Insulating a radiant slab (C) Daniel Friedman

Active Solar Blockbed Floor Design Details

Q&A on use blockbed concrete block radiant heat floor with warm air heat from a sunspace
What is the correct pressure drop for a blockbed active solar floor design?
Rules of thumb for block storage in solar design - airflow, heat transfer, pressure drop specifications
Block duct floor designs in solar applications & radiant heat floor designs
Solar Age Magazine Articles on Renewable Energy, Energy Savings, Construction Practices
Questions & answers about blockbed solar designs
References

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In this first of our series on active and passive solar heating designs, this article discusses the design specifications for blockbed floor designs in radiant heated floor active solar applications. We discuss design rules of thumb for blockbed floor airflow, pressure drop, and solar design. 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.

Readers should also see ROCK-BED SOLAR HEAT STORAGE 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.

Active Solar Heating Systems: Blocked Heat Storage System Design

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

Q&A on Blockbed Floor Design Specifications for Radiant Floor in Solar Installations - PDF version, use your browser's back button to return to this page

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

Blockbed Design for Radiant Heated Solar Floors

Question:

In designing a concrete-block radiant heated floor with heat supplied by warm air from a sunspace, how do I determine the correct pressure drop?

Is there an optimum length for an air passage using hollow core concrete blocks? -- Herman Blumen. Eden UT

Answer:

Solar designer Mike Nicklas of Innovative Design Ind., (Raleigh NC) reported the following rules of thumb that work well for concrete block storage of heat in a solar-heated radiant-heat floor.

First, size the airflow to exhaust 2-5 cfm (cubic feet per minute) per square foot of sunspace glazing.
Then size the blockbed to take 25 to 50 cfm of air through each block core.
For the best heat transfer from warm air from the sunspace into the concrete block bed of the radiant-heat floor, a maximum core length of 16 feet has been set.

These rules of thumb for radiant heat blockbed floor designs seem to hold true regardless of the sunspace size. The optimum run length is 12-14 feet.

For this length of masonry block duct, the pressure drop is 0.1 inches of water, assuming the standard 8" x 8" x 16" concrete blocks, which have a concrete block core diameter of about 5".

Smaller concrete blocks have a greater pressure drop because the smaller core opening size presents greater resistance to airflow.

For an alternative design approach to storing heat in solar heating designs see 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.

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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."
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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