here are the energy bills of our 2 story, all electric icf house in jensen beach, fl. 34057
it is used as a home/office year round.

           2012    2011    2010    2009    2008 
      
jan          91        93        82        91  
feb          62        96      124      107  
mar         57        77      111      130        82 
apr          61        77        79        83          0 
may        72         76        76        83      163 
jun          91      late       138       82       152 
jul                      233      149      103      114 
aug                    135      151      162      111 
sept                   143      148      145      138 
oct                     109      139      167      123 
nov                      62        85      157      118 
dec                       71       85        96        91 
      
      
people      2          3           3          3          3
      
2800 sf living space, single car garage with attic    
3 bedrooms, sun room, 3 baths, 2 offices, 3 lofts, storage attic     
2 - 2 ton a/c units - seer 12, electric strip heaters    
kitchen all electric
single pane impact windows and doors
all openings covered with wood or vinyl louvers or blinds
6' concrete overhangs on south side
     
all walls 6" core icf    
all roofs 10" insuldeck with 3" concrete slabs     
      
home owners insurance 1789.00/year     
hurricane coverage not included/needed     

2011 and 2012 were very mild winters  

if anyone wants more details or pictures email me at

[email protected]
[email protected]

I'm trying to figure out the relevance of Peter's contribution to this thread beyond the mere spam.

Dana1 - play nice. Ask him.

I respect your opinion that homes under 2009 were already meeting 3ach... but it is just an opinion. Can you not see that the home tested in this case had a hard time getting to 3 ACH? with the sprayfoam and 1" of exterior XPS? And an air barrier. I dont see that as a regular approach. It simply means that you have to go the extra mile to have the same ach on a wood frame home... extra money, materials, labor...

Here's the mandatory stuff you have to do (and prove ach 3) that is really not a big deal for ICF homes. The list looks pretty nice to me... Just wait for the next IRC edition

I can probably dig up an online reference source for the average IRC2009 compliant home air tightness results if you need to see it to believe it, but I didn't just make it up (either that or my memory is playing havoc with me this month!)

Exterior XPS does very little for air tightness unless detailed as an air barrier, and the same is true for housewrap. The air barrier method on the test houses wasn't specified, so it's hard to guess why it failed to perform. Open cell foam cavity fill doesn't seal the wall- only the cavity, and even there the skill of the installer matters. Closed cell foam is more reliable as an air sealer, but perfectly tight cavities mean little if foundation sills are un-foamed, stud plates uncaulked, etc. We simply don't know how or if the primary air-barrier was defined, let alone implemented.

Without more info we can't say why this house wasn't tighter, but as I stated previously, Canadian R-2000 homes beat 1.5ACH/50 with margin EVERY DAY when air-tightness sensitized crews & designers are used, and it's not expensive or complicated to get it right. All volunteer crews less familiar with the detailing requirements are likely the bigger factor in the failure of the Habitat for Humanity house to hit R-2000 levels, but we don't really know. An air-barrier perfectly implemented on a paper design is easily defeated in the field, but generally won't be if the installers have the experience. It would be curious to know where the specific failures were in this case though (and if they're even retrofit-fixable, which they might be.)

I'm reasonably familiar with IRC2012 provisions, but none of the methods for air sealing are rocket science or new to those who have been designing & building with air-tightness for awhile, it just the ABC basics of "how it's done" to get repeatable & reliable results.

Yes, air sealing ICF & SIP really is easier than with stick-built (no news flash there) but that doesn't mean it's always going to be tight. The more idiot-proof you make a system the smarter & more creative idiots become, which is why you still have to test, eh? ;-)

But the fact that they're comparing a lower-R and leakier stick built as the example is still a straw-man test, even if it does highlight the relative ease of air-sealing ICF.

Posted By Dana1 on 12 Jun 2012 03:51 PM

But the fact that they're comparing a lower-R and leakier stick built as the example is still a straw-man test, even if it does highlight the relative ease of air-sealing ICF.

Do you believe the "fix" is in? If so, is the USGBC in on it??

Posted By Dana1 on 11 Jun 2012 06:30 PM

FWIW: I never hear my antique stick-built house creak in high wind, despite plank sheathing lack of rack-bracing of any type. (Full dimension 2x4, 16" o.c. circa 1923, 9" clapboards.)

My 2006 wood framed home (2-story) makes noises when 40MPH+ wind gusts hit it. It's a little unnerving. Maybe it is the lack of OSB shearing on these homes out in Phoenix Arizona?

I've lived in a masonry home (CMU) and wood homes for almost 40 years. I prefer the strength, longevity and quietness of masonry/concrete. Hence why my future home will be ICF/concrete.

If you've ever been in a wood home with 70MPH+ winds, trust me, the house will rack and creak.

Peter, it's good to see some real world info. on the cost of an all icf home.

Posted By Lbear on 13 Jun 2012 02:35 AM

Posted By Dana1 on 12 Jun 2012 03:51 PM

But the fact that they're comparing a lower-R and leakier stick built as the example is still a straw-man test, even if it does highlight the relative ease of air-sealing ICF.

Do you believe the "fix" is in? If so, is the USGBC in on it??

It's simply a stupid test on the face of it, no conspiracy-theory necessary.  Not enough factors are isolated to render a meaningful comparison.

A leakier lower-R house isn't likely to exceed the performance of a tighter higher-R house independent of mass-effect, unless the occupant behaviors are so different between the two as to nullify the inherent advantage (which is possible, if not likely.)  Neither house is going to be an energy-pig if they keep the doors & windows closed, but the advantage goes to the tighter higher-R house with the higher incorporated mass.

The performance difference is readily (and accurately) modeled with even 2-D tools like DOE2. If one were trying to isolate one of the factors (wall-R, air tightness, or mass-effect) to highlight that as the difference under test you'd have to at least start out with the other factors being nominally the same. Here three significant factors known to be different on day 1, so what is the test demonstrating, really? (Not much, sez me!) It's stupid if it's intended as a comparison between high/low mass construction, or even comparing best performance stick built (which this clearly isn't) to pretty-good ICF.  This feels more like comparing "nice try, but probably would have failed Energy Star inspection" stick-built to so-so ICF.  Almost any resulting data would warrant a "Yeah, so, and...?". 

But the performance difference is likely within the behavior-difference if it's being tested only as-occupied rather than with identically controlled & monitored T-stats, etc. (As was done in the ORNL side-by-side test where the R values and mass differed, but the air leakage was comparable rather than more than 2x greater.)

Posted By smartwall on 13 Jun 2012 08:20 AM
Peter, it's good to see some real world info. on the cost of an all icf home.

It would be interesting to know how much better it would be if it had something higher performance than single-pane windows & sliders.  Direct & indirect window gains could be as much as half the cooling bill unless the exterior blinds are deployed often. The mass wall moderates the effect of that high gain/loss glazing, but R0.8 holes in ~R20 walls (any mass) still leaves a lot to be desired even from a conducted heat point of view.  (Any glazing that gets direct sun delivers an even greater cooling load to handle.)

Denominating energy use in dollars is meaningless without the per-kwh/rate.  But Peter is still looking like ~$1400-1500/year- the current FL state average is about $0.115/kwh, so that's over 12-13,000 kwh/year for  a "typical" year.  That's more than my space + water heating bill (for 3) with roughly buck-a-therm gas in a comparably sized low-R stick-built in a ~6800HDD/300CDDclimate.  (My cooling bill is less than $50/year @ ~$0.16/kwh, the bulk of which is summertime latent-load.)

Peter's is roughly a ~4000CDD/400HDD climate.  His R-values roughly 2x mine, but U-values of his glazing is also about 2x mine- a potential Achilles heel on energy performance.   His (all electric) total energy costs are about 60-65% of my (gas + electricity) total energy costs, and my electricity is ~40% more expensive.  Given the more temperate climate and higher-R high-mass roof I would have expected a bigger cost delta as well as energy-use delta than that, which leads me to think window gains on the east & west sides really ARE cutting into the potential performance of an otherwise high efficiency building envelope. (Even a hard-coat low-E single-pane could make a measurable difference in heat rejection.)

But it could also be plug loads of office equipment (if used as an office for 40 hours/week) adds a big chunk to total power use & cooling load that it might not otherwise have if used solely as a residence. 

Four tons of cooling seems like a lot for a 2800' high-performance house (peak loads are probably under 2 tons for the whole place with the window-louvers closed) but not so oversized as to create an efficiency issue.  Very-high SEER variable speed,  cooling/heating heat pumps or mini-splits are probably worth springing for when it comes time to replace the pair of 2-tons units, for both whisper-quiet comfort as well as efficiency.  (Are 12 SEER air conditioners even legal anymore? The line has been drawn at 13 near me for some time now.)  The fact that 1.5 ton heating/cooling mini-splits with SEER performance well north of 20 are available at reasonable cost (under $5K installed) is worth keeping in mind.  If your baseline non-heating/cooling power use is ~600kwh/month ($69/month $828/year with 11.5 cent electricity), that means the other $700/year  for heating & cooling could be cut by about half with best-in-class variable refrigerant volume systems. That wouldn't necessarily pay for scrapping the existing system(s) to make the change at current electricity prices, but any delta in upfront cost would be paid for several times over within the lifespan of the equipment when replacement time comes. (These things have gotten crazy-efficient over the past decade, but it's real, not smoke & mirrors test data.)

I'm still clueless as to what this has to do with the side-by-side test in IL though.

The thing that always baffles me in regards to tyvek is how air sealed could you possibly get it? Let's say you tape the seams, use button cap nails, tape around the windows and doors. It all looks great, then you blast a thousand nails in it hanging siding. How air thight is it now?

Posted By jeepster on 13 Jun 2012 07:48 PM
The thing that always baffles me in regards to tyvek is how air sealed could you possibly get it? Let's say you tape the seams, use button cap nails, tape around the windows and doors. It all looks great, then you blast a thousand nails in it hanging siding. How air thight is it now?

If you read the fine print, Tyvex does NOT claim to be a moisture barrier. In other words, when you make a thousand holes in it with nails, each of those holes is a potential spot for moisture/water to get through. Tar paper is a better moisture barrier. There are many homes out there that have and will experience wood rot and water damage with Tyvek wraps. A study from the Pennsylvania Housing Research Center showed that installed plastic housewraps like Tyvek, "In the majority of the houses where staples have been installed with an automatic staple gun, tears and holes in the housewrap were common”

Green Building Home - Tyvek

While tar paper is better, if they rip the paper with staples or nails, that is a potential water leak. Ask me how I know. Well, my current home has tar paper and I had water leaks/damage due to ripped tar paper. The installers ripped the paper and it did not show-up until heavy wind driven rains. I literally had water coming through the drywall into the home. Even with tar paper, it is NOT 100% waterproof. Eventually it will also let in water also. The only thing you can do is make sure the wall can dry out afterwards. Even tar paper can rot if it doesn't dry out.

Study on Sheathing Wraps

Housewraps have been touted as weather resistive barriers and air barriers, but never as moisture barriers. They're all QUITE vapor-open, and in theory give better drying capacity for the structure. It's highly oversold on all aspects IMHO.

While they CAN be detailed as an air barrier under rainscreened siding (that gets fastened to furring, not nailed through the housewrap), the "typical" methods would violated it's air retardency 10,000x over.

Traditional 15# felt has a lower (and variable) permeance relative to housewraps. It's more waterproof to bulk-water incursions, but it retards drying of the sheathing, and can't be detailed as an air barrier.

There's really no great subsitute for back-ventilated siding on wood-sheathed stick built, but in structures with exterior foam insulation it matters less, as does the choice of weather resistive barrier. With air-barrier detailed housewrap between the insulating sheathing the structural sheathing the air-tightness results can be pretty good, providing the siding isn't just long-nailed through the foam & housewrap. Using furring long-screwed to the structural sheathing over the foam as something on which to hang the siding is the preferred method, since the fastener penetrations of the housewrap are orders of magnitude fewer and under pressure, making the more gas-tight, and the siding is then inherently back-ventilated & drained by the furring-gap.

But who knows how they actually built up the leaky side-by-side example?

I don't have data, but if I built with wood I'd use two air barriers. For example, MemBrain on the interior and taped foam on the exterior. Plus cellulose in the middle and furring on the outside.

Air sealing as many layers as can be easily done is always the right way to go. But defining the primary air barrier that is continuous on all sides of the cube with no gaps or offsets where walls meet floor/ceilng/windows is a necessary starting point.

Without the primary air barrier defined in the plan you can have lots of air-tight layers that aren't tied at the edges/interface, blowing the integrity of the balloon. But yes, finish interiors should be air tight too, even if they're not the primary air barrier. (Just as taping & sealing the rigid foam is necessary, as well as the seams & edges of the structural sheathing, etc.)

Building a super-tight & air tight wood homes utilizing Tyvek, tar paper or whatever moisture/air barrier, is somewhat of a "new" practice here in the USA. 90% of the contractors will do a sloppy job and water will infiltrate the homes walls and insulation. That is why the old phrase of "a wall needs to breathe" is commonly stated by contractors. When water enters the walls cavity, it has to dry out or you will have serious rot on your hands. I've seen many OSB shear panels that were soaked after a few years because the house wrap was poorly done.

From what I have read and seen, these tighter wood homes, if not detailed 100% correctly, it will pose rot issues in the future. More so than a leaky home. When wood got wet, as long as it was given a chance to dry out, it was OK. However repeated moisture exposure is not good either. The problem that is being observed with super-tight wood framed homes is that when water does enter, it cannot dry out and just sits there. The rotting is multiplied exponentially.

If you build it tight, make sure it is detailed perfectly.This was never an issue before because homes leaked a lot of air and mechanical ventilation was never required. Now with air tight homes, mechanical ventilation is mandatory.

This issue was observed in wood roof SIPs, as they trapped moisuture and could not dry out and "SIP rot"started to appear in a few years and cost people $40k to replace their 3 year old rotted SIP roof. Now they are recommended venting above the SIP but it still is NOT standard practice to vent.

Let's say you have a wood frame ceiling with adequate polyurethane spray foam insulation on the interior of the sheathing. Can you get into vapor trouble by removing your air barrier sheetrock and whatever vapor resistance the accompanying paint offers and going to a T&G wood ceiling which is much leakier?

The reason I am partial to icf's, less parts less potential areas to miss. The floor is hung from the interior walls. If you want higher r-value slap some more foam on the outside.

Posted By ICFHybrid on 14 Jun 2012 10:53 PM
Let's say you have a wood frame ceiling with adequate polyurethane spray foam insulation on the interior of the sheathing. Can you get into vapor trouble by removing your air barrier sheetrock and whatever vapor resistance the accompanying paint offers and going to a T&G wood ceiling which is much leakier?

In a word, yes.

But not always.

The particulars matter, including what is meant by "adequate". If the foam at the decking is part of the defined continuous primary air barrier the risk is somewhat lower lower than if the ceiling gypsum is the primary air barrier.  T&G inherently leaks air, and isn't amenable to be part of an air-barrier system.

If the foam at the decking is part of the defined continuous primary air barrier

Yes, I believe it is. Under your excellent tutelage, my gut feeling about the change is that it will facilitate inward drying and not be a problem with interior household moisture.

Here's another side-by-side real-world test comparing stick-built to ICF in a cooling dominated climate:

http://eec.ucdavis.edu/ACEEE/2002/p...04_289.pdf

Table 1 indicates just how far off the assumption that ICF=air-tight can be unless maintaining air-tightness design &  protocol, including a verification/remediation step.  All four were somewhat  tighter than typcial "don't care" construction, but none made it to IRC 2012 levels, and were pretty comparable overall.  The tightest of the four was an ICF that tested at 4.3ACH/50. The leakiest of the four was the other ICF house at 5.6ACH/50 (go figure!?)

This contradicts the assumptions and of quoted marketing fluff of ICF vendors indicating  <2ACH/50 is "typical" of ICF construction.  (If true, where's the the actual third party field data?)  While it's UNDOUBTEDLY easier to air seal ICF than stick built structures, simply assuming that that it's air-tight is always a mistake- there's no substitute for verifying (except maybe vigilant inspection during construction.)  Even in stick-built more than half the air leakage is usually through the ceiling, and in construction with ducts penetrating the  ceiling it only gets worse, in terms of increasing  leakage cross sectional area, but also due to duct-leakage/air-handler driven infiltration.

And just like the houses, the ducts were pretty leaky- more than 600 CFM/25 for all of them, (the proposed new duct leakage standard for CA  is 24 CFM/25, more than 95% tigther), but leakiest of the four duct systems were in the stick built units, a factor they attempted to null out by normalizing it  via DOE2 modeling. Still the location of leakage points matters, so there's a inherent error in the normalized number that's impossible to quantify.

Figure 2 (and elsewhere) the document mis-states the wall-R of the stick built by using it's center-cavity R (R15) rather than whole-wall R (R12) with framing factored in, which masks the true difference in actual wall-R.  The ICF wall has rougly 83% higher R value, not merely 47% higher R, and it shows in both the DOE2 simulation and the measured results. (DOE2 uses it's own internal whole-wall U-factor based on construction type and cavity-insulation, and is less confused about the true differences in wall-R.)  But clearly the mass effect is more beneficial in Dallas than in the Chicago side-by-side test, and that shows too, both in simulation and measured result.

Occupancy use differences were noted but not directly measured, and according to the authors both of the ICF homes used less lighting & appliance power than the stick frame, which accounts for some of the difference in modeled vs. measured cooling power use. That factor too was normalized out of the cooling load using the simple COP of the  AC system (but that would have big inherent error, since the COP varies with the actual outdoor temp.)  Occupant behavior can make as much or greater difference as mass-walls.  But on 2-story houses like this having nearly double the wall-R trumps both mass effect and the observed occupant behavior differences.

Tighter ducts and a tighter houses arguably would have been cost effective, independent of construction type.