I'm building a home in Southern California and have been interested in considering SIPs construction. It seems that every article and every post I read however discusses the merits of SIPs in cold weather. Usually in Canada, Michigan, or somewhere else cold. Where I'm building, I'll NEVER see a day below freezing and we got 5 days last year that broke 100. I know that the cost of SIPs is "roughly" the same, but also consider the complexity and time that I'll have to incur by converting my stick plans to SIPs. Is it really worth it to do this in Southern California, or should I stick to stick and use modern insulation materials like spray foam? I would prefer pragmatic responses as opposed to philosophical. Thank you in advance. -Ryan

Hi Ryan,

I am in San Diego and have built homes here with our panels here.  They are very cost efficient, lightweight with high thermo protection.

Please take a look at our web site and after if you have additional questions please call or e-mail me!

Thank you,

David

KwikBuildPanels.com

Hello Ryan,

We manufacturer SIPs in California. We ship them all over CA, including Southern Cal, and also into Arizona, where the weather is warm. People that build with them save a tremendous amount of money on their utility bills. Air conditioning is very expensive. Please let me know if you have any other questions or if you would like a free estimate.

Thank you

Ryan,

It's all about user comfort -- it's why we build structures to separate us from the elements -- so the simply arrived answer is YES.

ALL buildings are affected by THERMAL TRANSFER that impacts comfort -- that is HEAT >>> moving >>> to COLD. Whether it is moving in or moving out of a building, slowing down thermal transfer is very important.

ALL buildings are affected byCONDITIONED AIR MOVEMENT out of a building that impacts comfort. "Leaky" structures account for tremendous extra cost to maintain comfort. Slowing air movement down is the answer.

ALL buildings are affected by[ b]RADIATIVE TRANSFER that impacts comfort. Controlling radiation to your (seasonal) benefit is the answer.

ALL buildings are affected by OCCUPANT HEAT GENERATION that impacts comfort. You will cool (or even heat) your space someday to maintain comfort. Higher performance in the three other factors makes this easier and more predicable.

To-date, SIPs have proven the most effective way to control the first two elements.

How important is fire safety to you?

Best luck with your project, Greg

Posted By ocryan on 20 Oct 2011 09:06 AM
I'm building a home in Southern California and have been interested in considering SIPs construction. It seems that every article and every post I read however discusses the merits of SIPs in cold weather. Usually in Canada, Michigan, or somewhere else cold. Where I'm building, I'll NEVER see a day below freezing and we got 5 days last year that broke 100. I know that the cost of SIPs is "roughly" the same, but also consider the complexity and time that I'll have to incur by converting my stick plans to SIPs. Is it really worth it to do this in Southern California, or should I stick to stick and use modern insulation materials like spray foam? I would prefer pragmatic responses as opposed to philosophical. Thank you in advance. -Ryan

Air tightness is a bigger factor than R value for wall systems in a SoCal climate.  R-values and heat-rejection properties of the roof is bigger factor than walls, followed by the heat rejection of windows (and window shading systems.)

It's pretty easy to air-seal a SIP, but it's also easy to fully seal stick-built with 1-2" of closed cell foam on the OUTSIDE of the sheathing of a stick built structure also works.  A 2" shot of exterior foam on the exterior of a 2x4 stick built costs ~$2 per square foot of wall area and makes a continous R12 insulation & air barrier, performing about as well as 2x6 construction with 5.5" of open cell foam (~R14).  If you need more than R12, doing a stud-cavity fill of wet-sprayed (or dense packed) cellulose brings it up to ~ R22 for relatively low money and doesn't interfere with your primary air-barrier.

Alternatively, it's not very tough to air-seal the sheathing with caulk/tape/mastic/spot-foam, and put an inch of taped/sealed rigid foam on the exterior too.  An inch of iso on a 2x4 cellulose-fill wall makes for a whole-wall value of ~R16, and on 2x6 studwall it comes out at about R20 (for less money than the 2" spray foam solution, but requiring more air-seal detailing.)  R20-ish  whole-wall R is the target-value for your climate- more than that gets harder to rationalize on a cost/benefit basis.

Don't leave air-sealing to chance- as soon as the shell is up and windows/doors are installed use a blower door to find & fix every leak you can find, before any further insulation or finish materials are installed.

Whatever you do for wall assemblies air sealing the attic/living space boundary is critical, since whole-house stack-effects will drive conditioned-space air into a vented attic if it's leaky. It can be lot of detailing to get right, with a lot of spot-foaming around plumbing & electrical penetrations.  And don't even think about putting air handlers & ducts above the pressure & insulation boundary- putting them in the attic can nearly double the peak cooling load on the system.  Even if you have to increase the framing height 1.5-2' to accommodate the ducts inside the air-tight & insulated envelope, it's worth it.  An R50 roof is cost-effective if done with cellulose (14" settled depth, 16" new), but design the ceiling to be able to accomodate the load.  A layer of OSB will support a LOT more weight than 3/4" gypsum. Be sure the trusses are designed with sufficient "energy heel" at the edges to be able to get full depth out over the tops of the stud or SIP walls too, and that the truss chords can handle the ~2lbs per square foot of static load.  It may call for a few more trusses to make that loading, or fatter truss chords. Treat the OSB layer as your primary air-barrier- mastic-seal or foam the seams & edges before blowing insulation, and PLEASE forgo the recessed lighting (a common weak point for air leakage.)

Doing an all-foam solution to the roof R get's to be out of hand cost-wise even at code-min values, but if going with fiber it's not bad. Cellulose will outperform low-density fiberglass due to better infra-red opacity and lower air-permeabilty, so it's worth it on performance & comfort, even if it costs you an OSB layer and a couple extra trusses to handle the weight.

As an aside just to point it out, the whole-wall R of 16" on-center studwalls with typical 20% of the wall area as the framing fraction work out to about these numbers:


2x4 w/open cell foam R3.5/inch------------R10

2x4 w/ wet-spray cellulose R3.5/inch-----R10

2x4 with closed cell foam R6/inch---------R12.5

2x6 with open cell foam---------R14.5

2x6 with cellulose----------------R14.5

2x6 with closed cell foam-------R18.5

The thermal bridging of the studs robs the assembly of the center-cavity performance, which is why beyond simple air-sealing putting the foam on the exterior works better. By putting the foam-R between the stud edge and the siding, you get the full performance out of the foam. Putting it only in the stud bays also leaves air leakage a the studwall plates and rim joists. By putting 2" of foam on the exterior of a 2x4 wall and using low-cost cavity fill you end up using only 2/3 of the amount of foam, and you end up at nearly double the R-value at roughly the same total cost. Foam isn't inherently green- less is more, and type matters but in the context of air-sealing it's hard to beat closed cell foam. The blowing agents used for EPS and iso are a lot more benign from a greenhouse gas point of view than those used for spray foam or XPS.

Paying attention to window type & glazing and location/size for solar gain aspects also makes a huge difference on heating & cooling loads. Double hungs & sliders all leak air like crazy compared to awnings & casements. The same is true for doors- swinging patio doors offer a lot more access area and leak a lot less air than sliders. Minimizing window size where you can allows you to open up where the views are worth the freight. Building in some overhangs on the S side doesn't hurt (although the high summer sun angles take care of solar gains quite a bit at that latitude via total external reflection), but building in or planting some shade on the west side can make for higher comfort, even if it means you miss some sunsets (you should be at the beach then anyway, what are you thinking? :-) )

Dana1,

When you say, " A 2" shot of exterior foam ...." Are you talking about spray foam or rigid board? If the former, how is the siding applied to the less than smooth surface?

Thanks,
Bruce

Beyond energy efficiency, homes constructed of SIPs provide superior resistance to earthquakes.

Superior to what?

Superior to conventional construction practices. Actually, all the added structural reinforcing added to conventional construction to resist earthquake forces, would make SIPs more competitive from a cost point of view. Each SIP is automatically a shear diaphragm and is ideal for resisting lateral forces.

Yes Alton. I know you were a university professor, so I will accept your constructive criticism. However, you should PM me, so I can edit my post and then you won't have to hijack the thread with a spelling lesson. (That's my constructive criticism:-)

SimonD,

You are right.  I should have sent you a private message so that you could have quietly corrected the typing error.  Now back to the original thread.  Sorry about that.

Thank you for all the input everyone, I am in the process of getting bids on SIPs vs Stick construction to evaluate the cost differences.

I built a SIPs cottage in Riverside and a SIPs house in the mountains above San Diego. I'll never live in a conventional stick built house again. I love my SIPs house. And please remember I have put my money - about $300,000- where my mouth is. I did the cottage as a test of SIPs and liked it so much I then built a 1575 sf house. It feels different inside a SIPs house, and it took me a while to figure out why: there is not much air movement inside and I don't have hot and cold spots like in a stick house. The temperature is pretty uniform throughout the house.

I used OSB SIPs for both, but if I ever did it again I would try to find panels that already had the exterior and interior walls  finished. Don't know if there is such a thing but I imagine if there is it  would save time and some hassle in the building of it.

Anyway, good luck with whatever you decide.