Dean M Rantala
Computer
- Nov 19, 2021
- 5
Initial disclaimer: I am not a contractor or any type of mechanical/civil engineer!!
To begin, I have been considering new home construction here in northern Colorado. Given the ridiculous prices of lumber right now, it got me thinking about alternative building methods - specifically ICF. Yup - the ones with styrofoam on each side.
Now, a little background about myself before I continue... I grew up around construction until I was nearly 21. By 2003, I had decided construction was not what I wanted to do for a living and went down the path of software development and systems engineering. That said, I am not a complete idiot in regards to common building practices and methods.
But my interest in the title subject of this post is deepened by my experience as a part-time expat (Hidalgo, Mexico) and the construction methods used there.
Most homes in Mexico are built with virtually no insulation. Instead, we rely on very dense (clay-based) red brick to help form a thermal mass. Now, granted - this is certainly not the best in the hotter or colder regions, it got me thinking about the ICF vs CMU debate.
The ultimate question boils down to this: would it not be more efficient to have a simple CMU wall with a single 4-inch layer of rigid foam insulation on the outside -vs- a ICF wall with 2 inches on each side?
My reasoning is as follows: with an ICF wall, the concrete itself is essentially serving as a thermal-break (WITH thermal mass) between the two layers of insulation. However - if a simple CMU wall had a single 4 inch layer of insulation on the outside, then you would have a much better advantage: You still have the same effective total R-Value worth rigid foam, but you are now utilizing the thermal mass of the concrete to directly help regulate the interior temp of the home.
This question further ties in with the fact that I would consider concrete and CMU for the entire construction (interior walls as well as roof - as is typical in Mexico). This additional concrete not only adds even more thermal mass to the interior, but further eliminates wood needed for construction.
Homes in Mexico do not usually use drywall - the raw concrete walls are finished smooth with a stucco-like blend. Very durable as everything in the interior is basically solid concrete. Very common to see a home in near-pefect condition that is over 100 years old. Mice can't eat the walls, a kitchen fire cannot burn your home down, a busted water pipe will cause virtually no interior damage (just mop up the water)...
Finally, it seems to me (after having watched a few dozen YouTube videos at least) that the idea behind ICF is one of them "death by a thousand cuts" scenarios. Sure, it is "quicker" to stack the ICF forms - vs - laying traditional block. But that seems to be where the savings end. Plenty of wood must be purchased to properly brace the ICF walls while they are poured (one-time use!) and the additional zip-ties, inter-locking rebar and extra adapters to attach the bracing (rental in many cases) adds to the cost and time. By comparison, a CMU wall is pretty damn straight-forward. Cheap mixer from harbor freight, some straight line, a plumbob, only a few straight 2x4s, cheap concrete saw (found all over craigslist) and the materials.
Watching the instructional videos from some of the ICF vendors starts to make my head hurt. All the extra steps, all the additional "little" things that need to be tended-to. The additional cost of the forms themselves (after which, you are STILL paying for the concrete). It just does not add up - when a simple CMU wall with 4" of rigid foam seems to effectively accomplishes the same end-goal.
Now, part of the cost-aspect of this is assuming a DIY job. A contractor who does this every day will likely already have all the bracing, special attachment hardware, will be familiar with the assembly, caveats, etc. But that same contractor will likely negate any possible cost savings that could be realized.
To begin, I have been considering new home construction here in northern Colorado. Given the ridiculous prices of lumber right now, it got me thinking about alternative building methods - specifically ICF. Yup - the ones with styrofoam on each side.
Now, a little background about myself before I continue... I grew up around construction until I was nearly 21. By 2003, I had decided construction was not what I wanted to do for a living and went down the path of software development and systems engineering. That said, I am not a complete idiot in regards to common building practices and methods.
But my interest in the title subject of this post is deepened by my experience as a part-time expat (Hidalgo, Mexico) and the construction methods used there.
Most homes in Mexico are built with virtually no insulation. Instead, we rely on very dense (clay-based) red brick to help form a thermal mass. Now, granted - this is certainly not the best in the hotter or colder regions, it got me thinking about the ICF vs CMU debate.
The ultimate question boils down to this: would it not be more efficient to have a simple CMU wall with a single 4-inch layer of rigid foam insulation on the outside -vs- a ICF wall with 2 inches on each side?
My reasoning is as follows: with an ICF wall, the concrete itself is essentially serving as a thermal-break (WITH thermal mass) between the two layers of insulation. However - if a simple CMU wall had a single 4 inch layer of insulation on the outside, then you would have a much better advantage: You still have the same effective total R-Value worth rigid foam, but you are now utilizing the thermal mass of the concrete to directly help regulate the interior temp of the home.
This question further ties in with the fact that I would consider concrete and CMU for the entire construction (interior walls as well as roof - as is typical in Mexico). This additional concrete not only adds even more thermal mass to the interior, but further eliminates wood needed for construction.
Homes in Mexico do not usually use drywall - the raw concrete walls are finished smooth with a stucco-like blend. Very durable as everything in the interior is basically solid concrete. Very common to see a home in near-pefect condition that is over 100 years old. Mice can't eat the walls, a kitchen fire cannot burn your home down, a busted water pipe will cause virtually no interior damage (just mop up the water)...
Finally, it seems to me (after having watched a few dozen YouTube videos at least) that the idea behind ICF is one of them "death by a thousand cuts" scenarios. Sure, it is "quicker" to stack the ICF forms - vs - laying traditional block. But that seems to be where the savings end. Plenty of wood must be purchased to properly brace the ICF walls while they are poured (one-time use!) and the additional zip-ties, inter-locking rebar and extra adapters to attach the bracing (rental in many cases) adds to the cost and time. By comparison, a CMU wall is pretty damn straight-forward. Cheap mixer from harbor freight, some straight line, a plumbob, only a few straight 2x4s, cheap concrete saw (found all over craigslist) and the materials.
Watching the instructional videos from some of the ICF vendors starts to make my head hurt. All the extra steps, all the additional "little" things that need to be tended-to. The additional cost of the forms themselves (after which, you are STILL paying for the concrete). It just does not add up - when a simple CMU wall with 4" of rigid foam seems to effectively accomplishes the same end-goal.
Now, part of the cost-aspect of this is assuming a DIY job. A contractor who does this every day will likely already have all the bracing, special attachment hardware, will be familiar with the assembly, caveats, etc. But that same contractor will likely negate any possible cost savings that could be realized.