Air vs. Water: Heat Transfer Efficiency

What is Meant by Air and Water Heat Transfer?

Air heat transfer involves the transfer of heat from warmer air to colder air. In space heating, this refers to convection or, more commonly, forced air heating systems, which are typically heated by a furnace. Another way to describe this is air-to-air heat transfer.  

Water heat transfer refers to hydronic systems. Typically, this requires a boiler or pump to heat the water (or other liquid) which then heats the air. This heat transfer can occur via water-to-air (i.e. a hydronic air handler), water-to-water (i.e. pool heat), or by conduction (i.e. floor warming).

Which Method is More Efficient?

In terms of efficiency, water heat transfer is undoubtedly more efficient. This is because water has a higher specific heat capacity (4.184 J/g C) than air (1.012 J/g C), meaning it is better able to regulate and retain heat than air. Additionally, water has higher thermal conductivity (~0.6W/m K) than air does (~0.24W/m K), which essentially means that heat transfers more easily from a water source than it does from an air source.

This doesn’t necessarily mean that liquid transfer heats a space faster than an air transfer system. However, it does suggest that a hydronic system heats a space more efficiently than forced air. Explained another way, this is because heat transfer happens 2.5x more easily in water than in air and can retain that heat 4x better than air can.

Other Benefits of Liquid Heating/Cooling

There are other added benefits to choosing a hydronic heating system:

1. Efficient: Hydronic systems, as explained above, are more efficient at heating than forced air systems.

2. Quiet: Forced air systems can be noisy due to large internal fans that produce a humming sound. A hydronic system is a quieter choice.

3. Comfortable: Hydronic systems typically heat the home more evenly than traditional forced air systems, which creates more comfortable living conditions.

4. Low Maintenance: Boilers do not require monthly/quarterly filter changes like furnaces do.

If you’re interested in learning more about hydronic heating systems, give us a call today and one of our experienced professionals will help you assess and determine what type of system is best for your home or project.

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