Glycol for Heating Systems

Glycol Heating System Options

Two primary types of heat transfer fluids are ethylene and propylene glycol:

• Propylene Glycol – A non-toxic, low-toxicity option. Commonly used for in-floor heating, hydronic boilers, and solar heating systems.

• Ethylene Glycol – Higher heat transfer efficiency but is toxic and requires careful handling, which is why it is more commonly used in industrial systems where human exposure is not a concern.

Propylene glycol is the preferred choice over ethylene glycol for residential and commercial heating systems because it is non-toxic, safer to handle, and more environmentally friendly.

Glycol Solution Options

A glycol mixture helps lower the freezing temperature of the system’s heat transfer fluid, preventing pipes from freezing and bursting in cold weather. At the same time, it raises the boiling point, reducing the risk of overheating and vaporization in high-temperature applications.

We offer three glycol concentration options to meet the needs of different heating systems:

40% Propylene Glycol Solution

A solid option when freeze protection is important but extreme cold isn’t a constant threat. A 40% glycol mixture keeps heat transfer efficiency high, meaning it moves warmth more effectively through your system. Less glycol also means lower viscosity, so it flows more easily, reducing strain on pumps and system components.

It protects down to -10°F (-23°C), making it ideal for solar heating systems, hydronic boilers, and radiant floor heating in moderate climates. If temperatures tend to drop lower, you might need a stronger concentration to keep things running smoothly through winter.

Best for: Solar heating systems, hydronic boilers, and radiant heating applications

50% Propylene Glycol Solution

One of the most widely used concentrations, especially in cold climates. A 50% glycol blend delivers solid freeze protection without sacrificing heat transfer efficiency. It’s strong enough to handle freezing temperatures while still flowing easily through pipes, pumps, and heat exchangers.

With protection down to -30°F (-34°C), it’s a reliable option for in-floor heating, closed-loop hydronic systems, and any setup that needs to withstand harsh winters. Plus, it’s formulated with corrosion inhibitors, helping to extend the life of your system by preventing rust and scaling inside metal parts.

Best for: Cold climate heating systems, in-floor heating, and closed-loop hydronic distribution systems

100% Propylene Glycol Solution

For extreme cold, 100% glycol offers the strongest freeze protection available. When properly diluted, it can prevent freezing down to -60°F (-51°C), but that doesn't necessarily mean that pure glycol is always the best choice. It’s more viscous, meaning it doesn’t flow as easily. It also has lower heat transfer efficiency than diluted solutions. That’s why most systems require a balanced glycol-to-water ratio—too much glycol, and you lose efficiency.

Why the Right Heat Transfer Fluids Matter

Using the wrong glycol concentration can wreck your system. Too much glycol, and heat transfer efficiency drops. Not enough, and pipes freeze, pumps fail, and expensive repairs pile up. Here’s what can go wrong:

• Inefficient Heat Transfer – If the mix is too concentrated, it lowers thermal conductivity, meaning your system has to work harder to heat or cool the space.

• Corrosion and Scaling – Without the right inhibitors, pipes, pumps, and heat exchangers start to break down, leading to rust and mineral buildup.

• System Damage from Freezing or Overheating – An improper glycol mixture can leave pipes vulnerable to ice damage or cause the system to overheat, which can destroy components.

• Higher Maintenance Costs – Poor fluid quality shortens your system’s life expectancy, which could mean more frequent repairs.

Hydro Solar – High-Performance Products for Reliable Heating & Cooling

At Hydro Solar, we know that a hydronic heating system is only as reliable as the fluid circulating through it. 

Choosing the right heat transfer fluid isn’t just about keeping a system running. It’s about protecting your investment for the long haul. Too much glycol, and heat transfer efficiency suffers. Too little, and pipes freeze, pumps fail, and costly repairs add up. Balancing performance, protection, and efficiency is key to getting the most out of your heating system.

Not sure what you need? Our team is here to help you. Contact Hydro Solar today if you have specific questions or use our design request form to get your project started.