I am designing a 4600 sf residence in central Washington state, and my client is interested in ICF construction. Finding a structural engineer with meaningful ICF experience is proving difficult.
Have any of you worked with ICF, and if so, could I ask you how you arranged structural engineering?
Non Sequitur
Sep 29, 21 6:54 pm
I’ve got a few on the books at the moment. It’s really not more difficult than typical foundation, just need to get the re-bar and footings dimensions. Most of ICF design benchmarks are listed in my local building code too.
JonathanLivingston
Sep 29, 21 6:58 pm
I have used them and experienced no change from the structural engineer's perspective. The foam formwork replaces wood removable forms but the concrete, bar, foundation, and everything else is the same so the structural doesn't typically care. It might change shoring design depending on your site. The bigger challenge is a contractor willing to not throw a high price at it because it's different than their traditional construction method. Find a contractor early.
Non Sequitur
Sep 29, 21 7:02 pm
ICF is currently coming in way cheaper than typical poured concrete in my area. I even had a client swap out wood studs+sheathing (above grade) for it a few weeks back.
bowling_ball
Sep 29, 21 10:43 pm
Same NS. Doing ICF on a 50k SF building right now because it came in cheaper than wood. Crazy.
Chad Miller
Sep 30, 21 10:21 am
Same here in western Colorado. ICF is cheaper than wood or metal formed concrete.
JonathanLivingston
Sep 30, 21 3:23 pm
This is great to hear! The last project I used it on was ~ 2.5 years ago. I had a couple of smaller contractors bulk at it and priced it higher just because they were not familiar. Sounds like many have learned and ad
apted pricing accordingly.
Everyday Architect
Sep 29, 21 8:13 pm
The Washington Aggregates & Concrete Association's office utilized ICFs. Structural Engineer was DCI Engineers.
Not sure if they get into residential at the scale of your project, but it's at least a start.
Wood Guy
Sep 30, 21 9:34 am
I hope your client will reconsider building with materials that have such high levels of embodied carbon emissions, when there are many low-carbon ways to build safe homes. Just plain wasteful. Though if they want a 4600 sf house, they probably don't care about their impact on our environment.
Chad Miller
Sep 30, 21 10:40 am
Question Wood. Wouldn't a concrete foundation wall with exterior rigid EPS or XPS insulation be just as high as a ICF with EPS insulation?
An ICF is around 6.02 kgCO2e per square foot.
What assemblies have you found that reduce the embodied carbon for insulated concrete foundation walls?
Thanks!
Wood Guy
Sep 30, 21 11:08 am
Chad, I'm not rigid about it, I just try to choose lower-impact materials and assemblies when possible. I've used ICF on one foundation (https://www.finehomebuilding.com/2016/07/27/high-performance-foundation); that was because it was sponsored by Amvic and the builder wanted to form it himself, so it was a natural fit.
When I do full basements or crawlspaces I insulate the interior with polyiso foam (if unfinished) or just enough polyiso for condensation control with the rest in fluffy insulation (preferably cellulose, my go-to in most cases--https://www.finehomebuilding.com/project-guides/insulation/cellulose-perfect-insulation). In most cases the thermal mass of the concrete does not help the performance of foundations, ICF marketing aside, so the total R-value is what matters. Putting the insulation on the interior means the exterior doesn't have to be parge-coated.
To answer your first question, whenever possible I don't use foam above grade; I use double-stud walls with cellulose or sometimes Larson-truss type systems. When I do use foam I encourage clients and builders to use reclaimed foam, salvaged from commercial roofs. Or I use rigid wood fiber (https://www.finehomebuilding.com/project-guides/insulation/284-in-favor-of-wood-fiber-insulation).
There are no perfect solutions but there are optimized solutions for various conditions, and I try to find the best for each situation.
I realize this looks like I'm showing off or hawking my articles, which isn't the case. I'm just trying to show that I've put a lot of thought and research into this kind of topic.
Chad Miller
Sep 30, 21 2:09 pm
Thanks for all the great info! Don't worry, I know you're not showing off or hawking your articles. You're just that good. ;)
Wood Guy
Sep 30, 21 3:20 pm
Haha, I don't know about that but it does build confidence with clients when I can cite my own articles. With builders it can go either way.
justavisual
Oct 1, 21 12:55 pm
Wood fiber insulation all the way. We never use foam unless absolutely necessary. On another note we heard a few months ago that CLT is now 2-2,5x as expensive as 1 year ago. Hoping the prices come down again soon...!!
Almosthip
Sep 30, 21 10:42 am
I worked in a Canadian Structural Engineering firm and we did lots of IFC foundations and structural walls. The design is more about design of concrete and rebar placement within the forms. You need an installer that can pour the concrete correctly, and vibrate the forms or you get voids within the forms that you cant really see.
whistler
Sep 30, 21 8:05 pm
Almosthip has it right!, nothing difficult and given the way our regional building codes are going it really helps on the overall energy modelling. Concrete mix is critical particularly as you get into taller walls to ensure the concrete is distributed throughout ( patching is a bitch ). Connection to framing is pretty straightforward but if trades are experienced you should be good. Most of the supply companies we deal with actually do a fully modelled shop drawing of all the connections / layout etc makes it very easy for even for "the dumbest tool in the shed"!
jeiffert
Oct 1, 21 6:49 pm
Thanks for the comments everyone.
I should have mentioned that in addition to the foundation walls, my client is interested in using ICF for above-grade walls and main floor structure as well. (lower floor will be slab on grade).
I wouldn't have nearly as much concern about engineering coordination if the use of ICF was restricted to just the foundation walls.
I am designing a 4600 sf residence in central Washington state, and my client is interested in ICF construction. Finding a structural engineer with meaningful ICF experience is proving difficult.
Have any of you worked with ICF, and if so, could I ask you how you arranged structural engineering?
I’ve got a few on the books at the moment. It’s really not more difficult than typical foundation, just need to get the re-bar and footings dimensions. Most of ICF design benchmarks are listed in my local building code too.
I have used them and experienced no change from the structural engineer's perspective. The foam formwork replaces wood removable forms but the concrete, bar, foundation, and everything else is the same so the structural doesn't typically care. It might change shoring design depending on your site. The bigger challenge is a contractor willing to not throw a high price at it because it's different than their traditional construction method. Find a contractor early.
ICF is currently coming in way cheaper than typical poured concrete in my area. I even had a client swap out wood studs+sheathing (above grade) for it a few weeks back.
Same NS. Doing ICF on a 50k SF building right now because it came in cheaper than wood. Crazy.
Same here in western Colorado. ICF is cheaper than wood or metal formed concrete.
This is great to hear! The last project I used it on was ~ 2.5 years ago. I had a couple of smaller contractors bulk at it and priced it higher just because they were not familiar. Sounds like many have learned and ad apted pricing accordingly.
The Washington Aggregates & Concrete Association's office utilized ICFs. Structural Engineer was DCI Engineers.
https://www.washingtonconcrete...
Not sure if they get into residential at the scale of your project, but it's at least a start.
I hope your client will reconsider building with materials that have such high levels of embodied carbon emissions, when there are many low-carbon ways to build safe homes. Just plain wasteful. Though if they want a 4600 sf house, they probably don't care about their impact on our environment.
Question Wood. Wouldn't a concrete foundation wall with exterior rigid EPS or XPS insulation be just as high as a ICF with EPS insulation?
An ICF is around 6.02 kgCO2e per square foot.
What assemblies have you found that reduce the embodied carbon for insulated concrete foundation walls?
Thanks!
Chad, I'm not rigid about it, I just try to choose lower-impact materials and assemblies when possible. I've used ICF on one foundation (https://www.finehomebuilding.com/2016/07/27/high-performance-foundation); that was because it was sponsored by Amvic and the builder wanted to form it himself, so it was a natural fit.
When I do full basements or crawlspaces I insulate the interior with polyiso foam (if unfinished) or just enough polyiso for condensation control with the rest in fluffy insulation (preferably cellulose, my go-to in most cases--https://www.finehomebuilding.com/project-guides/insulation/cellulose-perfect-insulation). In most cases the thermal mass of the concrete does not help the performance of foundations, ICF marketing aside, so the total R-value is what matters. Putting the insulation on the interior means the exterior doesn't have to be parge-coated.
To answer your first question, whenever possible I don't use foam above grade; I use double-stud walls with cellulose or sometimes Larson-truss type systems. When I do use foam I encourage clients and builders to use reclaimed foam, salvaged from commercial roofs. Or I use rigid wood fiber (https://www.finehomebuilding.com/project-guides/insulation/284-in-favor-of-wood-fiber-insulation).
For foundations I prefer slab-on-grade homes, include concrete-free slabs (https://www.greenbuildingadvisor.com/article/minimizing-concrete-in-a-slab-on-grade-home).
Or build on piers--in my spare time I'm building an addition for my MIL on helical metal piers (lead image here: https://www.greenbuildingadvisor.com/article/all-about-helical-piles).
There are no perfect solutions but there are optimized solutions for various conditions, and I try to find the best for each situation.
I realize this looks like I'm showing off or hawking my articles, which isn't the case. I'm just trying to show that I've put a lot of thought and research into this kind of topic.
Thanks for all the great info! Don't worry, I know you're not showing off or hawking your articles. You're just that good. ;)
Haha, I don't know about that but it does build confidence with clients when I can cite my own articles. With builders it can go either way.
Wood fiber insulation all the way. We never use foam unless absolutely necessary. On another note we heard a few months ago that CLT is now 2-2,5x as expensive as 1 year ago. Hoping the prices come down again soon...!!
I worked in a Canadian Structural Engineering firm and we did lots of IFC foundations and structural walls. The design is more about design of concrete and rebar placement within the forms. You need an installer that can pour the concrete correctly, and vibrate the forms or you get voids within the forms that you cant really see.
Almosthip has it right!, nothing difficult and given the way our regional building codes are going it really helps on the overall energy modelling. Concrete mix is critical particularly as you get into taller walls to ensure the concrete is distributed throughout ( patching is a bitch ). Connection to framing is pretty straightforward but if trades are experienced you should be good. Most of the supply companies we deal with actually do a fully modelled shop drawing of all the connections / layout etc makes it very easy for even for "the dumbest tool in the shed"!
Thanks for the comments everyone.
I should have mentioned that in addition to the foundation walls, my client is interested in using ICF for above-grade walls and main floor structure as well. (lower floor will be slab on grade).
I wouldn't have nearly as much concern about engineering coordination if the use of ICF was restricted to just the foundation walls.