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Interlock House

Walls and Windows

One of the most important aspects of any energy-efficient home is its insulation, which prevents heat from escaping the house in the winter and entering it in the summmer. Heat loss is measured in terms of thermal resistance, or R-Value. A high R-Value means it takes longer for heat to move through an object.

The Interlock House's walls and roof consist of seven inches of BioBased insulation, a closed cell, soy-based, spray-in foam. This was combined with an additional one inch of batt insulation manufactured from recycled blue jeans. Combined these give the walls and roof an R-Value of 50. With heating and cooling accounting for 40-60 percent of a house's energy costs, increasing R-Value can pay large dividends.

No matter how high the R-Value of the the walls, windows remain a major point of heat loss in any house. The Interlock House uses windows manufactured by Serious Materials. These windows consist of two panes of low-emissivity glass filled with krypton gas. They have an R-Value of 12, four times the R-Value of windows in the average American home.

For more information on walls and windows in our and your house:

Sun Porch

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The literal and figurative center of our house is the enclosed sun porch. The sun porch is a semi-private indoor/outdoor space with southern exposure that allows it to collect sunlight throughout the day. This sunlight is absorbed as heat in the thermal mass of the sun porch’s floor, which consists of ceramic tiles backed by cement board. In the winter months, this heat is distributed throughout the house via a series of vents. Doors on the northern end of the house along with a collapsible NanaWall that defines the edges of the sun porch, can be opened to allow cross-ventilation though the house and drive off excess heat during the spring and autumn months. During the summer, a resident may opt to open only the exterior wall of the sun porch, making it a shaded extension of the house’s deck.

Find more information about passive solar home design and what we used to define our sun porch:

Daylighting and Louvers

The Interlock House lighting strategy is based upon minimizing the need for artificial illumination and optimizing daylight through the use of windows on the eastern and southern faces of the house, as well as clerestory lighting along the northern wall.

Windows on the eastern and southern sides of the house incorporate moveable louvers, allowing a resident to control the quantity of light entering the interior from these directions. This is important both for privacy and reducing direct solar gain, which occurs when heat from sunlight radiates directly into the interior of a building. The louvers on the southern and eastern faces of the house also incorporate thin film photovoltaics, which produce additional electricity when the louvers are closed.

The northern face of the house incorporates several clerestory windows placed high in the wall, thus allowing indirect light to subtly brighten the interior of the house. Because the northern light is indirect, there are no issues of glare or direct solar gain with which to contend. A light-colored ceiling ensures that this light is reflected to the deepest spaces of the house.

Learn more about daylighting in residential construction:

Major sponsors Iowa State University U.S. Department of Energy Solar Decathlon U.S. Department of Energy National Renewable Energy Laboratory