Adding insulation on the inside of ICFs
eyremountllc
| Posted in Green Products and Materials on
A while back when I started researching ICFs I saw a manufacturer that made an ICF that you can add insulation (eps) on the inside of the forms. I didn’t think at the time that I would consider that but now I am. I can’t remember the name of that company does anyone know?
Thanks
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
i don't know the name of the co, but i think you are making a good call to r them up. i am not impressed w/ the r-value of icf's. that said, is this below grade? just curious. i see them as way to spendy to use above grade, unless there is a real need for them. good luck. j
Roger,
I agree with J. Klingel
I don't understand why you are so attracted to ICF
It seems like you are gearing up to design and build your FIRST Spec house.
There is a lot more to it than just stacking up a bunch of Leggo Blocks.
Every ICF project that I have seen has taken MUCH longer to construct than Stick built.
And as JK points out the R-Value of ICF is not-so-great.
You may get more tornado tolerant walls..but what about the roof?
There are other ways to achieve good airtightness.
There is little/no benefit from thermal mass unless it is on the inside of the thermal control layer.
Concrete is not-so-green
I don't get it.
Thanks for the feedbacks, John and John.
This is actually the second spec house we are building but I am always the first one to admit our lack of experience. I think this fact may also explain our reasoning. When we started researching this project, four construction methods were considered, stick-built, modular, SIPs and ICFs. In the beginning, we leaned heavily toward modular because of the cost and time savings. However, we were not satisfactorily convinced that we can get the house sealed to Passive House standard when most of the air layer is already behind drywalls, when I can actually start working on it. Plus, modular also means some design constraints.
I've never liked stick built for a number of reasons. First, in our limited experience renovating houses and our last spec home, I've never been satisfied with the quality of conventional stick framing. This may just be because I don't know really good framers. To me, stick framing leaves too many places for mistakes that requires constant supervision. I guess I feel you really need to have good people to do stick framing well. So this is a quality of labor issue. Secondly, highly skilled labor is very expensive. We are in the D.C. area and that is certainly true. Thirdly, our own lack of expertise. Having spent years reviewing legal and financial documents for a living, I don't have the expertise to know for sure how things should really look like when they are being framed. I have people I trust but unless I know how to do things myself I can never be sure if they are doing things correctly. I respect the years, decades of experience some of you have but I can't let that deficiency slow me down. So, my solution is to simplify things.
SIPs is another very attractive option but the quotes I am getting are coming in more expensive than the ICFs. I think this again is due to the fact that a good SIPs structure requires very skilled labor. I may be making some misguided assumptions here but it does seem to me that an ICFs building requires labor with significant less skill. I am not saying that I am going to pick up guys at Home Depot and have them put up my lego house for me but simply that it's harder to mess up the structure, the air-tightness and just generally fewer places to mess up. With that said, I am planning to use a SIPs roof and still am considering to use it for everything above ground.
In terms of cost, the ICF forms, rebars and other accessories cost the same whether I am building here D.C. or say in Detroit, the concrete prices will differ some but difference in labor costs will be the most significant. Obviously, real estate is a local business, housing prices are also very different. So, an ICF house may be prohibitively expensive to build in some places due to material costs may not be in some areas. To me, if all the other material costs are about equal but I can command a much higher price simply because of my house's specific location, the most important thing for me to do it to keep labor costs as low as I can. Let me know if that makes sense.
I understand the R-value is not great with ICFs, I really am having difficulties with this. I love the strength of concrete but the high conductivity really bugs me. Hence, the original question posted here and my crazy idea about adding perlite to the concrete mix.
I have to disagree that concrete is not-so-green. I think it builds a longer lasting structure and much of that concrete can be recycled.
ICF construction I feel requires higher caliber labor than stick framing.
Keeping ICF walls plumb and precision of window rough opening requires an experiences crew.
Keep in mind that very heavy liquid concrete is poured into light foam forms that are dry stacked.
If the bracing is not sufficient blowouts at corners and rough openings can happen.
It is also much more difficult to adjust window/door openings in the field that may arise due to design changes or errors made during the construction process.
Roger I've seen a couple examples of ICF form that increases the thickness of the insulation to the OUTSIDE of the form. It makes less sense to add further insulation to the inside because the floor system would interrupt that added depth.
Roger,
Is it the aesthetics, the structure or the airtightness quality of stick frame that does not satisfy you?
How do you plan to construct the interior walls? ICF or stick frame?
Concrete is the second most used substance on earth, after water. Because of that and because of it's very high embodied energy and global warming contribution, it is one of the most ecologically impactful materials.
Petro-chemical foam is a close second in its enviromental impacts, and both materials have significant negative human health effects from their manufacture.
Durability alone does not make a material or technique "green". A long-lasting problem is not "green". In fact, it's arguable that the most green materials are those that quickly decompose back into the environment into non-toxic constituents.
The primary advantage of concrete in a thermal envelope is its dymanic thermal mass effect, but placing it between two layers of petro-chemical foam almost completely eliminates that benefit. Such a foam sandwich also leaves both the outer and inner skins vulnerable to exposure issues, including insects, UV, physical damage and fire. This makes ICFs the worst possible combination of foam and concrete.
And, as J Chestnut points out, anything formed with as unforgiving a substance as concrete requries a much higher level of skill, care and diligence than a structure made from an easily manipulable material like small-dimension lumber.
It doesn't appear that you're aiming for quality, but rather for quick and cheap and for maximizing your unearned income (i.e. profit). That's a terribly un-"green" approach to creating shelter.
Thanks. J.C. , your suggestions make sense. Like I said, I might be misguided about ICFs due to my inexperience.
J.B. I think stick framing is necessary at least on the interior. I think I mischaraterized it. What I mean is that I can't seem to find good framing contractors.
Robert: I aim for quality. However, I am an investor not a craftsman. It is true, I am trying to maximize profits but I am not looking to sacrifice quality. I admit lack of experience as a builder which I hope to accumulate over time. In the meantime I am simply trying to build a high quality house using the simplest techniques and methodologies. I mean, what is wrong with finding a way to build a high quality house inexpensively? Isn't that a worthy objective that may be applied to low/mid/high income housing? Some of these efforts may be a fool's errand but at least I am willing to spend the time to look for it. So please DO NOT accuse me of trying to make a quick buck because that is very discouraging.
Now, I got those responses out of the way. Please try to stick with my original question.
Thanks
Investors should play on Wall Street, manipulating financial instruments at the expense of the main street economy and then getting bailed out by taxpayer money.
Builders (that is craftspeople who actually create something of value) should build houses.
There are building technologies which might appear inexpensive to the investor who's concerned only about maximizing financial return (through unearned income, illegitimate by definition) and values nothing that doesn't have a price, but are extremely costly to the social and environmental economies.
The goal of "green" building is to create shelter with the lowest possible cost to the earth and its living creatures. Nothing that you're considering fits that description. The one system that has potential to meet those goals, you've rejected out of hand.
Far too many "greenwash" builders (I mean developers) put profit before ecology, sustainability, social and cultural values, ethics and health.
Roger, I'd like to gently suggest that if you are an investor who wishes to optimize profit with an environmentally responsible product you avoid marginal building systems such as ICF's altogether. There are very good reasons, both environmental and economic, that wood-framed houses have been the norm over most of this country for most of its history. Framing lumber is cheap, plentiful, and renewable: it acts as a very effective long-term carbon sink, and the skills to work it are widely available. The finished product can be precisely tuned to the widest variety of local climate conditions. Find yourself a good framer. It's not that hard.
Thanks James. I will take your suggestion to heart.