Radiant Heated Floor Slab Tubing & Fluid Choices
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Suitability of rubber or plastic tubing for radiant-heated concrete slabs
Choices of heat-conducting fluids for use in radiant-heated concrete floor slabs
Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
Questions & answers about the different types of tubing & fluids used with radiant heating systems

Radiant heat tubing choices, advice: This article discusses the suitability of various tubing materials for radiant heated concrete floor slabs, and choices of heat conducting fluids for radiant floors.

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Radiant Floor Slab Tubing & Fluids: Choices, Features, Advice

Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Readers should also see RADIANT HEAT and RADIANT HEAT Floor Mistakes to Avoid, and see SLAB INSULATION, PASSIVE SOLAR. For flooring choices over a radiant slab, see RADIANT SLAB FLOORING CHOICES.

Our page top photo shows polyethylene tubing emerging from a radiant-heated floor slab under construction in Two Harbors, MN in 2007. Note the nice detail, use of a larger diameter tubing around the heating distribution plastic tubes, protecting the heating tubing from bending damage where it emerges from the slab.

"Radiant Slab Fluids" - links to the original article in PDF form immediately below are followed by an expanded/updated online version of this article

Tubing Choices & Heating Fluids for Concrete Floor Slabs - PDF form, use your browser's back button to return to this page

The question-and-answer article about radiant slab fluids and radiant slab tubing, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Questions about radiant slab floors:

What is your opinion about the relative suitability of various plastics (e.g. polybutylene, EPDM, etc.) for carrying heat transfer fluids in concrete radiant slab floors?

Which radiant floor slab tubings are acceptable for use with water, propylene glycol, Syltherm 444? -- C.R. MC, East Lansing, MI

Answers about radiant floor tubing and fluids:

Plastic radiant heat tubing (C) Daniel Friedman

Plastic piping varies in wall thickness, density, and chemical composition.

Consequently, each grade of plastic tubing that might be considered for radiant heated floors has its own temperature, pressure, and chemical compatibility limitations.

High-temperature polybutylene pipe is rated for 200 degF continuous use at 80 psi with water and/or glycols used as heat transfer fluids.

This makes polybutylene piping applicable to many radiant floor designs including the radiant floor design shown in the photograph at the top of this page.

Our photo (left) shows brass or copper connectors used at the transition from an electric boiler to in-slab radiant tubing. These fittings should have not been used in the concrete itself.

Radiant floor tubing types (C) Daniel Friedman

EPDM tubing, the type used in SolaRoll™, will handle up to 300 degF. for water and glycols.

Neither EPDM tubing nor polybutylene tubing is recommended for use with silicone oils or hydrocarbons [so watch out when choosing the antifreeze product to be used in radiant heat floor systems when this tubing is selected].

High density polyethylene tubing, not the type commonly found in retail building outlets, can also handle water temperatures typical of radiant heat floor systems, but with glycols and silicone oils, temperature limitations apply.

For a given radiant floor heating application, it would be wise to consult with the manufacturer of the specific tubing material and its connectors before making your purchase. Some manufacturers do not recommend the use of brass fittings embedded in concrete. If possible, buried tubing joints should be avoided altogether.

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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FLOOR, WOOD RADIANT HEAT - guide to installing wood floors over radiant heat systems
RADIANT HEAT - usage guide, strategies for using radiant heat
RADIANT HEAT TEMPERATURES - at the boiler, in tubing, under floors, floor surface, thermostat & control settings
RADIANT SLAB FLOORING CHOICES - wood vs ceramic tile over a radiant heated floor
RADIANT SLAB TUBING & FLUID CHOICES - tubing and fluid choices for radiant heating
RADIANT HEAT Floor Mistakes to Avoid - proper and improper radiant tubing depth in slabs & slab insulation needs - what can go very wrong when the building contractor substitutes brawn for brains
SLAB INSULATION, PASSIVE SOLAR - slab insulation & vapor barrier placement in heated floor slabs
WOOD FLOOR DAMAGE - from radiant tubing run too hot

  FLOOR, LAMINATE PLASTIC
  FLOOR, RESILIENT VINYL or CORK
  FLOOR, WOOD ENGINEERED & LAMINATED
  FLOOR, WOOD SOLID STRIP, PLANK
  FLOOR, WOOD ENGINEERED, LAMINATE, INSTALL
  FLOOR, WOOD FINISHES
  FLOOR, WOOD INSTALLATION GUIDE
  FLOOR, WOOD MOISTURE
  FLOOR, WOOD RADIANT HEAT

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.
Portland Cement Association: www.concretethinker.com/Papers.aspx?DocId=8 indicates that
- tubing for radiant heat in a concrete slab is installed UP TO two inches below the surface of the slab
- the slab is insulated from the ground at all sides to direct heat upwards to the living space [this is our preferred design for a cold northern climate]
The Radiant Panel Association: www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=1 offers design guidelines at http://www.radiantpanelassociation.org/i4a/pages/index.cfm?pageid=115 including these insulation R-value and coverage details:
Application#, Minimum R-Value, and Insulation Coverage
The following insulation alternatives are given for Slab on Grade construction:
Alternate #1 [(Ti-To)x0.125)=R-value, with coverage from perimeter to below frost line ["Ti-To" means we calculate the necessary R-value as (Ratio of indoor to outdoor temperature) x 0.125]
Alternate #2 R-value=5, with coverage 4' horizontal or vertical at perimeter
Alternate #3 R-value=5, with coverage under entire slab and slab edge [this is our preferred design for a cold northern climate]
The Radiant Panel Association offers education and publications in radiant heat design. See radiantpanelassociation.org
Takagi radiant heat systems: Takagi offers pre-assembled radiant heating system installation packages including for do-it-yourself'ers, and including systems that combine radiant heat flooring with domestic hot water production using a gas-fired tankless water heater. See takagi.com for more information. "The T-KJr model (gas inputs up to 140,000 BTU per hour) is the smallest unit in the Takagi line-up. The T-KJr is perfect for light residential (i.e. small apartment units) and radiant heating applications." Also see Tankless Water Heaters.
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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Radiant Floor Slab Tubing & Fluids: Choices, Features, Advice

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