Barron Heating AC Electrical & Plumbing Blog: Archive for the ‘Comfort’ Category

The Importance of Air Sealing Attic Penetrations

Wednesday, April 30th, 2014
Can light sealing by CAZ Energy Services. Photo: Hunter Hassig

Many times when homeowners are looking at home improvement solutions for cold spots or high energy bills they think insulation. While insulating your attic and crawl space sub-floor up to code standards is very important for whole home comfort and energy efficiency it is insufficient on its own. This is because in almost every home there are numerous holes in the ceilings that allow air to move freely between your attic space and the conditioned living space of your home. Insulation is a thermal barrier NOT an air barrier. To further illustrate this think of insulation as a sweatshirt. It will keep you warm on a calm day but on a windy one you will need a wind breaker or rain jacket to stay comfortable. Air sealing those holes in your ceiling that lead to the attic creates a consistent, level air barrier that acts as a wind breaker for your home.

Where exactly are these holes? According to The Homeowners’ and Trades Resource Center the three most common areas are wiring penetrations, plumbing penetrations and where your drywall meets up with the framing. Some other trouble areas include soffits, dropped ceilings, chases, vents, exhausts, bath fans, recessed lighting (ie. can lights), and ductwork in your attic. In order to seal small holes like those around bath fans, use silicone caulk or expandable foam. To seal bigger gaps like those found in dropped ceilings and soffits, use rigid foam or drywall (depending on local code) to bring that area to the same level as the rest of the attic and then seal around it with foam or caulk. Sealing these holes will not only save you money on your utility bills but will lead to a more even temperature in the house and many times improve indoor air quality as well.

Some content from: http://blog.sls-construction.com/2011/air-sealing-attic-penetrations

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Light Bulb Buying Guide

Friday, March 14th, 2014

Before energy saving light bulbs were so readily available, we would purchase light bulbs based on how many watts or how much energy they used. With newer light bulbs you can achieve the same level of brightness for while using up to 80% less power. When shopping for bulbs today, look for lumens not watts. Light bulbs usually include a label on the packaging.

On the ‘Lighting Facts’ you will see how many lumens (the measure of brightness), the estimated yearly cost of energy to use this light bulb, the lifespan, and the color tint of the bulb. Warm is a yellowish color, while cool is more blue. You can see that in this example only 13 watts of energy are used, however, if you are used to using 60 watt bulb then this 800 lumens will provide the same amount of light using only 21.7% as much energy.

For more information on buying the right kind of bulb, or lumens-to-watts conversion, check out this informational video.

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Clean Air Plants for Your Home

Tuesday, February 11th, 2014

Projects like installing new carpet and painting walls can release chemicals that pollute indoor air. Luckily, some houseplants moonlight as efficient purifiers. For the best results, put as many plants as you can care for in the rooms you use most, says environmental scientist Dr. Bill Wolverton. That means you’ll want at least two plants (in 10- to 12-inch pots) per 100 square feet of space; if you’re in the middle of major renovations, aim for more plants. One tip: Be sure not to overwater, as too much soil moisture can lead to mold growth.

Here are 10 smart options you can buy at your local nursery. To learn more, pick up Wolverton’s new book, “Plants: Why You Can’t Live Without Them” (Roli Books; $25).

Article by This Old House
Read More This Old House

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Wintered-In Improvements

Friday, December 6th, 2013

This cold winter weather can sometime leave us feeling stuck inside our homes more than any other season with the wind, the rain, the snow, the sludge… oh winter! All of this extra time spent inside reminds you of all the improvements you’ve been meaning to make to your home, but never had the time for. We’ve got 3 rainy day fix-ups that will put your mind at ease and keep you feeling productive if you find yourself stuck at home.

  1. Are your carpets stained from summer fun and tracked in dirt? Winter could be the perfect time to get them cleaned up before its too late. This stain removal recipe is from This Old House
    “Mix 1 teaspoon OxiClean with 2 cups water in a spray bottle and spritz the stain liberally. Cover with a damp white rag, then apply an iron on medium-low heat and let the steam do the work.”
  2. We say there’s no better time for a relaxing bath than in the winter time. But is your tub ‘soak ready’? Its common for tubs to get full of grime and stuck on dirt after a few uses. We have another great recipe, a  favorite from Pinterest, for a cleaner made with items in your pantry that will do wonders for your bathtub. This one requires a little bit of planning ahead, but very little elbow grease
    “Mix 1/2 cup of white vinegar that has been heated in the microwave for 90 seconds. Pour into a spray bottle and add 1/2 cup of dish soap. Shake gently and spray on dirty surfaces of your tub. Let sit for 1-2 hours and simply wipe away!”
  3. Kitchen clutter is a problem we often don’t realize until the winter when we are making large meals and baking regularly. Take a few days and explore Pinterest for ideas on DIY pot racks. These racks keep your pots exposed, giving your kitchen a modern twist. The project can be as big or as small as you would like to make it. It may be easiest to buy a standalone structures or a curtain rod that you can easily attach hooks to. Our favorites are all here. Notice you can use this technique to de-clutter kitchen tools and the lids to your pots and pans as well.

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Turning down the heat will save you money. Simple really

Tuesday, November 12th, 2013

There are literally dozens of things you can do to cut back on your heating (and cooling) costs. These range from things like getting a high energy efficiency system to just making sure that you have adequate insulation in all parts of your house. But too many people overlook one of the simplest things that you can do to cut down on your monthly heating bill, and that is to turn the thermostat down.

Of course, you did not pay for that high tech home comfort system just so that you could walk around cold all winter long. You certainly want to keep your house at a temperature that is comfortable, but what does that really mean?

The normal default setting for a home heating system is usually somewhere between 72°F and 75°F. If you have your thermostat set somewhere in this range in the winter, you are probably quite comfortable indoors. In fact, you might not even need a sweater. But would you really notice if it was a degree or two cooler? Would it be incredibly inconvenient to put on a sweater or sweatshirt after all?

The truth is that most of us will be just as comfortable at 69°F as we are at 72°F, and the effect that small adjustment can have on your heating bill is actually pretty significant. In fact, you will save an average of 3% on your monthly bill for every degree you turn your thermostat down. Drop the temperature down by three or four degrees and that will give you up to a 10% monthly savings – hardly something to turn up your nose at.

And setting the regular temperature in your house a bit lower is not the only way your thermostat settings can save you money. You will also save quite a bit if you take the time to turn down the temperature when you leave the house and when you go to bed at night. There simply is no reason to pay to heat your house when you are not there and you will certainly be rewarded with a lower energy bill for your efforts.

Posted by Wes Diskin

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Is it CHI or CHEE?

Saturday, October 12th, 2013

The Chinese have a term ‘CHI’ that is defined as: The light, refreshing, uplifting feng shui energy that is beneficial to your health and well-being. We’d like you to consider your ‘CHEE”
They tell us that Good Chi, takes many forms, such as:

  • The energy you experience walking by the beach (high amount of negative ions are beneficial to your health)  
  • The energy you experience in a lush forest (Japanese have the expression of “wood bathing”)
  • In a harmonious interior environment with a good flow of feng shui energy, clean air and plenty of natural light.

At Barron, we can’t help you with the FengShui design of your home or suggest which local beach or forest might put your spirit in the best position to receive ‘good Chi’ (probably any of our great outdoor areas will do the trick)…but we can help in positioning your home to be in the perfect condition to control, clean and condition the indoor environment we will spend most hours of the day in.

Many homes can’t keep windows open during good weather due to allergens and outside air moving into the home and causing respiratory issues. This leaves a home feeling stuffy or uncomfortable.  Then to make matters worse, when they lay down to sleep in the evening in a home that may be too warm or uncomfortable to provide the beneficial sleep…the home can go into a state (due to negative pressure) that brings a tremendous amount of dust, contaminants & allergens into the home.  The contaminants enter through can lights, attic hatches, electrical switches or under wall plates and pollute the air we breathe.  Ever wonder why you wake up more stuffy than when you went to bed?

At Barron, we appreciate the CHI but we’re more about the CHEE.

What’s CHEE?  We’re glad you asked…

CHEE stands for the Comfort, Health Energy Efficiency of your home.  Creating the perfect balance of those three is Barron’s specialty and what we feel is the key to providing the perfect indoor living environment.  We work hard at good CHEE so that the path to your front door can bring the same feelings of peace and serenity that a walk on the beach or next to the forest can provide.

Take a look at the different Services we provide to improve the CHEE around your home as you work toward your own perfect balance.  We’d love the opportunity to help.

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The Beauty of Zone Heating

Thursday, October 10th, 2013

While it might not technically be a necessity, there are a lot of reasons why you might want to look into having a zone heating system installed in your home. Whether you’ve been using the same home heating system for a long time or are looking to have a new one installed, there’s never a bad time to have a zone heating system put in.

Most people think that the only thing that affects their home heating and cooling bills is the energy efficiency of their furnace or heat pump. However, that’s simply not always the case. Certainly, the more efficient your furnace or heat pump is, the lower your energy bills will be. But that doesn’t mean they’re as low as they could possibly be.

After all, if you don’t have a zone control system installed, you’re paying to heat your entire house every time you turn on the heat. Depending on the size of your house, that could mean you’re heating anywhere from two to 10 rooms or more that are unoccupied at the time. In fact, you could be paying to heat an entire empty wing of your home. And while you’ll pay less than you would if your heating system was less efficient, you’re still paying more than you need to.

With a zone control system, you can heat your home much more efficiently because you can control which areas of the house get the heat and which ones don’t. You can set multiple different temperatures for the different zones of your home, which allows you to keep the occupied areas warm while not forcing you to waste energy to heat unoccupied spaces.

Aside from the economic benefits of only heating the areas of your home that you need, zone control systems also can put an end to some of those contentious thermostat wars that go on in so many households. If the members of your household can never agree on what a comfortable temperature is, they can simply each set their own temperature for their own area of the house.
That way, everyone is happy and no one has to suffer uncomfortably. After all, you paid a lot for your state of the art home heating system. It’s only fitting that you should be able to get the most possible out of it.
Posted by Wes Diskin

 

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The Book on Radiant Heating: When it makes sense and when it might not

Monday, June 3rd, 2013

Alex makes some great points here, but the thing to keep in the back of your mind is that this is coming from the perspective that you are going green crazy on your house. Even if you are just building a reasonably green home, bang for your buck is definitely something to consider, give me a ring if you would like to discuss your options. -Wes

The following article was written for the Environmental Building News by Alex Wilson. Copyright © 2002 by BuildingGreen, Inc. All rights reserved; reprinted with permission. www.BuildingGreen.com

Radiant-Floor Heating: When It Does—and Doesn’t—Make Sense

During judging of the Northeast Green Building Design Competition last spring, I was struck by the number of residential entries with really stellar passive solar design and super-high-performance building envelopes. Clearly, I thought as I began reviewing the features, we’ve come a long way in high-performance residential green building since my first experience with passive solar in the mid-1970s. But something also seemed odd. A majority of these entries had sophisticated radiant-floor heating systems. After going to all the effort and expense to superinsulate the envelopes of these houses and provide passive solar design, did they still need $10,000 heating systems? And did those systems really make sense from a performance standpoint? I wasn’t sure, and decided to dig into these questions.

I’ve long been a fan of the comfort delivered by radiant-floor heat, and strong arguments are often made about energy savings and indoor air quality advantages. But is this really the best match for high-performance green homes? In the most energy-efficient buildings, the answer seems to be “no,” though radiant-floor heating can offer both comfort and IAQ benefits. This article provides a quick overview of radiant-floor heating, reviews the benefits of this heat-delivery approach, and reviews when these systems do—and do not—make sense in homes and small commercial buildings.

Radiant-Floor Heating Overview

Radiant-floor heating has its origin in ancient Rome, where fires were built beneath the floors of villas. Early Korean buildings were similarly heated by channeling flue gases beneath floors before venting those gases up through chimneys. Frank Lloyd Wright piped hot water, rather than air, through the floors of many of his buildings in the 1930s—a practice that has become common in custom homes today.

Radiant-floor heating turns a floor into a large-area, low-temperature radiator. In most modern radiant-floor heating systems, warm water circulates through plastic tubing either embedded in a floor slab or attached to the underside of subflooring. With slab systems, one can use either a standard concrete slab-on-grade, or a thinner, lightweight gypsum-concrete slab poured on a subfloor or over an existing finished floor. In either case, the thermal mass of the slab holds heat and radiates it slowly to the living space above.

In addition to hot water as the heat source, radiant floors can also use electricity or hot air. Due to the high cost of electricity in most areas, radiant-electric floor heating usually makes the most sense when off-peak electricity is available for charging a slab at night and during other off-peak hours. Production of electromagnetic fields (EMFs) is also a potential concern with radiant electric heating (see EBN Vol. 3, No. 2). Radiant-air floors are occasionally used in commercial buildings but are generally impractical and too expensive for residential applications.

For hydronic radiant-floor systems, copper piping has been used in the past, but most systems today use either rubber or cross-linked polyethylene (PEX) tubing—the latter being by far the most common. Design of radiant-floor heating systems is quite complex and should be done by someone with adequate training or experience. Various design manuals, manufacturer-specific installation guides, and software tools are available for use in designing and sizing radiant-floor heating systems. The length of tubing required per square foot of floor depends on such variables as tubing diameter, type of radiant-floor system (thick slab, thin slab, no slab), climate, heat load of the building, and type of boiler and controls used. Manufacturers have done a great job in recent years in packaging the various components to simplify the design of radiant-floor systems.

A key requirement for most radiant-floor heating systems is adequate insulation beneath the heated slab or beneath the tubing (when tubing is attached to the underside of a subfloor). Most manufacturers recommend a minimum of 1” (25 mm) of extruded polystyrene (XPS) for concrete slab-on-grade radiant heating systems, but significantly higher levels are justified in cold climates.

Zoning of radiant floors is usually done with advanced manifold modules that allow the water temperature to be varied in different zones. This provides flexibility for maintaining different temperatures in different rooms and for allowing differential heat delivery to spaces with and without solar gain.

Finally, sophisticated controls are often installed to ensure optimal comfort and to maximize energy performance. Some radiant-floor systems rely on separate temperature sensors outdoors, within the floor slab, and in the living space—with microprocessor control to regulate just when and where hot water should be delivered. Because of the long lag-time with concrete-slab radiant-floor heating systems, standard set-back thermostats usually are not effective, though set-back thermostats that have a built-in anticipation feature may work well for this application, says building consultant Andy Shapiro, of Montpelier, Vermont.

Benefits of Radiant-Floor Heating

Radiant-floor heating offers a number of significant benefits:

Comfort. By far, the biggest selling point for radiant-floor heating is comfort. The large radiant surface means that most of the heat will be delivered by radiation—heating occupants directly—rather than by convection (the primary mechanism of heat delivery from conventional hydronic baseboard “radiators”). Warmer surfaces in a living space result in a higher mean radiant temperature, a measure of surface temperatures in a space that influences the rate of radiant heat loss from occupants). With higher mean radiant temperatures, most people are comfortable even at lower air temperatures. Delivery of the heat at floor level with a warm floor surface also allows occupants to walk around barefoot even in winter—a very popular feature. Enhanced comfort should be a big selling point in any green home, so a strong case can be made for this heating approach.

“Until you’re lived with this form of heat,” says Radiant Panel Association executive director Larry Drake (who got involved with radiant heating after years of working with solar houses), “it’s hard to understand how comfortable it is.” He argues that with green homes in particular, after going to all the effort and expense to incorporate healthy and sustainable materials, ensuring high levels of comfort with radiant heat should be a top priority.

Energy savings

There is potential for saving energy with radiant-floor heating through several mechanisms, including lower thermostat settings, lower-temperature boiler settings, and reduced infiltration. Homeowners with radiant-floor heating are likely to be comfortable at lower air temperatures because of the elevated mean radiant temperature in such homes, the lack of significant airflow (as occurs with convective hydronic heating and forced-air heating systems), and the delivery of heat at floor level. Proponents of radiant-floor heating argue that someone normally comfortable at 72°F (22°C) will be comfortable in a building with radiant-floor heating kept at 68°F (20°C). If this is true, one would expect people with radiant-floor heating to keep their thermostats lower and thus realize significant energy savings.

The second opportunity for energy savings with radiant-floor heating is through keeping the boiler temperature lower than is necessary with conventional baseboard hot water distribution. The typical European approach with radiant-floor heating is to circulate fairly low-temperature water on an almost-continuous basis, varying the water temperature as needed to satisfy the load. This practice might reduce heat loss into unconditioned space if boiler and piping are located in an unheated basement, but experts EBN spoke with suggest that the savings would be very small at best—especially because of the additional electricity consumption to operate pumps for long hours. Green building consultant Marc Rosenbaum, P.E., of Meriden, New Hampshire, suggests using a low-mass boiler that is fired on-demand, rather than a high-mass boiler operated almost continuously.

The third opportunity for energy savings (over forced-air heat) is that radiant-floor systems do not increase the rate of air infiltration. Standard forced-air heating systems can significantly increase or decrease air pressure in different parts of a building, which in turn can increase air infiltration/exfiltration rates—at least in a conventional, leaky building. With radiant-floor heating, as with baseboard hydronic heating, this will not happen. (A well-designed, properly balanced forced-air system should not increase infiltration.)

Potential for use of solar energy

The relatively low temperature required for circulation water in a radiant-floor heating system provides an opportunity to utilize solar hot water. This approach works best with concrete-slab systems; higher-temperature water is generally required when the tubing is attached to the underside of wooden floors. While such systems are fairly complex and expensive, radiant slabs offer one of the best ways to make use of solar energy for heating portions of a building without direct access to sunlight. Most practical are systems in which solar energy heats water in a storage tank that can then be circulated through the slab. According to an EREN Consumer Energy Information Brief (www.eren.doe.gov) titled “Solar Radiant Floor Heating,” such systems typically cost at least $14,000. Backup heat is still required and can be provided with a wood stove, through-the-wall-vented gas heater, electric resistance heat, or backup heating element in the solar storage tank.

Increased boiler life. By operating a boiler at a lower temperature, its life can be extended. Radiant-floor heating systems typically use water temperatures of 85–140°F (30–60°C), compared with baseboard hydronic systems that typically operate at 130–160°F (55–70°C). At these operating temperatures, boiler life can exceed 45 years, according to information from DOE. (Shapiro is skeptical of this claim, however, pointing out that newer boilers are made for cold-start operation and should hold up well with this temperature cycling.)

Quiet operation

Radiant hydronic floor heating is extremely quiet. Unlike forced-air heat, there is no noise from a fan or airflow through ducts; and unlike hydronic baseboard heat, there is usually no gurgle of water through baseboard radiators or creaking from expansion and contraction. The primary noise will be the sound of circulating pumps and the fan used in power-venting the boiler. With radiant-floor systems that have tubing attached to the underside of wood flooring, there may also be some creaking from expansion and contraction.

Flexible room layout

Because there are no baseboard radiators or air registers with radiant-floor heating, there is much greater freedom as to where furniture can be placed. Radiant-floor heating systems are “invisible.”

Improved indoor air quality

An argument can be made for improved indoor air quality in houses with radiant-floor heat. Compared with a conventional forced-air distribution system, there is likely to be less dust circulated around the house. And unlike electric baseboard or forced-air heat, there will be no surfaces hot enough to burn dust particles—which could introduce volatile chemicals or toxic particulates into house air (even passing through filters). This concern would be greatest for people with acute chemical sensitivities. In fact, veteran builder Max Strickland, of Burkholder

Construction in Travers City, Michigan, first became interested in radiant-floor heating several years ago after his wife became chemically sensitive. He’s worried about “frying the air” with conventional heating systems and feels that conventional filters on forced-air systems are not effective. Strickland went on to build an American Lung Association (ALA) Health House in Travers City three years ago, and he now incorporates radiant-floor heating into all of his homes (typically 4 to 6 high-end custom houses per year).

So What’s Wrong with Radiant-Floor Heating?

In the right application, radiant-floor heating is a superb heat-delivery system—in fact, perhaps the very best. You usually pay more for it, but the enhanced comfort, potential energy savings, and other benefits can easily justify the extra cost. That said, however, super-energy-efficient green buildings may not be as well-suited to radiant-floor heating. Here’s why:

Economics

It can be reasonably argued that a green home in a moderate-to-cold climate should have very high levels of insulation (at least R-25 walls and R-40 ceiling/roof), extremely low infiltration rates, high-performance glazing (unit U-factors below 0.3), and at least some passive solar gain or sun-tempering.

We’re not talking about conventional houses, mind you, but high-performance green homes. Such a house will use very little heating energy—probably less than 2.0 Btu/ft2 · degree-day (41 kJ/m2 · °C), which would translate into very low heating costs. To achieve that level of energy performance requires a significant investment in the building envelope (for example, double 2×4 walls). In such a house, putting in an expensive heating system doesn’t make good economic sense. As Rosenbaum notes, “It just doesn’t make sense to put in a $10,000 heating system to provide $100 worth of heat per year.”

Investing so much money in the building envelope and still putting in an expensive radiant-floor heating system eliminates the potential for offsetting much of the extra cost in building envelope improvements through savings in the mechanical equipment—one of the key principles of integrated, whole-systems building design. In most highly energy-efficient houses, the same high level of comfort provided by a radiant-floor heating should be achievable simply by installing one or two small, quiet, high-efficiency through-the-wall gas heaters (such as those produced by Rinnai) or a few short sections of electric baseboard heat. At $1,000 to $2,000 apiece for Rinnai heaters (installed) or a few hundred dollars for electric baseboard vs. $10,000 for a typical radiant-floor heating system, savings of $6,000 to over $9,000 would be possible—and that savings could pay for most of the envelope improvements required to bring the heating load so far down that space heating (instead of distributed heat) becomes a viable option.

Even Larry Drake, a strong proponent of radiant-floor heating systems as executive director of the Radiant Panel Association in Loveland, Colorado, admits that radiant heat is more difficult to justify in high-performance buildings. “The tighter the envelope, the less the amount of savings of a radiant system,” he told EBN.

Heating performance with micro-loads

Along with the economic questions about the wisdom of radiant-floor heating systems for high-performance green homes, there are building science reasons why this may not be a great fit. Heat is transferred from an exposed slab to the space at a rate of about 2 Btu/ft2 · hr · °F (11 w/m2 · °C), according to Rosenbaum. In a well-insulated house, this rate of heatflow means that even when it is very cold outside, the slab can only be a few degrees warmer than the rest of the room or the room will keep heating up. For a concrete slab to feel warm, however, it needs to be about 80°F (27°C). Thus, for most of the heating season, the greatest feature of radiant-floor heat—a warm floor—won’t occur. With moderate solar gain, heat delivery from a floor slab will be even less. Because the floor is insulated underneath, it will be more comfortable to walk on than most slab floors, but the benefit will be from the insulation, not the radiant heat.

The time lag of heat movement through concrete can also be a problem. In a very well-insulated house, that lag time can result in overheating, particularly if there are other sources of heat being delivered to the space, such as passive solar. If a concrete slab is “charged” with heat during the early morning hours and the surface is warmed to the point where it cannot readily absorb solar radiation striking it, that solar heat will more directly heat the air, increasing the risk of overheating. The same thing happens to a much greater extent in high-performance passive solar homes with masonry heaters because the surface of an operating masonry heater is at a higher temperature. In such houses, occupants usually need to check weather forecasts—if they load up the masonry heater firebox in the morning and it turns out to be a bright, sunny day, the space will very likely overheat. A radiant floor maintains a much lower surface temperature than a masonry heater, so the floor will effectively “turn off” as the room warms up with solar gain. “If the floor temperature is 76°F,” says Rosenbaum, “then the radiant system can’t heat the place to hotter than that.” Therefore, this isn’t a huge problem with radiant-floor heating systems, but it may mean that homeowners will have to open windows periodically in the winter and their overall energy savings from solar energy will not be as great. Shapiro counsels against the use of radiant slabs in areas of houses with passive solar heat. “It’s a waste of energy,” he says, though just how much waste occurs is unclear.

The risk of overheating with concrete-slab radiant-floor heating systems in very energy-efficient buildings leads some designers to incorporate sophisticated control systems. Rather than a simple room thermostat, many radiant-floor designers install control systems that also adjust the circulating water temperature based on outside air temperature and the temperature of the slab. It can also be important to have different zones in a concrete-slab radiant-floor heating system—so that less heat can be delivered, for example, to portions of the slab that are warmed by solar gain. However, according to Rosenbaum, a radiant-floor slab is somewhat self-regulating when it comes to solar gain. If the floor slab begins absorbing solar heat and warms up, it will extract less heat from the circulating water; that heat will return to the boiler and can be circulated to nonsolar zones.

Heat loss into the ground

With slab-on-grade radiant-floor heating systems, there is potential for significant heat loss into the ground. According to Paul Torcellini, Ph.D., P.E., of the National Renewable Energy Laboratory, even with insulation under the slab, 20% of the heat entering the slab can be lost into the ground. This reduces the overall efficiency of the radiant-slab system, offsetting the potential savings described above. Typical manufacturer recommendations for 1” (25 mm) of XPS insulation beneath a radiant slab are clearly inadequate; even 2” (50 mm) may not be enough. Shapiro recommends up to 4” (100 mm) in cold climates. In place of ozone-depleting XPS, one can use high-density expanded polystyrene (minimum 1.5 pcf, 24 kg/m3 foam recommended).

It is ironic that most people want radiant floor heat because they don’t like a cold floor, yet there has long been resistance to insulating beneath concrete floor slabs—which would dramatically reduce the cold-floor problem. They solve the problem with an expensive radiant-floor heating system (including rigid insulation under the slab) when the rigid insulation alone would solve most of the problem. (To be fair to radiant-floor heating proponents, the only way to make a slab floor actually warm to the touch is to provide radiant-floor heating—because the high conductivity of concrete makes a slab feel cool even when it is at or slightly above room temperature.)

Challenges with cooling

Most radiant-floor heating systems cannot provide cooling, and most homes and small commercial buildings are being built today to provide cooling—even in relatively cool climates. This is why forced-air systems are far more popular than hydronic heating systems nationwide—the ducts used for forced-air heating can also be used to deliver chilled air (see further discussion under “Radiant-Floor Heating vs. Forced-Air Heating” below). One of the problems in turning a floor into a heat sink is the risk of condensation on the cool surface. (Condensation occurs when a surface temperature drops below the dew point—which can be quite high in more humid parts of the country.)

Radiant cooling (generally with ceiling panels) is used quite commonly in Europe, where humidity levels are generally not as high as in eastern North America and where the comfort envelope of building occupants (the temperature range at which they are comfortable) is wider than here. That said, there is some interesting research underway in the U.S. on radiant cooling. This concept is being tried out, for example, at an architecture school studio at Penn State University. Chilled water is circulated through ceiling panels to provide radiant cooling, with 100% fresh air used for ventilation. The key is that the ventilation air is dehumidified before delivery to the conditioned space, thus eliminating the potential for condensation on the radiant ceiling panels. This system is saving energy in two ways: because pumping water requires less energy than moving air, and because the chilled water has to remove only the sensible heat loads—not the latent loads. With the 100% outside-air supply, the total amount of circulated air is reduced by about 80%, compared with conventional recirculating systems.

Predicted vs. actual savings

The final concern with radiant-floor heating systems is that much of the assumed energy savings may not be occurring. There is very little hard data to back up the common claim that radiant-floor heating systems save a lot of energy because people with this form of heat are comfortable at lower temperatures and thus keep their thermostats lower. In fact, the only study we could find shows this not to be the case.

Last winter, the Canada Mortgage and Housing Corporation (CMHC) carried out a study of 75 houses in Nova Scotia: 50 with radiant-floor heating and 25 with other heat distribution systems—research that was first reported in the December 2001 issue of the Journal of Light Construction. These houses were visited during daylight hours on weekends, and thermostat settings were recorded. Thermostat settings in the houses with radiant-floor heating averaged 68.7°F (20.4°C), while settings in the control houses averaged only 67.6°F (19.8°C). Although the sample size was small, this study shows no evidence that homeowners with radiant-floor heating keep their thermostat settings lower; in fact, it shows the opposite. Don Fugler of CMHC, who managed the research project, told EBN that they launched the study after a radiant-floor heating product manufacturer contacted CMHC asking for more detail on standard information the agency had been giving out about the energy savings from radiant-floor heat. He cautions that this was a very superficial study, but that it points out the need for additional research into the common claim about energy savings.

Larry Drake of the Radiant Panel Association says that the CMHC study was very interesting and the conclusions being drawn from it are misleading. “To assume that people don’t feel comfortable at lower temperature is conjecture,” he said. He argues that the relationship between comfort and mean radiant temperature has been well established by ASHRAE for decades. He speculates that if homeowners with radiant heat have opted to keep their thermostats about where they keep them without radiant heat, they have opted to increase their level of comfort rather than going for the energy savings. He also suggests that homeowners may tend to set their thermostats numerically, irrespective of comfort—so that if they used to keep their thermostats at 70°F and then put in radiant-floor heating, they may well still keep their thermostats at 70° (and end up being more comfortable).
Andy Shapiro prefers not to make claims about energy savings with radiant-floor heat. “Radiant heat can be a wonderful amenity in a house,” he says, “but to sell it as an energy saver stretches the point.”

Radiant-Floor Heating vs. Forced-Air Heating

Many people who opt for radiant-floor heating do so because they don’t like forced-air heat. There is a common perception that forced-air heating systems dry out air and generate dust. “Nothing could be farther from the truth with a properly installed forced-air system,” says Betsy Pettit, AIA, of Building Science Corporation in Westford, Massachusetts. Forced-air systems, she argues, offer the benefit of being “all things to all systems.” A forced-air system can provide heat, air conditioning, ventilation, and filtration—all through a single system of ducts and with shared fans. A radiant-floor heating system, on the other hand, only does one thing, according to Pettit, and it does it at a cost that is typically higher than that of a forced-air system serving those multiple functions. “For me it’s just a hard sell,” she told EBN. “If you insulate the slab and if you build your building envelope correctly—that is to say, leak-free—you can be more comfortable for less money with a ducted distribution system,” she says.

Pettit could think of no tract-home builders in the U.S. who install radiant-floor heating, though there are many custom and spec builders who are very happy with radiant-floor heat. Max Strickland confirms that cost is indeed higher for radiant-floor heat—typically 50% higher than for forced-air—but he notes that if you provide the same level of zoning with forced-air, the costs would be much closer. He deals with air conditioning in houses that have radiant-floor heat by putting in ductless mini-split air conditioners made by Fujitsu, Sanyo or Mitsubishi, which he says are very efficient.  Drake was unaware of any large tract-home builders who have adopted radiant-floor heating over forced-air systems.

When and Where Radiant-Floor Heating Makes Sense

It has been pointed out that radiant-floor heating systems may not be the best choice for extremely well-insulated, passive solar homes. So when do they make sense?

  • In houses and small commercial buildings with conventional levels of insulation and standard insulated-glass windows—especially those in climates with minimal cooling loads—where the extra comfort of radiant heat is desired and the budget allows.
  • In buildings with large open spaces and tall ceilings.
  • In buildings where air-flushing is common, such as garages, fire stations, airplane hangars, and industrial spaces (because the large-area radiant floor allows quick recovery).
  • When cost is not an issue and satisfying most or all of the heating load with solar energy is a high priority.
  • When building occupants have acute chemical sensitivity or allergies—in which case there may be concern that dust could be distributed through a forced-air system or that high surface temperatures from a gas burner or electric heating element will burn dust particles and cause health problems.

Final Thoughts

It’s hard to express doubts about something that’s really popular. Like ground-source heat pumps, radiant-floor heating has a loyal and zealous following of builders, designers, and homeowners who consider it to be the best heating option around—and appropriate in almost any situation.

One of the reasons radiant-floor heating is so popular is that it is so much more comfortable than what most of us have experience with: older, drafty houses where there is significant floor-to-ceiling temperature stratification. If more people realized that the same—or at least a similar—level of comfort could be achieved simply by creating a really well-insulated, tight building envelope, we could be keeping a lot of people extremely comfortable while also saving a huge amount of energy, without needing radiant-floor heat. “A house with a good enough envelope to be called green—well-insulated and tight—will have a very high level of comfort no matter what type of heating system is used,” says Shapiro, “as long as that heating system is well designed.”

In homes with conventional levels of insulation and typical glazings, radiant-floor heating is an extremely comfortable heat-distribution option. It does not contribute to IAQ problems, and it might well even save a little energy if homeowners can be convinced to turn down their thermostats to a level that will provide the same level of comfort as a house without radiant heat. But in an extremely well-insulated, green home, radiant-floor heating usually is not the best option. If you’ve gone to all the effort and spent all the money to achieve a truly stand-out energy-conserving envelope with passive solar gain, why not offset that cost by dramatically reducing the cost of the heating system?

– Alex Wilson

For more information:
Radiant Panel Association
P.O. Box 717
Loveland, CO 80539
800/660-7187, 970/613-0100
970/613-0098 (fax)
www.radiantpanelassociation.org
For subscription information contact: Environmental Building News,
122 Birge St., Suite 30, Brattleboro, VT 05301 (USA). E-mail: ebn@
BuildingGreen.com. Web site:www. BuildingGreen.com

Posted by Wes Diskin

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