Posted By jonr on 14 Jan 2012 09:57 PM
I have yet to hear from someone living in an ICF house that they were lied to.
Do you know anyone living in an ICF house that has the ability to do a properly controlled comparison to equivalent R and infiltration value stick framing?
Most people living in an ICF house are living in the best performing house they've EVER lived in, and don't have a good basis for comparison with other higher-than-code thermal performance buildings. Moving from a typical 2x4 ~R10 whole-wall stick built that leaks 8-12ACH/50
into a 3ACH/50 R22 ICF there would be significant boost in comfort- it
might feel like a palace to some.
ICF has a nice solid feel, they're very quiet & reassuring- most people who live in 'em like 'em (as well they SHOULD), but it's another "so what"? Most people living in tight, code x 1.5 stick-built or SIP houses find them a lot more comfortable and preferable to than anything they've lived in previously too.
The people who were told that their R20 ICFs performed like R50 sometimes even believe that, but that performance level isn't supportable by the facts (and it's arguable they were lied to, even if the installer was a true believer.) To be sure, very few of us have lived in a home with R50 walls, so making that comparison would be difficult. But the same people who believed R50 might also believe that center-cavity R values of stick-built is the R value of the wall too.
An R13 (R10 whole-wall) isn't terrible, but it sure isn't as cushy as R22 whole-wall with center-mass to take the edge off the peaks, making it arguably R30ish or higher from a comfort point of view when standing next to the wall during the heating & cooling peaks, if not as measured by the utility costs. Most people aren't doing even the most rudimentary math on any of it, nor do they understand the heat transfer aspects of the building as a whole, but they
think they understand what R value is about and tend to put a lot of importance on it, even at R-values where infiltration and windows dwarf the importance of R value from an energy use point of view. You can't really "feel" R50 relative to R25 very much, but you can sure measure the difference in performance. Similarly the difference between 1ACH/50 and 5ACH/50 has a pretty subtle distinction as felt by the occupants (unless it's underventilated and humidity is though the roof), but has a measurable performance difference in energy use.