Roth FAQ Radiant Heating Systems

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FAQ - Radiant Heating Systems

What is radiant floor heating and how does it work?

Radiant floor heating systems use your floor as a large radiator, like the big cast iron steam or hot water radiators, but because your floor has so many more square feet of surface area for heat transfer than a radiator, it only needs to be warm to keep your house comfortable. There are three ways to transfer heat: convection (heating the air), conduction (a warm object touches a colder object and transfers heat to it) and radiation (like sunshine). Radiant heating actually uses all three methods to heat your home but mostly works like the sun to warm you. It does not rely on warm air circulating around your house to keep you warm. It is similar to standing outside in the shade on a cold day and then taking a single step into the sunshine. You were cold in the shade, but the sunshine warms you up even though the air temperature hasn't changed. The sun is producing more radiant heat than your body, so you are actually gaining heat from the sun. The reverse is also true. If you are near colder surfaces, your body tries to transfer radiant heat to those surfaces in order to warm them up. If you are in a supermarket in the canned goods aisle and the air temperature is 70°F (21°C), and all of the items on the shelf are at the same temperature as the air, you feel comfortable. When you turn the corner to the frozen foods aisle, you suddenly feel colder because there is a large mass of cold objects that are drawing the heat radiated from your body away, but the air temperature is still the same as it was only a short distance away. Because about 40% of the heat loss from your body is radiant heat, if you warm up the surfaces in a room to equal that of your body, you can still feel comfortable because you are not losing radiant heat to those cold objects.

Forced-air heating systems, and even baseboard convection systems (which also primarily heat the air), rarely run long enough to heat up the surfaces in your home, and even when the air is warm, you can still feel chilly because your body is trying to warm up the objects in the room. When you are using warm air to heat your home, the heat tends to be at the ceiling because warm air rises, and your feet feel cold because cooler air sinks. When your upper body is comfortable, your lower body is still chilly. Radiant floor heating systems have the opposite result: the floors are warm, keeping your feet comfortable and, since you are not primarily heating the air, the heat stays low instead of collecting on the ceiling and being wasted. Radiant floor heating is concentrated on the first 8' of elevation where everyone is living. Since you are not heating the air primarily, you can maintain a lower room temperature than you can with forced-air heating systems, and still feel comfortable. Typically, you are as comfortable (or even more comfortable) with a radiant floor heating system when the air temperature is only 65°F (18°C) compared to a forced-air heating system with an air temperature of 70°F (21°C). It is like standing in the sunshine on a cold day.

Why is radiant floor heating better than other systems?
  • You are saving energy all day long because you are maintaining about 5°F (3°C) lower air temperature.
  • You are not drying out the air by overheating it and then having to humidify it again.
  • You get fewer upper respiratory problems caused by hot, dry air irritation.
  • Your wood furniture is not subjected to overly dry air.
  • You don't have drafts and blowing dust associated with forced-air heating systems.
  • You don't have cold spots in the room due to poor air circulation.
  • You can easily have different temperatures in different rooms: cooler bedrooms that are more comfortable for sleeping and warmer bathrooms for when you get out of the shower.
  • Your floors are warm and comfortable instead of cold and drafty.
  • The heat stays down at the "people level" instead of on the ceiling.
  • Entry areas and bathroom floors dry out faster because they are warm.
  • Finished basements are much more livable when the concrete floors are warm.
  • The energy savings over a residential forced-air heating system can be as much as 20%.
  • You don't need to worry about furniture blocking vents or radiators.
  • The list goes on and on...
How is radiant floor heating installed?
Radiant floor heating is installed by circulating warm water in the floor. The most often used method is to put PEX tubing (a polyethylene tubing that is specially processed to have added strength) in a layer of lightweight concrete — about 1 1/2" thick — poured over the subfloor or in the concrete slab of a basement or a "slab on grade" house, but the tubing can also be installed in the floor joist cavity under the subfloor. A hot water heating boiler and the appropriate controls are then connected to the system to provide the water temperature needed to heat the house. In some smaller applications the system is connected to a water heater with a heat exchanger (used to separate your potable water from the heating water). The fuel that you use to heat the water — natural gas, propane, fuel oil or electricity — really doesn't matter for the system. You can select the fuel that least expensive or most commonly used in your area. There are advantages and disadvantages to the various installation methods and these should be discussed with your installer during the planning stages.
How do I plan for radiant floor heat in my new home?

You should start the planning process as soon as you start to design your home. The builder will need to make adjustments to the construction to accommodate the extra weight and height of the concrete over-pour (if this method is used) and allow for additional space in the mechanical room for the equipment and controls. The earlier you start to plan your radiant floor heating system, the easier it is to incorporate it into your new home.

What kind of flooring materials can we use with a radiant floor heating system?

Radiant floor heating is ideal for any "hard surface" flooring such as ceramic tile, stone, decorative concrete, vinyl linoleum and tiles, etc. but a properly designed system can also work under hardwoods and carpeting. There are limitations and special considerations for some flooring, especially hardwoods, and it is important that your installer knows all of your finished floor materials so the system can be properly designed to give you the performance and comfort that you expect. There are also special carpet pads that are specifically designed for radiant floor heating systems. Always discuss these options with your installer before selecting your flooring materials.

How do I find and select a good radiant floor heating system installer?

A good place to start looking for an installer is to get recommendations from friends or acquaintances that have had a system installed. You can also check with the local chapter of the Radiant Panel Association, a trade organization that provides training and certification for installers and designers. You can visit their website for valuable information and the latest technology. If your builder has already done homes with radiant floor heating, ask for his/her suggestions. It's always important for everyone on the team to have a good working relationship since building plans often change during the project, and all of the trades need to react appropriately and in a timely manner. Another good source of information is the heating department of your local Roth wholesaler. They usually know who the good installers are in your area.

Once you have gotten the names of the installers that you would like to use, you can start the interview process. A good radiant floor heating system installer will always do a room-by-room heat loss calculation so that the system will work equally well throughout the house. Proper system design is the most important step that can be taken to guarantee that you will get the comfort and efficiency you want. Many installers have a book of pictures and recommendations from past projects and customers that can be used as references. Remember that training and experience have costs. A good installer may not be the least expensive, and you may get what you pay for if you take an unusually low bid.

What type of equipment do I need for a radiant floor heating system?
First, you will need a good brand of PEX tubing to circulate the warm water through your floors. Roth PEXc tubing is a leading brand in Europe and is among the most environmentally friendly types of PEX tubing available because we do not use any chemical additives in our cross-linking process. In order to heat the water, you will need a good hot water heating boiler and, in order to get the correct water temperature for your system, you will need a good control package. There are many accessory items that can be added to a system to enhance comfort, convenience, and performance (indirect water heaters, heat recovery ventilators, towel warmers, etc.). You should discuss all of these items with your installer and decide what works for you. In small systems (a bathroom or kitchen), you may be able to use your water heater and a heat exchanger to provide heat. It is important to understand that water heaters have a limited capacity and you may be short on hot water for normal usage if you are using some of that capacity for space heating. Your installer can offer the best advice when selecting your equipment
Can I heat just some selected areas with radiant floor heating, and use a different method to heat the rest of the house?
Partial radiant floor heating is a very popular option. Heating the basement and warming the floors of the bathrooms and kitchen with radiant floor heat, and then heating the rest of the house with forced-air (a blower assembly with a hot water coil to heat the air) or baseboard convectors. You can add air conditioning or electronic air cleaners to forced-air systems if you want. These are called "hybrid" systems, and may be less expensive than a full radiant floor heating system. You should discuss these options with your installer to determine if they may be right for you.
Can radiant floor heating be installed only in new construction?
Radiant floor heating can be installed in almost any home (or room) during a remodel. The installation method may vary a bit from a new construction project, but it is certainly possible. Roth has many products available specifically for these applications such as our Floor Panel System (a foam board product that is used instead of lightweight concrete to hold the tubing), our Shunt Systems (a packaged circulator and temperature control valve), and C-Fin heat plates (for under floor joist heating applications). Your installer should be aware of these products and able to help you select the best options for your application.
Can radiant floor heat be installed in a small area?

Yes it can. Using our MiniShunt system, you can have radiant floor heat in a bathroom or kitchen. This unit is designed for heating small areas of up to 400 ft² (37 m²). You should discuss this option with your installer to make sure that the system is properly designed.

Can I also have air conditioning or air filtration with a radiant floor heating system?

Air conditioning, air filtration, and air exchangers (heat recovery ventilators, etc.) can all be used when you have radiant floor heating systems. Several manufacturers have "high velocity" air conditioning systems that blend very well with radiant floor heating systems. These systems should be discussed with your installer to determine what approach is best for your application.

How much do radiant floor heating systems cost?
Radiant floor heating systems are generally more expensive than forced-air systems. How much more expensive depends on the complexity of your system, and type of heating equipment that you are using. The thing to remember is that you are making a long-term investment in both comfort and efficiency when you are selecting a radiant floor heating system that cannot be matched with a forced-air heating system. Discuss the options with your installer so you can have a system that will fit your budget and still give you the comfort and efficiency that you are looking for in a heating system.