Where is the love for ICF?
sethery05
| Posted in Energy Efficiency and Durability on
The more I read and watch YouTube on high performance building / air tight envelopes it seems like there is no love for ICF. It looks like the consensus is conventional stick frame + Zip R sheathing + Rain Screen + Rockwool insulation + Good air sealing details.
Is ICF just a DIY cult following or why is it not getting more wide acceptance as a complete building solution? Not just for foundation walls. What am I missing? Is it actually not a good system? R-value not as high as advertised? Too challenging to work with the embedded plastic studs?
Just curious…
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The idea that there is a superior alternative to the standard way of building is very appealing, particularly for novices with a limited understanding of construction. Whether ICFs, SIPs, shipping containers, haybale, cob, rammed earth, etc. The reality is they all have different properties that may or may not be beneficial for a particular project, but generally speaking are a net negative if budget is a consideration.
A lot of the downside is that if they are not common in your area, tradespeople won’t be familiar with how to work with them. You’ll likely end up having to pay someone to learn as they go, and will receive the quality level of someone’s first attempt.
Then as the cherry on top, concrete and foam are near the top of the list in terms of upfront carbon emissions, on the other hand, framing lumber is ~50% carbon.
In terms of what is standard practice for high performance building, it is highly regional since climates, material availability, and historic practices dictate different approaches, so you would need to do some research. I'd also recommend checking whether the content you’re reading is sponsored. One could be forgiven for thinking every high performance builder under the sun uses Zip/Zip-r and Rockwool, when the reality is that Huber and Rockwool have massive budgets for sponsoring content that gives them disproportionate visibility.
ICFs serve a purpose below grade, especially for smaller projects that a builder or skilled homeowner can DIY instead of trying to schedule (and pay for) a concrete contractor. When used above grade, they provide a reasonably well-insulated and quite airtight building envelope.
BUT--they don't address the gaps and cracks around doors and windows that account for a lot of a typical home's air leakage, they require a lot of concrete to be pumped which risks a major blowout, and, for me, most importantly, they use the two building materials with the highest embodied carbon emissions of anything we build with.
After all that, they still require extensive, non-standard finishing inside and out, complications when running wires, renovations and additions can be very challenging, the stated "R-value equivalents" are grossly exaggerated because the thermal mass of the concrete rarely functions to the level that people think it does, etc...
Not everyone thinks it's important that we don't excessively pollute our atmosphere and contribute to climate change with the homes we design and build, but as a full-time home designer I have not found the need to use foam above grade in over ten years, except for very specific situations. And I generally design well above code-minimum insulation levels.
That second to last point drives me nuts. The ICF industry is full of people who have enormous claims of Rvalue. One company actually used less foam and more concrete claiming it had "more thermal mass for better performance."
If we say "thermal mass" once more, DCContrarian is going to appear and let us have it! ;-)
Beat me to it!
How about thermal inertia?
How about heat capacity?
"Inertia" and "mass" have specific meanings in science and engineering that have nothing to do with heat. It's like saying "thermal height" or "thermal aroma."
ICF has a massive carbon footprint. For above-grade portions of a building there are many building assemblies that will give you better performance for a fraction of the carbon cost (and dollar cost).
This is GREEN Building Advisor. ICF is just about as far away from green as you can get.
To be fair, "green" means different things to different people; some still consider it to be only about having low operating expenses, or using only naturally-sourced materials, or being entirely off-grid and using local biomass for heat and sometimes for cooking. But like you, I strongly believe that it should include the building's net contribution to carbon emissions and other types of pollution.
I reject those other meanings. I think they are rooted in either a misunderstanding, or just lack of knowledge. Low operating expenses is, presumably, just a surrogate for less consumption, in which case it's just wrong. Similarly, I think most people who yearn for being off grid perceive it as being better for the planet, but the opposite is true (at least in most cases).
I agree on all counts. But unfortunately I can't force others to agree with me ;-)
I dont think I agree with "Similarly, I think most people who yearn for being off grid perceive it as being better for the planet, but the opposite is true (at least in most cases)."
I think that statement has been repeated countless times with very little evidence. especially considering the huge lack of clean energy storage options on a large scale. Utilities are getting to the point where they are actually shutting down renewable energy due to huge daily fluctuations and lack of storage.
Also consider the huge impact the utility caused wildfires have. Really the only large component missing from a house with solar to be off grid is a battery system (the component not being addressed with large power grids) and maybe a slightly better inverter/charger. ok well most regions also require backup power but if you size correctly this can basically never run.
I think it most likely doesn't make sense financially in most cases but I don't think I have ever seen a good analysis that shows it is not better for the environment. If you have a resource that shows this please post.
Also consider in California they have started to implement Public Safety Power Shut offs that cut peoples power for days on end multiple times a year in an aim to reduce risk of fire. Many of these people have started running generators continually during these in order to have power.
In order to compare the impact of the grid with off-grid living, you'd have to account for everyone being off grid. The amount of batteries needed for that is mind boggling, most likely not even physically achievable.
I think the burden of proof is on the off-grid claim, not the other way around.
In reply to #27
I think the burden of proof should be on the person making a factual claim. also "In order to compare the impact of the grid with off-grid living, you'd have to account for everyone being off grid." why in the world would you need to do that? That seems a bit ridiculous and does not account for any context. For instance, I'm sure cities would benefit from centralized power storage and grid systems. That is like saying well yes, sheep wool is an environmentally friendly insulation but really its not because what if everyone in the world used it as insulation? we would be overrun by sheep!
But ok, lets put some numbers to it, with the caveat that I am not an expert (obviously) on power infrastructure.
Lets say you need 50 kwh battery bank for your off grid system (which is generous and probably oversized, especially considering vehicles will be able to supplement in times of extended reduced solar)
A quick google search brings up 73kgCO2/kwh of lithium battery to produce, so for our example 3650 kgCO2 or 3.7 metric tons
The US produces 4.23 trillion kilowatthours and emits 1.65 billion metric tons for all energy sources. this equates to basically .4 kg per kwh
The average house uses about 30 kwh per day. that equates to 12 kg CO2 per day. So to offset the battery emissions would take 3650/12=304 days.
I'm sure this equation will change as large scale storage solutions come online but the fact is that currently, we still use .4 kgCO2 to produce that kwh of energy.
As for can we make that many batteries? the us currently produces 224Gwh of lithium batteries per year in 2021. with 1.4 million new houses built in 2023 that would only be 70Gwh of lithium batteries.
Ref:
https://www.eia.gov/tools/faqs/faq.php?id=74&t=11
https://www.consumeraffairs.com/homeowners/how-many-houses-are-built-every-year.html#:~:text=The%20overall%20value%20of%20the,%241.85%20trillion%20value%20in%202022.&text=The%20number%20of%20newly%20completed,an%20increase%20of%20about%2090%25.
https://www.energy.gov/sites/default/files/2021-06/FCAB%20National%20Blueprint%20Lithium%20Batteries%200621_0.pdf
https://www.agwayenergy.com/blog/average-kwh-per-day/#:~:text=According%20to%20the%20most%20recent,and%2030%20kWh%20per%20day.
https://www.changeit.app/blog/2021-03-26-environmental-impact-of-lithium-batteries/#:~:text=Electric%20cars%20are%20moved%20by,7300%20kg%20of%20CO2%2C%20respectively.
I'm hoping to redirect this conversation. The Green conversation and Carbon footprint is important and needs to be addressed. However, if there was a way to compare ICF to a high performance stud wall system Apples to Apples. Where does ICF fail or win? It just seems like, at a gut level, that the continuous monolithic system could have many benefits that everyone is trying to achieve on here.
Does anyone agree with this assessment?
Insulation value = + 1 for stud wall (assuming no value in ICF thermal mass)
Ease of construction = +1 for stud wall
Air tightness = +1 for ICF (assuming good detailing around openings)
Moisture / vapor control = +1 for ICF (assuming ICF to roof line)
Durability = +1 for ICF
Adaptability = +1 for stud wall (interior finish / exterior finish options)
Cost = ???
What else am I missing?
The problem with this method of evaluation is that it's too general and binary. Some of these things are gradients, and some don't really matter. For example, insulation you've got as +1 for stud wall, but in theory it could be + or -, and if you're looking at best vs best of each option, +1 probably doesn't really cover it. It could be more like +5. For air tightness you've got +1 for ICF. While it may be true that the average ICF is more air tight than the average stud wall, it's possible to detail a stud wall air tight enough to be a non-issue. My stud wall house has an air tightness of 0.22ACH. It wasn't very difficult to achieve, either. Durability? Yes, the ICF could withstand more. But my stud house isn't going to fall down, so that's good enough.
Cost is definitely in favour of the stud wall.
Durability is way over-rated. Stick-built buildings last forever if they're cared for, the wood doesn't wear out. And buildings don't get torn down because they're worn out, they get torn down because they're functionally obsolete.
It always amazes me how common it is to demolish skyscrapers that are not that old, 30-40 years seems to be the useful life, at least around here. They tear them down not because the concrete and steel has worn out, but because it makes more economic sense to build a new building than to work with the existing one.
When it comes time, those ICF buildings create a lot more waste.
And if you eliminate durability then ICF has no advantages on that list.
im from oklahoma and even here with tornadoes icf still seems like a rough sell over a well built wood home that buys the entire simpson tie catalog.
My projects (all stick-framed) routinely test below 1.0 ACH50 without a lot of extra effort. They have tested at 0.1 CHC50 with some extra effort. So I don't buy the airtightness comparison.
I'll give you half a point for moisture/vapor control. It's quite easy to design and build a stick-framed home with excellent details for these, without having to use foam, but if you don't want to think about it then an ICF is easier.
To me, durability includes the ability to adapt the building over time; just as 100 and 200 year old buildings today need updating for modern life--a majority of my work has been doing that in one way or another for 30 years--homes built today will need to adapt to life 50 or 100 (or even 20) years from now, and that's much easier to do with a stick-framed building.
I have never priced an ICF home but I doubt once all is said and done that it's less expensive to build than a stick-framed home with equivalent quality.
Assuming each of your categories should be weighted equally, which I don't think is the case, that leaves stick framed at 1.5 points above ICF.
Add in the contribution to climate change and stick framed is up by 2.5 points. At least.
Plenty of wood built buildings in Europe that are many hundreds of years old and plenty of concrete buildings in the east of the US that need the basements replaced after 20 years. I guess there are many factors outside of building material that impact longevity.
I won't even give the half point for moisture control without pushing back. It can be hard to detail windows and doors and other openings in ICF so that they don't leak. "Outie" windows and doors are easy, but "innies" can be a nightmare. I've worked on houses that had flat PT window bucks used for the sill that leaked like crazy and the water went everywhere, not just straight down. Getting details right for moisture and vapor control is not too hard, but also not automatic for builders used to stick frame. The openings need to be designed for the proper details up front, not after the windows arrive on site.
A truly green home is a cave in a mountainside, just check for bears before taking up residence.
Except that would require open fires, which are horrible polluters. And not healthy for the occupants, which is (or should be) part of any construction, especially "green" building.
Blame the caveman for climate change !!
A cave in a mountainside in a Mediterranean climate then.
That takes care of most campfire emissions, then, but it still gets down around freezing occasionally along south of France and it's generally pretty cool in the winter. And still leaves the issue of indoor air quality due to dampness, which would vary among caves. ;-)
ICF advantages are regional and climate dependent. ICF performs better in desert or high-desert climates. The vast diurnal swings (90F daytime/50F nighttime in summer & 20F nighttime/60 daytime in winter) is where ICF performs best. While concrete doesn't have any measurable R-Value, what it does have is thermal mass (TM) and TM is very slow to change in temperature swings. So while most ICF comes in at R-23, it's "effective R-Value" has been scientifically shown to perform as high as R-50+ in areas that experience vast diurnal swings.
Borst Engineering and Construction has great online calculators and resources you can use. They have done scientific studies that showed ICF performed as high as R-60 in some climate areas.
https://www.borstengineeringconstruction.com/About-Us.html
http://www.borstengineeringconstruction.com/ICF_Performance_Calculator.html
As the ORNL DBMS study shows, it is the dynamic outdoor temp profile that determines the dynamic thermal mass temp (i.e., the temp of the ICF concrete core) for ICF. It is the real time difference between the building interior temp and the thermal mass temp (i.e., NOT the outdoor temp) that then determines the interior building heat transfer rate and hence the real time effective R-value for ICF.
Other key points to ICF:
Fire protection rating of 2-4 hours
No air infiltration through a solid ICF wall
No wall cavities for rodents, bugs, mold or rot
Better sound barrier to stop exterior noises - STC 51 Rating
Greater strength - ability to withstand 190 mph winds and airborne debris
ICF also doesn't have "thermal bridging" like a wood frame does. Each time there is a wood stud or header (especially around doors & windows which are stud heavy), that is a source of thermal bridging. Sure, exterior foam can help reduce that.
I built 2 homes and 2 garages out of ICF and I love the structures and how they perform. I live in a wildfire area and having a concrete wall plays a huge role in fire safety. Of course, I also have metal roofs, laminated windows, steel insulated doors, fireproof stucco on exterior walls, defensible space.
I've done my own experiments. It was in the mid 90's outside in the daytime, with temps dropping into 50Fs at night. I ran NO A/C but would open the windows at night and close them in the daytime. The house temps stayed at 70-73F. This was done for about 2 weeks to get a good baseline.
One needs to get a qualified ICF installer. This is not a DIY system and the best wood framer will still be the worst ICF installer. It takes someone who specializes in ICF. Pay attention to window and door details to keep it tight.
Jack,
"They have done scientific studies that showed ICF performed as high as R-60 in some climate areas."
If you are going to make a claim like that surely you should link to the studies, not to the About Us page of what appears to be a one man engineering firm.
You know what performs really well in areas with "vast diurnal swings"? Well-insulated houses.
How fast a house gains or loses heat is determined by the ratio of insulation to heat capacity. Increasing the proportion of insulation to heat capacity gives the same result whether you do it by increasing the insulation or increasing the heat capacity. However, if you do it by increasing the insulation you also get benefits on days when there aren't big diurnal swings, or when you don't switch between needing heating and needing cooling.
I think the big misunderstanding is the belief that conventional construction is somehow lacking in heat capacity. A typical 4-bedroom frame-construction house weighs on the order of 100,000 pounds. You're much better off thickening the insulation than adding unnecessary concrete.
I like Borst's calculators. But their ICF R value one has a major flaw. If I remember right, it does a simple 24 hour model based on a starting temp of the concrete. Without getting too deep into it, that assumption is where the model falls apart.
They also don't assume that the house has heat capacity other than the concrete in the wall.
I typically design double-stud walls with cellulose insulation. Very little thermal bridging and it's easy to get R-40 or higher when called for.
I can't recall the exact STC rating but I'd estimate it in the high 50s at least.
Cellulose-filled walls (or wood-fiber filled, or mineral wool-filled) also have excellent "thermal mass" and are very resistant to fire. And don't leave micro-plastics all over the site like ICFs do.
I agree that the diurnal temperature swings in deserts are the one place that "thermal mass" (in quotes; see DCcontrarian's arguments) may help enough to actually matter, but adding a little more R-value would be just as effective, and works all year, in every climate.