Insulating a radiant slab (C) Daniel Friedman

Slate Thermal Mass for Heat Storage - Design Details for Passive Solar Heating Systems

Use slate as thermal mass for storing solar heat in passive solar design?
- What is the coefficient of expansion for slate - how much will slate expand in length per degree in temperature rise?
- How should slate be bonded to the concrete slab for thermal mass storage and heat transfer?
Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
Questions and answers about the use of slate as thermal mass for storing solar heat in passive solar design
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Thermal mass effects of slate: this article discusses the properties of slate as a medium for thermal mass in passive solar heating system design and greenhouse or sunspace thermal mass material.

Active Solar Heat Storage Using Rock Bed Storage Systems

Accompanying text is reprinted/adapted/excerpted with permission from Solar Age Magazine - editor Steven Bliss. Our page top photograph shows a ceramic tile floor installed in Buenos Aires. Using ceramic tile finish flooring over a rock bed heat storage system is one method of design for a solar-heated radiant heat floor system.

Readers should also see BLOCKBED RADIANT FLOORS - SOLAR DESIGN for an alternative to block bed solar heat storage, and for supporting heat storage design details see FLOOR, CONCRETE SLAB CHOICES and PASSIVE SOLAR FLOOR TILES, PHASE CHANGE. Also see SLAB INSULATION, PASSIVE SOLAR and other articles at SOLAR ENERGY SYSTEMS. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

The question-and-answer article below paraphrases, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

Thermal Properties of Slate for Solar Heat Storage and Radiant Heated Solar Floors

Question: how to install slate for use as thermal mass for sunspace or greenhouse passive solar heat storage

A client of mine has a unique storage material to use in his solarium - 30 one-inch thick slate pool table tops.

Will the thermal expansion and contraction affect the thermal bond to the concrete slab below?

Should we buffer the joints between the slabs of slate to prevent damage to the edges? - Tom Deal, alternative energy consultant, San Francisco CA

Answer:

Slate's coefficient of expansion is 0.0000058, meaning that for every foot of length slate will expand 0.0000058 feet, or about 0.00007 inches for every degree Farenheit of temperature rise.

A 60 degF temperature rise will cause an 8-foot long slate slab to increase in length by 0.0336 inches - roughly 1/32 inch.

If the sunspace experiences wider swings in temperature, the expansion and contraction of the slate will of course be greater.

Kevin Callahan at the National Concrete Masonry Association recommended using Type M mortar, which has a higher compressive strength than mortar normally used for concrete blocks. He commented, though, that the mortar might not bond very well to the slate, which does not have a very porous surface.

Bedding the slate in mortar should, however, create a fine thermal bond.

Also see

THERMAL MASS in buildings
  THERMAL MASS FLOOR SLABS
  THERMAL MASS in UPSTAIRS
  THERMAL MASS WALL DESIGN
  THERMAL MASS in HOMES - STUDY

For an alternative design approach to storing heat in solar heating designs see BLOCKBED RADIANT FLOORS - SOLAR DESIGN, and and ROCK-BED SOLAR HEAT STORAGE DESIGN, and for solar designs that combine greenhouse solar heat gain and trombe wall designs see GREENHOUSE DESIGN for SOLAR HEATING.

For more on radiant slab floors see "Radiant Floors", Solar Age 5/82, and the following articles online:

RADIANT HEAT
RADIANT HEAT Floor Mistakes to Avoid
RADIANT HEAT TEMPERATURES
RADIANT SLAB FLOORING CHOICES
RADIANT SLAB TUBING & FLUID CHOICES

Other articles you'll want to see on passive solar floors, ceilings, and walls, include

The question-and-answer article above, quotes-from, updates, and comments an original article from Solar Age Magazine and written by Steven Bliss.

The link to the original Q&A article in PDF form immediately below is preceded by an expanded/updated online version of this article.

Q&A on Slate as Thermal Mass for Solar Heat Storage- PDF version, use your browser's back button to return to this page. Original article, Solar Age Magazine, November, 1985, adapted and updated for InspectAPedia.com December 2010.

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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."
"Passive Principles: Rockbeds", Solar Age Magazine, March 1982 - sizing and design of rock bed heat storage systems
"Building it Right", Solar Age Magazine, June 1982, practical design guidelines for rock bed heat storage systems
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: info@buildingadvisor.com
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
Ar-Lite Panelcraft, Inc., 13030 Wayne Rd., Livonia MI 48150
Colloidal Materials, Inc., PO Box 696, Andover MA 01810
Pennwalt Corp., King of Prussia, PA 19406
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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The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

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