My wife and I want to build our own home within the next few years. We'd like to take on as little debt as possible considering the way the economy is headed. We're both experienced builders, her Dad is a licensed electrician and plumber, and we know lots of good folks to do work we can't or don't want to do. We both have our own businesses so we have fairly flexible schedules.

We're located in Vermont. We won't finalize our design until we purchase land, but our preliminary designs usually work out to be around 20x30 and two stories. Basic gable standing-seam roof. Probably a frost protected slab. Just enough space for us and hopefully two children. We can add a barn and more space later as we can afford it. We want to take as much advantage of passive solar as possible.

I haven't run all the numbers yet. Stick-built would likely be 2x6 or offset 2x4 walls. ICF would likely be Durisol. I know the ICF is going to be more, but it would also save money in the long run. Does anyone have some opinions and/or experience to offer?

Well I'm all eyes on this thread! I'm not 100% sold on ICF as to cost versus ROI. I do not want to spend a fortune on building and having to wait 25 years for the pay back. I don't have that much time left and the kids already have there share! LOL

John

The payback/benefits with ICFs start immediately upon completion. The only time that time applies to the payback is if you do not get financing or give a mortgage on your home. That is because if you make payments on your home you will pay 3-5% larger payment to the mortgage holder, because the all ICF house will cost you 3-5% more than a minimum code wood framed house, this will remain a constant for the life of your mortgage. Your utility cost will be much less than a conventionally framed home and I will bet energy costs will go up. So the cost of ownership of an ICF home will be little if any additional now, and in the future will likely be less, to live in a safer, quieter more comfortable home.

ICFs are not as well suited for the DIYer as there is no fixes to a wall placed incorrectly. A DIYer is better off hiring out the shell of the house, and then taking it from there. A large advantage of ICF for the DIYer is that they can take their time installing exterior cladding, siding, doors and windows because the ICF walls will not be damage by the weather like other framing methods. I had one customer that took two years to side.

Vermonter,

I do agree with ICFconstruction, but would like to add a few things. He is right that ICF for a DIYer is difficult as it is very difficult to correct wall once poured, but if you have an experience distributer with bracing and technical knowledge, its not overly difficult. That said, I often feel its easier for everyone to hire an ICF professional if its possible.

If I were you I would check to see if there is an ICF distributer and/or ICF installer nearby to assist you with advice. I did a google search and came up with Vermont Insulated Concrete Forms in Waterbury, VT. I would argue that its more important to find a local distributer and/or installer to help you with your project, rather than settling on the block first. If there is a durisol distributer nearby then great, if not, I would consider an ICF block that has better support in your area. Also, look at where the block is made, as freight could be an issue.

As for the rest, I think that ICFconstruction is pretty much correct.

renangle

renangle

The 3-5% figure is factoring in reduced labor for ICF, correct? So it's likely not accurate when comparing for DIY, especially if the ICF needs to be done by someone else.

If we go ICF we're pretty set on the Durisol. I know the polywhatever is supposed to be fine but we don't want to live in a styrofoam house, and the Durisol is much more stable and durable, and keeps more thermal mass within the insulation. Also seems easier to DIY since the blocks are unlikely to blow out.

We also have a local concrete company that does insulated pre-cast. Might be worth getting a quote from them on the shell. Although then we'd be needing lots of foam-board on the outside for proper insulation.

IF you are just going to use the ICF and then drywall on top, fine, but in my situation where I have to heat the house for seven months and use AC for 6 to 8 weeks, the rest of the time the windows are open, I don't see an advantage.

I have a super insulated passive solar home ALL stick built, basement is PWF. The next one I build will have very little passive solar capability to heat up a thermal mass that the ICF has, if I had the solar passive capability I would consider it more closely. From a lot of the reading I have done in the last few months I have to admit I have a concern with humidity control. I do have an HRV that runs pretty much most of the year, except when the window's are open in my stick built home. There have been a lot of threads and questions about breathability (drying) of the exterior walls and at the moment I'm very confused as to what to do, building code here is 6 mil and you must have one! That is not what you do with an ICF wall?

I'm still not convinced that I would go ICF even for the foundation (basement) but then again I'm not sure yet, building on slab I might!

John

Posted By Vermonter on 26 Aug 2010 01:42 AM
My wife and I want to build our own home within the next few years. We'd like to take on as little debt as possible considering the way the economy is headed. We're both experienced builders, her Dad is a licensed electrician and plumber, and we know lots of good folks to do work we can't or don't want to do. We both have our own businesses so we have fairly flexible schedules.

We're located in Vermont. We won't finalize our design until we purchase land, but our preliminary designs usually work out to be around 20x30 and two stories. Basic gable standing-seam roof. Probably a frost protected slab. Just enough space for us and hopefully two children. We can add a barn and more space later as we can afford it. We want to take as much advantage of passive solar as possible.

I haven't run all the numbers yet. Stick-built would likely be 2x6 or offset 2x4 walls. ICF would likely be Durisol. I know the ICF is going to be more, but it would also save money in the long run. Does anyone have some opinions and/or experience to offer?

I'm certainly no expert, but from my own research I'd guess that SIPs are better-suited to DIY than either ICF or stick framing.  I really wanted to build a SIP house but couldn't work it into the budget.  The biggest problem for me was that our builder had never worked with SIPs before.  The general rule is that the materials are more expensive, but because they go up so quickly, the labor is significantly less.  Our builder wasn't comfortable committing to any savings in labor since he hadn't worked with them before.  We were on a tight budget, so we couldn't risk getting into a bind if things didn't work out as planned. 

If you do go the stick-built route, take a look back at some of my old posts.  We tried to build in as much thermal break & air sealing as possible, & I think it's working.  We've had a horrible string of hot, humid days this summer - temps consistently in the 90's with humidity well above 70%.  The windows have been closed & the AC on most of the summer, but the biggest utility bill we got was around $100.  That was also while we were still moving in, running the dishwasher constantly, doing tons of laundry from stuff that had been packed away, etc.  

"it (ICF) would also save money in the long run". Not counting windows or roof systems, your statement (cost savings) depends on: the (actual) R value of your wall system, the infiltartion rate of your wall and the amount of thermal transfer through studs etc. ICFS and SIPS are both excellent at cutting down on infiltration because they are inherently solid, and both have little thermal transfer (excepting the concrete of course) . The R value of each system varies with the amount and type of foam used. The "heat storage" value of ICFs is questionable since the storage - concrete- is insulated from the living space, and is typically only insulated from ambient air (outsided) by R8 or 12 foam, so while the R-8 or 12 on the inside allows some heat to get to the concrete, the R-8 or 12 on the outside allows a corresponding amount of cooling. SIPS are of course typically available in a wide variety of thicknesses and materials. I'd suggest for a house that is very efficient heat-wise you'd want to be looking for an R30-R35 wall, thermally broken and very tight. A double stud system can be built with few thermal breaks and allows you to easily adjust the R value by increasing the cavity depths. One builder I know has used 1-1/2" foam panels between the two stud walls to help decrease the infiltration rate. I prefer the outsulation method; both are good.

The lowest cost will probably be the stick framed wall - either double stud or stud with outsulation (foam outside the sheathing). The difficulty is usually in keeping the infiltration rate low, but thats exactly where the DIY or concientious builder can make a substantial difference in paying attention to details that will affect infiltration and therefore overall performance. Tight framing, caulking, taping the joints of ZIP sheathing and taping the seams of the outsulation can yield the results you need.

SIPS, or ICFs installed by professionals should be priced to be as competitive as possible to stick framing, and given that the quality and longevity of the wall is dependent on a good installation, probably very worthwhile.

With whatever system you choose, get a blower door test done prior to installing loose or batt insulation and definitely before drywall and take the time and care to find and fix the leaks. Another testing method option is the use of a theater type fog machine which will send clouds of water vapor through any leaks.

Good luck & let us know what you decide and how it comes out!
Bob

Vermonter,

You are in very good position, as you and your wife are both experienced builders and you have family/friends in the trades. Plus with you planning on building in a few years, you have time on your side to research, plan, and get estimates for everything, whether going ICF or stick built route. Brainstorm and write down everything that is important to you and your family, that you would like in your house... example; low heating/cooling bills, low/no maintenance on the exterior, DIY friendly, low initial cost AND low operating cost, greatest return on investment, radiant floor heat, geo-thermal HVAC, quality and energy efficient windows and doors that don't have air leaks or condensation forming on the inside during winter, etc..
Once you have your "must have list", you can figure out how to get there making a list for ICF and another for stickframing. Determine what you are able to do yourself, or with the help of others, get some estimates for material, also estimates for the areas that you need to subcontract out. There will probably be some give and take, as with myself, my wants sometimes take precedence over my needs.

You are on the right track with either 2x6 or 2x4 staggered studs if you decide to stick build. Tight construction and proper air sealing is very important, also consider at least 1" thick XPS or EPS foam board on the exterior of the wood framing, taping and sealing the seams... from the foundation to the trusses/rafters. This will greatly reduce the heat loss through thermal bridging in the wood framing, also making the walls air tight. For insulation, 1" or so of closed cell spray foam between the studs with the balance filled with spray in cellulose is a cost effective and energy efficient way to go. Spray foam the rim joist with closed cell spray foam... also spray foam 1" or so of closed cell in the attic on top of the drywalled ceiling and over the top plates of the exterior walls to air seal, you can then blow-in cellulose over the spray foam to any depth you want, to achieve your desired R-value.

If you build this way, I'm not sure how much different your heating & cooling bills would be in your climate compared to going with ICF for the exterior walls; the windows/doors, attic insulation being the same... something that you could do is consult with an energy auditor. They may be able to run either REScheck or manual J calculations for both. From there, you could decide which route you want to go, maybe try windows with different U-values, solar heat gain, etc. to see if there is a drastic enough savings in heating/cooling to justify the increase in up-front cost with any option.

Jere

The thermal mass benefits of ICF are going to be much lower in ~8000-heating degree-day VT than it would be in more moderate climes. Don't count on it outperforming it's ASTM C 518 R value by much in winter, but it will in summer. The highest R-value offered by Durisol is R28, which is what you'd get out of a 2x6" studwall with low density spray cellulose cavity fill & 1.5" of exterior XPS sheathing, which is well-within the capabilities of DIYers at a much lower material cost. Going double-studwall it's probably cost effective to go for R40 ( maybe even R50) with an all-cellulose fill (and rainscreened siding to maximize drying capacity, with no interior vapor retarders other than latex paint.) For other ideas see:

http://www.buildingscience.com/documents/reports/rr-0903-building-america-special-research-project-high-r-walls

and

http://www.yestermorrow.org/

In VT a fully insulated slab is cost effective with standard heating systems & fuels, not just frost-protected. Going with EPS rather than XPS under the slab will save a bit of cash. (Even low-density goods used for roofing insulation can handle the floor loading in residential apps.)

It's probably worth springing for the PassiveHouse tools in the design phase to figure out the best tradeoffs, but odds are you can plow the cash that might have gone into a heating system into a better thermal envelope and still use less energy than a high-efficiency heating system. Glazing size, type & orientation become dominating factors once you're at ~R30 & higher on the clear-wall Rs. (R30 is about the minimum you could go to get a decent fraction of the heat out of passive solar in your climate.)

See: http://www.passivehouse.us/passiveHouse/DesignTools.html

Jere has it right- air sealing the place is critical to performance in high-R assemblies, and while ICF makes air-sealing relatively simple, it's still possible for DIYers dedicated to the detailing to get it PassiveHouse-tight.

Once you're into a double-studwall approach, then it's all about the cost of the R- framing sheathing & finishing a 15" thick double studwall isn't dramatically more expensive than framing a 10" thick double studwall, but the volume & cost & R-value of the fill changes. Cellulose is cheap stuff, and doable as DIY in a thick-wall dry-blown application. Leaving the space between the studwalls open and continuous with the attic insulation A:reduced thermal bridging from framing, and B: allows easy access to top it off in 20 years if it settles over time. (Using only "stabilized cellulose" that comes loaded with water-activated adhesives for wet-spray apps will minimize settling even when dry blown, and it contains only non-corrosive borate fire-retardents, unlike some of dry-blow-only goods.)

Thanks for your reply Dana1, I'm still doing a lot of reading and your links have been extremely helpful and educational, onward through the fog!

John

Vermonter,

"The 3-5% figure is factoring in reduced labor for ICF, correct? So it's likely not accurate when comparing for DIY, especially if the ICF needs to be done by someone else."

   The 3-5% is what GCs came up with of increase in build cost ICFs vs wood framing, both done by professionals, in my area, Twin Cities, Minnesota. ICFs are more labor intensive than wood framing.

"If we go ICF we're pretty set on the Durisol. I know the polywhatever is supposed to be fine but we don't want to live in a styrofoam house, and the Durisol is much more stable and durable, and keeps more thermal mass within the insulation. Also seems easier to DIY since the blocks are unlikely to blow out."

Expanded Polystyrene is very stable and lasts a very long time when not exposed to ultra violet light. That is why many people don't like EPS is because it lasts so long in landfills. EPS vs wood chips, my issue with Durisol is the wood and what happens to it when it gets wet, it rots and molds. EPS does not have much thermal mass because it is a better insulator, light and full of air cells. Duisol is a screen grid of concrete, not a strong as most ICFs, which are flat wall. Although I have not used Durisol, it appears to be more difficult to build with as it does not lock together like EPS ICFs.

For me the benefits of ICFs are much more than energy efficiency, energy efficiency is behind strength/safety, mold resistance and longevity.

Have you seen any cases of the Durisol rotting or molding? I thought the processing made it unable to rot or mold.

Durisol has slots for placing alignment wedges.

I have not seen anything built with Durisol. I don't see how being coated with cement would keep the wood chips from rotting. But I am forming my opinion on what what I do know about it. I saw it has slots for alignment wedges, which may be comparable to a tongue and groove ICF.

It's not just coated with concrete, it's a process. From http://www.durisolbuild.com/wood-concrete.shtml :

2. What is the wood treatment process?

This means the wood is chipped to specific gradation, the fine particles are removed, and the wood is
mineralized. Mineralization is the proprietary process by which we remove the sugars from the wood and
render the material completely inert, and no longer susceptible to rot or termite damage. The wood then
becomes an inorganic aggregate similar to stone aggregate in concrete. Durisol is also known as
“wood-concrete”. It is the mineralization process that allows the cement to hydrate or “strengthen” in
the presence of wood particles.

The mineralization process is an interim process only and all Durisol products, once made, are comprised
of cement and wood fiber only. There are no residual chemical properties whatsoever from the wood processing.

----------------------------------------------------------------------


If you haven't seen any Durisol, why did you say "my issue with Durisol is the wood and what happens to it when it gets wet, it rots and molds. " ? What exactly DO you know about it? You have no experience with it and are not familiar with the manufacturing process. I appreciate input from everyone, but these posts could be read in the future by people trying to find good products for their homes. Let's keep it to solid facts.

I may be sounding like a Durisol rep, which I am most definitely not. I'm just frustrated by opinions being stated as if they have some experience behind them when in fact they don't.

Posted By Dana1 on 02 Sep 2010 11:31 AM
The thermal mass benefits of ICF are going to be much lower in ~8000-heating degree-day VT than it would be in more moderate climes. Don't count on it outperforming it's ASTM C 518 R value by much in winter, but it will in summer. The highest R-value offered by Durisol is R28, which is what you'd get out of a 2x6" studwall with low density spray cellulose cavity fill & 1.5" of exterior XPS sheathing, which is well-within the capabilities of DIYers at a much lower material cost. Going double-studwall it's probably cost effective to go for R40 ( maybe even R50) with an all-cellulose fill (and rainscreened siding to maximize drying capacity, with no interior vapor retarders other than latex paint.) For other ideas see:

http://www.buildingscience.com/documents/reports/rr-0903-building-america-special-research-project-high-r-walls

and

http://www.yestermorrow.org/

In VT a fully insulated slab is cost effective with standard heating systems & fuels, not just frost-protected. Going with EPS rather than XPS under the slab will save a bit of cash. (Even low-density goods used for roofing insulation can handle the floor loading in residential apps.)

It's probably worth springing for the PassiveHouse tools in the design phase to figure out the best tradeoffs, but odds are you can plow the cash that might have gone into a heating system into a better thermal envelope and still use less energy than a high-efficiency heating system. Glazing size, type & orientation become dominating factors once you're at ~R30 & higher on the clear-wall Rs. (R30 is about the minimum you could go to get a decent fraction of the heat out of passive solar in your climate.)

See: http://www.passivehouse.us/passiveHouse/DesignTools.html

Jere has it right- air sealing the place is critical to performance in high-R assemblies, and while ICF makes air-sealing relatively simple, it's still possible for DIYers dedicated to the detailing to get it PassiveHouse-tight.

Once you're into a double-studwall approach, then it's all about the cost of the R- framing sheathing & finishing a 15" thick double studwall isn't dramatically more expensive than framing a 10" thick double studwall, but the volume & cost & R-value of the fill changes. Cellulose is cheap stuff, and doable as DIY in a thick-wall dry-blown application. Leaving the space between the studwalls open and continuous with the attic insulation A:reduced thermal bridging from framing, and B: allows easy access to top it off in 20 years if it settles over time. (Using only "stabilized cellulose" that comes loaded with water-activated adhesives for wet-spray apps will minimize settling even when dry blown, and it contains only non-corrosive borate fire-retardents, unlike some of dry-blow-only goods.)

Thanks for the good info. I've already read many articles at BuildingScience.com, including the one you linked. Yestermorrow is just over the mountain from me. Interesting place. I'm a bit skeptical of rammed-earth and cord-wood construction, especially when it comes to moisture management.

Luckily my father in law designs heating systems and can help with the calculations. Things are a bit warmer than they used to be around here, but who knows what will happen in the future.

It is I question in more than what I do know about Durisol. If it really can't rot, can it mold? Why don't they mineralize all wood instead of green treating it? Does it wick moisture? Why doesn't anyone else make something similar?

But it is still a screen grid of concrete. Does not have an interlock like EPS ICFs. EPS is a better insulator. I am still skeptical of the Durisol process and EPS is proven. I have expressed my opinion on why I haven't any experience using Durisol. I have no idea the cost either.

Durisol is more comparable to Composite ICFs made with recycled EPS.

Vermonter, a neighbor of yours builds with Larsen trusses (build a 2x4 house, add continuous 2x3 to exterior braced back to frame). http://www.builditsolar.com/Project...nTruss.htm

I honestly don't think you can build a less toxic, lower cost house in your area, his wall assembly is shockingly simple and minimalist: air tight drywall, cellulose, metal lateral bracing, tyvek, 1x shiplap siding (no sheathing!). You might want more layers to suit other concerns, but it's a very interesting effort at building a vapor open, natural materials, "breathable" low-cost house.

Riversong consults in your area, but you need to be building a small house that lines up with his ethics, or he won't be interested.

Double stud wall houses are more conventional and easier for mainstream contractors to wrap their heads around, we've found better success with that method.

Both, however, have been far cheaper to build for us in the northeast than either SIPs or ICFs. If you want tough for other reasons, ICFs have value, and if you want speed, SIPs can be the best choice, but if cost is dominant, other methods typically beat them out.

Hi Brad:

I respectfully have to disagree with you pretty much on all your points. If you took the time to investigate Durisol and speak with them directly they can provide you with all the necessary information including testing data. All of your assumptions are incorrect and addressed.

1. It does not rot nor facilitate mold. the nature of the Durisol material is hygroscopic which means that in has hygric mass (storage capacity) - just as the concrete core has thermal mass. This combined with vapour permeable wall aseemblies, you end up with wall that regulates RH. In order for mold to grow, you need RH around 85% and a food source. Not only does the Durisol not provide a food source (because of the minerlization process) it also does not allow for RH abouve 75% which means you can not have the humidity required for mold to grow (unless there is a leak and open water source, in which case your drywall paper might get mold). This is proven with a 2 year study conducted at the University of Waterloo Building Science Department where they built a test facility which was 20degrees celcius and 50% RH on the inside and the outside of the house was normal Ontario, Canada weather (38 degrees and 100 RH in summer and -30 degrees and 20% RH in the winter approx). Over a 2 year period with an R-8 Durisol wall and no vapour barrier and unpainted drywall as the interior finish they measured RH within the wall system and did not see RH rise above 70 - 75%. So the answer is no it does not rot nor does it mold, nor does it facilitate mold in other wall components. This is also supported with their 60+ year history.

2. They don't mineralize green wood because the point of the mineralization process is to allow the bonding of cement with the wood particles. In order to mineralize green wood, you wood need tremendous pressure to get through the entire piece of wood. Otherwise you would only get a superficial mineralization at the wood surface. In the case of Durisol the particles are small enough and have sufficiently large surface area as a function of the volume to make the mineralization process effective. Other products like Hardiplank and other cement bonded wood materials do use a similar basic process with varying degrees of pressure and temperature based on the desired end density.

3. It does not wick moisture becasue of the large pores that do not create capillaries small enough to allow capillary suction. This is not the case with higher density cement bonded wood fibers and other materials (wood, concrete block,, concrete, etc).

4. There are 14 Durisol plants around the world. They are the original, and most experienced. Other companies do exist in Europe. Isospan, Herekith, some others too. Also the nature of the material is such that it has many desirable properties that allow it to be used in different industries (acoustic materials, noise barriers for highways, building forms, etc).

5. It is a screen grid of concrete which some perceive to be inferior. In fact it is better because you use a little less concrete and still get the benefits of concrete core (sound, fire, thermal mass) mixed with the benefits of Durisol (sound, fire, thermal mass, hygroscopic, recycled). You still need to design to applicable design codes and so whether it is screen grid or monolithic concrete wall, they need to resist the same loads with the same safety factors. If you believe that a solid wall is "stronger"., you are mislead. An engineer is supposed to design efficiently and economically with respect to concrete strength and rebar schedules. Overdesigning might increase the safety factor but also increases the cost. That is a subjective decisiion and you can overdesign with both Durisol or another system. It always comes down to concrete cross section, concrete strength and rebar. When you design to the building code, all systems have the same safety factor and can resist the same loads.

6. It does have an interlock both horizontally and vertically. They allow for flexibility of building (there is no top, or bottom, etc). The truth is that because the blocks are heavier, they don't need to be as interlocking as EPS. The blocks don't shift or float, etc. Also, since the material can hold a screw or nail, it is often easier to just set a block and nail it with small finishing nail to the block below or behind. This is something that you can't do with EPS. The interlocking for EPS is required because the EPS material is not as versatile.

7. EPS is a better insulator, but when you look at the overall Durisol system with integral insulation on the exterior of the concrete core and no thermal bridging through the webs, it certainly is not an inferior wall aseembly.

8. Durisol is actually more proven than EPS. It started in the mid 1940s before EPS existed. It is still around today and grows worldwide.

9. You should try the Durisol before espousing all the problems with it.

10. The only negative about the Durisiol is that it is heavier (which some think is a positive) and depending the on block type, it can cost a little more. But in my opinion the extra cost is easily justified with the end product that you get and the performance that you get as well (same insulation or better than EPS ICF, better surface burning characteristics and can leave exposed, easier to screw to at any point on the surface, correctly positioned insulation according to most building science experts, impact resistant substrate for stuccos and finishes, etc., etc).

11. Durisol is not comparable to composite EPS cement ICFs because the material is more durable, easier to work with and the R-values are higher.

I just thought I would set the record straight as quite often, people's opinions appear as the undeniable truth.

I would like to try it. But to question is good.