Build a Water-Wall Home

Construct your very own water-wall home and learn about calculating water storage requirements, wall construction and solar basics.

| November/December 1983

In many ways, passive solar homes are superior to those with active (mechanically assisted) heating and cooling systems. After all, passive solar systems don't rely on auxiliary energy sources to perform (so they'll work even when the power is off)... are generally simple and low in cost, combine energy collection and storage functions, have a long life, need little maintenance, and can often be built and installed by the home handy person, without special training or equipment.

But precisely because such "non-moving" systems have no pumps or controls to circulate warm or cool air, they typically rely on one key element: the thermal mass that stores and gives off absorbed heat or cold. A number of different items can be used to provide this energy-holding capacity, but just about the most effective and economical "To a water wall (a term that is a shorthand way of saying "contained water for thermal mass in passive solar homes").

Water-wall systems deserve much greater recognition than they've yet received... for a number of reasons. First, they can be very economical, especially since such units can often be installed — in either new or retrofitted homes — with standard construction techniques. Second, they are effective for both heating and cooling, particularly in areas with low nighttime temperatures. (Some heat-storage mediums, such as phase change salts, don't work for cooling.) Third, water walls can be attractively accented or practically invisible, as desired. Fourth, water is a more efficient storage medium than are the other common sources of thermal mass. (See Table 1 in the Image Gallery for a comparison of water, concrete, and phase-change salts.) Consequently, water walls take up less room than other storage systems. This allows the house to offer outside views — avoiding the claustrophobic sensations possible with a full masonry (Trombe) wall, which often completely block off south windows — and permits the easy installation and operation of movable window insulation. And finally, the fine radiating and temperature moderating qualities of water walls make for very comfortable homes.

Start With The (Solar) Basics...

Building a water-wall structure can actually be a straightforward proposition. To begin with, the home should incorporate the basics of good passive solar design. The most obvious of these fundamentals is proper orientation: A major wall should face south. Likewise, most windows should be on the south, with some on the north... but comparatively few on the east and west. The dwelling should also have excellent insulation (a minimum of R-19 in the walls and R-30 in the ceiling) and weather stripping (infiltration can easily account for one half of the heat loss in a well-insulated but poorly weatherized building). The design should incorporate good summer shading, too... particularly on any east and west windows, which, if unshielded, can let in a surprising amount of the summer sun's radiation. Then again, the dwelling needs adequate natural, induced, or mechanical ventilation. And last, it needs double — or tripe — pane windows with some form of movable insulation... either thermal shutters or drapes.

If you construct a conventional house with these passive features and a water wall, the building should achieve very good thermal performance. The results of a study conducted for the California Energy Commission — shown in Table 2 in the Image Gallery — document the performance of standard tract houses with water walls. And if the homes had the insulation levels recommended above they would perform considerably better. In fact, my experience in Davis, California suggests that these calculations are even conservative, as water-wall dwellings there-without movable insulation on the windows-have met 80 percent of their own heating needs and have provided full cooling. Similar or better performance could be achieved in most of the growth (Sunbelt) regions of the United States.

...Then Add Water

To figure out how much water storage a home needs, you first need to calculate its glazing requirements. The amount of south glass necessary for heating a passive solar house can be estimated from the anticipated climatic conditions, available sunshine, and the design and configuration of the building. As a rule of thumb, a well-insulated house should have an amount of south window area equivalent to 10 percent of the dwelling's floor space (a less heat-tight retrofit might need a glazing-to-floor ratio of 1 to 4). From there, you can calculate how much water you'll need by allowing three to six gallons of liquid (four to eight in a retrofit) per square foot of south facing glass.

5/3/2013 12:00:08 AM

Anybody that has the knowledge with it can assemble a water wall by first verifying the width and tallness of the rock wall. The ground might as well likewise be exhumed. A gap ought to be dug to fit the liner. And in some case a reputable professional help can get this job done without any harm can be a great idea just to be sure on everything in it…

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