Thermal perforamce is the same for keeping cool when it hot outside as it is for keeping warm when it is cold outside. Remember temperature is just a measure of the energy and since the goal is to keep higher energery (warmer) from lower energy (cooler) the temermal equations of heat transfer work the same either way.

Max,

The question you asked provides this forum the opportunity to really let everyone take their understanding of SIPS out for a test drive and for those of us, myself not yourself, who are lees experienced in the ways of SIPS to learn more about them with every posting.

Let me address you question in a different way. There is in Economics the law of diminishing returns. That is to say that if you continue along a certain productive path at a certain point the process you ar employing will begin to reap less porductive ends. Think of thickness in SIPS the same way.

SIPS are part of a system so let's look at it from that standpoint. First, there is a set number of times and for a set amount of time air needs to be recycled in order that it be clean, healthy, fresh and either cool or warm. This number is probably contingent upon the filtration system as well as the R-Value of the walls and deilings in the home, but nonetheless the number is fixed. So with that as a benchmark we then build the heating and cooling system to that magic number.

Now we want to condition the air as often as necessary, but we do not want to cool the air or warm the air more than necessary because herein lies the cost of the system. So R-value becomes importatnt because the temperature of the interior we want to remain constant without loosing cool, in our case here in the desert, to the intrusive heat of the outside. So if we go with a 10" SIP we are building an ice chest. It will allow you to keep beer cool on the counter, even in Arizona, but you are still recycling the air so you have reached the law of diminishing returns. You have in place more insulation than is necessary to accomplish what you need in order to stay cool/warm and healthy.

If we were building your home I would recommend 6 1/2" walls and ceilings. We build here in El Paso and never have we had a need for anything thicker. Don't loose sight of the real issue here; how do I recycle (condition) my air the necessary number of times without loosing money by having to introduce more cool or warm air than my system efficiently is built to do. Also, how do I rid myself of the unwanted hot air so the air I introduce into my home need not be so costly and cool. Thus my initial statement, that while SIP's are the way to go, they are but part of an overall, efficiency seeking system.

Sorry for the rant, but man I love this stuff. My background is an Adobe building and had I discovered SIP's sooner I would have started doing this a long time ago...

True. But the law is based(when talking about insulation) on a fairly costant energy cost. In many places the cost of natural gas(or propane) has increased over 100% in a single year. And, due to using natural gas for electricity generation(a real bad idea) the costs will continue to escalate. So, to determine whether an increase is insulation is 'diminishing' one needs to project the costs of energy. Something that is impossible, but we do know that that cost will probably increase faster than inflation. If I were a betting man, I would Super Insulate now and worry about the ROI later.

And, of course, it's Location, Location & Location. What makes sense here in Colorado may be a poor investment elsewhere.

Or, with all due respect, build a more affordable, well insulated home now and update your HVAC systems later. Initial costs savings against "Super Insulating" and the ongoing fuel cost savings can be reinvested into newer and more efficient technology down the road.

Though the point about location is probably the truest of all. Dry heat is easily combatted by moving air as opposed to 700 degrees below zero when I would think nothing helps. I know I spent several months in the Persian Gulf along the Iraqi border. Just being in the shade makes life almost bearable. If you had a fan you thought you had died and gone to heaven.

I only know that the needs in the desert differ greatly from those in the Rockies. We have no need for portection against the cold and the ability to maintain comfort with refridgerated air is relatively inexpensive if your home is well insulated and your air handlers move that stale hot air out of the home often enough.

Greg

Unlike the above posts, I really don't know either SIPs or construction -- I'm low on the learning curve; but, I'd tend to come down more closely aligned to PanelCrafter's comment to go to a thicker panel.

However, clearly, you wouldn't need 30" foam walls -- so where do you stop . . . 4", 6 1/2, 8?  You and your builder need to do a detailed cost trade off of all the systems that will make up the house.  The three obvious elements that will be cost drivers will be the shell (how thick do you make the SIPs), the windows (what quality and what style -- double hung leak more than awning windows), and what type and size of heating and AC.  That will tell you where you ought to spend your next dollar of investment in the house's structure.  If you want lots of windows, then I'd guess that it really won't matter how thick your SIPs are because the infiltration and heat loss through the windows would probably overwhelm the walls and roof.  Each iteration should cause you to re-evaluate your inital assumptions:  Do you really want all the glass you first envisioned?  Etc.

Gsfrey notes that he (sorry for the sexist assumption) would probably recommend 6 1/2" SIPs.  So my first question would be what's the marginal cost to go to the next thicker or thinner panels?  You're already paying for extensions on windows and doors, so that won't significantly change.  You're already paying for any cost difference in constructing with SIPs, so that won't change.  You're already paying for the skins and connections, so that won't change.  The cost addition would seem to be just the cost for the extra foam, so my guess is that, as compared to the cost to build, the cost to add the insulation would be fairly low.  I'd consider the change if for no other reason than adding insulation in the future could be markedly more expensive. 
But. . .  we don't know how Gsfrey got to 6 1/2 inches.  If the a rough analysis said 4" and he bumped it to 6 1/2, then he's already adopted PanelCrafter's approach.  On the other hand, if the rough analaysis said 7 and he used the closest panel at 6 1/2, then that's a different answer.  And he will not have done the analysis yet -- it's based on experience and history in his region. 

Good luck,
Larry

I'm confused. If 1 pound is good, 1 ton must be great?

First my recommendation to 6 1/2" panels was because there was but a marginal increase in price and for EPS only. Cost of EPS is roughly .155/ board foot. You can do the math, but the increase in panel cost is about 32 (the square feet of a panel) x 2 (the increase in the thickness of the panel) x .155 (the cost per board foot of EPS) and you get the incremental price increase of a 4' x 8' panel that is 6 1/2" rather than 4 1/2" thick. This price increase provides the most insulation before you begin to incur the additioinal costs you spoke of. But that is where that ends. You can find windows and doors designed for 6 1/2" walls. No need to pay for or install extensions. The window and door manufacturer we use can supply doors and windows for either 4 1/2 or 6 1/2 walls.

What I was trying to say was 6 1/2" is the thickest you can get to before you begin to amass ancillary costs that also cost you time on the job site. The number was hardly arbitrary since I was recommending a panel that would correspond to dimensional lumber for the sake of other components in the home.

I must have stated my case poorly, I apologize.

I estimate the cost to be about $0.50 per size increment. So, from a 6.5" to 10.25" I'd estimate about $1 to $1.25. For a 40' x 40', 1,600 sqft structure with 8' high walls you are looking at 1,280 sqft of panel or $1,280 to $1,600 to upgrade to what I call Super Insulated(near R-40). Please also understand that the costs include utilizing 2 x 10's for all plates and window and door wraps. That's why the cost is more than just the foam.

It may not seem worth it unless you really require a lower Heat Loss. Such as trying to heat with active or passive solar. I had 2 clients in very cold locations choose the 10.25" SIP walls. And, they'll save $$$ because of their decision.

Gsfrey, I didn't mean to slam you, I just phrased it poorly.

PanelCrafters,

That's actually less than I'd have guessed for the upgrade -- which puts it closer to a just do it answer.  But it's not clear what the actual improvement would be.  What's a nominal wall area for windows -- 10% - 20% ?  What R and infiltration effects would there be with a mid-grade window given that area? 

If you assume that the 1600 sf house has that much glass, and that the first-pass spec assumed mid grade (or lower, builder grade) windows, what would the average wall R value be including windows with 6 1/2 and 10" SIPs? 

Then the two follow-up questions would be:
What would the same $1,600 buy in improvements to the windows?
And what would be the average wall R value be for a 6 1/2 panel wall with the window upgrade?

Then there'd be a basis to select one of those solutions (after you traded it against a HP upgrade).

I'm REALLY impressed with SIPs and I want to build my next house with them.  But my naive guess would be that the cost-benefit curve's knee would be in the 4 1/2 to 6 1/2 range (right where Gsfrey stopped).  I'd probably go to one size thicker simply because the analysis would be a best guess; I really wish that the SIP industry would do and publish that analysis.  Builders will tell me what it will cost for cosmetic changes and layout options, but NONE of them seem ready to show me where to spend my structural $ and why.  Not all people, but many people are interested in hybrid and diesel cars because they can see the additional cost and easily grasp the long term implications of the gas milage improvements.  Why don't builders offer the same information, not guesses and assurances and rules of thumb, but fully detailed engineering analysis of each option with the estimated additional costs and the estimated operating cost reductions. 

PanelCraftes, my rant isn't aimed at you -- you're one of the half-dozen posters whose answers I always read.  Rather, it's a generic complaint.  The SIP industry wants builders to change, builders won't change until buyers request it, and buyers won't until they have a reason to. 

Oh well, bed time.

Very respectfully,
Larry

Larry;

For what its worth ............. I am ready to retire too, but won't for about 10 years yet.
However, my current SIP home has 4" wall s and 6" roof .    
 I plan to build my (final) retirement home in 2 years.
I will use 6" walls and 8" roof, as I don't feel any benefits beyond that.
One thing to consider for extra thick walls is they will take away from valuable useable floor space, which at times can be critical depending on the size of the home.
a 1800 sq. ft. home with aperimiter of 180lft. would lose 60 sq. ft. if increased from 4" to 8"

Thats like losing the space for one full bathroom

Chris,

Oh, I'm ready, but my banker won't allow me to retire until my youngest finishes college in 4 years.  So I'm learning, looking, and lot shopping until then.

That's an interesting perspective that I'd not considered.  My immediate response was
"no problem, just extend the slab 2 inches on each side." 
But that ignores the rational grid size for the layout. 

Thanks for pointing that subtlety out.

VERY respectfully,
Larry

Larry;

I never get too hung up on trying to get a plan to fit a grid or modular size. there is usually someplace you can utilize a small drop from a wall and even if you worked out a perfect modular size for the walls, then the roof layout doesn't work perfectly.
I arrive at what the customer wants and then utilize the panel layouts to their fullest. Any unuseable drops of  substantial size, I carry forward to the next project.

Thanks for all the input. My main problem is with the builders and other folk in this town. You see, I live in Kingman, Arizona and the only thing anybody knows about SIPs is from a beer can. I talked to a dealer in Phoenix about ICF's a couple of years ago and he wouldn't come up here for any amount of money. So it boils down to a few facts. No one wants to work, no one is reliable and no one can pass a drug test. This is a project that I will have to do myself, because if it's not framed with a 2 x 6 it's HUH???

I am a green design/builder/remodeler in southern Maine. One thing I wanted to add to this thread. A quote from an article by the Rocky Mountain Institute in Colorado based on the work of Amory Lovins and others. The article is entitled: "Big Savings Often Cost Less than Small Ones", subtitled: "Tunneling Through The Cost Barrier". It discusses the idea of diminishing returns, and why proceeding on that premise doesn't always work. I'm sorry for the length, but in the context of this thread, I think you will find it very enlightening.  Excerpts from the article follow:

There is an ordinary-looking tract house in Davis, California that defies conventional wisdom. It has no furnace. Despite temperatures of up to 113F, it has no air conditioning system. It uses 67 percent less energy than comparable houses in the area, saving $490 annually. The house, part of an experimental program sponsored by Pacific Gas & Electric, illustrates an important principle: big savings can be easier and cheaper to achieve than small ones if you combine the right ingredients in the right way.

The usual way to redesign a product is to analyze its components or subsystems separately and optimize the cost-effectiveness of each in isolation. But components interact in ways that aren’t obvious when you’re looking at them separately, and optimizing one part may “pessimize” the whole. Often you can reduce the total cost of a technical system by spending extra on certain components.

That’s what happened, many times over, with the Davis house. To give just one example: Having reduced the building’s cooling requirements by two-thirds with various cost-effective measures, the designers found that other measures, previously screened out because they didn’t save enough energy to pay for themselves, were now worth doing because they could together eliminate the remaining cooling requirement. That saved $1,500 on the capital cost of air conditioning and ductwork.

Most of us view efficiency as a process of diminishing returns. Let’s say you’re trying to make an office building more efficient. You prioritize all the things you could do, from the highest return on investment down to the lowest. You work your way down the list until either your budget for improvements is used up, or the return on your investment is so small that you’d be better off spending the money on something else. You’ve reached what we call the cost barrier.
This is a fine way to identify simple, cost effective improvements, but it’s limited in what it can do. This approach would have eliminated two-thirds of the Davis house's cooling load, for instance, but it would have left the remaining third, which would have necessitated retaining the cooling system, leaving the whole house costing more, not less.

Conventional wisdom says you’ve got to stop when you get to your cost-effectiveness limit. But as the Davis house demonstrated, there are times when, by allowing yourself to exceed that threshold temporarily, you can tunnel through the cost barrier and drop back down the other side for even greater savings at lower total cost.

Such breakthroughs happen all the time, usually thanks to new technologies. But what we’re finding is that inspired design and whole-system engineering can often accomplish the same thing, even with old technologies.

FOUR PRINCIPLES

Tunneling through cost barriers is as much an art as a science. There’s no formula for doing it, but here are four principles that we at RMI find helpful:

1. Capture multiple benefits from single expenditures.

This might seem obvious, but the trick is properly counting all the benefits. It’s easy to get fixated on optimizing for energy savings, say, and fail to take into account reduced capital costs, maintenance, risk, or other attributes (such as mass, which in the case of a car, for instance, may make it possible for other components to be smaller, cheaper, lighter, and so on). Another way to capture multiple benefits is to coordinate a retrofit with renovations that need to be done for other reasons anyway. Being alert to these possibilities requires lateral thinking and an awareness of how the whole system works.

When prioritizing efficiency measures, the standard method is to pursue those that pay the highest rates of return first, then work down the list until the “cost-effectiveness limit” is reached. This method does not work well.

2. Start downstream to turn compounding losses into savings.

Think pipes again. An engineer looks at an industrial pipe system and sees a series of compounding energy losses: the motor that drives the pump wastes a certain amount of electricity converting it to torque, the pump and coupling have their own inefficiencies, and the pipe, valves, and fittings all have inherent frictions. So the engineer sizes the motor and pump to overcome all these losses and deliver the required flow.

But starting downstream—at the pipe instead of the pump—turns these losses into compounding savings. Make the pipe more efficient, as Jan Schilham did, and you reduce the cumulative energy requirements of every step upstream. You can then work back upstream, making each part smaller, simpler, and cheaper, saving not only energy but also capital costs. And every unit of friction saved in the pipe saves about nine units of fuel and pollution at the power station.

3. Get the sequence right.

Achieving big energy savings is a process of multiplying little savings. That means breaking the task down into many steps and tackling them in the right sequence.

Amory Lovins has created a list of six guidelines for doing this, which he’s reduced to sound-bite brevity:

1. People before hardware;

2. Shell before contents;

3. Application before equipment;

4. Quality before quantity;

5. Passive before active; and,

6. Load reduction before supply.

We don’t have enough space here to explain each of these best-buys-first principles, but here’s an example that illustrates some of them. Suppose you’re considering making your office lighting more efficient.

First you should improve seating and surface configurations (people before hardware),reduce glare (quality before quantity),harness natural light (passive before active) through better window and building design (shell before contents), and only then improve the technical efficiency of your lights and how thoughtfully they’re used and maintained.

4. Optimize the whole system, not parts.

Optimizing an entire system takes ingenuity, intuition, and close attention to the way technical systems really work. It requires a sense of what’s on the other side of the cost barrier and how to get to it by selectively relaxing your constraints, as the designers of the Davis house did when they decided to pay extra for better windows.

Whole-system engineering is back-to-the drawing-board engineering. It doesn’t rely on rules of thumb, which are typically based on single components, operating costs only, old prices, and very high discount rates. Nor does it rest on theoretical assumptions (for instance, that efficient components must cost more—they often don’t). And, importantly, it incorporates “feedback” to make the design process intelligent, cyclical, and capable of continuous improvement based on measured performance.

My Problem is the same as maximchuk's if not worse. I live in an extremely cold winter climate in Wisconsin in a rural area and "builders" who you ask to use 2x6 instead of 2x4 think you are just a hippie putting on airs. I don't know if they would pass a drug test, but I hope not, that would at least mean they might be curable. Seriously, the manufacturer for the SIPs I would like to use (I have no skills to do it myself), maintain that any qualified builder can easily adapt to building with SIPs, but that is not what I have found. Does anyone know of a good team that will travel? Given the speed with which a good team could put up the shell at least, it would be costly, but even adding $10,000.00 or whatever (not WHATEVER) would be better than schlock work, and we have excellent Amish workers who will finish the insides, but won't do the SIP work. Any ideas? I have been looking for SIP info for six months and never found a forum even close to this one for great information. Thanks so much.