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By James Dulley, Published October 16 2009

Foam block/concrete strong building method

Dear Jim: I want to build a house that is very efficient and strong to withstand tornadoes. I prefer one made with concrete because the resource is so abundant. How good are foam block houses filled with concrete? – Paul P.

Dear Paul: There are many new super-efficient house construction methods that are also very strong. Many can easily withstand the power of tornado- and hurricane- force winds. In addition to the building materials, just the shape of the house can have a major impact upon how well it withstands winds. A circular or spherical shape, as most animals build their nests and dens, is best.

This type of combination foam block and concrete house you mentioned is one of the strongest and most energy efficient. It is one of several construction methods often referred to as stay-in-place forms. The forms that hold the wet concrete are not removed and provide the insulation and substrate surface for installing the interior and exterior wall coverings.

People often think of concrete as being cold and a poor insulator, and they are correct. With the foam block house construction, the concrete provides the structural strength for the walls. It is totally encapsulated by high R-value rigid insulating foam. Depending upon the thickness and shape of the foam blocks you select, the wall insulation can be as high as R-40. Keep in mind, more thickness does increase the material costs.

The hollow foam blocks are made to your house plans. They are designed such that there is an open cavity throughout the entire wall once they are stacked together. They interlock so they stay together. The homeowner can actually help stack the lightweight blocks to lower labor costs. Concrete is poured into the top of the wall cavity by a concrete pump truck.

The wet concrete flows throughout all the interlocking block cavities and sets up to provide extreme strength. If you would strip away the foam blocks, you would find the interlocking concrete framing inside. With this construction method, you have many architectural design options from a traditional house to very contemporary.

There are several deviations from the true foam block design. Several use flat foam panels with plastic or metal webs between them to create the hollow blocks. This reduces the amount of foam needed. Others use very large flat foam panels with metal ties between them. When filled with concrete, the end result is similar.

Cement (main ingredient of concrete) is an abundant resource. Some companies make their hollow blocks using a mixture of cement and recycled sawdust or plastics. These blocks are heavier than all foam ones, but the walls are assembled similarly. With any of these foam/concrete methods, there is a substantial amount of thermal mass inside the insulation envelop for even room temperatures.

The following companies offer foam/concrete housing materials: Conform Global, (800) 266-3676, www.smartblock.com; Eco-Block, (800) 293-3210, www.eco-block.com; ICF Industries, (877) 423-4800, www.iceblock.net; Shelter Works, (541) 929-8010, www.faswall.com; and Lite-Form, (800) 551-3313, www.liteform.com.


Dear Jim: I installed an attic fan several years ago. It keeps the attic cooler, but it is too loud, especially at night. I was thinking of installing a solar attic fan. Are they as noisy as electric ones? – John J.

Dear John: Electric attic vent fans usually are not noisy enough to be annoying. Make sure yours is installed properly and all the mounting screws are tight. If they are loose, this could explain a noisy vibration.

Solar attic fans operate almost silently. Even the large ones do not move as much air as an electric one, so there is little wind noise. Also, a solar fan only runs during the daytime, so it will not disturb sleep.


Send inquiries to James Dulley, The Forum of Fargo-Moorhead, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit www.dulley.com