There is an article on Page 49 of the July 2007 Greenbuilder magazine.  They built 4 single story 2,048 sq ft duplexes with different technologies including sips (looks like steel/eps), icf, autoclaved aerated concrete (aac) and stick built and compared construction cost, heating cost and colling cost.  This was sponsered by PATH and Hughes Construction in Lexington, N.C.

The following is the breakdown (labortime, heating, cooling)
ICF   131    hours,  448 kWh,  206 kWh
SIP   68.7   hours,  486 kWh,  253 kWh
Stick 33.9   hours,  514 kWh,  247 kWh
AAC  186.4 hours,  464 kWh,  233 kWh

I would like to hears others comments since these results really surprised me.  They show it costing more to cool the SIP structure than a stick built structure.

Thanks,
Chuck

They show it taking more labor for a SIP than a Stick as well??? Does that seem realistic to you guys?

Dick Mills

There is no mention of roof construction techniques. My experience indicates that roof construction is more vital to energy savings than any other factor. If they used the same techniques on all four projects, I would be surprised that the difference is as large between SIPS and ICFS as it appears to be. And my practical experience with various types of construction suggests that the 'stick' construction techniques would have to be upgraded considerably above the 'average' to get anywhere near the same results as SIPS. This also does not mention local climate conditions during the test period. If the weather was mild for the test period, then differences would not be as evident as they would be under more harsh conditions.

This makes no sense to me.  Let's say the panels and sticks show up the same day.  It takes me longer to unload and place the SIPs.  I have to add a bottom plate for the SIP panels.  However, once my wall is up, it already has insulation and sheathing on the outside.  How is the stick quicker?

Hmmm, what are they trying to tell us? I am looking at an electric bill for an all electric townhome at an elevation of 8,600' in the Colorado mountains. For the period from mid June to mid July the usage was for 462 kWh. The townhome does not have A/C and it's doubtful that the heat ran much at all.

So, the usage was for H/W, refrigerator, cooking & lighting, and a little heating. 462 kWh.  Now these totals ranged from 654 kWh to 761 kWh. I'm sure that when winter rolls around(very soon now up here) that this townhome, for a 1 month period, will exceed any of the totals listed.

So, my best guess is these amounts are for 1 month? And, they were taken during a time when the structure used twice as much heating as cooling, and used both Heating & Cooling?

Am I missing something?

TMSU,

Do the panels that you use come with door and window openings already cut out? Or do you cut the openings after you erect the walls?

Dick Mills

Mr. Mills,

The panels all came with the doors and windows cut out.  These were called out in plans I sent and then reviewed the panel company's plans for size and placement. 

Tmsu

Tmsu,

I haven't read the article in GreenBuilder, but it is possible that they used whole panels and had to cut the door and window openings at the build site. That could be one reason for the counterintuitive labor figures???

Dick Mills

The main item that stands out to me is the thermal qualities.  I will have price quotes before I get started so while cost matters I don't expect that to be a major surprise.  I expect that a SIP home would cost more than a stick built home.  My whole reason for considering SIPs is the expectation that heating/cooling costs and comfort will be far superior to a stick built house.  Considering the added foam of SIP versus ICF I would have also expected the SIP to outperform the ICF.  The results that stick outperformed a similar SIP home in the same environment for cooling causes to question if there is any reason to consider SIPs.  Does anybody have a reasonable explanation of how this could have happened?

Since I have not read the article, I have no idea what the figures represent. And, how would labor have any correlation to energy used? And, as I already stated, the amount of energy is very low, so what was the duration of testing? And when?

The PATH report is available at http://www.toolbase.org/pdf/FieldEvaluations/HughesInterimReport.pdf

NOTE: in the report the duplexes are identical, but the orientations are different which may or may not contribute to different heat gains/losses. Also the SIPs are not true SIPs as I know them, they are thermasteel's composite panels ( not stress skinned SIPs)- they look like studs with foam in between -  it appears that they may have thermal transfer issues as I look at the photos.
SIPs are not included in this report!

jc,

I don't think that anyone has tried to correlate the extra labor for constructing a SIP structure with it's thermal efficiency. But, one of the selling points that I hear bandied about regarding SIPs is that they it takes less time to construct a structure using SIPs. This GreenBuilder Magazine article appears to contradict that - which seems somewhat counterintuitive.

Dick Mills

Dick; 

The walls in the GreenBuilder article are not SIPs, Chuck 07 eroneously mis-quoted the article

"I see," said the blind man.

Dick Mills

I appreciate the link to the full article on the PATH website.  This explains a lot of the results that were not clear from the magazine article.  A 3.5" thick panel probably doesn't allow for much thickness for the foam, perhaps less than the ICF.  I think there was a house shell built out of these in the parking lot at the 2007 Int'l Builders Show in Orlando. 

The labor may result from the wall requiring more assembly than most SIPs.  The hours appear to reflect the difference between experienced framers versus inexperienced crews for the alternatives. 

Note that these are in fact SIPs (Structural Insulated Panels) by definition as also noted on the Thermasteel website.  Otherwise the designation should be something more like SSPs (Stressed Skin Panels).

Looking at the Thermasteel website and the PATH article there is no thermal bridging except at the top and bottom of the panel.  This is the same circumstance for metal SSPs (like Structall or Metals USA) which also include significantly more metal in the panel than Thermasteel.  It appears to me there is a real potential to lose significant overall insulating value when going with a metal versus wood skin panel.  Wood may not be a great insulator but at least its not a great conductor - metal is a great conductor (Think about cooking - You use aluminum and steel pans but never wooden pans).  If you compare thermal conductivity steel is almost 400 times more conductive than wood and aluminum is over 2000 times that of wood.  I would like to see a study that compares wood and metal panels with the same internal thickness and type of foam.

An additional note for comparison on conductivity Wood (Yellow Pine) is only about 5 times more conductive than Expanded Polystyrene.

chuck07;

 

As the former General Manager (housing division) for Stuctall, I can tell you that thermal bridging is not a concern in the southern states, as our homes have been tested with thermal imaging equipment by the Florida Solar Energy Center (FSEC) there was only a thin pencil line of transfer at the base and top cap.
Now in colder climates thermally broken, bases, caps and channels are utilized, corners are mitered so no thermal loss there.
Steel sips have been used as far north as Calgary with no thermal issues and the reverse can be said for the thousands of refrigerated - freezer ware houses built in the hot climates that need to overcome drastic temperature differences by utilizing  thermally broken accessories.
A properly built steel SIP system could have less thermal conductivity than wood systems relying on solid wood splines, solid wood bucks, etc.
There is a good reason why steel SIPs are used more than wood for commercial refrigerated spaces, They work better!, They also perform better in housing as well, providing greater span capabilities, longer panel lengthstermite and rot resitance as well.

This is really surprising to hear.  There is a SIPS product that costs less and it is ThermaSAVE.  The original company is located in north Alabama and the number is 256-766-3378.  The owner has been building with structured insulated panels for over 25 years.  The buildings that have been built with the ThermaSave panels show a huge energy savings over stick built.  There is an article in Ultimate Home Design magazine, November 2006 to name one and also several articles and Discovery Channel interviews with the owner.