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A Solar Trombe Wall? Now Your Wall Can Heat Your Home!

Cuddle up with your walls

Passive Solar Wall 1Who ever said walls were just for hanging pictures? A Trombe wall is a sun-facing wall designed as a passive solar collector; people can enjoy its benefits in the toasty comfort of their homes. Instead of running your home heating system, you can use the radiant heat flow from an original design. The Trombe wall, also referred to as a solar wall, was popularized by Felix Trombe in 1964 although it was patented by Edward Morse in 1881. The system is becoming an increasingly popular addition to home designs because of its heating benefits, energy efficiency, low maintenance, inexpensive, and quick construction. In addition, its ability to be incorporated as a functional yet beautiful part of interior decorating makes it a top choice for ‘green’ living or remodeling. The wall is built from materials that act as a thermal collector: stone, metal, concrete, adobe or water tanks. In the original design by Felix Trombe, the heat flow moved freely between the interior and exterior of the wall, once the outdoor temperature decreased the home received little heat. Modern engineers solved the issue of heat loss by adding a few adjustments to the design and construction.


The sun’s not just for great tans

Passive Solar Wall 2A Trombe wall is an energy-efficient masonry wall designed to absorb heat from the sun during the day and radiate it into the interior during the night. The building interior is heated as the warm air flows indoors by convection. With the assistance of vents, the rising heat enters the living quarters while the cool indoor air enters the bottom vent to assist in circulation.Vents may be adjusted to accommodate seasonal heat variation and to prevent heat loss. Energy efficiency can be improved by closing the bottom vent, which allows air to escape to the exterior during the evening or winter. In addition, to reduce heat loss, double glazing windows can be added to the design in order to trap the fleeing geothermal heat in a layer of inert gas between the two panels.

During the day the sunlight passes through the glazing (the outer, bi-layer window) and heats up the dark thermal mass wall (usually concrete), warming the surface by absorption of solar energy. Then the hot air between the glazing and the thermal mass (via heat conduction) rises to the top vent, along with the convection-produced heat.As a result, the heat flows into the building interior and warms the area.

It is important to construct a hanging awning over the Trombe wall. During the summer, this will semi-shield the glazing from additional sunrays preventing over-heating of the building interior. However, the awning will not negatively influence heat gain during winter days since the sun is lower in the sky, energy-efficiency will remain constant.


Location, location, location

The systPassive Solar Wall 3em is most effective if installed facing south. A previously built home can be easily remodeled to add a Trombe wall on the south facing side, especially if windows are already present. Constructing the Trombe wall on the south side of a building will promote even air and heat circulation within the interior.

A Trombe system can also be installed within a home chimney. By adding a double paned glazing to the top of the chimney it will collect solar energy, which can be used to heat the building interior like a Trombe wall. On a winter day with full sun, temperatures in the chimney can exceed 140 degrees Fahrenheit. To prevent heat loss during the night, install one-way flaps to control air circulation within the chimney.


Don’t sweat your heating costs

The Trombe wall is most effective as a passive solar collector in regions that get many days of clear skies and direct sunlight. Zion National Park’s Visitor Center installed an energy-efficient Trombe wall to supplement their central heating system. The National Renewable Energy Laboratory (NREL) tested the efficiency of the Trombe wall 2001-2002. It was determined that the constructed Trombe wall contributed 20% of total heating to the building and the electric heating system used 22,680 kWh over the year. The NREL calculated that the efficiency of the Trombe wall over the year contributed 13% of the energy to heat the building. The savings are approximately $134.29, from the annual $1,033 bill for a minimum efficiency house.

Passive Solar Wall 4

Infrared pictures of a) Zion Trombe wall December 16, 8:30 p.m. and b)NREL SEB Trombe Wall January 21, 8:00 p.m.

Eager to install?

It is important to contact a contractor who can provide you with a design layout to accommodate the area you are working with. Check out Sierra Club Green Home to find a contractor near you.

For all DIYers, check local ordinances and codes and, if necessary, obtain a building permit before building. Certain wood frame buildings cannot adjust to support the heavy weight of an added masonry wall. Before adding a Trombe wall, the new weight load must be calculated to determine if the house qualifies for an installation, or it may need to be modified to meet building codes.


Bang for your buck

Trombe wall construction cost was analyzed by Menelaos Xenakis from EcoArchitects. He estimated that the cost of 12-inch thick concrete Trombe house wall is $734. If desired, a 24-inch thick wall can be constructed for about double the cost, $1470. Construction includes support systems, vents, and concrete. To finish the Trombe wall a glazing window must be added at an approximate cost of $912. Ultimately, the average completed 12-inch Trombe wall will cost $1,650.


Benefits…

… to your wallet. A heating report published by the State of Illinois stated that the average cost of installing a new heating system is approximately $2,000 to $4,000. Installing a Trombe wall is a relatively inexpensive way to make your home more energy-efficient, helping you minimize your monthly heating bill.

… to your health. Not only is it easy on your wallet, it’s great for your health. By installing a Trombe wall you get evenly distributed, natural, and constant radiant heat throughout the year, while improving indoor air quality. This eliminates the need to rapidly blast your AC or heating system, thus decreasing the possibility of temperature shock to the body and reducing drafts.

… to the Earth. In addition to enjoying reduced heating bills and health benefits made possible by a Trombe wall, you can be environmentally friendly. A Trombe wall cuts down on the use of central heating, materials due to simple installation, and air purification. The passive solar collector is an eco-friendly approach to indoor heating because it uses the sun’s energy to produce heat. No fuel required. To gain a few extra ‘green brownie points’ a Trombe wall can be constructed by rammed earth, crushed recycled concrete, recycled glass, and zero VOC paint for façade design.


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