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Even More Frequently Asked Questions (FAQ)
(of a technical nature)

  1. What about heat coils in the ceiling?
    • Heating coils in the ceiling can work very well.  Some issues to think about are that the work is often inaccessible and heat losses upward can be high unless extra insulation is added.  You would lose the comfort advantage of warm floors, but a radiant ceiling application is nevertheless very comfortable. Furniture placement is not affected.
  2. What about freezing with an open system?
    • Freezing does not harm Radiantec tubings so the real issue is the possibility of freezing damage to the rest of your home.  An open system cannot operate if it is frozen.  An open direct system can be purged of water by draining or with compressed air.  You do not need to get all of the water out.
  3. How thick does a topping slab need to be?
    • A topping slab will need to be at least 1 ½" thick in order to accommodate the tubing plus some reinforcing mesh over the top and then to have about ¾" of concrete over everything.
  4. What about insulation underneath the topping slab?
    • You must not compromise structural integrity for insulation. Insulation has very little weight bearing strength. A topping slab over extruded polystyrene is satisfactory only for light residential loads. If you cannot insulate underneath the slab, then you should insulate well at the perimeter where most heat loss occurs. An uninsulated slab may not be as responsive as one with insulation, but the overall heat loss could be acceptable.
  5. What does Radiantec think about thin foil type bubble insulation?
    • It is our opinion that this material is overrated, underperforming, and too expensive. There is no technical basis to claim an r-value more than 3 ½ per inch.
  6. Does Radiantec sell a product that goes right into the subfloor like Warmboard?
    • Radiantec products are compatible with these products, but Radiantec does not sell this special type of subflooring material.  It is quite expensive.  This subfloor heating method will put out more heat, but if the area does not need the extra heat, then the money is not well spent.  It will not be more energy efficient.  Radiantec Company offers an installation supplement that shows how to make your own subflooring material with considerable savings.
  7. Can I use my existing boiler for both radiant heating and baseboard radiators?
    • Yes you can.  All you need to do is provide a Radiantec mixing valve to step down the temperature of the water to the radiant circuits.  You mix hot water from the boiler with return water from the floor to provide a lower temperature.
  8. Will my existing water heater provide enough capacity to also heat my home?
    • Most water heaters are only in service for 2-3 hours per day and they often have enough capacity to do extra work.  If the BTU heating output of the water heater is equal to or greater than the heating load, you can probably use it to heat as well.  Look at the label on the heater for the BTU output.
  9. Will my water heater have a shortened service life if I heat with it?
    • Most water heaters do not "burn out"; they start to leak because of corrosion.
  10. I have heard some bad things about the Polaris in the internet.
    • We have had good luck with the Polaris, but it does require competent installation.  You should have a competent gas man do the work.  This is not a good do it yourself project.  Some people should have been given their money back instead of getting a new Polaris, because the problem is at the site.
  11. What can be done about nails protruding through the subfloor?
    • Nails should not be unnecessarily long in the first place.  Floors can be glued and then shorter nails can be used along with the glue for a superior and very quiet job.  The aluminum fins can be formed so that the tubing hangs down lower than the protruding nails.
  12. How much heat is lost downward with the staple up system?
    • That depends upon the amount of insulation beneath the floor and the conductivity of the flooring material.  If heat loss downward is entirely wasted, more insulation is indicated than if the heat is just misdirected.
  13. How much antifreeze should be in the system?
    • Use a 50% solution of glycol based antifreeze solution to water for a system that must operate at very low temperatures. If only freeze protection is needed, a 20-25% solution is usually adequate because the more dilute solution forms a non rigid slush that will not flow well but will not damage the tubing.
  14. What type of antifreeze should be used?
    • If there is any possibility that a rupture of the tubing could contaminate the potable water, use non-toxic propylene glycol. If contamination is impossible, automotive type ethylene glycol may be used.
  15. Are there any advantages to the tubings that have an inner core of aluminum?
    • In our opinion, there are no advantages. Heat transfer or conduction is not improved. Oxygen diffusion benefits are usually irrelevant and if an oxygen diffusion barrier is needed, another method should be selected. Freezing conditions can rupture the aluminum portion of the tubing.
  16. Can I use radiant tubing in place of a radiator?
    • Ordinarily the radiant tubing must run at a lower temperature than the baseboard. This means that a mixing valve is used to provide a lower temperature for the radiant heating tube. It might be possible to avoid the expense of the mixing valve if the baseboard can be run at a lower temperature and if you select a radiant tubing with a high temperature rating, but the situation will not be ideal.
  17. Is there a problem in combining radiant heating with forced hot air?
    • No, the system will combine the comfort of radiant with the responsiveness of hot air. It may be desirable to control the radiant with a floor sensor.
  18. Can I use the direct system if I have hard water?
    • Yes you can. Mineral buildup is a problem where the water is heated, i.e. in the tank. The water is being cooled in the tubing so mineral buildup is not possible in the tubing. Mineral buildup in the tank can be minimized by using a powerful heater so that you can have low operating temperatures. Mineral buildup is not likely at temperatures below 1400 F.
  19. What is the less expensive fuel choice?
    • The least expensive energy choice is solar.  Presently, oil and natural gas are about equal.  Propane is more expensive than both.  Electricity is more expensive than everything.  This information may be subject to important regional differences and they are certainly subject to fluctuations because of politics.
  20. Does a radiant system make sense in a warm climate?
    • Yes, very much so, as long as you pay a fair price for the materials. The open direct system is very attractive in warm climates because of the low cost and the limited free cooling.
  21. Does a radiant system make sense if the building will not be very energy efficient?
    • It is always best to be energy efficient, but if not, it is still best to use radiant because you will use less energy and spend less money. You may need a supplemental heat source on very cold days, but radiant heating is the only way to be truly comfortable in a room that is not energy efficient.
  22. Can radiant heat be used with wide pine floors?
    • With radiant heat, the temperatures the floor temperatures tend to be stable and low. These are favorable conditions for wide pine floors. It is best to use material that has low humidity from the beginning.
  23. Does the radiant heat need to be installed in our loft?
    • Probably not, if the building will be energy efficient. While heat will tend to rise, you are asking one floor to do the work of two and you may want to over design the first floor.
  24. Can I use zone valves instead of pumps?
    • You cannot use zone valves with the open system because of the need for flow during the off season. You can use zone valves with a closed system although we find that it is more costly and not energy efficient. You need to buy one large pump that will waste energy if only one zone is called.
  25. Can CPVC or PEX tubing be used instead of copper?
    • Yes, but you should watch the cost of fittings and plastic must be supported every two feet. Do not substitute fittings with Radiantec tubing. If you are using an open system, be sure that the materials are rated potable.
  26. Does acid etching of a concrete floor affect the poly tubing?
    • All Radiantec polyethylene tubing is highly resistant to nearly everything. The reactivity charts show only a slight reaction to fuming nitric acid (above 1700° F)
  27. What about ventilation requirements in a very tight house?
    • It will be satisfactory to unlock or crack a window. This is a comfort issue that the occupant will naturally address. Heat exchangers can recover the energy that ventilation loses.
  28. Is an electric water heater out of the question?
    • It should be .There will be low heat output and high energy cost. They may be acceptable in intermittently occupied buildings or as a back up only. There will be a prompt payback of the added cost of any other form of energy.
  29. Can we use radiant heat if the subfloor is more than 2 inches thick?
    • Yes, but it is possible that you will need supplemental heat.
  30. What should you do if you are not sure that you will get enough heat from the radiant floor?
    • See page 5 of the Design and Construction manual.
  31. How should the interior walls be built with a radiant heated floor?
    • No nailing guns. Use concrete adhesive.
  32. How should radiant tubes cross a control joint or expansion joint?
    • A control joint may be crossed without special consideration. An expansion joint should not be crossed at all. If absolutely necessary, sleeve the tubing with pipe insulation or PVC.
  33. I can get the Polaris somewhere else a lower price. Will you come down on your price?
    • Any time we give one person a better price than another there must be a very good reason; otherwise it wouldn't be fair. What is the very good reason? We know our prices are very low. The cost savings would not be very much. If it is, then there is pricing mistake somewhere, or a bait and switch.
    • Most of the time, our prices are highly competitive, but once in a while, you can get something from someone else who doesn't carry the expenses of providing design assistance and who cannot provide any support because they don't know anything.
  34. I want to get some of my stuff from you and some of my stuff from someone else?
    • This can lead to problems. If you buy a Ford engine and then put a Chevy carburetor on it, you are likely to have problems. It is also likely that neither Ford nor Chevy can help you. There is a reason for everything we do.
  35. Are there safety issues or Legionella bacteria problems associated with the domestic water heater based systems?
    • Domestic hot water systems compare very well with other heating systems and National code officials have seen fit to approve them. Radiant heating systems in general have significant health benefits. Low temperatures and low pressures are always good for safety. The "open direct system" is mechanically identical to so called "recirculation" systems which are very common and do not seem to be causing undue problems. Legionella bacteria cannot withstand temperatures above 115° F. You can always reduce the risk of contamination by bacteria by increasing the water temperature, but you will then increase the risk of scalding. It is our opinion that the risk of Legionnaire's disease in domestic hot water systems is "an emperor with no clothes" that is largely created by special interests groups in the heating industry. Legionnaire's disease is a reportable disease according to law and public health authorities make every effort to determine the cause when it appears. We are not aware of even a single case of Legionnaire's disease that was caused by a domestic hot water based heating system. If it were a real issue, there should be many. The National Center for Disease Control is a respected authority in these matters and the following link may provide useful information. http://www.cdc.gov/ncidod/dbmd/diseaseinfo/legionellosis_a.htm
  36. What can be done to increase heating around doors and windows?
    • You can increase tubing, increase aluminum fins or improve insulation.
  37. Can our systems be installed using an existing steam boiler?
    • Yes, this is entirely possible. Temperature control is the issue. You can use one of our heat exchanges to change the steam to hot water. Then you can use a mixing valve to control temperature of the hot water. You may want to consider the use of a safety control.
  38. What is the best way to run water tubes under ground?
    • If tubing is placed underground, the run should be well insulated and as short as possible. Make provisions for expansion and contraction with ells and serpentine loops. You can make your own pipe insulation with a site built extruded polystyrene box.
  39. Can tubing be placed in the same joist bay as recessed lighting?
    • Yes you can, but keep the tubing away from the fixture and insulate the tubing in proximity of the fixture and follow manufacturers instructions.
  40. Are there certain types of cement that are better with radiant heat than others?
    • This is a concrete question more than a radiant heating question. All concrete applications must be structurally satisfactory. There is no important difference between concrete mixes from the heating standpoint.
  41. Is solar heating feasible in my area?
    • If you live in a region that has long cloudy spells, a backup heater will be needed. The system could still be economically practical if it is reasonable in price. A quality solar heating system will pay for itself many times in energy savings and tax credits may apply. A solar system must not detract from the architecture of the building or it will lower real estate value. Click here for more information.
  42. How much will it cost to heat my building with radiant? How much will I save?
    • There are too many variables to predict this right now. This depends upon how well constructed the building will be, the efficiency of the heating unit, how cold it will be, and other factors. What we do know is that the cost will be lower with radiant heat because radiant is more efficient. You can expect savings of about 25-30%. Click here for a scientific explanation of the reasons.
  43. Is it OK to insulate with polystyrene if we will be placing heavy equipment on the slab?
    • You may need to ask that question of an engineer. There are different grades of polystyrene. The concrete will tend to spread out the weight of the heavy load. Polystyrene is able to withstand the weight of 3 feet of earth without problems. You can place insulation at the perimeter instead.
  44. What can be done about ants and termites?
    • This is not really a radiant issue. Radiant heat will neither help nor harm this situation.
  45. How do I make a thermal break with a walk out basement?
    • Insulate on the heated side of the footing and underneath the flooring.
  46. If I use radiant, will I still need a humidifier?
    • You will not need the humidifier as much because the air is more stable and not being changed as much.
  47. What is the efficiency loss of a heat exchanger?
    • Whenever you have a heat exchanger, you must have a temperature difference in order to force the heat to cross the heat exchanger barrier and go to the other fluid. No heat is really lost, but the heating unit may run a little less efficiently at a the higher temperature.
  48. How do you avoid melting the wax ring at the toilet.
    • Avoid it and insulate in the vicinity.
  49. Do the Radiantec systems make noise in operation?
    • No, Radiantec systems are silent in operation. The pumps are extremely quiet and the heat emission fins do not make noise either. I do not know exactly why other systems have noise problems. One reason could be an excessive fluid temperature requirement causing expansion and contraction. Another reason could be at the oxygen diffusion barrier.
  50. What is heat?
    • Heat is the motion of molecules within a material.
  51. What are the three major methods for heat transfer and describe them.
    • Conduction, convection and radiance
  52. How is heat transferred (lost) from a building? Say all of the ways.
    • Conduction, convection radiance, chimney stack effect, wind.
  53. What effect does radiant have of all of these?
    • It lowers them.
  54. Why is radiant more efficient?
    • Answer is above.
  55. If you do not heat the floor, what will be the floor temperature of a residential building when it is very cold outside? Why?
    • Cold air from infiltration falls. Cold air from conduction falls. Floor temperature falls in temperature by radiant loss to that of the average surface temperature. Your floors will be cold ( 50° F is not uncommon) unless you heat them no matter how well you insulate.
  56. How do the solar systems control overheating in the summer?
    • First method is by orienting solar panels to the position of the sun in the winter. That means that the angle of the sun is well off the summer position. Second method is by switching operation to domestic hot water only. A mechanical heat dump can also be used.

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Open Direct System
Installing the Closed System
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Radiantec Basic Solar Domestic
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Radiantec Basic Solar Domestic
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