Insulating concrete forms
From Wikipedia, the free encyclopedia
Insulating Concrete Forms or Insulated Concrete Forms (ICF or ICFs) are stay-in-place formwork for energy-efficient, cast-in-place reinforced-concrete walls.
The forms usually take the form of foamed plastic blocks separated by plastic or carbon-fibre spacers which lock together somewhat like Lego bricks. They serve to create a cavity, or mould, for the structural walls of a building. Concrete is pumped into the cavity to form the structural element of the walls. Usually, reinforcing steel (rebar) is added before concrete placement to give the resulting walls flexural strength, as in bridges and high-rise buildings made of concrete (see Reinforced concrete).
After the concrete has cured, or firmed up, the forms are left in place permanently to serve as:
- Thermal and acoustic insulation
- Space to run electrical conduit and plumbing
- Backing for gypsum boards on the interior and stucco, brick, or other siding on the exterior
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[edit] Benefits
This method has several advantages compared to traditional building materials, especially in residential and light commercial construction. The advantages of structures built with this method include:
- Minimal, if any, air leaks ? comfort, less heat loss
- Superior energy performance ? Lower energy bills
- Fast construction ? Competitive costs
- High sound absorption ? Peace and quiet inside
- Little waste, local materials, long life-cycle ? Environmental friendliness
- Time-tested structural integrity ? Resistance to forces of nature
- Low maintenance, high durability, very long lifespan ? Higher resale values
- Flame-retardant EPS ? If a fire occurs, the expanded polystyrene (EPS) will only burn while a flame is applied directly to the foam; the resulting smoke from burning EPS is said to be "less toxic" than wood smoke
- When the building is constructed on a concrete slab, the walls and floors form one continuous surface. This keeps out insects.
[edit] Disadvantages
- Adding or moving doors, windows, or utilities is somewhat harder once the building is complete (requires concrete cutting tools).
[edit] Types of systems
The forms are usually made of foam insulation, such as expanded polystyrene (EPS), and are either separate panels that are connected with plastic connectors or ties; or pre-formed interlocking blocks.
Different ICF systems also vary in the shape of the resulting concrete within the wall:
- "Flat" systems (3rd Generation) form even thickness concrete throughout the walls, like a conventionally poured wall. In high seismic and wind threat zones, flat wall systems predominate as the systems of choice.
- "Waffle Grid" systems (2nd Generation) create a waffle pattern where the concrete is thicker at some points than others.
- "Post-and-Beam" or "screen grid" systems (1st Generation) form discrete horizontal and vertical columns of concrete. The areas within the grid are solid insulation, increasing the overall R-value but offering very little overall fire resistance.
[edit] Construction costs
The cost of using ICF rather than conventional construction techniques is most sensitive to the price of labor, wood, and concrete. In the southern USA in 2006, a brick-clad ICF home cost around 5% more than a conventional brick-clad timber-frame home.[citation needed] However, the energy savings of an ICF home usually result in positive cash-flow from Day One compared to most conventional construction.
[edit] External links
- Insulating Concrete Forms Association (US)
- Insulating Concrete Formwork Association (UK)
- ICF Info by the Portland Cement Association
- PATH Tech Inventory: Insulating Concrete Forms
- Concrete-Home.com - Online Forum on ICF Construction
- ICF Builder Magazine - Online how-to articles for ICF contractors and do-it-yourselfers