Sobotender, I am glad you were able to begin finding useful information here. I have been at the Geoexchange site for years, and more recently this site. I found that this site really gives you the details you need on all aspects of construction instead of just heat plant. My dream home which I will someday build will be, like yours, as sturdy as i can reasonably make it and as efficient as I can reasonably afford. I have come to find that ICF is the likely answer. With your desire for steel and strength, you will want to at least consider adding "Helix" to your concrete mix. You can find much about helix in ICF construction. It is twisted steel bits added to concrete to increase strength.

WOW! I would have never thought of adding something like that, I will definitely make a note to see if it can be added. Yeah I have never liked the idea of stick built and sheetrock homes. They have always seemed...cheap and poorly constructed to me. It's like building a house out of marzipan instead of concrete. Marzipan can be made to look really nice on the outside, but the inside is very fragile.

ICF is a great choice, especially if you live in a climate that has a diurnal temperature variation about the desired indoor temperature. We have DIY software that will accurately predict the effective R-value (which results from the thermal mass effect) that you can expect given your seasonal temperature variation.

Borst ICF Performance Software

Helix has gained much more industry acceptance and much wider use since we last discussed this product:

GBF Anyone used Helix?

Thank you very much for the links; they are very informative. I wouldn't know the first thing about using that calculator, though. There are many terms I do not recognise.

Please forgive my ignorance.

Have no worries, the associated software instructions explain all the software parameters in great detail. More importantly, the software parameter default values are already setup to run standard ICF (i.e., 2.5” interior EPS insulation + 6” concrete core + 2.5” exterior EPS insulation). There is likely little reason to change the concrete properties other than perhaps the thickness if you will be using something other than 6”. There is also likely little reason to change the insulation parameters unless you perhaps want to evaluate the effect of using more or less interior/exterior insulation thickness. Mostly, you just have to obtain and enter your seasonal temperature profile data. Or just don’t give this a second thought, as you will likely be pleasantly surprised with the actual ICF performance in any event.

While the dynamic thermal benefits and "effective R" of ICF is a useful data point it's 1% of the problem regarding the design of an OFF-GRID PASSIVE SOLAR house. It will require a much deeper simulation & analysis to get it right, and I'm dubious that ICF is the right solution here.

Given the potential for high and extended cooling loads, with off-grid passive solar it's useful to have both more thermal mass than an ICF offers, and thermal mass that isn't isolated from the interior by R10 foam (2.5" of EPS).

ICF is always by far the best choice for a passive solar design in all climates as it can provide much more thermal mass than any other option. Having a concrete slab floor and some masonry interior walls can also significantly increase interior thermal mass. What you don’t want for a passive solar design is 2x anything no matter what the R-value or wood/carpeted floors. Yes, you absolutely do have to accomplish an analysis to get it right...something like this as a minimum:

Sample Passive Solar Analysis

Yes, it can make a significant difference where the majority of the thermal mass resides...on the interior or exterior. Depending on your climate, you will likely be better off using more or less interior/exterior insulation thickness (i.e., changing the interior/exterior insulation ratio). The aforementioned software allows one to precisely evaluate what is best for any given seasonal temperature profile. If you live in a climate that has temperatures that always stay well above or well below the desired room temperature all day, you can further enhance ICF performance by getting even more exotic and placing hydronic tube to further regulate the concrete core temperature. TF Systems is by far the best for placing hydronic tube in ICF walls although it isn’t the best ICF for more general applications. You can’t just use simple “design rules of thumb” or typically available energy simulations to design a passive solar building even though there is no shortage of “experts” that still make good money doing so.

Well, ICF is the best for my situation. I did not see any instructions for that particular page, but I will look at it again, and see if I can fill it with accurate data so I can get a good analysis. I don't think I want to go as far as putting hydronics within my walls. Apparently radiant flooring is extremely expensive, I am sure that putting them in walls would be astronomical.

The first sheet of the instructions is a bookmarked Table of Contents (TOC) organized in columns that are the colors of our company logo...red, orange, blue and green. Red is for heating related projects. Orange is for passive solar projects. Blue is for water work projects. Green is for green building and miscellaneous items. The green column on the far right contains the bookmark to the specific instruction set for the aforementioned ICF Performance software (i.e., please see that it is 6 items down in this green column). Just click on this bookmark to be taken to this specific instruction set. The “Return to TOC” link at the bottom of each instruction set will take you back to the TOC again.

Hydronic radiant floor heating is often the lowest cost heating solution if you are constructing a new building and you will be pouring concrete floor slabs for other reasons. A concrete slab hydronic radiant emitter is always by far the most efficient hydronic radiant floor emitter that can be constructed. Hydronic radiant floor heating is always by far the most comfortable and most desirable heating solution. Yes, hydronic radiant floor heating can get very expensive and also very inefficient if you try to force it into an existing building. We only install hydronic radiant floor heating in new commercial or new residential buildings. Placing tube in ICF is no more expensive than placing tube in a slab. However, to the best of my knowledge, only the TF System vertical ICF approach (as compared to the more conventional horizontal ICF block approach) currently enables placing tube in ICF.

Okay I read over that PDF and I still have no idea how to add this information to the solver, because most of that data appears to be arbitrary. I'd rather either pay someone to fill in this stuff, or just use 'best building practices' for my area. There's no way that I will be able to know the indoor and outdoor moisture for any given time. All I can tell you is that where I plan to live in Texas it gets hot in the summer and not very cold (but OCCASIONALLY freezing) in the winter.

Sabotender,
Received your PM please feel free to contact me at www.futurestone.com. We have a strong installer in the Lago Vista area.
regards,
Cameron

Sabotender,
If you want to contact you include an email or phone number in your next PM.
Regards

Not to put too fine a spin on it, but I respectfully disagree that ICF "... can provide much more thermal mass than any other option." Both adobe and rammed earth provide much higher thermal mass, and the mass is not as thermally isolated from the interior space it's moderating. In an off-grid situation limiting the amount of power used for air conditioning is critical to living within your real-time usable PV output, and with R10 between the house interior and the thermal mass you'd have to put quite a bit of thermal mass elsewhere fully inside the thermal envelope of the house to moderate those peaks. The alternative is to severely limit the amount of window area to kill solar gain, which is then limits the wintertime uptake.

I'm trying to figure out the real costs of ICF construction. If there's any builders who can look at my proposed floorplan, along with the minor modifications I would like to it, and can give me a near-exact cost, please let me know. I want to take out a loan, and pool my various assets to fit the situation. I spoke with my loan officer today and she told me that this would be a good first step, since I know what I want, but I don't know if it is in my budget. Its silly to just ask for an arbitrary loan from a bank when it might be too much or too little than what I actually need.

Dana1, I don't think I would be happy with either adobe or rammed earth. I'm willing to deal with the energy efficiency that ICF provides. It seems that you keep talking about extreme cases, when I don't think my real life experience would be anywhere close to what you are talking about. I would like to focus on ICF at this point. As I am ready to get this project started ASAP.

Thermal mass works best when exposed to the interior. And note that in a well sealed/insulated house without much solar gain, you quickly reach the point of diminishing returns.

I just got back from a month in a hot climate, no AC, SCIP (foam between concrete) house. It has some E/W window solar gain (a very bad thing) and isn't well air sealed. So it was only cool until about 3pm. Put some exterior shades on the windows and air seal better and I see no reason for more mass than the 1.5" of interior concrete + 4" concrete/tile floor that it has. More night-time air flow through the house would also help considerably (an often overlooked element of passive thermal mass design in unbalanced weather). Just the R value of the interior air film restricts heat transfer out of the thermal mass. BTW, the place was off-grid but now also has utility power.

A friend built with ICF in the same area - he uses AC :-). He also built a well vented "over roof" - seems to work well, although more overhead foam might have been more cost effective. For E/W exterior walls, I'd use a highly reflective white paint (neither house does this). Perhaps a 50/50 mixture of barium sulfate and white paint.

For ICF wall cost estimating, you are probably looking at ~$15 +/-$3/sq ft of wall area - this includes window and door openings. Just figure out home many feet it is around your house and multiply that by the wall height then multiply by $15 to get a rough estimate of the cost to have an ICF wall installed. Factors that affect the cost are 1) thicker walls use more concrete which is a significant cost - most above grade ICF walls use 2.5" of EPS foam on either side of a 6" concrete core for a total thickness of 11", 2) more corners takes more time to install and costs more in labor - a perimeter wall with 4 corners costs less than a wall with 8 corners.

Posted By Sabotender on 26 Feb 2016 09:51 AM
Dana1, I don't think I would be happy with either adobe or rammed earth. I'm willing to deal with the energy efficiency that ICF provides. It seems that you keep talking about extreme cases, when I don't think my real life experience would be anywhere close to what you are talking about. I would like to focus on ICF at this point. As I am ready to get this project started ASAP.

Don't build it until you actually design it, and simulate it's thermal performance when there is NO mechanical cooling available. The happy-factor of higher thermal mass fully inside the thermal envelope will become apparent.

I'm curious. When I built in TX, which admittedly wasn't in this century, banks didn't lend to owner/builders. You needed a general contractor to get a construction loan; only he could make draws. I finessed it by hiring a builder as an adviser for a flat fee. Has that changed?

Owner/builder brings its own set of problems. Most construction loans have a duration of 6 months under the (wise) assumption that something is wrong if it drags on longer. Ditto for insurance. Nor will banks give you the full price of premium building systems under the (again wise) assumption that they won't get those premiums back in a foreclosure sale. Gotta say I'm surprised that a lender would entertain off-grid at all, although there are mortgages that will fund 120 percent of appraisal for Energy Star homes.

You might be better off if you kept your ambitions to yourself and got a conventional meter hookup. You don't have to use it, but in a resale you'll will definitely want to to sell off-grid as an a feature rather than a requirement.

If I had to guess, most off-grid homes are not bank financed, but I'd be curious to know if/how lenders would actually deal with it. That could be a whole other thread topic for sure!

The cost of bringing grid services can be pretty substantial in remote areas, and the cost of bringing municipal water completely prohibitive, which is why in lots of low density rural areas private wells & septic are the norm. On a recent PassiveHouse bin Maine they estimated after the fact that it probably would have been slightly cheaper to be off grid, after paying several 10s of thousands to have a power line brought in to a house designed for Net Zero Energy with grid tied solar. (Not sure if/how that project was financed.)