# 1 – Comfort: Why a hydronic heating system is more comfortable than forced air

To answer this question, if helps to first understand how your body reacts to a room environment and how you know when you're comfortable.

A common misconception is that the way to make your home comfortable is to provide enough heat to keep your body warm. In fact, your body loses heat to its surroundings and the rate of that heat loss is what makes us comfortable – or not. You may remember from science class that heat always travels to cold because the environment is always trying to achieve thermal balance. Your body reacts the same way to its environment – giving off heat to the surrounding air and surfaces. The rate at which your body gives off that heat determines your comfort level. The slower your body gives up its heat, the more comfortable you feel. The job of your heating system is to slow the body's rate of heat lost to the environment.

Your body loses heat four ways:

• Radiation (heat lost to cooler surfaces in the room)
• Convection (heat lost to the air around you)
• Conduction (direct contact with cooler surfaces)
• Evaporation (from your skin)

About half of this lost body heat is through radiation, with another third through convection, and smaller amounts to conduction and evaporation.

Of these four, a hydronic heating system uses radiation as a large component of its heat-delivery method – which means it heats the objects in the room rather than just the air. Your body senses these warmer surfaces and gives off less heat to them. A forced air furnace delivers warm air to the room and heats the room surfaces through conduction, resulting in cooler surfaces and a less comfortable environment.

A hydronic system also delivers heat through convection. This creates a gentle, natural air flow as cooler room air flows across the radiator and is warmed by conduction. This air flow is imperceptible to your body but acts like a blanket of warmth. By contrast, a forced air furnace creates air flow using a blower, causing a cooling effect when that air contacts your skin. It's the same feeling you get when standing outside on a sunny but breezy day. The thermometer may indicate that the air temperature is warm, but the sensation on your body is that it's cooler.

Because the surfaces in a hydronically heated room are warmer to the touch, you lose less body heat and feel more comfortable when you touch other things or surfaces in the room. A great example is a radiantly heated floor. Your feet lose no heat to the floor, so your body feels more comfortable – even at a lower room air temperature. A conventional, forced air heated room will often have a “comfortable” air temperature but you'll feel cold because your feet are in contact with a floor that is several degrees cooler than the air, and much cooler than your body.

The last way your body loses heat is through evaporation. Your skin cools as its moisture is lost to the surrounding air. A hydronic heating system doesn't dry out the air as a forced air system will. This reduces the evaporative effect on your skin and leaves you feeling more comfortable.

When it comes to comfort, hydronic heat offers clear advantages over forced air.

Next week I'll discuss how hydronic heating systems are more efficient than forced air.

Heidronically yours,

Wayne

Top 7 reasons why a hydronic heating system is a better choice than forced air

1. Comfort – Your body naturally loses heat to the cooler surfaces in a room (windows, walls, floors and furniture). When those surfaces are warmer, you feel more comfortable. No system is more comfortable than a hydronic system, because it heats the objects and surfaces in the room. But because a forced air furnace heats the air, you only feel comfortable when the furnace blower is on.
2. Efficiency – There's more to heating efficiency than just the AFUE (annual fuel utilization efficiency) rating of a boiler or furnace. For example, a furnace blower can pressurize the room and force heated air out through small cracks in a building's walls, roof and floors (also called the “building envelope”). Hydronic heating systems don't pressurize the room during heating cycles, so there's less heat loss.
3. Reliability – It's not unusual to find well-installed 30- or 40-year-old cast-iron boiler still providing reliable service. Forced air furnaces have a typical lifespan of 15 - 20 years.
4. Versatility – The design flexibility of a hydronic system makes it exceptionally versatile. Systems can be configured to provide independent heating zones, domestic hot water or snowmelt, as just a few examples. A hydronic system is also a perfect complement to a ground-source heat pump (geo-thermal). A forced air system can't begin to compete in this category.
5. Quiet – There is no quieter heating system than a well-installed hydronic system. (If you hear a lot of noise in the pipes, something needs fixing!) Compared to forced air's noisy blower and frequent on-off cycles, there's just no contest.
6. Cleanliness -- With no blowers or leaky ducts, there's no dust blowing through the house. That means there's less housecleaning plus a healthier indoor environment, especially for people with allergies.
7. No need for humidification – A hydronic system doesn't dry out the indoor air because its water temperatures are usually much lower than the air temperatures of a forced air furnace. Because forced air makes indoor air so dry, most people need additional equipment (such as a humidifier) to add moisture back into the air to feel more comfortable.

Stay tuned. Starting next week, I'll expand on each of these seven advantages in more detail.

Heidronically yours,

Wayne

What is a hydronic heating system?

Webster's defines hydronics as “of, relating to, or being a system of heating or cooling that involves transfer of heat by a circulating fluid (as water or vapor) in a closed system of pipes”.

If you live with a hydronic heating system, you might define it as comfortable or efficient, or quiet, or all three.

It can be as simple as a 1950's system consisting of a cast iron water boiler and simple finned tube baseboard radiators. It can be “old school” hydronics like a 1920's one-pipe steam system with cast iron standing radiators. Or it can be a modern, state-of-the art high-efficiency system consisting of a modulating, condensing boiler and radiant panels.

It's luxurious comfort. But if you've ever lived with a hydronic heating system, you already know that.

Using water or steam as the medium to transfer heat from the source (boiler) to the living space is an incredibly efficient and versatile system. Unlike forced air heating systems, very little heat is lost in the delivery process. And with a radiant hydronic system, that heat is delivered directly to the objects and occupants in the room.

Hydronic heat can be used with traditional cast iron radiators or copper finned tube baseboard, modern panel radiators, radiant floors, radiant ceilings (yes, ceilings!) and walls, towel warmers, and much more. Modern controls provide energy conservation through zoning and outdoor reset control and added comfort with indoor reset and floor sensors. It can also provide almost unlimited quantities of domestic hot water for showers, laundry, and other household uses.

While the official definition is all about water, I think it's really all about comfort.