Hydronic heating is a system that uses water as the medium to distribute heat throughout a home, rather than relying on heating air. In simple terms, this means that water is used as the heat-transfer fluid used to warm the living space. Although hydronic heating offers many advantages, it can be challenging to incorporate into an existing home which is why it is usually incorporated when building a new home or home extension. This guide will walk you through everything you need to know about hydronic home heating.
Understanding hydronic radiant heating
People often confuse the terms radiant heating and hydronic heating, but they are not synonymous. While hydronic heating involves water as the heat-transfer medium, radiant heating refers to heating surfaces to the point that they emit infrared radiation, which then warms objects and people directly.
Unlike traditional air-based heating systems, which focus on warming the air with a furnace, radiant heating focuses on warming solid objects, including people, which tends to create a more comfortable environment. The most common radiant heating setup is floor heating, as warm floors provide the greatest comfort, particularly since people generally feel more comfortable with warm feet and cooler heads.
Hydronic radiant heating systems are typically either 'wet' or dry'. Wet installations are most common in new builds, where PEX pipes are embedded in concrete floors. As hot water circulates through these pipes, it evenly heats the floor and the surrounding space. For existing homes or where a poured floor isn’t feasible, 'dry' installations use PEX pipes placed in joist spaces or beneath suspended wood floors, distributing warmth through the floor above.
Hydronic under floor heating systems are comfortable, efficient, and can help maintain healthy indoor air quality as they do not circulate air and dust particles. Heat delivery happens by circulating hot water through a closed-loop network of pipes embedded in a floor, which is typically poured concrete.
This system requires a boiler to bring water up to temperature if the intention is to provide sufficient heat for the entire home. A standard water heater is a possible money saving option if the intention is simply to warm the floor for comfort and not to condition the entire space.
Other types of hydronic heat for homes
Hydronic radiators and baseboards: These are an alternative to electric baseboard heaters. The delivery of heat is the same, but rather than electric resistant wire heating, it uses water as the heat delivery medium.
Hydronic radiators are a more complicated system than electric wires and they have greater risk of causing damage as they can leak. if you have a geothermal home heating system or an air to water heat pump then it can be a money saver, but if not, you may be best to just stick to standard electric baseboards, or electric convection heaters.
Hydronic radiant wall heat: Radiant floors are something most people in colder climates may be aware of, a less common radiant home heating system are radiant walls. This is a very uncommon home heat delivery system that does have its benefits, but it has many drawbacks as well.
How hydronic under floor heat works
As heated liquid is pumped through a floor it heats the mass around it, such as concrete. That heat then warms the air and furnishings of the home and the people in it. Water leaves the boiler and circulates in loops in the floor before returning cooled and ready to be heated again.
Typically for residential systems you would use half inch Pex tubing with zones no more than 300 hundred feet long. If zones are too long, they will cool off and perhaps not provide sufficient or balanced heating.

Energy efficiency and sustainability of hydronic floor heat
Hydronic systems can be more energy-efficient than traditional forced-air heating systems as they heat the space you occupy, meaning floor level rather than ceiling level. Learn more here about what affects your thermal comfort in a home.
So, with a radiant heated floor it is possible to keep you more comfortable with less energy injected into a home, as it is concentrated at floor level, which is your contact point with the house. Standing on a warm floor you will feel more comfortable with a lower air temperature than when standing on a cold floor.
Should you use glycol or water with hydronic under floor heating?
Glycol is used in hydronic radiant floor systems primarily when there is a risk of the system freezing, such as with garages, seasonal homes, or areas where pipes may be exposed to freezing temperatures. Unlike water, glycol prevents freezing, reducing the risk of pipe damage.
However, glycol has lower thermal conductivity than water, which means it transfers heat less efficiently. So the delivery of heat may be a bit slower, but that should not have a very noticeable effect on comfort.
Additionally, glycol systems require more maintenance as glycol can degrade over time, forming acids that could harm pipes and components.
The use of glycol also increases costs due to the antifreeze additive and the need for periodic fluid replacement. In systems where leaks are a concern, glycol is less eco-friendly and more expensive to replenish than water. For most indoor applications in controlled environments, water is the more cost-effective and efficient choice.
A last thing not to be overlooked about a glycol hydronic system is if there is a leak, which can contaminate ground water. There are some cases where insurance companies do not look favorably on glycol systems due to the risk of contaminating the ground below, so a quick call to your insurance provider to get a clear answer on that may be a smart move.
Hydronic floor heating with renewable and efficient energy sources
When paired with renewable energy sources, such as solar thermal water heaters or geothermal systems, hydronic heating becomes a sustainable option that significantly reduces carbon footprints.
Additionally, the even distribution of heat eliminates the need to overcompensate for cold spots, allowing the thermostat to be set lower without sacrificing comfort. This efficiency is further enhanced by the thermal mass of materials like concrete or tile, which retain heat longer and reduce the need for constant operation.
Pairing a hydronic system with a air to water heat pump is a very efficient method of heating water, it would however still require passing through a boiler to get it up to temperature.
Comfort and performance
Hydronic systems provide consistent and uniform heat, avoiding the drafts and dry air often associated with forced-air systems. The absence of moving air also means less dust and allergens, contributing to improved indoor air quality—a crucial factor for those with respiratory sensitivities.
However, hydronic systems are slow to heat up or cool down due to their reliance on the thermal mass of flooring materials. This characteristic can be a drawback in homes where rapid temperature changes are needed but is beneficial for maintaining stable temperatures in well-insulated spaces.
Installation and maintenance of hydronic under floor heat
Installing a hydronic radiant floor system requires careful planning and is best suited for new constructions or major renovations. Retrofitting can be complex and costly, particularly in homes not designed to accommodate the added thickness of embedded pipes. Once installed, the system has fewer moving parts compared to forced-air systems, resulting in lower maintenance needs and a long lifespan.
Given that the system is pressurized, care must be taken during the installation of tubing so as not to puncture them. Be very careful with walking on them, or placing them on top of potential hazards such as the cut ends of steel reinforcement mesh.
It is recommended to pressurize the system to check it for leaks before pouring concrete, as that is about your last chance to make a repair if one is needed.
Be sure to have a clear and accurate zone map so you know where tubes are located. Be sure they are sufficiently deep so there is ample concrete coverage on top, aim for at least 3/4 inches. You must also be diligent with the installation of division walls afterwards, avoid concrete fasteners that may pierce a tube.
Are electric or gas boilers better?
Like forced air furnaces, a radiant floor heating system can be powered with gas or electricity. The only argument in favor of heating a home with gas is that if you live in an area where gas is cheaper than electricity still. I say still because it won't be for long, and setting yourself up with a seemingly cheaper system now may cost you a lot more money in the near future.
See here about why gas is being phased out as a home heat source, even more importantly see here the health impacts of gas cooking and heat in homes.
Pros and cons of hydronic under floor heating
Pros
- Energy efficiency: Requires less energy to heat spaces compared to forced air.
- Comfort: Provides consistent, even heat without drafts or dry air.
- Air quality: Does not circulate dust or allergens.
- Sustainability: Can be paired with renewable energy sources.
- Longevity: Durable with minimal maintenance.
Cons
- Slow temperature response: Longer time to heat up or cool down.
- Installation complexity: Best suited for new builds or major renovations.
- Upfront costs: Higher initial investment compared to some systems.
- Limited cooling capabilities: Requires a separate system for cooling.
Hydronic radiant floor heating stands out as an energy-efficient and sustainable option, particularly for homeowners looking for long-term comfort and cost savings. While the initial investment and installation challenges can be significant, the benefits of lower energy consumption, improved air quality, and a longer lifespan often outweigh these drawbacks. For environmentally conscious homeowners seeking modern comfort, hydronic radiant heating is certainly an option worth considering.
Now you know more about hydronic heating systems for comfort and efficiency. Find more pages about sustainable construction below and in the Ecohome Green Building Guide pages.
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