This has probably got to be a FAQ, but a quick skim didn't turn up anything...

We're currently living in the city of Chicago, but thinking of moving to the burbs. Looking at our budget and some of the new home prices, we're thinking a custom build might be a valid option for us. But we need help determining whether or not that's actually true!

An energy-efficient home has been a longtime dream of mine. I'm by no means an expert, but from periodically lurking on these forums, I'm leaning towards an ICF build. A lot of the "secondary" benefits appeal to me, e.g. sound-, wind-, fire-, insect-proofing. And I'll be honest, I like the idea of living in something that might be considered "overbuilt". :)

But I'm not married to the idea of ICF. Bigger goal is to get something that is tightly sealed and well-insulated, say whole-wall of R30 or better. Above code-min, but my impression that going whole-hog (e.g. PassiveHouse certification) can be costly. I'm looking for the "value sweet spot", wherever that may be. (And I'm sure there are differing opinions on that.)

We have a general idea in mind of what we'd want: a ranch of about 2500 square feet on the main floor, plus a full-sized basement. The main floor would have everything we need, the basement would be mostly unfinished.

In the areas we're looking, we want to be within walking distance of a commuter train (Metra), so finding an empty lot might not be feasible; getting a "tear-down" is more likely. (Not sure if that makes a difference other than the obvious additional cost of the tear-down.)

So, having said all that...

- What kind of building cost might we expect for such a house? I know there is a huge range here, but just looking for rough ballparks to get an idea. We want a "nice" trim level, not super fancy, but high quality. (E.g. nice full hardwood, but doesn't have to be exotic or hand-planed; granite or quartz kitch/bath counters; "Consumer Reports top rated"-grade appliances, a step or two below Viking/SubZero; exterior of concrete fiber or maybe steel; metal roof; etc.)

- When building costs are quoted in terms of square feet, does that include the basement? I.e., given my 2500 square foot ranch with full basement, is that a 2500 square foot build or a 5000 square foot build?

- What's the best way to select a builder that "gets" what I'm looking for, and also one that I can have reasonable confidence will meet my expectation? Clearly there are obvious things such as looking at existing work, checking references, doing an "interview" to make sure personalities are compatible, etc... but are there specific red flags I should look out for? Specific targeted questions I should ask?

- Are there any recommended books out there I can read that might answer some of the above questions? E.g., I will effectively be the manager of whatever builder I hire. I think finding the right builder is only step one, I think I'll need to be actively engaged throughout the whole build process, so I want to be as informed as possible.

Thanks!

Go to PHIUS.org & look up the Certified Passive House Builders and Consultants near your area. These pro's understand high performance building, and probably have examples you can see.

Given the still rapid cost learning curve of solar, building Net Zero Ready or even fully Net Zero Energy can be cost effective, and possible at R30 whole-wall.   The cost of small scale PV has dropped by half since 2010 and continues to fall, and efficiency has risen from about 15% to about 20%.  Back in 2009 some folks at Building Science Corp estimated the building performance required to fairly easily hit Net Zero Energy with a PV array that still fits on the house.   Take a peek at Table 2, p.10 of this document and you'll see that even with 15% efficiency PV that's possible at R30 whole-wall in a zone 5A type of climate (which is all of northern IL).

Getting to R30 whole-wall with ICF is pretty expensive way to purchace thermal performance.  A typical 2.5" + 2.5" ICF comes in at ~R22-23 whole wall depending on siding and interior finish options, and in your climate the modest benefit from the thermal mass is good for a bit more in terms of annual energy use.  With U0.18- U0.20 windows (standard triple-panes, not super-performance) and obsessive air sealing rather than the U0.24 recommended in Table 2 you can probably still get there with the rest of the building envelope being guided by the factors in the BA-1005 table.  But it's good to simulate energy use while tweaking in the design.  Familiarize yourself with BeOpt, which is pretty good at predicting annual energy use if you give it the real numbers.  The tool is designed for cost-optimizing the building envelope.

Using better class cold climate mini-split air source heat pumps helps too. Back in 2009 when that document was drafted pretty-good mini-splits were running HSPF 10-ish and SEER 16-ish, but now there are multiple models good down to -13F that test at HSPF 12+ and SEER 25+.

A 2500' house with a finished & heated 2500' walk-out basement might be called 5000', but if it's an insulated a below grade basement (not walk-out), from a heating & cooling point of view its pretty similar to a 2500' slab-on-grade house.

The folks over at GBA have come up with the Pretty Good House concept, which ends up being roughly what it takes to get to Net Zero in a zone 6 climate (cooler than yours). There are lots of ways to get to PGH with different cost structures, but if it's an ICF you have to be willing to pay for more than just thermal benefits.

A 2500' house built to these levels with a bit of care and optimization will have a design heat load in the 15,000 BTU/hr or a bit less range at Chicago's ~0F 99% outside design temp.  That is within the output range of most 1.25 or 1.5 ton cold climate mini-splits, which can end up being a cost savings on mechanical systems.  The better the building, the higher the comfort, and the simpler/cheaper the HVAC can be.  With any new house build to IRC2012 or better air tightness you will need mechanical ventilation, but at your low loads you DON'T want to use the heating/cooling system for ventilation.  A ducted heat recovery ventilation system separate from the heating & cooling doesn't have to be a large expense if you plan for it.

Still waiting for HVAC manufactures to build smaller concealed air handlers to create smaller zones......

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You might have to use water (vs air) as the distribution medium to get that.

Posted By jonr on 29 Apr 2016 12:42 PM
You might have to use water (vs air) as the distribution medium to get that.

HTP's thin profile hydronic air coils aren't exactly hidden, but they're pretty quiet (under 25 dB according to the marketing fluff) and not too visually obtrusive.  It's a decent micro-zoning solution for low-load homes heated with a water heater.

Plus there are in-wall fan-coils. They can't be used on most exterior walls, but I'd rather have a hidden fan-coil in the same room on an interior wall than anything in the next room. And a little radiant in the bathroom is nice.

Dana, thanks for the helpful and detailed response, much appreciated.

Posted By Dana1 on 28 Apr 2016 04:26 PM
Getting to R30 whole-wall with ICF is pretty expensive way to purchace thermal performance.  A typical 2.5" + 2.5" ICF comes in at ~R22-23 whole wall depending on siding and interior finish options, and in your climate the modest benefit from the thermal mass is good for a bit more in terms of annual energy use.

Emphasis mine, can you elaborate on that a bit? A while back I looked at one ICF manufacturer's offerings, and they basically had "more R" for increasing insulation thickness. One builder I briefly spoke with here suggested the main cost with ICF is the concrete... so are the thicker (more foam) ICF blocks dramatically more expensive? Or is the marginal cost increase overshadowed by the cost of concrete itself? I'm basically assuming we're going to have walls that are 14 inches thick, give or take.

Do you think I might save significantly if I went with what seems to be the oft-recommended stick frame + cellulose + several inches of exterior foam strategy?

Posted By Dana1 on 28 Apr 2016 04:26 PM
A 2500' house with a finished & heated 2500' walk-out basement might be called 5000', but if it's an insulated a below grade basement (not walk-out), from a heating & cooling point of view its pretty similar to a 2500' slab-on-grade house.

OK, I think I get it. In practice, I think it would end up somewhere in the middle. A hard requirement for me is to have eight-foot finished ceiling height in the basement. So the basement won't be entirely underground. Furthermore, does it make sense go dig the basement a foot shallower than all the neighbors as one (of many) dry basement strategies? The net result is that the "basement" might end up being 1/3 above ground.

We might have to give up on the ranch idea anyway, as I'm told they are more expensive to build. Likewise, once the garage is factored in, we're looking at either a huge lot, or giving up all our yard. So it might have to be a 2-story + basement. In that case, we'd probably target about 1300 SF per floor (2600 above grade, 1300 mostly below grade).

I took Bob I's suggestion above, and reached out to a few builders listed on PHIUS.org. I seem to have a chicken-and-egg problem here, as the builders want to know more detail than I have available at this time. E.g., what style, what budget, what construction method, etc. I can't answer most of those questions until someone helps guide me through costs and tradeoffs. I understand the builder's perspective, they don't want to sink a lot of time into answering all these questions for me if there's not a high chance that they'll get a job. But I can't commit to anything until I understand the details...

It has been discussed on here quite a bit that ICF can sometimes 'perform' at a much higher R-value than it's basic rating. During the shoulder seasons, it out-performs its own rating by a considerable degree. In our relatively mild SC climate, we can go for long spells without using the HVAC at all. The ICF seems to buffer the temperature extremes to a large degree. Someone on here actually studied and measured it, but I don't remember who.

I do the same without ICF - just a reasonably insulated house with overhangs. Performing similar to something with higher R value isn't worth much (in BTU or $) when the weather is mild. And the effect goes away when the weather is completely hot or cold. So I suggest doing any performance comparisons in the far less misleading units of $/year.

Posted By jdebree on 04 May 2016 07:23 AM
It has been discussed on here quite a bit that ICF can sometimes 'perform' at a much higher R-value than it's basic rating. During the shoulder seasons, it out-performs its own rating by a considerable degree. In our relatively mild SC climate, we can go for long spells without using the HVAC at all. The ICF seems to buffer the temperature extremes to a large degree. Someone on here actually studied and measured it, but I don't remember who.

My take on that was that in a climate like mine (northern Illinois), you don't really get the thermal mass benefit of ICF. My understanding is that the thermal mass benefit is useful when you have wide temperature swings over fairly short periods of time. E.g., desert-like climates where it's hot in the day and cold at night. The concrete's thermal mass buffers that.

When we have temperature swings like that around here, it's usually fall or spring, where we open all the windows, and the energy performance of the house doesn't matter. In the winter or summer, it gets cold or hot and stays that way. :)

My interest in ICF is for the perhaps "tertiary" benefits. No wood-boring insect risk, sound/noise insulation, somewhat fire-proofing, tornado-proofing... and, frankly, I like the idea of living in something that might be considered "overbuilt".

Sounds like you should also consider concrete poured in conventional forms.

https://cshub.mit.edu/sites/default/files/documents/ThermalMassBenefit_v10_13_0920.pdf

Fair enough, and as you point out, there are other benefits. ICF is not completely immune from wood boring insects, though. They have been documented tunneling considerable distances through foam to reach wood, and of course they would be completely undetected. I feel like our house is pretty well protected here in our 'extreme' SC termite rating, and we are under an annual termite contract, as we were in our all-concrete FL home. We got termites in that house; they came up through the seam between the garage floor and the main slab to reach interior wood framing. I once bought an antique musical instrument, and there active dry wood termites in the wood case! Unless your house has NO wood at all, it is never truly immune.

We do like the other benefits; our house is very quiet and strong, and coupled with steel interior framing, the entire structure is very stable, with no cracks or screw pops in the drywall as of yet. The lumber that is available, at least around here, is horrible.

Infill lots present the opportunity of the other kind of green building -- reusing onsite materials rather than trucking the dozed remains off to a landfill and then trucking in new materials. From the '60s back, reclaimed lumber is automatically "overbuilt" compared to today's manufactured wood products. Floor joists will be 3-bys and quality wood. Deckboards instead of plywood. Finish trim in hardwoods though probably painted over. If you can incorporate the foundation, it might also qualify for the third kind of green building, as in less cost.
They just don't make wood like they used to. I salvaged heart pine from a 140-year-old barn to get 95 percent of my master bath completed. Happily, my trusty, usually inexpensive Mennonite planing mill had heart pine for sale -- for the modest price of $8/bd foot.