Radiant Floor Heating Systems
In the past few weeks, we have received numerous e-mails regarding installing radiant floors and many more e-mails regarding heated driveways. In this article, I will cover installing radiant floors, the types and how to install information along with resources for acquiring more information.
This winter, as like last winter, is especially cold for most parts of the country, especially in the Midwest states. People are searching for ways to stay warm without going broke in the process, and radiant heat is a real good choice for heating your home. Radiant floor heating is the "Trickle up" theory, a very efficient system. It envelops the entire room with heat, as opposed to the "trickle down" theory, which is very in-efficient and costly. For proof of the in-efficient and cost of "trickle down" theory, just watch our governments handling of the "bailout"! Well, a conventional forced air heating system is a trickle down system.
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.
Radiant Floor Heat Systems offer many advantages over traditional heating systems. Perhaps the most important advantage is the improved comfort level achieved with radiant floor heat systems. Radiant Heat allows a room to be heated evenly by increasing the room's average surface temperature. Another key benefit of radiant heat is energy efficiency. Customers are able to save money on energy bills with Radiant Heat Systems due to comfort at lower temperatures, room by room zoning, and lower water temperatures. Other advantages include no visible components, noise reduction, and dependability.
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.
Installation Methods For Hydronic system:
Slab On or Below Grade: In this installation method the tubing may be either tied to a wire mesh or rebar using wire or zip ties. If under-slab in being used, the tubing may be stapled to the under-slab insulation. Edge Insulation should be used in this application around the perimeter of the slab. Under-slab insulation should be used when there is a high water table or the soil is moist, bedrock is present, floor covering values exceed 2.0, or the linear feet of the perimeter is high in comparison to the gross foot area.
To install the tubing without under-slab insulation, first place the wire mesh or rebar on the compacted base material. Using wire or zip ties secure the tubing to the rebar or wire mesh. Space the ties every three feet along straight runs. When making 180-degree turns, tie the tubing at the top of the arc and once on each side, 12 inches from the top of the arc. This prevents the tubing from floating up into the pour. The tubing should be pressure tested to 60psi.
To install the tubing when there is under-slab insulation, you can use staples to secure the tubing to the insulation. Staples should be placed every 3 feet along straight runs, and when making 180-degree turns it should be treated similar to wire mesh installation.
Pour Over Existing Slab:
This application is used in residential retrofit situations. An example of this is finishing an existing basement. Under-slab insulation should be used in this application, and the pour should be at least 1-1/2" thick. The pour should be ¾" over the top of the tubing, so if 1" tubing is used, the pour should be greater than an 1-1/2" thick. In this application tubing is secured to a wire mesh or rebar in the same manner as a slab installation. An alternative would be to staple the tubing to the under-slab insulation. However, when making 180-degree turns, a tie or staple should be placed at the top of the arc and 6" from the top of the arc (one on each side). Tubing should be pressure tested to a minimum of 60psi.
Radiant Heat Installed in Concrete
So Which Is Right For You? Hydronic or Electric?
While most of the press about radiant heat has focused on hydronics, makers of electric cable systems also report a healthy growth in their business. Electric radiant floors aren't appropriate for every home, but they can be an excellent solution to certain design problems. Choosing the right system means knowing what you want it to do, and looking past manufacturers' claims to the system's real costs and benefits.
Here are some guidelines:
Hydronic Tubes vs. Electric Cable:
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.
What is hydronic radiant floor heating?
Hydronic radiant floor heating is a system of plastic or metal tubes/pipes laid within a floor that carries hot water into specific rooms or "zones", dispersing the heat through the floor surface.
One type of tubing commonly used is a new leak-resistant, non-toxic, high temperature, flexible piping called cross-linked polyethylene (PEX). PEX is a durable tubing that doesn't become brittle over time and isn't affected by aggressive concrete additives or water conditions. PEX has been used in Europe since the 1970s and was introduced to North America in the early 1980s.
By applying heat in this manner the heat radiates from the tubing up through the floor. Exactly like heat from the sun, radiant heating warms objects rather than air. Unlike forced air systems which warm air and then transfer the heat to objects such as walls, furniture and people, radiant heat provides the heat where it is needed efficiently and effectively. Forced hot air systems create stratification that cause upper layers of air to be warmer than lower layers so that in a typical room floor to ceiling temperatures can vary as much as 10 to 15 degrees. With radiant heating the floor temperature is warmer than the ceiling temperature creating a reverse type stratification and perfect comfort.
Hydronic radiant floor heating systems typically rely on a boiler or water heater to heat up the water and also a pump to circulate the now heated water into plastic pipes or flexible tubes buried in the floor or installed within a concrete slab. The pipes, once embedded in the floor, transports heated water that passes that warmth on to the surface of the floor where it broadcasts the energy out and into your the room. The floor absorbs this energy, then gives it off as radiant heat, which warms people and objects in the room.
An electric system works the same way, but instead of tubes, electric heating elements warm the floor. Unlike its hydronic counterpart, electric radiant heating systems do not require a full room remodel to be installed. This is due to the installation process which allows for it to be installed into a small amount of thin-set lying on top of the subfloor. Electric systems are easier and less expensive to install than their hydronic counterparts. They're also less expensive to zone. They can be used to heat a whole house or to provide spot comfort in kitchens and baths. Radiant heating systems are ultra-thin, flexible and designed to be conveniently installed by the DIY homeowner or floor covering professional. There is no need for any special tools and prior experience in the installation process, although helpful, is not required.
Electric elements can consist of cables coated with electrical insulation, or of fabric mats with the cables woven into them. Like hydronic tubes, electric elements are embedded in the floor system. Depending on their purpose, insulated cables use anywhere from 8 to 15 watts of electricity per square foot of floor area (the upper limit permitted by code).
The closer the cables are to the surface, the closer together they must be spaced to distribute heat uniformly over a given surface area. This makes mats more expensive per square foot than free-form insulated cables. Free-form cables are usually embedded in a 1-1/2-in.-thick slab of gypsum underlayment or lightweight concrete. As with hydronic tubing, you need to consider the ability of the framing to support the slab's weight and make adjustments to window and door heights for the slab's extra thickness.
Mats resemble electric blankets and consist of loops of cable embedded in a substrate, which is often a mesh fabric. The loops use approximately 12 watts per square foot and are spaced closer together than embedded cables. However, mats are less expensive to install, because the installation is a lot quicker and they generally require less floor thickness than cables. Mats can often be placed in a mortar bed beneath floor tiles. This adds as little as 1/8 in. to the floor height. Some can be rolled out on the subfloor beneath a carpet and pad. Mats come in a range of standard sizes. Most manufacturers will also make custom sizes or shapes.
Radiant Floors-Performance Issues:
Makers of floor-warming mats like to cite their products' fast response time. One company points out that when a radiant heat source is buried 1 in. deep in a concrete slab, it takes several hours to fully heat the slab. By comparison, it takes only 65 minutes to heat up a tile floor that has been laid over a mat. What this comparison leaves out, though, is the effect of thermal mass. Like everything else, thermal mass has its pros and cons. The thick-slab system will take longer to heat up, but the slab's thermal mass will keep the home warm for a longer period of time. On the other hand, if you need quick temperature changes, thermal mass tends to work against you. For example, quick warm-ups are needed in areas used only occasionally, such as a workshop that's used a couple of hours per night, or a bathroom where the home owner wants to warm up the floor before shower time. Be aware, however, that fast systems may not be best for all floor coverings. For example, quick temperature changes will put a lot of thermal stress on wood flooring. Wood floors tend to fare much better with constant or slow-changing temperatures, which is what you get with a thick-slab system.
For more "how to" information on installing radiant floors, watch the following video's. There are 3 of them showing step by step the process for installing an electric system.
Installing Radiant Floor Heating Step 1 - Install my Roll
Installing Radiant Floor Heating Step 2 - Install my Floor
Installing Radiant Floor Heating Step 3- Install my Control
For more information on Install Radiant Heat Floors, see also: Install Radiant Floors Cost
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