I am not a socal residential architect, but it is never a good idea to not insulate any building anywhere. What about heat? Cooling will seep right out of the building and rack up costs for the facility user.

What does your building code state?

this is my recommendation Proto: http://buildingsciencepress.com/bookstore/books/builders-guide-hot-dry-mixed-dry-climates

mydream, I'm not suggesting no insulation. Continuous insulation (ci) has been part of the ibc since 2009 and many state codes have adopted it, and it's finding its way into the residential codes too. A simplified version of it is using exterior insulation (there's more to it than that, but i'm not going to explain it beyond that.). It might be, however, overkill, and i'm hoping someone more local than me can chime in.

non-sequitur, the CA code will allow several strategies, including ci. as noted above, just looking for a little local wisdom regarding cost/benefit (& I am in the PNW, fwiw)

makingspace, i have that book in the various flavors of climate, thanks...looking for a little local wisdom

to all, i'm referring to the insulating & air barrier strategies proposed by lstiburek's building science corp and wondering if that is over the top for a place where the temperature swing is minor through the seasons.

cal green is going full passive haus/self sustainable in the next 20 years...if you want to cheap out on insulation, now is the time to get it through.

My firm tends to, but we also shoot for high LEED certifications. 

thx chigurh & natematt

When applying The Canadian National Energy Code, stud wall framing and and end of joist framing are not considered to break the continuity of the insulation. So in providing insulation in wall framing meets the intent of the CNEC.

Adding more insulation always leads to a return on the investment. The question is what is that return. An energy model would show you the relative savings. My guess is that in a mild climate it would not be the best investment. I figure a 10% ROI is pretty smart, 5% is borderline and less than 2-3% is hard to justify. Some use "payback" instead of ROI, but if you have extra money you invest it, and typical investments are gauged by ROI.

Continuous insulation has other benefits as well, including resistance to moisture accumulation, which leads to mold of course. From an environmental impact point of view, it depends on what material you are using. XPS has a high global warming potential to due its blowing agents, which last at least 1000 years in the atmosphere. EPS and Polyisocyanurate are much better, with pentane-based blowing agents not much worse than CO2 for contributing to the greenhouse effect. Mineral wool is fairly benign, but also the most expensive and hard to install.  

wood guy, not going to get an energy model done yet but that's probably the only real way to figure this

in san diego's climate, the delta swings are so limited (temp & humidity), it just makes me wonder if significant insulation matters (or, at least, how much)

obviously, more is more better, but...when is it just extra?

any san diego architects out there?

Town codes are way to generic and restrictive in some cases. I always insulate my projects to the max as long as budget allows for it.

It gets really really cold in SoCal, San Diego and Los Angeles and the temperature in Summer can get really hot. Having a continuous Envelope can even out the temperature swings. Foam is very cheap and the cost for adding foam is very marginal over the life of the structure.

I currently have a house that is not insulated and its very old and the temperature swings are really massive. I live in a more modern concrete structure and the difference in temperature is highly highly noticeable. The modern concrete structure does not loose cooling or loose heating like the older structure does. 

So a direct answer to your question is that I feel that the continuous envelope is a good thing and the cost is very marginal to the benefit.