Engineered Concrete Frequently Asked Questions
Simply A Better Way To Build
An Insulated Concrete Form (ICF) is two molded sheets of expanded polystyrene (EPS) foam held together by rigid webs. In addition, the webs carry horizontal rebar to reinforce the concrete which is poured in the form to construct a wall. Top and bottom edges of the forms interlock similar to Lego blocks, allowing a wall to be stacked, say 10 – 15 feet tall, poured full of concrete, and extended a second, third, or more stories.
Straight blocks typically make up 85% of the ICF wall assembly on most residential & commercial jobs. The straight block has six (6) strong full length injection molded plastic ties made from polypropylene (PP) regrind resin that are well marked with the word “Fox Blocks” located on both sides of the block. These ties secure the two pieces of 1.5 pcf density modified Expanded Polystyrene (EPS) foam together that makes up each block type. The blocks are stacked tightly together and inter-locked end to end to the desired wall length. Once a single layer or course of ICF blocks is installed, horizontal reinforcing steel bars are inter-locked securely together in the ties of the blocks, then another course of straight blocks are placed firmly on top as the wall is built. To improve construction wall strength during installation, each course of blocks should have their end-joint connections staggered in a running bond method from the course adjacent to it.
The several advantages of ICF construction include:
Elimination of Drafts, Reduced Air Infiltration
Self Construction Options
Design Options, e.g. beam or cantilevered walls
Deeper window sills
The question is similar to “How much does a car cost?”
Value engineering usually says ICF construction pays, not costs, considering all lifetime costs of a residence or light commercial building.
Industry says initial capital cost increase may be up to 5% of the total cost of a typical residence.
Material costs of ICF forms, rebar and concrete run around $7 – 8 / sq ft of wall.
Installed contract prices run around $14 and up, depending on a variety of factors, e.g. size of job, location, complexity of design, backfill heights, waterproofing requirements, openings, …
Laboratory measurements of the forms indicate an R value of 23+. ASHRAE 90.1 methods dictate steady-state measurements. Because of the thermal swing of external temperatures, decreased air infiltration, and the heat capacitance of the wall concrete, power necessary to maintain internal temperatures indicate an apparent R value near 50 near Atlanta, based on computer simulation of ICF construction. ORNL Thermal Mass Calculator Dynamic R-Value Equivalent yields “Greater than R 32.”
Homes built of Fox Blocks High Performance Walls typically include 40% reduction in size of HVAC unit required, and cost less than 50% monthly to heat and cool.
Fox Blocks homes may cost 0 to 5% more initially.
Take worst case, 5%, on a $150,000 home = $7,500 increase in capital cost.
At 6% interest, mortgage payment increases $48/month.
Fox Blocks High Performance Wallsystems reduce heating/cooling costs 40 to 70%.
If conventional home heating/cooling costs $215.00/month, using worst case 40%, heating and cooling costs are reduced $86.00/month.
+ $86.00 energy savings
– $48.00 mortgage increase
+ $38.00/month in your pocket
plus a whole lot of comfort, safety, peace of mind and quietness. Energy savings will increase as the price of oil increases.
With 99.9% certainty you can build the home you wish to live in, or the light commercial building you would like to occupy. Is it feasible to do so? Most probably so. Architectural and Engineering design capabilities are enhanced with ICF construction methods.
Absolutely! 90° corners, 45° corners, T-forms, radius forms (for building curved walls), ledger forms (4” kickout for starting brick, for example), taper-top forms (to provide more than 6” concrete width at top),
ICF construction is increasing in our geographic area, even though we are in a temperate area, not prone to hurricanes, etc.
Lack of familiarity with the materials and methods of ICF construction. “I’ve never built using ICF’s.”
Entry level homes strive for the lowest possible mortgage payments.
Failure to consider the long-term, lifetime costs of the building.
Design decisions are often recommended, influenced or made by someone (architect, engineer, builder, relative, friend) other than the person who will pay the operating expenses of the building.
The advantages far outweigh the disadvantages, but,
The necessity to think soundly.
The necessity to plan.
Additional initial capital costs.
If no special order forms are required, we can usually have forms delivered to the job site within 3 – 5 days, assuming truck freight can be scheduled.
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