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Radiant Heat: Usage Guide, Strategies InspectAPedia®  -     When to make use of radiant heat in buildings Radiant heat use strategies How radiant heat works in buildings What are the pros and cons of radiant heating? Operating cost comparisons for types of radiant heating Floor gaps caused by under-floor radiant heat systems? Odor complaints associated with some radiant heat tubing materials? Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices

This article discusses the basics of radiant heat for auxiliary heating or basic heating in buildings, including strategies for using radiant heat. The article also compares the costs of types of heating system use. Sketch at page top and accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. The sketch explains that the radiant heat effect of a hot surface depends on the angle that the surface forms with the subject. Large surfaces facing and close to the subject provide the most radiant heat. Readers should also see RADIANT HEAT Floor Mistakes to Avoid for an example of what can go very wrong when the building contractor does not know much about radiant heating systems. Also see SLAB INSULATION, PASSIVE SOLAR for specifications on slab insulation and vapor barrier placement in heated floor slabs.

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Article on Radiant Heat Use in Buildings: when, why, how to use radiant heating

"Radiant Heating, how it works, when to use it" - links to the original article in PDF form immediately below are followed by an expanded/updated online version of this article.

• Radiant Heat Use - use your browser's back button to return to this page
• Radiant Heat Use - part 2
• Radiant Heat Use - part 3

The table (left) included in this radiant heat article provides a typical fuel cost comparison for space heating.

The basics of Radiant Heating Systems

This article explains how radiant heating systems work, it describes the comfort of radiant heating systems, and it provides strategies for using radiant heat in buildings effectively. The author, Steven Bliss, explains how to use radiant heat most comfortably, citing the ability to heat large areas to relatively low temperatures (rather than providing concentrated heat source), the evenness of radiant heat, and the importance of mass inside the structure to help keep temperatures even and comfortable through the thermostat cycling on and off where radiant heating systems are installed.

The author describes relatively low-cost in-floor radiant heating systems using hot water as well as electric heating elements. In-drywall radiant heat products are also explained and described for ceiling use.

Advantages of radiant heating systems

• The radiant heating system is unobtrusive - in fact not visible in the occupied space, saving floor space as well
• Radiant heating systems are quiet and clean and require little or no maintenance (depending on the heating source: an oil fired heating boiler supplying a radiant heated building will still require annual maintenance).
• Radiant heating systems save energy compared with comparable convective heating systems where the same fuel is being used to produce btu's of heat. Savings accrue from lower air temperatures as well as the omission of duct or pipe heat losses in the system.
• Heating savings from radiant heat systems depend largely on the amount of thermostat set-back that the occupants find comfortable. Occupants of a radiant-heated building often are equally comfortable (compared with other heating methods) setting back the thermostat 5 degF - about a 20 to 25% savings on heating fuel expense.
• Radiant heat "feels special" or "like being heated by the sun" - (an opinion difficult to verify objectively).

Our photo (above) shows a radiant-heated concrete slab under construction in Two Harbors, MN in 2007.

Disadvantages of electric radiant heat systems

• Electricity can be the most expensive way to provide heat in some areas of the country. Check with your local utility company as special rates may be available for homes using electric heat. One of the many foul-ups of the contractor whose radiant heat system was described at RADIANT HEAT Floor Mistakes to Avoid was that he failed to install a separate electric meter to provide service to the building where the electric radiant heat system was installed (although the meter was included in the job specs ignored by the contractor), precluding the owners' ability to take advantage of lower electrical utility rates. Our photograph (left) shows a really nice looking electric boiler used for the radiant heat system discussed at RADIANT HEAT Floor Mistakes to Avoid - unfortunately although the boiler remains installed, the radiant floor heating system is not usable.
• Extra ceiling or under-slab insulation will be needed for ceiling-mounted radiant heating systems. The worst foul-up of the contractor whose radiant heat system was described at RADIANT HEAT Floor Mistakes to Avoid was that he buried the in-floor radiant tubing so deep in the floor slab that more heat was transmitted through the under-slab insulation than reached the occupied space - rendering the heating system not usable. Don't make this mistake. See SLAB INSULATION, PASSIVE SOLAR for under-slab and slab perimeter insulation specifications.

Floor Damage, Gaps, & Odor Complaints with Radiant Heat Installed under Wood Floors

We (DJF) have investigated a number of complaints of gaps opening between the boards of finished wood flooring and complaints of odors emitted from some types of tubing used in radiant floor heating systems.

Diagnosing gaps in finished wood flooring can be tricky, since these may appear with or without under-floor radiant heating systems installed, especially if the flooring is installed too quickly, without having adjusted its moisture level to that of the building. Installing wood flooring that is at too high a moisture level risks shrinkage and floor gaps as the building dries out.

In some cases that we investigated, flooring gaps appeared after an installer or owner pushed the radiant floor heating system to a temperature higher than recommended by the equipment and tubing manufacturers.

The temperature push was made in an attempt to "cook out" odors emitted from the radiant floor tubing when the heating system was first fired up.

Typical Cost of Radiant Heating Systems

Heating system costs are divided into installation or "first" costs, regular maintenance costs, and operating costs. Our photograph (left) shows two Therma-Ray electric radiant heat panels being installed in the ceiling of a 1960's home in Poughkeepsie, New York. These panels were replacing previously damaged ceiling components. Be careful about cutting holes in drywall ceilings where electric radiant heating panels have been installed.

• The installation cost for most radiant heating systems is between electric baseboard and conventional air or hydronic (hot water) heating systems.
• Electrical radiant heating systems, if that's how your radiant heating system works, requires the least maintenance - practically none.
• The fuel costs, if your radiant heat system uses electricity, will be higher than oil or gas in most areas of the country.

Here we include solar energy, solar heating, solar hot water, and related building energy efficiency improvement articles reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss.

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ENERGY SAVINGS RETROFIT LEAK SEALING GUIDE
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FURNACES, HEATING
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ODORS FROM HEATING SYSTEMS
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OIL BURNER INSPECTION GUIDE
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OIL FUEL TYPES & CHARACTERISTICS
Oil Odors: Leaky Oil Tank Piping
OIL SAFETY VALVES
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OIL TANK GAUGES
OIL TANK LEAKS
OIL TANK SLUDGE
OIL TANK TESTING
OIL TANKS, BURIED
PLASTIC HEATER VENT
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RADIANT HEAT Floor Mistakes to Avoid
RADIANT SLAB FLOORING CHOICES
RADIANT SLAB TUBING & FLUID CHOICES
RADIATORS
Safety Recalls
  BLUERAY Recall
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  Lennox Furnace Manuals
  Lennox WARNING
  Weil McLain RECALL
SAFETY DURING HEATING INSPECTION
STEAM HEATING SYSTEMS
TANKLESS COILS
THERMAL EXPANSION of MATERIALS
THERMAL MASS in BUILDINGS
THERMAL MASS in UPSTAIRS
THERMAL TRACKING & HEAT LOSS
THERMOSTATS
Transite Pipe Chimneys & Flues

• Solar Age Magazine was the official publication of the American Solar Energy Society. The contemporary solar energy magazine associated with the Society is Solar Today. "Established in 1954, the nonprofit American Solar Energy Society (ASES) is the nation's leading association of solar professionals & advocates. Our mission is to inspire an era of energy innovation and speed the transition to a sustainable energy economy. We advance education, research and policy. Leading for more than 50 years. ASES leads national efforts to increase the use of solar energy, energy efficiency and other sustainable technologies in the U.S. We publish the award-winning SOLAR TODAY magazine, organize and present the ASES National Solar Conference and lead the ASES National Solar Tour – the largest grassroots solar event in the world."
  
• Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education. Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
  Excerpts with updates and annotations expanding the original Best Practices Guide text can be found in the online review and book summary at BEST CONSTRUCTION PRACTICES GUIDE and also at DECK & PORCH CONSTRUCTION, at INDOOR AIR QUALITY IMPROVEMENT GUIDE, and in other articles found at InspectAPedia.com such as HOUSEWRAP AIR & VAPOR BARRIERS, SOUND CONTROL in BUILDINGS, and other topics.
• Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Passive Solar Design Handbook Volume I, the Passive Solar Handbook Introduction to Passive Solar Concepts, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v1.pdf
• Passive Solar Design Handbook Volume II, the Passive Solar Handbook Comprehensive Planning Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v2.pdf [This is a large PDF file that can take a while to load]
• Passive Solar Handbook Volume III, the Passive Solar Handbook Programming Guide, in a version used by the U.S. Air Force - online version available at this link and from the USAF also at wbdg.org/ccb/AF/AFH/pshbk_v3.pdf
• The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083 is available at Amazon.com and via the The Passive Solar Design and Construction Handbook, Steven Winter Associates (Author), Michael J. Crosbie (Editor), Wiley & Sons, ISBN 978-047118382 or 0471183083 is available at Amazon.com and via the InspectAPedia Bookstore
• "Passive Solar Home Design", U.S. Department of Energy, describes using a home's windows, walls, and floors to collect and store solar energy for winter heating and also rejecting solar heat in warm weather.
• "Solar Water Heaters", U.S. Department of Energy article on solar domestic water heaters to generate domestic hot water in buildings, explains how solar water heaters work. Solar heat for swimming pools is also discussed.
• "Heat Exchangers for Solar Water Heating Systems", U.S. DOE describes the types of solar water heater heat exchange methods between the sun and the building's hot water supply
• "Heat-Transfer Fluids for Solar Water Heating Systems", U.S. DOE, describes the types of fluids selected to transfer heat between the solar collector and the hot water in storage tanks in a building. These include air, water, water with glycol antifreeze mixtures (needed when using solar hot water systems in freezing climates), hydrocarbon oils, and refrigerants or silicones for heat transfer.
• "Solar Water Heating System Maintenance and Repair", U.S. DOE
• "Solar Water Heating System Freeze Protection", U.S. DOE,using antifreeze mixture in solar water heaters (or other freeze-resistant heat transfer fluids), as well as piping to permit draining the solar collector and piping system.
• "Scaling and Corrosion in Solar Water Heating Systems", U.S. DOE
• www.energysavers.gov/your_home/water_heating/index.cfm/mytopic=12850 is the base U.S. DOE website for these articles
• "Active Solar Heating Systems", U.S. Department of Energy, including
• "Radiant Heating Systems" U.S. DOE
• "Absorption Heat Pumps & Coolers", U.S. DOE
• "Solar Air Heating" U.S. DOE also referred to as "Ventilation Preheating" in which solar systems use air for absorbing and transferring solar energy or heat to a building
• "Solar Liquid Heating" U.S. DOE, systems using liquid (typically water) in flat plate solar collectors to collect solar energy in the form of heat for transfer into a building for space heating or hot water heating. The term "solar liquid" is used for accuracy, rather than "solar water" because the water may contain an antifreeze or other chemicals.

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