ICF FAQ
Q. What is ICF?
A. ICF stands for Insulated Concrete Form. It is a molded foam block with inter locking fingers on the top and bottom, allowing them to be stacked. Once they are stacked and properly supported, concrete is poured into the form, making a solid concrete wall that is fully insulated on the inside and out.
Q. Do you leave the foam on?
A. Yes. The foam is a very important part. First it is the form, then it is the insulation, and finally it is the structure you fasten sheet rock, siding, or whatever you are covering it with.
Q. How do I fasten drywall to the foam?
A. Depending upon which ICF block you are using, the plastic ties are located inside of the foam. Some are 8 inches apart and some are 6 inches apart. The company we use the most is Amvic. The cross ties are located every 6 inches from the top of the block to the bottom. When stacking the blocks, the installer should take care to keep the ties lined up. This gives you a mounting tab that is over an inch wide every 6 inches. On the exterior of the foam there is normally a deeper groove, or markings to let you know where the mounting area is at.
Q. Will the plastic tie hold a fastener as well as a wood stud? What do you use as a fastener?
A. We normally use a drywall coarse thread screw as a fastener. According to Amvic specs, this type screw will hold 198 #’s of pull out force. If you can find an ICF block, run a screw into it and drive a drywall nail into a wood stud. Use a claw hammer and pull them out. You will find it very difficult to pull the screw out of the ICF, whereas the drywall nail will take very little effort.
Q. I was told if termites get behind the foam they cannot spray for them. Is this true?
A. This question usually comes from a potential user that has been talking with a simple concrete wall person. They use this to try to combat a superior wall. We at Mi-Tre’, insist that all of our new structures be pretreated for termites by a professional exterminator, regardless to whether we are using ICF or not. This is just good standard practice. To answer the question, the ICF foam is very dense and chemical resistant, so it is true you cannot get the spray to penetrate. If for some reason the walls were not pretreated, or termite infestation does occur, then a bait system works very well.
Q. I heard the foam is fragile and when you pour it, there are blowouts.
A. Again, this type question normally stems from a conversation with a simple concrete wall builder. Actually, ICF is very strong. Try to tear one apart, you will see what I mean. The Amvic ICF block is manufactured to with stand the pressures created when filling it with concrete. On occasion, the installer did something wrong, or once in a great while, one might find a damaged block. We have been using ICF for 10+ years, and I can safely say blow outs are not a problem if you use a quality block and properly construct the wall.
Q. If there is a blow out, what do you do?
A. Experience helps. We very seldom have a blow out. Over the years we have learned what “not” to do, but in the event one does occur, it is not a big deal. Normally a blow out will happen in the bottom area of the wall during the intial pour. Usually a small area, 6 inches wide and no more than 16 inches tall, will break. First you stop pouring in concrete, then you remove the broken piece of foam, dig out enough concrete to allow room to place the broken foam back into the hole. Using a plywood bandaide, measuring 16 inches tall and 24 inches wide, screw in over the patch, using the mounting tabs located near by. Start pumping concrete. The whole event might take 5 minutes and normally you will not lose over a shovel or two of concrete. Let a metal or wood formed wall blow out and see what happens. Normally the project is shut down.
Q. Is an ICF home tornado proof?
A. An ICF wall, when properly built, will with stand 250 MPH winds. It will take a projectile hit of a 2 x 4 at 100 MPH ( this is what it estimated the debris inside a tornado will be flying around at). There are many photo documentation’s showing an ICF home, or commercial building still standing after a tornado has wiped out every thing around it. Most of the time, the limitation to an ICF home in a storm is the roof and windows. If a person wants to maximize there protection, then an ICF safe room should be designed into the home or building. Amvic offers an entire foam formed system for the walls and roof, making an entire room that is safe. To say anything is tornado proof is a large step, but a proper built ICF safe room will offer you the most protection available. I have never heard of one failing when tested by man made created environments, or mother nature’s wrath.
Q. Why do you use Amvic ICF?
A. Since 1994 we have used many different ICF companies. Each time we changed it was always to the better. Most of the time is was a product issue, sometimes pricing had a little to do with it. About 3 years ago we were ask to look at a company called Amvic. Their interlock system, which was reverseable, was impressive. Their quality control was superior to anything we had seen. The density of the foam allowed for greater inter pressure’s, allowing us to vibrate where necessary, it reduced the potential for blow outs, their space of 6 inches, instead of 8 inches increased the side strength and made in easier to find a mounting tab when attaching to the wall. Overall, it was the best ICF wall block we had ever seen or used. Since then we have not found anything better. Amvic listens to their distributors and installers. If something is needed, they produce it. A recent ICF floor system has proven itself over and over again, making free spanning concrete up to 35 feet possible. No question when we look at ICF, Amvic is the best on the market.
Q. How can ICF have an R Value at 50?
A. To begin with, think of when the weather man tells you the outside air temp is 30 degrees, but taking the wind in to count the wind chill is 0. Although it is still 30 degrees, it feels like 0 with no wind. Now think about how an ICF wall is made. The R in R Value means the resistance to heat flow. The three main ingredients of energy efficiency is infiltration of air, insulation, and thermal mass. The density of ICF foam when combined with concrete, will not allow air to pass through. The ICF foam is an excellent insulation, especially when compared to fiber glass insulation. Although concrete itself it not a good insulation, it is a good thermal mass source, maintaining a constant temperature when encased by the ICF form. So, knowing this and thinking about wind chill, it is easy to see how an ICF wall can be considered R-50 plus.
Q. Will I notice a difference in my heating and cooling cost?
A. With the continuing increase of energy, this is becoming a huge factor when considering ICF. Energy cost savings will range from 30 to 70 percent, depending upon what you are comparing to. In new construction, this starts at the beginning. When the HVAC installer starts sizing the unit to the home, he will use smaller units when he finds out the home or business is being constructed with ICF. This means lower initial cost. With smaller units, the cost to operate will be less. Once you live or work in an ICF environment you will see the other energy saving’s properties. No draft’s. Once you have been around it, the list goes on and on.
Q. Is an ICF home going to cost me more to build?
A. Your up front cost will be more, between 9 and 15 percent, but don’t stop reading yet. In a basement, this cost can be easily offset by the finish process. If you hire someone to finish the basement, they don’t have to fir strip the walls and insulate prior to installing the dry wall or paneling. Hiring labor to do this can be very expensive. IF you do it yourself you will appreciate not needing to fir strip and insulate. The cost of the above ground walls is a little different when compared to the standard wood framed walls. The material cost of ICF are higher, but there is a little labor savings. The main way to recapture the additional cost will be in the long term, using energy savings. The biggest reason is peace of mind knowing you have a wall that will not come down.
Q. Does the walls need to be water proofed?
A. All ICF needs to be covered with something. Any walls below ground should be water proofed. There are many products available from peal and stick membranes to spray on water proofing. If you are in a rocky environment, there is a hard sheet material that goes on after the water proofing and prior to back fill. This protects the integrity of the water proofing during the back fill stage. The walls that will be exposed above ground do not need water proofing or house wrap. They should be covered with siding, masonry, stucco, or any other exterior finish you wish. The main thing is to cover the foam. It will last along time when exposed to the elements, but it will get pretty tough looking.
Q. Can I build an ICF wall myself?
A. Most ICF companies will not sell their product direct to an inexperienced user. Mainly due to the horror stories that surface when something goes wrong. In almost every case, problems are created by the installer doing something wrong. If you are building a short wall, 2 or 3 blocks (32 inches to 48 inches) you would probably get by with some supervision. When you start going any higher, you need to have the proper equipment to build with. We have several different height wall jacks and scaffolding These were designed for ICF. Without the proper equipment and knowledge, I would not recommend it.
Q. How do I know if I am getting a good installer?
A. Ask for referrals. Find out which ICF they are using, then contact the manufacturer or supplier. If the installer is qualified, the company will know. Talk with other home owners or commercial building owners. Ask for a copy of their contractors insurance. These are all things I would expect for a new customer to ask us.
Q. Are there a lot of buildings using ICF?
A. This is our track record and should not be considered a national average. Since 1994, with the exception of one, all of our basements were done with ICF. Out of the last 10 new custom homes we have built, 6 were ICF all the way to the roof. That’s 99 percent of our basements, and 60 percent of our custom homes. Nationally the number is not that high, but we specialize in ICF. Commercially I think the ICF is growing faster, as the long term maintenance and energy savings is much prevalent.