Anybody looking 60 years performance should review this document:

http://www.buildingscience.com/documents/reports/rr-1005-building-america-high-r-value-high-performance-residential-buildings-all-climate-zones

No 2x6 construction without exterior foam will ever reach R20 walls, the recommended values for zone 3 in table 0.2, p10. (Which includes all thermal bridging, not the center-cavity R.) The nominal recommended value for Zone 4, and you're located on the cusp of zone 3/4. With open-cell foam or cellulose cavity fill you're looking at a nominal ~R14 after thermal bridging, but an inch of exterior rigid poly isocyanurate sheathing would get you there. Alternatively, a 2x4 wall with 2" of extruded poly styrene makes it.

A minimalist ICF is ~R16, but if you add an inch of EPS you'd be there. The thermal mass will buy you a bit of performance in the summers, but not as much as adding another R5-8 to a low mass wall.

An R20 SIP is about the same thickness as a 2x4 +2" XPS solution.

Air tightness is at least as important as R-value, and never guaranteed, even with ICFs & SIPS. Shoot for sub 2 ACH/50 by-design, and verify/rectify with a blower door test. It starts by defining the primary air-barrier on all sides of the cube in the design, and monitoring the implementation like a hawk as it goes up. (Once the studwalls are up it's hard to put that bead of caulk under the stud plate, etc. Playing catch-up is more time consuming and expensive than implementing it as you go.)

At R20 the windows start to dominate the heat loss of walls. A 10 square foot U0.34 pretty-good window loses/gains as much heat as ~ 70 square feet of wall. Designing for minimum glazed area, and designing the S side window type & size and shading for optimal winter gain can make a significant difference in overall energy use and the peak loading. A 20% reduction in overall glazed area can be huge. Casements & awning windows are much tighter than double-hungs & sliders, and offer more egress & ventilation area per square foot of glazing than the latter.

Similarly sliders leak more air than swinging doors, and U0.2-0.25 (R4-R5) insulated doors do a lot better than solid-core hardwoods (~ R1.5-2).

Before sinking an extra 15 grand into geo, see what that buys you in an insulation package. If you take it up to R25+ and manage the glazing well, your heat loads can be manageable with a much smaller and as-efficient variable speed drive ductless mini- or multi-split air-source heat pump. They really ARE getting to be that good! (An example of ~R30 whole wall R is 3" of iso roofing insulation on the exterior of a 2x4 cellulose studwall or 3" of XPS on a 2x6 cellulose filled wall. R25 can be 2" of exterior XPS on a 2x6" or, 3" on a 2x4 wall.)

Slab on grade, or full basement?

Since you are an 'analysis paralysis' engineer type, why don't you go to your best local modular builder and convince/assist them in building a modular home to your desired floorplan using SIPS rather than sticks & batts? Seems like the best way for you to go in my humble opinion!! I'd like to see some of these modular guys start building with SIPS - no reason why they can't if it is properly engineered.

Do any of the modular homes offer an air infiltration guarantee? Seems like they could and should.

Another consideration for a 60 year outlook is to design the roof pitches to optimize for photovoltaic solar. Even if YOU don't implement it, there are already multiple businesses competing for roof space willing to give you a lower or fix your rate for 20 years in states with higher solar subsidies (that the installers/lessors cash in on.)

See:

http://www.solarcity.com/

http://www.sunrunhome.com/

http://www.sungevity.com/

According to the solar geometry and weather analysis in this study, your optimal angle would be 30 degrees, facing due south:

http://oldweb.hawaiirdp.org/hetl/AdvisoryGroup/tilt-az-paper-3z13.pdf

If you came to terms with a solar lease company apriori, it would be simpler to install and get right BEFORE you finished out the roof. But buck a peak-watt solar is destined to arrive (CIGS technology large panel goods from NanoSolar is pretty much already there, but not available for residential-sized applications... yet.) If you design your roof angles for it, the financial argument will be compelling well before 60 years is up.

There have been modular SIP homes built in the NE, with mixed results. It seems the customer is driving it, but the in-house expertise on truly high-performance building envelopes isn't always up to snuff.

See: http://www.gouingreen.com/ ( a lot of detailed info on that blog about what it took to get it truly air tight, etc.)

This page also poses useful aspect to consider: http://www.gouingreen.com/node/50

Every house I know of in this area is built on a crawlspace. Lot of good reading for me to do on the super-insulated & sealed.

Slim pickings on the modular builders in my area (4) and basically the only work they actually do is to sub out the foundation and utilities and have the manufacturer build, deliver, set, assemble, and trim out the modules. As for an infiltration guarantee, the Champion home I walked through on Thursday had pink insulation crammed underneath the wiring (which 15 minutes earlier the modular builder told me how superior their insulation was to things like spray in insulation)

I like the idea of designing for future solar, was already planning on the 2-car garage running east-west having a nice southern roof exposure with either a 7/12 or 9/12 (more loft space is nice)

I really like the concept of an ICF structure over one built with SIPs (we're in a hurricane area beside an active RR track with an interstate behind our back field). I've reached out only found a few ICF installers but they only build 2-3 a year, not the type of expertise I was hoping to find.

Is LEED Certified worth anything? Seen a builder or two who tout it on their website but I couldn't find any tools that help you search for LEED Certified anything in your area.

Posted By blueflamme on 17 Jun 2011 10:59 PM
.

Is LEED Certified worth anything? Seen a builder or two who tout it on their website but I couldn't find any tools that help you search for LEED Certified anything in your area.

In my opinion there is no value in LEED certification to the home owner, you can use LEED guidelines to create a healthier indoor environment and use Energystar certifiication to reduce energy costs. I think EnergyStar has some resale value and definitely long term savings in reduced utility bills.
We have stayed away from the LEED program (lack of beneifit) and stuck with EnergyStar, Build America and Builders Challenge

If there isn't much ICF experience, then you can also look at poured concrete with foam added either before or after the pour.

A crawlspace can/should be built as a mini-basement (and insulated) in a place a humid in summers as coastal VA.

You pay a premium for building with concrete, but HELL YES it is far more structurally resistance to wind loads in hurricane zones!  It's not something a modular builder is going to deliver on a truck though, eh?   IOF is easier to air-seal than timber-frame, but window & door framing/weather stripping and the roof design, flues & ventilation etc all have to be attended to in order to have even a remote shot of getting it unter 2ACH/50.

In-re hurricane resistance:  Even though it can be more expensive way to go high-R,  unvented attics don't experience nearly the roof-lifting forces that vented attics do in high winds, and hold up better.  To hit R-50-ish at the roof deck in an unvented design, using R15-R20 exterior polyiso roofing panels (Hunter Panels, Atlas, et al) above the structural roof deck, and 7-8" of open cell foam or spray cellulose on interior of the roof deck works.  Alternatively, an inch of closed cell on the interior of the roof deck and 10-11" of interior cellulose or dense-packed new-school superfine fiberglass such as Spider or Optima @ 1.8lbs+ density gets you there.  You may have to custom design the trusses to have a way of attaching interior OSB in the rafter bays to support a foot of insulation thickness though.  In some ways the exterior iso/interior spray is easier to get right.  On a project I'm advising on in zip 01610 they're putting 6" (R40) of iso on the exterior, and 5.5" of cellulose between 2x6 rafters for ~ R60 nominal, but the long fasteners (and the labor) for holding down the exterior rigid is not an insignificant cost-adder.

LEED certification is more about the bragging rights for the builder than the homeowner.  Net Zero Energy or Passive House is perhaps of greater value to the homeowner.

Blueflamme,

Have you looked at Superior Walls?  Is there a plant and crew available for your area?  Superior Walls can be used to build up to three stories.  I have found this system to cost less than cast-in-place concrete for houses in my area.  Additional insulation can be added to this system.

Dana1 I have a good tutorial on those energy terms? (2 ACH/50, U0.2-0.25)

So should I try to find the GC with the most experience building energy efficient or the best GC I can who will work with an energy consultant? (and if so how do I go about verifying I've found an energy specialist and not just a hyped up HVAC guy?)

I've heard of Superior Wall, conceptually not sure how a bunch of sections bolted together can compare to a monolithic pour, especially with insulation only on one side.

ACH/50 is the air exchanges per hour at 50 pascals pressure difference or the whole house. The test pressure for calibrated blower door testing use by most standards for such things i 50 pascals. The test equipment measures both the pressure and a volume-rate, such as cubic feet per minute (CFM). The air exchanges per hour (ACH) derived by calculating the volume of the building's interior dimensions, using the raw CFM numbers and very simple arithmetic.

Real-world air-infiltration rates are much lower than the ACH/50, since actual house pressurization/depressurization is normally an order of magnitude or more lower than 50 pascals. There are some attempts to estimate the natural air exchanges per hour based on the ACH/50 number, but those are very inexact since the configuration of the house and the locations of the air leakage can make an order of magnitude difference. Duct balance and air handler speeds can also make huge differences in the amount of induced infiltration driven by room-to-room pressure differences from HVAC systems, and are usually bigger than the natural ventilation rate, but still lower than the blower door test leakage rate. Bottom line, the lower the ACH/50 number the less the natural ventilation or HVAC induced infiltration becomes, and the effect on energy use is significant going from over 10 to under 2, independent of R & U values. Going from 2 to 0.6 (PassiveHouse standard) is still measurable, but only relevant at super-insulation type levels.

U-value is the heat exchange per degree per unit area. It's a common specification of windows & doors, and perhaps SHOULD be for wall systems. In the US, U-values are in BTU per degree Fahrenheit per square foot but most of the world uses metric units. Most people are more familiar with R-values, but not necessarily it's definition: R=1/U Thus, a window with a U value of 0.22 has an R value of 1/0.22= R4.5 Single-pane windows have U-values close to 1, (R=1), lower cost double-panes of decades past run have U values of 0.55-0.6 (R=1.8-ish), and might be 0.45-0.49 (R2 -ish) but decent quality low-E noble-gas filled goods these days run in the low-min 0.3x. Getting U 0.15 (R 6-7) or even lower is possible going with the state of the art cutting edge windows, but it gets pretty pricey. Getting the same performance improvement out of the whole structure design is usually more cheaply done by reducing the total amount of glazed area and reducing the U values of walls & roofs (higher-R walls & ceilings) rather than ultra-low U values on the glazing. For example replacing 10 square feet of U0.34 window with 10 square feet of U0.05 (R20) wall is a lot cheaper than replacing 10 square feet of 0.34 glazing with 0.18 glazing, and is a much bigger net improvement. Minimizing the amount glazed area whereever you reasonably can is a cost-negative way to boost whole-building performance, the exception being designing south facing window sizing/type and shading to optimize heating season solar gains against the increase in cooling season cooling loads. There are other aspects to windows that affect total performance too SHGC (= solar gain factor), etc., and what you put on the west side of the house won't necessarily be optimal for north or south facing glass. Freebie tools like RESFEN are pretty good at sorting out which window types/ratings work best for each side in your climate & site-shading factors (http://windows.lbl.gov/software/resfen/resfen.html ), but not necessarily optimizing for size relative to the thermal mass of the house and the U-values of the other elements.

Finding the true cost/benefit of the various elements for any particular design require a site & climate-specific energy use simulation for the whole building, which is not a trivial exercise. But freebies like DOE2, or HOT2000 aren't super-complicated to use, and are way better than WAG. For relatively short money the PassiveHouse tools are pretty good if you're going the super-insulation route, but it's not clear how good they are at hitting the numbers for more modestly insulated (but still way better than code) buildings.

As for how to find a GC who really gets it, hard to say. Builders of LEEDs certified or even EnergyStar rated buildings with respectable HERS ratings might be a start, or it could be that they're just good at keeping the books on punch lists, and leave the details to subs. But simply asking the typical/better/best ACH/50 numbers on their last 5 houses are shouldn't get a blank stare for a response if it's a GC at all serious about building a truly efficient house. It's the designer/architects, not the GC that should be defining the primary air barriers and U values of the different elements of the house, but the GC needs to have a clue going into it- the best designs poorly implemented won't necessarily perform. A super-insulated wind-tunnel with 15 ACH/50 leakage numbers will usually cost more to heat & cool compared to a building with R-values only 1.5x code-min that came in at <1.5ACH/50. (Which is why the R-2000 Canadian program calls for blower door testing to <1.5ACH/50, not just minimum R values.)

When building houses that tight active ventilation systems are a given, and in VA energy recovery ventilation (ERV) is recommended over heat recovery ventilation (HRV), since ERV reduces both latent & sensible cooling loads to the air-conditioning. In tight well insulated house with optimized glazing the latent loads will be several times that of the sensible load. Some amount of mechanical dehumidification will be necessary for days when outdoor dew points are in the mid-60s or higher, but the average daily temp isn't high enough to make much of a sensible-load for the AC.

Thanks for all the info, still digesting a lot of it.

What about a modular built with SIPS claiming a Whole Wall R-Value of 21.6?

http://www.classichomesbyhaven.com/Residential/Products/InsulatedPanels.php

I suppose that with modular homes, you might collect energy usage data and/or get blower test results from the existing ones to get an idea of how well they will do with yours.

IMO, ICF is great for strength and stopping sound, but framed construction + rigid foam is more cost effective. Frost protected slab on grade is also cost effective.