Frequently Asked Questions about Radiant Heat

• All Radiantec tubing is made from high-grade polyethylene, the material of choice in applications demanding long life and high resistance to chemical and environmental threats. Radiantec guarantees its products from age-related breakdown for 30 years. There is good reason to expect the material to last for 100 years and some environmental scientists maintain it will last for 600 years.

• This type of damage is most unusual, but once located, can be fixed in one hour with the use of an $8.00 repair coupling and a hand chisel. Radiantec recommends the use of glue, rather than a nail gun, when installing partitions to minimize this possibility. By installing several parallel rather than one long circuit, as Radiantec recommends, it is often possible to bypass the leaking circuit and avoid repairing it altogether.

• If the building is reasonably energy efficient, underfloor heat will not harm wooden floors. Much of the engineering data about underfloor heat was generated years ago when buildings were poorly insulated. As a result, floors needed to be maintained at temperatures of 90 degrees F or higher to keep the building comfortable, a temperature which caused wooden floors to split and crack. In an energy efficient building of today with R-19 insulation in the walls and quality thermopane windows, the floor need only be four degrees warmer than room temperature to heat the building to the mid-seventies when it is zero degrees F outside. The more stable humidity in an energy efficient building and the even temperatures that radiant heating maintains are actually good for wooden floors.
• Before installing radiant heat in an energy-inefficient building with wooden floors, please consult our technical specialists.

• An oxygen diffusion barrier, a special coating applied to the tubing, reduces the amount of oxygen entering the tubing from the surrounding air. Oxygen can shorten the life of some heat sources. However, those heat sources affected by oxygen are rare, an even in these cases, there are solutions to this problem which cost less and work better.
• Should you decide that you still want an oxygen diffusion barrier, Radiantec can provide it.

• If you want radiant heat and air conditioning, we recommend installing a distribution system for air conditioning within the ceiling and radiant heat tubing within the floor. Combining a forced hot air heating system and an air conditioning system utilizing floor registers is a less comfortable, dustier, and more expensive alternative than using two separate systems.

Ceramic tile, wood, and linoleum are fairly good conductors of heat and do not present any special design considerations. But carpet requires more temperature from below to force the heat through the carpet and into the room. This need for higher temperatures below the floor will likely require improved insulation underneath everything to prevent heat loss downward.

Follow these rules of thumb:

• Avoid carpeting high heat loss areas such as mudrooms and entryways.
• For structures that are reasonably energy efficient, 3/4 inch carpeting over a 1/4 inch pad is acceptable.
• In low heat loss areas such as the second story of a well insulated structure, carpet may be used.
• If you have questions about your own situation, talk with one of our technical specialists.

• In terms of efficiency – how much of the available heat stays in the building vs. how much is wasted-there is no difference between a concrete suspended slab system and a staple up system within the floor joists. There is, however, a performance difference, a difference in how much heat each system is capable of putting out. Slabs, suspended or on grade, put out more heat (50 BTUs/ sq. ft.) than systems within floor joists (35 BTUs sq. ft.). However, well-insulated residential structures need only 20-25 BTUs sq. ft. to maintain comfortable temperatures at zero degrees F, so either arrangement will provide sufficient heat.
• In rooms with high ceilings or extensive glass where higher performance is desired, there is an alternative to the suspended slab. By strapping the floor with 1x4s or 2x4s, placing the tubing in the spaces in between and filling in the areas between strapping and tubing with sand, dry mix or cement, you will gain most of the advantages of a slab without the cost and weight. Flooring is then nailed to the strapping. This procedure is described on page 10 of our Installation Manual.

• At a minimum, each floor of a building should be on its own zone, as should any area that has very different temperature needs or heat loss characteristics. Such areas might include sunrooms, great rooms with cathedral ceilings, a room with a window wall and rooms with three walls subject to outdoor temperatures. Generally speaking, in an energy efficient building, temperatures will tend to equalize regardless of the number of zones.
• The cost of each independent zone is $300-400. If you are in doubt about whether an area needs to be zoned separately, separate the plumbing but bring the lines back to one pump and control both with one thermostat. Use a balancing valve. If you later decide to separate the zones, you can do so for only the cost of a pump and thermostat-just what you would have spent had you done it initially.

• We think not. The capital cost is very high and they consume electricity, an expensive source of energy. As far as payback is concerned, consider this: If a ground source heat pump costs $15,000 more than a gas or oil system for a 2,000 sq. ft. home, at 8.5% financing the payback is never. Finance charges would be $1,200 which would exceed the entire gas or oil bill and this is before the costs of the electricity required to run the heat pump.

• They work well when they are used to heat only domestic hot water, where opening a tap creates the pressure differential to open the gas valve and modulate the flame. In closed radiant heating systems, this pressure differential must be created through the addition of powerful pumps, an expensive solution. In addition, many on demand water heaters require metal or masonry chimneys, an indicator of marginal operating efficiency.

• Solar heating systems operate best at the lower temperatures required for underfloor radiant heat and have proven quite successful in these applications. An Open Direct System can be converted easily to solar at any time. For more information on solar as a heat source, see Consider Solar.