The Nutter Green Home Uses Insul-Deck to Create Passive Solar Heating Thermal Mass
Insul-Deck’s lightweight insulating concrete floor forms were incorporated in the construction of the passive solar Nutter Residence in Cincinnati, Ohio due to the thermal mass benefits of poured concrete floors. For successful passive solar heating, two factors must be taken into account: appropriate glazing (window area) and thermal mass thickness. In this view of the finished home, note the solar Photo Voltaic (PV) electricity generating panels on the roof. On the right side of the roof are solar thermal panels that produce hot water.
To maximize the direct sunlight that heats the thermal mass floors, south-facing windows are incorporated with appropriate shading to reduce gain during the summer and increase exposure during the winter months. The more heat that is required, the more south-facing windows or glazing are needed.
Thermal mass acts like a storage battery for solar heat. Generally, thermal mass is any material that can absorb the heat from direct sunlight and slowly release the stored heat to warm the building or dwelling after the sun has set. Thermal mass is an important factor in passive solar heating, too much thermal mass won't release most of its heat overnight and not enough won't last through the night.
The two-story Nutter Residence maximized its passive solar heating by incorporating thermal mass poured concrete floors on the ground floor and south-facing windows. The Insul-Deck on the first floor is the ceiling of the basement. By using the proper ratio of thermal mass thickness, solar shading and glazing, the home will reduce heating requirements in the fall, winter and spring. The windows are shaded during the summer by exterior shading and special coatings that reflect the high angle sun.
General Guidelines for Thermal Mass Thickness and Glazing
The thermal mass thickness of concrete ideally should be about 2 to 4 inches to absorb and release heat daily in a Zone 4 climate (see map). Thicker floors (6-8 inches) release heat more slowly, which can radiate warmth in a room for several days during cloudy weather and would be appropriate for Zone 5 and above. The proper depth of the thermal mass reduces temperature swings for the specific climate zone.
Glazing should account for 7 to 12 percent of a home or building’s square footage. For each square foot of glass over 7 percent, the thermal mass must be increased to offset solar gain heat absorption. You can visit Home Power Magazine http://www.homepower.com for more information on proper thermal mass/glazing ratios. In addition, the south-facing windows should have an appropriate solar heat gain coefficient (SHGC) to allow the proper amount of visible and infrared light spectrum through the glass to heat the thermal mass. A solar heat gain coefficient on south-facing windows should be at least 50 percent (transmits half of the sun’s heat energy).
The Nutter Green Home near Cincinnati, OH is an excellent example of the proper use of thermal mass and many other energy efficient home building techniques. You can read about the architect/homeowner's entire home building process at the Nutter Home Blog. In one year, the Nutter Family only spent $200 for heating and cooling.
Kenneth Nutter pointing out the cavity, which is formed between the sections of Insul-Deck. Once poured with concrete it forms a standard concrete T-Beam, which according to the thickness of the Insul-Deck, determines the spanning capability of the application. The ability to vary the depth of the concrete beam can allow clear spans up to 40 feet using Post-Tensioning.
Photo illustrating the pouring of the final height of the Insulated Concrete Form (ICF) used for the walls of the basement while standing on the prepared Insul-Deck floor forms. Both the final wall section and the Insul-Deck concrete floor are poured at the same time to ensure proper structural integrity of the integral Insul-Deck T-Beam floor to wall connection.
Insul-Deck leave in place concrete forms need to be supported by the appropriate scaffolding to carry the weight of the concrete before the integral concrete T-Beams formed in the pouring process can carry the final loads.
Photo shows Insul-Deck forms in place and floor pouring and finishing taking place. Insul-Deck is the fast and easy way to form concrete floors and roofs with out the need for cranes to lift heavy forms.
Krista Nutter shows the concrete floor area that is warmed by the sun during the day. At night the warmth is released back into the room, reducing the need for supplemental heating.
Solar shading on the exterior of the Nutter Green Home prevents excessive sunlight from over heating the home during the summer. The depth of the shading is determined by the latitude of the site and the height of the window. Photos of the Nutter Green Home used by permission of Krista Nutter, Architect; for complete information on the Nutter Green Home please go to the Nutter Home Blog. All rights reserved.
In conclusion, the benefits of using the sun to heat your home are many, from reduced heating bills to the advantages of clean non-drafty radiant floor heating, a passive solar design is easy to integrate into every style of home. The thermal mass doesn't have to be only the floor. Walls of gypsum or tile can also absorb heat during the day and release it at night. Even furniture can act as a thermal mass. For many more applications and other energy saving methods go to HomePower.com. The inexpensive subscription will enable access to all sorts of passive and active home and commercial building power solutions.
Insul-Deck welcomes your comments and suggestions for future newsletter articles. If you have an especially helpful application please send us a few photos and description. There are many exciting uses for Insul-Deck from tilt-up to Bermuda roofs and we welcome yours.
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