EPS Foam Blocks Build Quiet Homes
QUESTION: I’m planning to build a super-efficient house on a limited budget. The house must be very strong since I live in the tornado belt. How efficient and strong are new concrete/foam block building systems?
ANSWER: Concrete/foam block construction actually includes several types of house construction. All the methods produce extremely strong, quiet houses with low utility bills year-round. They can withstand 150-mph winds. When I build my own new house, this construction method will be at the top of my list.
With the simple construction methods, you can do some of the work yourself. The exterior can be finished with siding, stucco, brick or any common material. Finished concrete/foam block houses (called stay-in-place-forms) look identical to any conventionally built house from indoors and outdoors.
This construction technique uses hollow, rigid expanded polystyrene (EPS or Styrofoam) foam blocks. Each block is typically 4 feet long, 1 foot wide and high, and weighs only 5 pounds. Most are made from recycled plastics.
The interlocking foam blocks snap together like a huge Lego set. Once the walls are snapped together and rebar is slipped into the openings, concrete is poured into the top block openings. To support the floors in a two-story house, a ledger board with anchor bolts is pressed in before the pour.
The concrete flows throughout the cavities in the foam blocks. When cured, this creates a monolithic, termite-proof, strong concrete post-and-beam structure in a continuous envelope of rigid insulating foam--up to R-30.
These are efficient for several reasons. Rigid EPS foam is a very good insulator; it is used in most coolers. There are no voids and little air leakage into the house, which reduces noise, dust and allergies.
The heavy concrete structure inside the walls acts as thermal mass to moderate indoor temperature changes. This is a significant advantage when air-conditioning and for summer comfort. With the high insulation, a smaller and less expensive furnace and air conditioner are required.
There are several concrete/foam block design variations. Polysteel uses two-piece foam blocks attached together with steel mesh with surface strips. This adds strength when the concrete flows through the mesh. The strips provide secure mounting locations for siding and drywall.
Conform offers a variable width wall using color-coded interlocking crossties between foam block halves. Rastra uses a lightweight mixture of cement and plastic foam to make 10-foot-long blocks. Concrete is poured in the cavities. This material is also fireproof without drywall applied.
Write for Update Bulletin No. 879, which lists 16 manufacturers of concrete/foam blocks, sizes, prices, R-values and construction details. Please include $3 and a business-size, self-addressed envelope and mail to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.
Help for Fireplace That Doesn’t Draw Well
Q: I am getting my fireplace ready for the fall. It doesn’t always draw well and the room gets smoky. I have heard that nailing a 5-inch board across the top of the opening will help?
A: The relationship of the opening width and height dimensions are important for a fireplace to draw well. Many fireplaces are designed for aesthetics with a tall opening, but they smoke like yours.
Reducing the height by 5 inches often helps. Do not use a wood board. Use steel or aluminum. A wood board would be a fire hazard and your entire house may become one big fireplace.
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Letters and questions to Dulley, a Cincinnati-based engineering consultant, may be sent to James Dulley, Los Angeles Times, 6906 Royalgreen Drive, Cincinnati, OH 45244; or instant download: www.dulley.com
