Are you thinking about using insulated concrete forms (ICF) to build your new home? We’ll cover what ICF is, how it works, and the pros and cons of ICF construction. Here’s what you need to know about this energy-efficient building material.
What Are Insulated Concrete Forms (ICF)?
Insulated concrete formwork, commonly known as ICF, is a construction method used in home building that utilizes styrofoam foundation forms to create a strong and well-insulated structure. It’s an alternative to traditional wood-frame housing.
Instead of framing the walls with studs, the walls are formed by styrofoam blocks, and the concrete is poured into those forms. Insulated concrete forms (ICFs) are the styrofoam foundation forms. They are light, simple, and easy to work with–they simply snap together like lego. They are permanent forms that stay put even after the concrete is poured, and they help insulate the home once the concrete is dry. The forms can be stacked and interlinked to form walls, ceilings, roofs, or pool walls that are filled with concrete.
What Is ICF Made From?
There are two main parts to an ICF: expanded polystyrene for the insulation and webs or cross ties that are usually made of polypropylene plastic.
Here are some specs and benefits of insulated concrete forms:
- Type II, closed-cell foam
- High R-value per inch (R4) – the higher the R-value, the greater the insulation performance
- Moisture-resistant and non-absorbent
- Resistant to rot and mold
- Contains a flame-retardant
- Non-toxic smoke
There are a wide variety of benefits to using ICF compared to wood-frame building.
Faster Build Time
Building with ICF may cut 2-4 months off the construction time of your home. That’s because ICF saves steps in both the exterior and interior construction. Also, one of the most time-consuming and yet important aspects of wood framing are all the many steps required to protect a wood frame from moisture. Wood will degrade and rot if not properly protected from moisture. So there are dual-layer and even triple-layer protection systems involved in protecting a wood frame from moisture. Concrete, however, is not subject to the same degradation. Plus, the ICF system is designed to allow moisture to exit the frame inherently. So, the time savings can be significant, depending on the design of the home.
While it used to be considered expensive to build with ICF, lumber framing labor has finally all but caught up with the cost of ICF construction, making it a comparable and affordable option for homeowners.
ICF forms cost an average of $3.50 to $4.00 per square foot. Once you factor in additional costs like concrete, rebar, hardware, labor, insurance, etc, the average total cost using ICF forms can be around 15-20% more than stud framing. However, there are significant savings realized from using ICF, and that will be discussed later.
ICF will not combust. Even if a fire ravages the inside of your home, the walls will stand through a fire. That also helps prevent the spread of fire from your home to another, stopping the fire when it reaches your exterior walls.
This home built with Insulated Concrete Forms narrowly escaped destruction in 2018’s California’s wildfires, which burned 18,804 structures and took 85 lives.
Other homes in the neighborhood were completely consumed by flames, but this one, built with ICF, survived.
With insulation on both sides of the concrete, your wall temperatures won’t change throughout the day, achieving a consistent R-23. Whereas wood frame walls do not have consistency and max out at R-19, but typically range from R-9 to R-15. That means less energy is required to heat and cool your home – a savings of 20% to 50%!
An independent study conducted by CLEB Lab concluded that an ICF wall provided 58% greater R-value and 43% energy-savings compared to the wood-frame wall. Rastra walls, made from rastra blocks, are an innovative alternative to conventional construction materials. These blocks are composed of recycled materials and provide excellent thermal insulation.
ICF walls are also less drafty than wood-frame walls. In fact, it takes almost three days for radiation, convection, or thermal heat transfer to make it through the exterior wall. The benefit of a less drafty home is the way the home feels and lives. With a more consistent temperature throughout the home, there is typically less need to change the thermostat up and down.
Walls made with Insulated Concrete Forms insulate sound better than traditional walls, so your home will be quieter. Standard wood framed walls have a Sound Transmission Class (STC) rating of 33-38, whereas an ICF home has a consistent STC rating of 54, which means that even shouting is not heard outside of the ICF walls.
Homes made with ICF are sometimes called “1,000-year homes” because there’s little to prevent them from surviving intact for hundreds of years. The walls are strong enough to withstand up to 250 mph hurricane winds and tornadoes, earthquakes, and are fire-resistant for up to 4 hours. They’re unlikely to suffer from slow degradation the same way wood-frame walls do, so they stand the test of time.
Here are a few examples of how ICF homes weathered the storm…
ICF Home Survives Hurricane Dorian
One of the worst natural disasters to hit the Bahamas, even Hurricane Dorian could not take down this ICF home on Grand Abaco Island after 36 hours of punishing hurricane winds.
Hurricane Michael Survivor
This ICF home in the Florida Panhandle was virtually the last home standing after 150+ mph hurricane winds hit it. Hurricane Michael completely destroyed 54% of homes in the area and another 23% were severely damaged, even though most Florida homes are built to withstand hurricanes (using concrete block and other systems to withstand wind loads). This home was built only a few hundred feet from the water’s edge and weathered the ferocious wind and storm surge with ease.
Storm Surge and Debris
This Cayman Islands ICF home survived the storm surge from Hurricane Ivan in 2004 despite being battered by cars, rocks, and other debris.
The storm surge forces and battering waves of Super-storm Sandy in 2012 were too much for the homes in Union Beach, New Jersey, but the family who built this ICF rode out the hurricane in their two story home while waves broke on the house itself.
Nontoxic and Healthier Air Quality
ICF contains no HCFC, formaldehyde, fiberglass, or asbestos and doesn’t suffer from off-gassing. And, no harmful CFCs (chlorofluorocarbons) are used in their manufacture.
ICF walls provide a tight, low air filtration wrap to your home. This is the first step in controlling the indoor air environment.
- ICF walls reduce air infiltration by 75%.
- Eliminate dust mites.
- Prevent dangerous and costly mold.
- The effects of hay fever, asthma, and other airborne allergies can be greatly alleviated as a direct result of the reduced leakage of outside air, which brings dust, pollen, and other pollutants.
- Indoor air pollution is a great health concern today. ICF walls are non-toxic. The measurement of air contents of actual ICF houses shows an almost complete absence of any emissions.
When paired with solar tiles, a home built with insulating concrete forms becomes net zero. The World Green Building Council (WorldGBC) defines a net-zero carbon building as one “that is highly energy-efficient and fully powered from on-site and/or off-site renewable energy sources.”
Unlike some other countries (like Canada), the United States doesn’t require new homes to be net-zero. However, WorldGBC is dedicated to supporting market transformation toward 100% net zero carbon buildings by 2050 to achieve Paris Agreement levels of global emission reductions.
Unlike using traditional forms, concrete can be poured into an insulated concrete form any time of year, regardless of how hot or cold it is. That means your home can be built at any time of year.
Lower Homeowner’s Insurance Premiums
Since walls made with ICF are so resistant to wind, fire, and flooding, your homeowner’s insurance premium will be lower than it would be with traditional wood-frame walls.
The Home of the Future
As energy codes become more and more stringent, as they are in Canada, we foresee a shift toward ICF or similar high-density exterior wall framing. In Canada, ICF homes are becoming the standard, and we are beginning to see that same trend moving across the states as well. There are several other options for creating a similar R-value to ICF, but none compete in terms of quality, economy, or time savings.
While ICF is a wonderful building material, it does have a couple disadvantages. These include:
- Difficult remodeling. Adding doors or windows in the future will be tricky since you’ll be cutting into concrete. You need to plan ahead when designing your floor plan, and it is best to use an Architect who has experience designing an ICF home.
- Floor space. Walls made with ICF are typically thicker than traditional walls, which means you’ll have less usable square-footage inside your home, but this is an insignificant difference.
- Note: these are just two of the reasons why it’s best not to construct all the interior walls with ICF.
Frequently Asked Questions
Here are answers to some of the most frequently asked questions about insulating concrete forms.
How Do Insulated Concrete Forms Work?
Insulated concrete forms are like hollow Lego blocks. Exterior walls are built using the forms, which go together like Lego blocks, the steel is placed in the built-in slots inside the ICF blocks, and then they’re filled with concrete. The forms stay in place and act as additional insulation. ICF blocks are usually 96 inches long and 16 inches high, but they come in varying shapes and sizes to accommodate corners and other needs.
What Do ICF Forms Cost?
As mentioned previously, ICF forms cost an average of $3.50 to $4.00 per square foot. Once you factor in additional costs like concrete, rebar, hardware, labor, and more, the average total cost using ICF forms is around 15-20% more than traditional stud framing. To put that into perspective, if the framing on a home is in the range of, say, 20% of the home’s overall cost, a 20% additional cost of the framing would equate to a 4% additional cost of the overall project. What is harder to quantify is the savings realized from using ICF. In addition to the ongoing energy savings and insurance savings, there are savings during the build. For example, waterproofing systems used on the exterior walls of the structure are all but eliminated since both the ICF blocks and the concrete are waterproof and weatherproof. Take, for example, house wrap. There is no need for house wrap on an ICF home. There is also no need for exterior sheathing in most cases. If there are exterior balconies, the waterproofing systems are modified for ICF. These are just a couple of examples. Depending on the design, an ICF home can be quite cost-effective especially if the specialty labor for performing the ICF framing is in-house, as ours is.
How long will an ICF house last?
Hundreds of years – they’re called “1000-year-homes” by some. ICF homes’ walls and EPS insulation lasts for centuries and doesn’t break down, collapse, decay, or fail when protected behind wall finishes.
Who Makes the Best ICF?
There is no precise way to determine who makes the best ICF. A few tips for choosing the best insulated concrete form blocks for your project include:
- Does the manufacturer offer excellent support?
- Are the blocks code approved?
- How high are the R-values (a measure of heat transfer)?
- Are the ICFs easy to assemble?
- Do they ship flat (which is a necessity for shipping and storing the blocks)?
More about Insulated Concrete Forms
If you’re looking to construct a highly energy-efficient building, it’s essential to hire an experienced insulated concrete form contractor who specializes in the installation of insulated concrete formwork. To learn whether insulated concrete forms (ICF) might be the best solution for your new home, contact us today. Click here or call 512.402.9222. We offer ICF and self-perform the work; so we can answer all of your questions about it.