, both forced air and infrared systems require accurate heat loss calculations to ensure they are sized and installed correctly for optimal performance. However, the specific factors that are considered will vary depending on the type of system being installed.