Q&A / 

Radiant Floor Heating

DEAR TIM: I am giving serious thought to incorporating a new hydronic radiant heating system into my new home. Is this technology reliable or is it just a fad? Can you install these systems in existing homes? How do you size the system? What are the disadvantages if any? Alicia P., Bennington, VT

DEAR ALICIA: Next winter you are going to be as snug as a bug in a rug. Hydronic radiant heating is not new by any means. It is just a fancy word for any system that uses water to deliver heat. Radiant heating systems have been used for thousands of years. Anyone who has warmed themselves in a cave or a room with a fire has felt the natural warmth of radiant energy. Romans used a primitive radiant heating system to warm public and private baths. Your parents most likely dried their snow packed gloves on top of steam or hot water radiators. Radiant heating is not a fad. It is reliable and simply superb.

There are numerous advantages to using radiant heating. It is a known fact that radiant heating systems produce higher and more consistent comfort levels than a forced air system. Hidden radiant systems that use piping inside of floors, ceilings, and walls permit unlimited design possibilities and furniture arrangements. Certain systems allow you to combine domestic hot water needs for bathing and household cleaning into your heating system. There is no need to buy a separate hot water heater. You can also easily create zones within your house. Electronic controls allow you to send heat to only those portions of the house that you occupy during the course of the day and night.

Even though your new house will have a specific heat loss that can be measured, tests over the years have shown that radiant or hydronically heated houses tend to have lower energy bills. The fans that push heated air in a forced air system pressurize the inside of a house. Heated air in certain instances can actually be pushed out of tiny cracks and holes in exterior walls and ceilings. Forced air systems tend to create layers of heat in rooms. Temperatures between the floor and ceiling can vary by more than 15 degrees. Houses heated with radiant systems tend to have uniform temperatures throughout each room.

If a friend or relative has a chronically cold room or area in their house, they can sometimes use certain radiant systems to make the trouble areas toasty warm. Some hydronic systems allow you to staple flexible piping to the underside of exposed wood floor systems. If the area to be heated is the size of several rooms, the heat source can often be a low cost hot water heater. These same systems can be used to heat entire houses. Other companies make reliable radiant nets that incorporate low temperature electric cables. These can be installed under ceramic tile, slate, or marble floors in bathrooms kitchens or entrance halls.

Hydronic and radiant heating systems are sized just like any heating system. Your heating contractor must do a heat loss calculation. The heating contractor measures the surface area of exterior walls and insulated ceilings, window sizes and glass type, thickness of wall and attic insulation, house orientation, and numerous other factors. These measurements are entered into a computer program that determines the amount of heat your house loses each hour. Based upon these calculations the contractor can select the correct sized boiler or water heater and produce the correct design of the hydronic heat delivery system. Do not underestimate the importance of this procedure. If you install a system that is too small, you will be uncomfortable. A system that is too large will waste energy.

There are few disadvantages to hydronic heating systems. If you require central air conditioning, your overall heating and cooling system equipment cost will be higher since you have to install two delivery systems (piping for the heat and ducts for cooling). You may also find it hard to locate a qualified and knowledgeable installer. Many contractors are resistant to change and may try to talk you out of an hydronic system. Contact various hydronic system manufacturers. Ask them for a list of qualified installers in your area.


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