Flooring Choices for Use Over Concrete Slabs Using Thermal Mass InspectAPedia® -
What finish flooring materials are best to use over a concrete floor slab to retain the thermal mass properties of the slab?
Flooring materials for passive solar floor slab designs where direct solar gain and passive solar heat storage are desired.
Questions & answers about how to choose a finish floor to be installed over a concrete slab where thermal mass is important
Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
This article discusses the best choices for finish flooring to use over a concrete floor slab intended to provide direct solar heat gain and heat storage.
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Accompanying text are reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Our page top photograph shows a well-designed radiant-heat floor slab being constructed in Two Harbors, Minnesota where it gets too cold to fool around.
The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article, (see links just above) from Solar Age Magazine and written by Steven Bliss.
What Flooring Materials are Best to Use Over a Concrete Floor Slab
Question:
I'm in the process of building a home.
Are there any floor-covering products I can install over a pre cast concrete second floor (see THERMAL MASS in UPSTAIRS) and a cast-in-place poured concrete first floor slab (see THERMAL MASS in buildings).
I want a resilient (soft clay, brick?) finish floor that will yet retain the thermal mass properties of the concrete slab below. I understand the necessity for thermal mass [in my passive solar design home] but I would like to find a more pliable floor covering [than ceramic tile].
Our photograph (left) shows a passive solar brick interior floor, constructed over a poured concrete slab. This building is on the Vassar College Campus in Poughkeepsie, NY.
Answer:
Assuming you are interested in using these floors for direct-gain passive solar heat storage, we see two possible approaches:
Try to find a finish flooring material that has a high heat capacity itself
Look for a finish floor material that has negligible heat capacity but has good absorptive and good thermal conductivity.
Either of these approaches will allow the finish floor covering to transfer heat into the concrete floor slab which itself has a high heat storage capacity.
We know of no soft floor covering with high heat capacity, but the second approach shows some promise. A 1980's study by industry researchers concluded that any floor covering whose thermal conductance exceeded about 10 BTU/hr-ft2 would not impair the thermal storage capability of the concrete slab.
This eliminates using even the thinnest floor carpeting (whose conductance C is about 0.8 BTU/hr-ft2), and some vinyl floor coverings.
But this criteria permitted use of vinyl-asbestos floor tiles (C = 43 BTU/hr-ft2) until that product was discontinued in buildings, and it probably permits use of the modern replacements of those products. It also permits use of sheet vinyl flooring on felt backing (C = 21.2 BTU/hr-ft2).
Beyond C=10 flooring products, increasing the absorptive does more than increasing the conductivity.
Light flooring materials absorb less solar radiation (heat) and are thus less efficient (as much as 40 percent less for pastel colors).
Also, it is important to install the finish floor covering so that it makes a very good thermal contact through a continuous bond over the floor slab.
Low-density brick and other "soft" masonry materials are not ordinarily considered resilient. If they are well-bonded to the slab, however, they will not reduce its thermal performance much.
Our photograph (above) shows ceramic tile installed over a concrete floor slab intended to provide both passive solar gain and heat storage as well as delivering heat from a backup in-floor radiant heating system. Readers constructing an insulated slab with radiant floor heating, whether by passive solar or any other means, should not fail to read RADIANT HEAT Floor Mistakes to Avoid.
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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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.
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
"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-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 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.
"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.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
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