I have had inquiries about Insulated Concrete Form (ICF) construction. What is ICF? Should I consider ICF house plans for my new home? Those who have read my profile know that for more than 20 years I have designed and built using solid construction systems. I did so because I believe solid construction methodology is superior in every way to conventional composition construction as in framed construction.
It is important when planning to design and build a house for your next home to take into consideration that when you clear a lot and build a structure you permanently change the ecosystem that was there.
Pinpoint your home’s ideal location on the property. Assess which trees to preserve and plan how to repurpose any timber you must clear. This strategic approach ensures optimal site utilization and minimizes ecological impact. Next, instead of just orienting your house to the street, consider orienting your house to the sun to take advantage of passive or active solar energy to heat and cool your home.
Survey your site for materials that complement your habitat. Look for stone or timber you can incorporate. Blend these elements seamlessly into your design. Consider how each resource enhances your plan. Integrate local materials to create a harmonious living space.
Is there water on your site? Is your lot large enough to use convection ground tubes or bore wells for geothermal heating and cooling? These are just a few of the things you should peruse when finalizing and implementing a plan for the construction of your next home. My point is your primary concern should be to reduce as much as possible your impact on the environment.
Now this brings me back to solid construction and the use of Insulated Concrete forms (ICF). Most of my experience has been in specializing in using a hybrid approach to designing and building a solid concrete house. I recommend using ICF as the best system for construction below ground level either in a basement or in an earth bermed house. For above grade I prefer using Autoclaved Aerated Concrete (AAC), which I will address in a future blog.
There are at least a dozen companies which have their own patented insulated forms. What is common to all of them is they make a permanent concrete form using polystyrene foam for the shell of the building blocks for the forms or as in the case of Rastra Forms they make a cement form blocks in which use polystyrene beads as an aggregate and insulating element.
Most of the companies use 2 inches or more of 2-pound density foam on the inside and outside walls of their form blocks. 2 lb. density polystyrene foam has a resistance to heat transfer from inside or outside with a rating of R-6 per inch so a standard 12” form has a rating of R-24 and the solid 8 inches of concrete on the inside has a thermal mass that is hard to calculate but is at least R-2.
Save Green by Building Green
These thick, airtight walls act like a warm hug for your home. Cozying you up while fending off sky-high utility bills. In fact, studies show ICF homeowners can slash energy costs by over 50%! But that’s just the start. These sustainable stunners will keep your wallet and Mother Nature happy for decades. Boasting fireproof forms, steel-reinforced durability, and low (like, hardly any) maintenance needs.
Fortresses for the Modern Age
Worried about wild weather? Scoff at severe storms when you live in an ICF stronghold! With their beastly steel-reinforced concrete cores, these homes shrug off raging winds and angry skies. They’ll keep your family safe and serene, no matter what’s happening outside. And that solid construction isn’t just brawn, it’s function too. With superior noise insulation, ICF houses hush the chaos of the outside world.
More Than Meets the Eye (And Budget!)
Okay, we know what you’re thinking: “This all sounds amazing, but what about the price!”
True, ICF houses can have higher upfront costs. But stick with us for a second! Over the lifetime of your home, those energy savings, low maintenance, and storm-defying strength, house resell value, more than make up for it. We’re talking decades of cost-effective comfort! Plus, with free ICF house plans and concrete house plans available online for every dream home—from snug cottages to sprawling estates—you can easily find an affordable fit.
ICF House Plans Advantages
Insulation
When you consider that a standard wood framed wall is R-13 using conventional fiberglass insulation between wood 2×4’s the difference is remarkable in energy consumption over the lifetime of your habitation. Another factor to understand is that fiberglass insulation ratings are primarily based on heat transfer from the inside of the house to the outside, but not so much from the outside in.
Solid foam insulation is superior in this respect because it is unbiased in that it is as effective in resisting heat induction from the outside and this can be very important especially in hotter climates in reducing cooling loads. Solid foam insulation is also at least twice as effective in sound isolation than fiberglass insulation.
Sound Isolation
Another advantage of solid insulation as in the use of ICF construction is its high sound isolation over conventional construction and insulation. Such solid construction makes for a quiet home, whether from the sound pollution from outside or the hum of mechanical systems.
Rebar
Another common aspect of ICF systems is that they all use an integrated way of placing rebar reinforcement in proper spacing both vertically and horizontally. This is critical to this form of construction.
Block Patterns
What distinguishes these different companies’ forms is primarily in how the blocks fit together, such as in a tongue and groove pattern or a waffle pattern.
Wall Attachments
The other factor is the method they provide for attachments to the forms such as sheetrock, furring strips or paneling.
Wall Strength
Concrete volume affects form strength and thermal properties. More concrete often yields sturdier structures, while less can boost thermal mass. These differences shape the forms’ performance and efficiency in construction.
Rest assured that there has been extensive engineering done in the design of these forms and when you meticulously assemble these systems with proper reinforcement placing, tying, and overlapping rebar, especially at corners, this is an extremely strong and reliable building system.
Withstanding Catastrophes
Solid construction’s standout feature lies in its monolithic nature when properly assembled. Unlike conventional framing, it forms a unified structure. This cohesion allows it to better resist extreme weather and natural disasters.
Like a ship riding waves, the unified system sways together. Storms, deluges, and tremors can’t easily topple this cohesive structure. Its synchronized motion defies nature’s fury. Harsh conditions can weaken parts of a composition’s structure. This stress may cause sections to separate, destabilizing the entire system. Such fragmentation risks total collapse if left unchecked.
Fires
In a fire a solid house’s integrity is not compromised, even if the foam forms melt — the concrete structure remains. These forms are resistant to fire and insulate the concrete and steel within from disintegrating with the intense heat. However, with intense heat over an extended period the forms will melt. Now on the other hand Autoclaved Aerated Concrete (AAC) is not affected by fire at all.
Infestations
ICF systems are generally resistant to insect infestation. Early on however it was discovered that termites will channel between the foam and concrete to get to wood. I recommend however not using wood structure in a concrete house.
Concrete & Wood?
Concrete and wood are not compatible. Wood is an organic material which expands and contracts while concrete and steel do not. This is why stucco sided houses have gotten such a bad reputation. Masonry stucco is intended for steel frame or masonry construction.
If you decide to use wood framing for partition walls in a solid built house, be prepared for cracked sheet rock joints especially at corners where the concrete meets wood. I believe that most of the ICF manufacturers have now lined the insides of their forms with boric acid which insects cannot tolerate.
To state what seems obvious, ICF houses are durable, strong, reliable and will not rot like wood. I cannot tell you in my 35+ years much of which was remedial work on wood (stick) frame houses, how many dumpsters I have sent to land fills filled with rotten or insect riddled wood and failed siding materials impregnated with formaldehyde. I do not think I need to tell you that cannot be good for our environment!
My experience with trying to correct poor workmanship, failed building materials and the general flaws of standard wood framed construction is what led me to seek out alternatives to overcome the typical issues I was addressing with clients’ homes.
This is what led me to using ICF for basements and AAC for above grade as a primary building system for my designs and construction. I did extensive research and training so that I could design and build these systems and train crews to do this work.
I discovered how important it is to anticipate ahead of time what can and cannot be done effectively on the building site and how to prepare various crews for the eventualities they may face in performing their work on the site. So, I prepare plans in such a way that most construction practitioners can understand.
One thing few people understand is that it can take years for concrete to cure to its highest compression strength. This is a stark difference between typical cast-in-place concrete using steel or aluminum forms. Permanent ICF forms allow the concrete to hold its natural chemical heating process and the moisture for it to cure completely achieving its intended compression strength. As soon as conventional forms are removed, and the concrete is exposed to the air the curing process ends and its compression strength.
So, Are There Cons to Using ICF Construction?
I have seen this system fail in two occasions. Both were a result of poor workmanship practices which failed. It is important to understand the system and follow the proper construction procedures.
Honeycombing
One house had a wall failure because of honeycombing, or voids in the concrete, which was a result of when the forms were poured, they did not vibrate the forms and they used too high of slump concrete, so consequently the concrete did not fill the forms uniformly.
Corner Collapse
The other failure was a corner collapse. First, this was a result of the workers not bending the rebar at the proper 90 degrees and proper tying and minimal overlap. Second, the corner was not adequately braced during the pour, which may have been providential in that it exposed the reinforcement failure which would have failed later after the construction of the second story.
When pouring concrete into these forms make sure you do not use more than a 4” slump concrete and use 3200-4000 psi concrete. Make sure that as the forms are filled, they are vibrated to prevent honeycombing. There is no grace in using this building system with faulty workmanship!
Strong Bracing Required
Another con is that it requires a great deal of bracing to hold the forms during pouring and curing. I cannot stand seeing construction materials not being salvaged and thrown away as waste. I highly recommend that all exterior and interior load walls be built with ICF forms and concrete.
All other non-load bearing partition walls should be framed with light gauge steel studs, so the bracing you use for the forms should be steel and salvaged after the concrete is cured, so they can be used for partition walls.
Blow Outs
There can be unforeseen blow outs during the pour which can be very frustrating and costly. Make sure before pouring to have ready plywood patches and screws to cover these blow outs quickly. Never try to do a pour with less than four skilled workers on site and certainly more on a larger house.
Form Bulges
Another thing that can happen unforeseen is permanent bulges in the forms. It is important to apply expanding polyurethane adhesive between form blocks for permanent bond and fill possible unseen voids between blocks. Also make sure to adequately brace the forms before the pour.
Proper Threaded Rod Placement
ICF is a part of a complete monolithic structure and should be built on a well reinforced monolithic concrete slab. I highly recommend forming a keyway joint and properly tying 5/8” threaded rods to the horizontal footing rods to extend through each story to the top bond beam.
With a plan that calls for or requires a basement I design specifying the use of ICF permanent forms and do a complete surround concrete basement in which I use as a heat/cold closet in integration with natural convection air flow to reduce heating and cooling loads.
Most of my experience has been in designing and building with two different ICF systems, which I can certainly endorse and share what you need to know if you use these forms. The first is American Poly steel Forms and the other is Rastra.
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Conclusion
Insulated Concrete Form construction is an excellent building system when proper procedure is applied. I use this system often in full surround basements in my designs. Because of its effective high thermal mass I use these basements as heat/cool closets in correlation with integrated natural convection air flow to highly reduce heating and cooling loads which translates into lower energy consumption.
If you have an interest in this form of construction or have further questions, please let me know. I am happy to work with you on such a plan and provide consulting for you and your builder. Contact us now!