Floors Warm Up to Radiant Heat
Toasty toes and money saved are just two benefits of radiant heat under your concrete, wood or tile floors
I write about interior design and architecture, and take what I learn into my own home (you may find me sanding and painting a kitchen table on the weekends). You can find my articles, published in Apartment Therapy, Architect, Eco-Structure, GRAY, Preservation, The Washington Post and more, at lindseymroberts.com.
I write about interior design and architecture, and take what I learn into... More »
Because altruistic ideas can often be impractical, I believe that the best reasons to use sustainable features in a home are to save money or for the pleasure of the occupants. (Saving energy is an important side effect.)
But for one feature that checks all three boxes, consider radiant heating. On a cold, rainy day, there's nothing that feels better upon waking than putting bare feet onto a warm floor heated by a radiant in-floor system.
Rather than rely on inefficient forced-air systems — which start with cold outside air, and then must expend energy to heat it before moving it inside — radiant heating uses a warm surface to transfer heat into a space. It's much like shining a light on a wall. And as we learned in physics class, warm air rises, so a heated floor soon means a heated room.
In general, there are two types of radiant heating systems, according the National Association of Home Builders: dry-system radiant tubing, with electric-powered tubes positioned above the floor and in between two layers of plywood, or under the subfloor; and hydronic radiant-floor systems, with looped tubes pumping heater water beneath the finished floor. The water is heated by gas, wood or oil boilers; solar water heaters; or a combination of sources. Hydronic systems tend to be the most efficient, says the U.S. Department of Energy.
But for one feature that checks all three boxes, consider radiant heating. On a cold, rainy day, there's nothing that feels better upon waking than putting bare feet onto a warm floor heated by a radiant in-floor system.
Rather than rely on inefficient forced-air systems — which start with cold outside air, and then must expend energy to heat it before moving it inside — radiant heating uses a warm surface to transfer heat into a space. It's much like shining a light on a wall. And as we learned in physics class, warm air rises, so a heated floor soon means a heated room.
In general, there are two types of radiant heating systems, according the National Association of Home Builders: dry-system radiant tubing, with electric-powered tubes positioned above the floor and in between two layers of plywood, or under the subfloor; and hydronic radiant-floor systems, with looped tubes pumping heater water beneath the finished floor. The water is heated by gas, wood or oil boilers; solar water heaters; or a combination of sources. Hydronic systems tend to be the most efficient, says the U.S. Department of Energy.
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by Hufft Projects
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| Can you imagine anything cozier in the morning than putting your feet onto a shag rug, warmed by radiant heat under the wood floors? A benefit of radiant heating for allergy sufferers: The absence of outside air moved in and around a home can reduce allergies. |
I've seen most radiant-flooring systems installed under concrete. But the material you choose to install over the systems doesn't have to be purely utilitarian. In one beach house, I saw a 3-foot-diameter, shallow-metal compass rose installed flush into the concrete over the flooring system. And the concrete was dyed green.
The concrete floors in this entry have slate leaves embedded in them, "to look as if they've just blown in," says Tali Hardonag Architect.
The concrete floors in this entry have slate leaves embedded in them, "to look as if they've just blown in," says Tali Hardonag Architect.
If you don't like the look of concrete, wood is a classy alternative to top radiant-flooring systems, as in this San Francisco house by Barker O'Donoghue Master Builders.
In addition to concrete and wood, radiant-heating systems can be installed under tile. This 15,000-square-foot house in Saratoga, California, by Conrado Home Builders features radiant-floor heating throughout — even in this traditional-looking, tiled entryway.
There are many different types of installation systems for radiant-floor hydronic heating, according to the Radiant Panel Association. In a concrete-slab system like this one, tubing is held in place until the concrete is poured, at which point the tubes become permanently embedded in the concrete.
Other systems include thin slab, subfloor plates, subfloor board, engineered subfloor, staple up and hanging in joist space. The Radiant Panel Association has one caution for installing wood systems: Don't use particleboard for the subflooring.
Photo by edgygrrrl via Flickr Creative Commons
Other systems include thin slab, subfloor plates, subfloor board, engineered subfloor, staple up and hanging in joist space. The Radiant Panel Association has one caution for installing wood systems: Don't use particleboard for the subflooring.
Photo by edgygrrrl via Flickr Creative Commons
by jacuzzi.com
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For a quick radiant fix, install radiant systems under tiles in only the areas that you want instead of under an entire floor. This system by Jacuzzi has a control panel to adjust the temperature.
by Hufft Projects
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The Curved House, by Hufft Projects, features radiant flooring in my number-one favorite place: the bathroom. There's no need for bath mats in rooms that are heated like this one; bare feet step onto warm tile.
One trick with radiant heating is to make sure it's turned up or down according to the outside temperature.
I recently stayed at this gorgeous building, the University College at Oxford University's boathouse, which has student rooms on the upper floors. The building is heated by radiant flooring, except when I was there, it was 70 degrees outside and we had all the windows open because it was so warm inside.
As with all green systems, if you're not using them right, you're not saving money.
Photo by Anders Sandberg via Flickr Creative Commons
I recently stayed at this gorgeous building, the University College at Oxford University's boathouse, which has student rooms on the upper floors. The building is heated by radiant flooring, except when I was there, it was 70 degrees outside and we had all the windows open because it was so warm inside.
As with all green systems, if you're not using them right, you're not saving money.
Photo by Anders Sandberg via Flickr Creative Commons
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by Hufft Projects
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| As for the financial savings, radiant flooring is reported to save 20 percent to 40 percent in heating bills, according to the National Association for Home Builders. Tell us: What questions do you have about how radiant heating works? More: 12 Ways to Warm Up Your Bath When to Use Engineered Wood Floors Houzz Tour: Zero-Energy Renovated Victorian in San Francisco |
Ideabook published on April 19, 2012.
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If the heating is in a slab - do you break up the slab to do any repairs? It seems with all the tubing, something is bound to go wrong every once in a while. It seems like this would be extremely expensive and messy.
Next, is the water a problem for a wood floor - can it cause warping, shrinking, etc?
My other question is an odd one - someone we know suggested putting radiant heating in a patio slab. We live in California where the weather is realtively mild, and this seems like an awesome idea for cool evenings! Is this crazy?
IMO, retro fitting radiant floor heating isn't the diy project televisions show portray them to be, and are better suited to houses built on a craw and is best suited for houses that are still in the construction phase- unless you have an unlimited budget that will include the cost of tearing up and repairing walls & ceilings, and possibly adding a new electric box. What's the point if your house is built on a crawl?
Radiant heat is just like shining a flashlight on a wall - both visible light and radiant heat are part of the electromagnetic spectrum. But radiant heat warms a room first by warming the objects in the room – including the people. There is some secondary warming of the air through convection, but the main reason radiant heat is so comfortable is because it warms the skin directly.
Response: You are correct, wood is a great insulator, but there is a difference between wood’s ability to heat up and its ability to radiate heat.
Heat is always moving from warmer to cooler areas of your home, how quickly it moves is a function of the material – a property called heat capacity. Bring a block of wood and a block of stone into a heated room from the cold outdoors and the stone will reach the temperature of the room first, but soon after, the wood will be just as warm.
Once they are heated, all materials radiate heat. The emissivity of a material is a measure of its ability to transfer heat through radiation. Most flooring materials have very similar emissivities and at the same temperature, radiate about the same amount of heat.
So if you’re looking to heat a room using radiant heat, the choice of flooring material affects only the amount of heat you need to put into the material to raise its temperature so it will radiate the needed amount of heat. This is done by changing the temperature of the water and the spacing of the tubing under the floor.
engine99 said: “Also, I would have concerns about excessive drying, shrinking and cracking of wooden flooring above a heat source. How would you prevent large gaps from opening up once the flooring has been in place for a heating season or two?”
Response: This is a common misconception about wood and radiant heat. Any dimensional changes in wood are a result of moisture changes in the wood and not temperature changes. Properly designed, a modern hydronic radiant under-floor heating operates at a temperature lower than body temperature – in a range of about 70 to 80 degrees F (see http://www.healthyheating.com/Page%2055/hardwood1.htm for an excellent discussion). Any large gaps, cracks, and warping are the result of poor humidity control in the room or the improper seasoning of the wood used for flooring.
Response: It is highly unlikely that anything would go wrong with the hydronic radiant heating tubing in a concrete slab. Modern radiant tubing is manufactured from cross-linked polyethylene plastic (PEX), to high quality standards. A hydronic radiant system operates at 15 to 20 psi; compare this to the city water system which operates at 40 to 60 psi. When professionally installed, the radiant tubes are air pressure tested before and after the cement is poured; before, to ensure that there are no leaks in any connections, and after, to ensure that the cement pouring process didn’t cause any damage. In the unusual case of a leak developing in a cured concrete slab, the leak is easily located, a small patch of concrete surrounding it is broken out, the tube or connection is repaired, and the concrete is patched.
slobarbara said: “Next, is the water a problem for a wood floor - can it cause warping, shrinking, etc?”
Response: Once properly installed and tested, there is no way for the water inside the PEX radiant tube to get outside the tube and damage floors.
slobarbara said: “My other question is an odd one - someone we know suggested putting radiant heating in a patio slab. We live in California where the weather is relatively mild, and this seems like an awesome idea for cool evenings! Is this crazy?”
Response: Not crazy at all, but perhaps a little energy inefficient. The additional patio heating might require a boiler larger than what you would need for just heating your home. So it really depends on how often you intend to heat your patio. If it’s just a few evenings a year that you require patio heating, it may be more efficient and economical to purchase and use a propane patio heater. Talk to your radiant heat contractor; he’ll do a proper heat loss calculation for your home, including your patio, and help you select the proper appliances.
Response: The short answer is yes, a hydronic heating system can be installed in an existing home. For more information on how and the cost to install, contact a qualified heating contractor in your area. You can also visit the Beautiful Heat website (www.beautifulheat.com). You’ll find a lot of information on the applications of radiant hydronic heating and how it can be installed in new or existing homes.
Response: While I can’t speak to your particular situation, it is more likely that the wood was damaged from a change in moisture content than from a properly designed under-floor radiant heating system. Factors like wood seasoning and your home’s humidity are more common causes of dimensional changes in wood flooring.
Response: Hydronic radiant systems can be placed in walls and ceilings and operate as effectively as if they were placed in floors.
It is a common misunderstanding that because warm air rises, then all heat rises. Air rises when warmed because heat changes its density, making it lighter than the surrounding air. In all other cases heat moves in all directions – especially radiant heat. Radiant heat uses electromagnetic waves – the same energy found in visible light – to transfer heat from warmer to cooler objects. Radiant heat moves through space in all directions without heating the air, but heats other objects like floors, furniture and people. That’s why a radiant heating system in walls or ceilings is just as effective as if it were placed in floors.
Response: Is it possible that by "hydronic system" you mean "radiant system" and the means of heating your concrete floors is electric wires? If that's the case, turning down the thermostat is your only option.
If you in fact have a radiant hydronic system - heated water flowing through tubes embeded in the concrete - you have a few options. A radiant hydronic heating system using a natural gas boiler uses relatively little electricity to power pumps, switches, and controls. "High electric bills" imply that you’re using an electric boiler. If that's the case, you could replace it with a natural gas fired boiler for some cost savings. Not only is natural gas less expensive than electricity, radiant heating utilizes lower water temperatures. Lower water temperatures allow the use of condensing boiler technology, which squeezes out as much efficiency as possible (up to 98%) from the burning of natural gas.
Ensure that either the TCNA (USA) or TTMAC (Canada) specification guidelines are followed for the installation.
White Marble Curbless Shower - Vancouver West Side 1
White Marble Curbless Shower - Vancouver West Side 2
White Marble Curbless Shower - Vancouver West Side 3
This barrier free shower we built in Vancouver is fully heated. Even the bench is warm.
To ensure we had a trouble free installation the shower's wet zone was covered with Noble Seal TS and the dry zone outside the shower with Ditra.
You can see both below.
On the flip side I have never had a failure nor heard of one with a wire system.
Look for a wire supplier that allows both the wire to be used as a primary heat source and also allows the wire to be installed in the shower. Most do not. Make sure you find this out.
JW