Concrete home - options and thoughts
Last Post 16 Aug 2022 03:54 PM by elic. 13 Replies.
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elicUser is Offline
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28 Jun 2022 05:29 PM
We are in the very early phase of designing and building a new home. We are currently interviewing architects.

If feasible, I would very much like to build a concrete home, including the roof. I know ICF would be the default option for many, but we would prefer to build without the EPS (don't intend to use spray foam either).

Planning on continuous exterior insulation and mineral wool seems to make the most sense to me.

I don't know of anyone that has used them, but would consider spider ties. Would there be a benefit vs traditional forms?

How much of an issue are cold joints above grade? Should any attempt be made to trying to get a mono-pour?

For the roof I am not familiar with different systems that may be available. If we used something like litedeck, can the EPS foam be removed and sold/re-used? Any other recommended systems for floors and roof?

We would like to do radiant heating and ideally cooling (absorptive cooling). Hopefully, with a very tight well insulated house, very few BTUs should be required for heating or cooling, minimizing the risk of condensation. Has anyone used or seen pex used in the walls of a concrete home in addition to the floor?
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29 Jun 2022 12:36 PM
We have ICF with concrete heated floors and due to the mass we don't need heat or ac for 1/3 of the year. We do use an attic fan when the temp and humidity are right to help bridge the gap between winter and summer also here in Michigan.

Not sure why you don't want EPS but are fine with concrete....if it is a CO2 think you are trapping the CO2 in the eps and concrete....I know the process uses CO2 but you get that loose back with the reduced heating and AC costs over the expected 100 year life of the building.

I did weave pex in 2 of our walls for what you are thinking but I have never hooked it up. We have a brick ledge on half of the house in the ICF and I was thinking to reduce the direct thermal bridge from the exposed brick I could pump water to control the temp change of the thermal bridge.

In a super insulated house the heated floors don't need to get that hot or cold to control the temp and you won't feel that much heat. My last house was R19 and the floors were toasty warm but we keep the therm at 73 year around, this house is R30

We cool our floors with well water in the summer and run the water through the floors before going to its point of use. So in the summer when the therm stage 1 calls for cooling it turns on a sprinkler and runs the 50 degree water through the floors to cool the house. When it is hot the grass usually needs water.

Good Luck with your project.
"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
newbostonconstUser is Offline
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29 Jun 2022 12:41 PM
Most houses have cold joints between pours, I don't see a major issue. I would just do a truss roof with energy heal trusses. Our floor cooling does get condensation on the pipes only but if you wrap them with pipe insulation that is taken care of. We keep our humidity at 50% year around to minimize expansion and contraction of wood and drywall cracks and for allergies.
"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
elicUser is Offline
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29 Jun 2022 02:02 PM
@newbostonconst



In regards to the EPS, my concerns

- any off-gassing

- termites (if any contact between EPS and wood)

- fire



We would like a stone house, so not sure how we will manage that with exterior insulation and avoiding thermal bridging. We want real stone, not structural, but not a 1" veneer either. It may require a double wall foundation, with the outer one being CMUs.



We do plan on having an ERV and humidifier and dehumidifier. Not sure how much demand there would be on the heating/cooling system. We have never lived in a house like this (tight and well insulated), and not sure what a comfortable temperature is when the structure itself is well thermally regulated.I would imagine a steady year round 70-72F and ~50% humidity would be good



For the roof, we really do want concrete. If we are having concrete walls and floors, we want to know the roof is just as strong. Certainly an engineer can help guide us here, but being less common for residential construction I hope to do some of my own homework and have a starting point.
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29 Jun 2022 02:18 PM
Elic, I donate my time to assisting homeowners that want to build with alternative building technology. I may be able to help you. Send me an email about your project.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period . 334 826-3979
newbostonconstUser is Offline
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29 Jun 2022 03:02 PM
I said half our brick ledge was attached to the ICF wall allowing brick temp to be transferred directly into the center of the ICF wall...well the second half of the brick ledge I poured a second brick ledge directly down to the house footing at 4 feet deep. This was to stop the brick from being thermally linked to the wall.

Where are you wanting to build?

Wondering if you could do pre stressed concrete to cut cost on the roof cement and still have the strength. We did an over under garage using pre stressed and it was very cost effective with strength to hold up vehicles.

https://www.google.com/search?q=prestressed+concrete+roof+residential&tbm=isch&ved=2ahUKEwjGiJj39tL4AhULkGoFHS2tAe0Q2-cCegQIABAA&oq=prestressed+concrete+roof+residential&gs_lcp=CgNpbWcQAzoECCMQJzoECAAQHlCiBliSJWDsJ2gAcAB4AIABXYgB1AiSAQIxM5gBAKABAaoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=YGm8YsbYA4ugqtsPrdqG6A4

https://www.google.com/search?q=over+under+garage&sxsrf=ALiCzsbKihm4QMxfiP-rcFraYwNEPam-PA:1656514828382&tbm=isch&source=iu&ictx=1&vet=1&fir=vI_8Pg_5ttr4kM%252C43GMfp6qcbqBHM%252C_%253BY-CtD1GQXZnD5M%252CG26AjllPWbKaHM%252C_%253BY-fSUJuJMCcbGM%252C43GMfp6qcbqBHM%252C_%253B5lL3XKt4SJvz7M%252Couhc7-PbHqUCeM%252C_%253BC1nL3iqj1588uM%252CNUWPZ5kQLHcORM%252C_%253BaS6h_EyMz2VKOM%252C0819_2PNWqmWVM%252C_%253BCWqiQJGLU4loKM%252CNUWPZ5kQLHcORM%252C_%253BAVsMN-H2ElT_zM%252Cmrr7NVnQ6WXQOM%252C_%253Bn4Wn_q6mX__IIM%252CCbbwpk54hTYzXM%252C_%253B8gj4D65ex0RiHM%252COIos9GfjP-hNdM%252C_%253BLmzedAQUvS9IIM%252CJwteON3aDmCriM%252C_%253B44Sx1SDdOo1JAM%252C43GMfp6qcbqBHM%252C_%253Bt4_NSiNr6f2xUM%252CrH2T3rhI5NRiPM%252C_&usg=AI4_-kR4-CGlQMr8OTtFJKm0Sfdvf_rguw&sa=X&ved=2ahUKEwj6_KPP9tL4AhUHD0QIHQ3JBTkQ9QF6BAgDEAE#imgrc=C1nL3iqj1588uM
"Never argue with an idiot. They will only bring you down to their level and beat you with experience." George Carlins
sailawayrbUser is Offline
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01 Jul 2022 12:50 AM
I recalled a person who frequented this site in the past, ICFBOUND, did something like you are considering...double wall, exterior stone/CMU wall, something lik3 24" thick rockwool in cavity and interior standard stud wall. I found this post that briefly described it:

https://www.greenbuildingtalk.com/Forums/tabid/53/afv/topic/aff/4/aft/85062/afpg/2/Default.aspx

If you Google "green building talk" with ICFBOUND and other descriptive, you might find more details about it. This person moved to Australia or New Zealand several years ago to avoid future of living under Taliban rule and like many people, no longer visits this site anymore.

Our home is ICF but has many of the other features you seek and it is described here with links to some of the details:

https://www.greenbuildingtalk.com/Forums/tabid/53/aff/12/aft/86467/afv/topic/afpg/1/Default.aspx
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
elicUser is Offline
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01 Jul 2022 06:12 PM
@Alton, TY. Look for an email from my gmail account



@newboston I am familiar with both prestressed and over-under garages. Prestressed may be a good way to go. For the roof there is just something that FEELS right about the whole building being one unit



@sailawaybr. Thanks, I have looked but haven't found anyone else talking about a double foundation wall. Not sure how else to support a heavy cladding with continuous exterior insulation.
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01 Jul 2022 08:48 PM
You just use an engineered footing to support your wall...the footing dimensions and rebar schedule are based on your soil and wall loading numbers. The footing for our ICF home was 1' thick and 4' wide...which was designed to handle a future second story and 9.2 seismic event.
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
AltonUser is Offline
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02 Jul 2022 03:48 PM
EPS does outgas pentane, especially right after it is made into beads. Most of the gas is gone by initial ageing. Pentane smells like gasoline. I have never detected the odor while working very closely with EPS on site. And I have not heard any of my crews complain about a gasoline odor.

Concrete will bond well with the EPS in the LiteDeck forms. Almost all of the EPS could be scraped away after the concrete roof reaches sufficient strength. But that would be a lot of work. A shop vac will be needed to clean up the mess since the EPS will break into a lot of beads and dust.
Drywall can be attached to the steel ribs in the Litedeck. Drywall should help curtail any residual pentane gas in the EPS. An ERV or HRV that brings in fresh air will reduce the concentration of pentane.

Only a few areas in USA will accept EPS for recycling. The metal ribs in LiteDeck forms can be recycled. I mention this because removing the EPS will dislodge the metal ribs.

Some roof systems that include the EPS as insulation require it to be covered with a cement based coat such as gunite, shotcrete, or mortar? Some of these systems can span up to 28', depending upon the snow load.

There are building systems that use EPS in such a way that outgassing, fire, and termites are not a problem.
Residential Designer & Construction Technology Consultant -- E-mail: Alton at Auburn dot Edu Use email format with @ and period . 334 826-3979
elicUser is Offline
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02 Jul 2022 04:58 PM
I realize some of my concerns about ICF may be unwarranted. In fact, we may end up going that way if finances force us to. It would not be our preferred path though.
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06 Jul 2022 02:40 PM
Im clearly not the first person to consider a second foundation wall:

https://www.icfmag.com/wp-content/uploads/2020/02/2006-04-Foolproof-Waterproofing-05.jpg

I found this a helpful discussion
ICF Ledge Forms.



Trying to find info on using something like ecospan for a sloped concrete roof
kenmceUser is Offline
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05 Aug 2022 09:38 PM
> I would very much like to build a concrete home, including the roof. I know ICF would be the default option for many, but >we would prefer to build without the EPS (don't intend to use spray foam either).

If you want the masonry, but not the foam, why not skip the ICF and build a regular masonry wall?
elicUser is Offline
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16 Aug 2022 03:54 PM
That is the plan. We plan/want to use concrete forms to do the entire outside walls, roof and floors out of concrete. Using a fluid applied over the structure, then continuous exterior rockwool insulation over the structure of the house, then exterior wall and probably a metal roof.
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