Historically basements were perceived to be cold spaces in the winter months and damp musty spaces in the summertime. Often times the basement level was used only for storage, mechanical equipment and laundry facilities. With new construction costs averaging $100 per square foot in today's home market, it is a very cost effective investment to construct a basement to be a dry, warm and comfortable living space.

One of the key features of the building site for the Millennium Star Home was the gradual south facing slope. This allowed for the design and construction of a walk-out basement (or a lower level as we like to call it). The lower level is fully exposed to the sun with large amounts of south facing glass, providing a bright and well lit living space.

For the Millennium Star Home we used the Arxx Insulated Concrete forms, manufactured by AAB Building Systems. The Arxx wall system consists of forms that are designed to remain in place after the concrete has been placed. The forms are made from expanded polystyrene foam and held in place for the placement of concrete by polypropylene ties called webs. The forms are laid up in courses, much like masonry blocks, with reinforcing steel inserted as per engineering requirements, via a snap in system. The insulated concrete form has an R-value of 22, compared to only an R-2 for an uninsulated block or poured wall.

Each block is 4 feet long, 16" high, and 12 1/2" thick. (about the size of six standard concrete blocks, but weighing only 6 pounds). The concrete wall thickness is 8" and the insulated forms are linked together by polypropylene (plastic) webs. These webs are placed eight inches apart and extend from the outer to the inner surface of the form. Sheetrock, siding, and finished wallboards are attached directly to the surface with screws or appropriate fasteners. Reinforcing steel is placed horizontally on each course and vertically every 2 feet. The polypropylene webs are grooved for the placement of the steel reinforcing rods.

After the walls are erected, window and door openings are appropriately placed and the entire wall is secured and braced with the Arxx Alignment system. The concrete is pumped or poured into the walls at a specified rate and truing or plumbing of the wall takes placed immediately after the wall has been poured.

An adhesive backed water proofing membrane is attached vertically to the exterior of the wall on the below grade surfaces. The soils at the building site for the Millennium Star home consist mainly of heavy non-porous material, such as clay or silt. A free draining or porous type backfill was used to drain water away from the wall and maintain a dryer, more comfortable basement. Insulated drainage boards are also available that direct water to the footing while providing thermal wall insulation. An impermeable top layer is added to prevent ground adjacent to the foundation from getting saturated. Soil should be sloped away from the foundation to direct all surface water away from the building.

Combining the well insulated R-22 basement wall, the drainage and water proofing material around the foundation, the large amount of window area to the south, the 2" rigid foam under the basement slab, and the hot water radiant floor heat, you end up with an entire lower level that is a bright, warm, dry and comfortable living space.

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