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Q&A Spotlight

Choosing a High-Performance Wall Assembly

Double 2x4 walls vs. a 2x6 wall with exterior foam insulation

Double stud walls vs. exterior foam

Double 2x4 exterior walls are one option for a high-performance house in a cold climate. This Habitat for Humanity project near Denver, Colorado, built with help from the National Renewable Energy Laboratory, used that wall construction method to achieve net zero-energy performance.
Image Credit: NREL

Jesse Lizer’s new house will be in Climate Zone 6, where he can expect 7,400 heating degree days a year. High R-values in the building envelope are a high priority.

As Lizer explains in a Q&A post at GreenBuilding Advisor, there are three possible scenarios for constructing outside walls:

  • A double-stud wall, between 10 in. and 12 in. thick, filled with dense-packed cellulose and sheathed with the Zip System OSB.
  • A 2×6 wall framed 24 in. on center with 1/2-in. OSB or plywood sheathing, insulated with wet-blown cellulose and wrapped with two layers of foam on the outside of the wall — 1 in. of XPS and 1 in. of polyisocyanurate.
  • A 2×6 wall with 1 in. of exterior polyiso over 3 in. of EPS, also with 1/2 in. sheathing and wet-blown cellulose.

In an unusually detailed post, Lizer lists two other important pieces of information: the cost of each option, and the nominal R-value of each wall system. The double-stud wall ($2.15 per sq. ft. in material costs) has an R-value of 40; the 2×6 wall with a total of 2 in. of foam ($2.05 per sq. ft.) is R-32; and the wall with a total of 4 in. of foam ($2.15 per sq. ft.) is R-41.

“Any big thoughts on the best approach?” he asks. “My thinking is leaning towards exterior thick foams would do a better job at sealing up the house from both vapor and air vs. the Zip and thicker wall. Since I will be building it (yes, I do have years of construction experience) I am thinking the 2×6 and thicker foam will be faster and easier to detail?”

That’s the topic for this week’s Q&A Spotlight.

The double-wall option

All three of Lizer’s proposed walls minimize thermal bridging, but the double 2×4 wall does so without the use of…

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  1. Expert Member
    ARMANDO COBO | | #1

    Coquitlam Test Hut
    Mark Gauvin’s presentation of his Coquitlam Test Hut is more than proof that all houses should include a wall and roof assembly with rigid foam on the outside no matter where the climate zone is built on. We also know that is or will be code compliant for everyone now or in a very near future. As you pointed out, it addresses moisture, thermal bridging, condensation (winter and summer) and durability issues. For more info:,

  2. user-723121 | | #2

    Wall choice
    I tried putting the poly on the outside of the inner double wall on the first superinsulated house I built, this proved to be very difficult and went to a warm side air barrier after that. Blower door tests for each house showed no advantage to either air barrier placement.

    A double wall house reduces thermal bridging to great degree, even the wide I joist walls (12" or greater) will show some thermal bridge with an IR camera.

  3. homedesign | | #3

    I looked briefly at the experiment you linked to.....and all I see for Walls is Fiberglass Batt Insulation.
    Did I miss something? was densepack cellulose tested?
    How does this experiment offer "PROOF" that ALL houses should be built with rigid foam on the outside?

    Peter Yost,
    does the Experiment prove anything for you?

  4. Expert Member
    ARMANDO COBO | | #4

    Read it again John...
    Come on John... read it again...what part of 1"XPS for outside insulation you don't understand. I'm talking about OUTSIDE INSULATION ONLY!!! Besides, these are old articles and Mark’s presentation was new stuff, as Martin also points out. But it does prove to me that between Joe L’s, Straube’s, Rose’s and Mark’s tests and experiments for many years, one of their conclusions is that walls with rigid foam perform better than walls with out the rigid foam on the outside; and I do happen to trust those guy’s teachings, in fact, for more than 15 years now. Maybe, you would believe if you do a wufi or ashrae fundamental analysis on your wall or roof assemblies, while not perfect, it does tend to give you the answers pretty clear. Another point, I didn't mentioned anything about any wall cavity's insulation... I still use it.
    I included the links to the test hut for better understanding of what Scotts article was... if you need more info, contact Mark so he can explain it to you.

  5. homedesign | | #5

    Link to the New Presentation?..the New Stuff
    Armando, I looked again at the links you provided...
    I see 10 wall assemblies and every one has Fiberglass Batt Insulation.

    Do you or Martin have a link to the "New Experiment" ?

    Have any wall assemblies been tested with Densepack Cellulose?

    My point is .... How can you draw conclusions about All Houses in All climate zones from an experiment that only tested walls with Fiberglass Batt insulation?

  6. GBA Editor
    Martin Holladay | | #6

    Response to John Brooks
    My comment was made in response to one person -- Jesse Lizer, building in Climate Zone 6. Jesse was considering several options, including a wall assembly with exterior rigid foam.

    My comments were not made in the context of "all houses in all climates," as your caricature of my comments implies.

  7. Expert Member
    ARMANDO COBO | | #7

    As you said, “I looked briefly at the experiment you linked to.....” so, you may’ve needed to explore one of the links and read about the experiment. In there, it lists the wall assemblies’ used in the experiments. Again, I’m just talking about EXTERIOR INSULATION… I did not say you did not need interior insulation, and I do not understand what wall cavity batt insulation has to do with my comment.
    Keep on reading…

  8. homedesign | | #8

    Questions about the British Columbia Experiment
    At a recent building science conference, Holladay saw a presentation of preliminary findings from a test building in British Columbia that had been sheathed with OSB. “There were photos showing mold growth on the interior side of OSB sheathing in walls without foam sheathing over the OSB – under some conditions (50% interior relative humidity),” Holladay writes. “The walls with rigid form over the OSB were clean and dry – no signs of mold.”

    Martin, Did the walls with mold growth also have fiberglass batt cavity insulation?

    Were there any wall assemblies tested with Densepack Cellulose as the cavity insulation?
    (The type of wall that Marc Rosenbaum frequently promotes)

    Martin, do you think the type of cavity insulation matters?

  9. user-995931 | | #9

    double wall, put the sheathing on the inside wall
    I generally use the interior wall as the structural load bearing and shear wall and have the floor sheathing cantilever out to pick up a non-structural exterior wall. you have to insulate inside and out, but it keeps the dense-pack from overwhelming the drywall, and it requires an extra layer - drywall inside, ply/osb in the middle (structural shear and air barrier), and then a fiberboard or denseglas on the exterior beneath the weather barrier. this keeps the sheathing 'warm' and you don't need foam - the wall dries both ways.

    Aside from the extra material layer required (fiber board), the other downside is the continuous thermal bridge that the floor sheathing creates - but it's not all that bad in the grand scheme - it can be held back an inch or so and insulated on the very outside.

    The upside is it's solid, and very easy to build.

  10. 69eTea3bwd | | #10

    Choosing a High-Performance Wall Assembly? Forget Wood!
    I'm always amazed by the endless 2nd, or maybe even 3rd rate building science discussions on these "Green" Building sites.

    Modern Building Energy Designs do not include wood framing, in any fashion! End of story! To delude yourselves, and especially clients otherwise drags the entire field into the moldy cesspool of dogmatic repetition of the past.

    For +80% of the non-frozen landmass of the planet, buildings less than 6 stories should have their envelopes composed of low mass steel veneered SIPs; and placing an exterior insulative radiant barrier as a thermal break, even the 1/8-1/4" kind, virtually eliminates thermal transmission to/from the exterior environment via the SIP wall system, even in SIP widths of 4"to 6", though larger widths may be required in taller/complex homes/building designs. Again, end of building envelope (walls, floors, celings, roofs) story.

    Framing, double framing, foaming wood, not foaming wood, cellulose, interior/exterior insulative sheeting, house wrap, double house wrap... are all discussions by the ill informed about 1-D Fick's Law, which they almost never understand is what we teach Freshmen engineering students so that they can become Sophomore engineering students, and learn 2-D Fick's Law...and eventually go on to become real building scientists who understand that R-Value is not reflective of integrated building energy design performance.

    In the real world, you may choose wood-framing because you like your builder, like your architect, like the old world charm of horse and buggy days gone by, or more likely, because its cheap..., but it's not because you are interested in building a green, let alone, a sustainable home.

    While I hope the editorial staff will allow this post to see the www, it should be noted that there are powerful forces who are making billions building, and trillions servicing, non-sustainable housing. I wrote this post to find out which side Green Building Advisor was on; Truth or Profit ...and so we shall see!

    Hope This Helps?


    [email protected]

  11. GBA Editor
    Martin Holladay | | #11

    Truth or profit?
    The GBA website has information on wood framing as well as SIPs; you can read about both in our GBA Encyclopedia.

    We favor truth over untruth. But I fail to understand why you assume that GBA might be profiting by writing articles on wood framing. Is there some secret lumber-promoting organization handing out checks to journalists? If so, I haven't heard of it yet -- and no one has sent me a check.

  12. 69eTea3bwd | | #12

    Truth or Profit
    Dear Martian,

    If you’re not getting your checks, then you’re probably siding with truth, which as a onetime journalist I can understand is distressing. If profit becomes more important in the future then you should check with the USGBC, Green Communities, Global Green, the NAHB Green Builder Program, Green Builder Media, ...who seem to value $$$ above all other things, and I'm sure they can mentor you into the “Green Building” check-for-integrity oligopoly.

    Yet I'm hoping that my point remains pretty clear?

    That being, there is no such thing as a high performance 2x4 or 2x6 wood-frame wall assembly. There are only low-performance wood-framed assemblies, and even lower performance assemblies, sheeted, foamed, doubled or otherwise!

    …with the possible exception of/for people who happen live in San Luis Obispo, CA (SLO), where the mean, and average temperatures falls within the human comfort zone for ~10.5 months of the year. Yet even in SLO, where corollary issues like flame-spread, insect infestation, structural moisture annealing, wood rotting fungus, mold growth, subsidence, oscillating wind loading and racking issues, render the eye catching “High-Performance” wood-framed wall assembly discussion moot, or at least equivalent to that of nuns discussing sex.

    While I have no interest in questing your integrity or that of GBA, it was the articles title that captured my attention and the discussion of the topics participants that urged me to try to put a stop to this arcane waste of time.

    Yes, people in North America build wood frame houses, yes we have built 100’s of millions of them, yet No, its never a good idea and wasting time and energy about how to do the wrong thing less bad, is a tragic commentary on the state of the planet!

    Just the way I see it!

    So Please somebody make a valid scientific case that demonstrates my error in analysis! Please!!!

    If not, then I would ask GBA to restrain from further references to HP wood-framed construction ever again! As there is no such thing!

    [email protected]

  13. user-659915 | | #13

    Martin: John Brooks' comment on 'all houses in all climates' was directed at Armando Cobo, not you. This from Amando's first post:

    "Mark Gauvin’s presentation of his Coquitlam Test Hut is more than proof that all houses should include a wall and roof assembly with rigid foam on the outside no matter where the climate zone is built on."

    With all due respect, and unless I'm reading it wrong, Armando's apparent extrapolation of the results of this worthy program to all houses, all climates is, I'm sorry, ridiculous. The authors of the study are quite clear about its focus and limitations in their general introduction: "The marine climate of Lower Mainland, British Columbia and the Pacific Northwest presents a building environment with unique exposure conditions and associated challenges for both materials and assemblies......"

    Further, on a quick reading the test assemblies seem to consist only of wood framing, fiberglass and foam in various combinations, so JB's comment on the absence of test data on e.g. cellulose assemblies (one can think of many more) is also on target. Scott's article is a comprehensive summary of a thoughtful GBA discussion thread with important and nuanced conclusions, and these don't need to be hijacked by simplistic generalizations.

  14. GBA Editor
    Martin Holladay | | #14

    Response to John Brooks
    Sorry for the delay in answering your question; I was fairly sure I knew the answer, but I wanted to check with Mark Gauvin before I answered to be sure I got the facts rights.

    All of the stud bays at the Coquitlam test hut are indeed insulated with fiberglass batts; your point that the conclusions should not be extrapolated to cellulose-insulated walls is well taken. According to Mark, "We did not use cellulose on any walls - simply because we did not have enough space to try all the possibilities. I guess another factor is that cellulose is not in widespread use in this area, at least not when we started the testing."

    Thanks for raising the question and making your point.

  15. jLbSC4Sd9g | | #15

    Choosing a High-Performance Wall Assembly
    By Scott Harris
    Vice President of Construction
    Advanced Tek Systems

    We have chosen a somewhat different strategy by dumping the wood and foam insulation, We have a wall system that is steel studs, has an R38 rating, is breathable, contains no products that will promote molds, mildews, is EMF and Radon shielded, and comes close to net zero energy. If you wanted to be net zero or zero plus, the equipment needed would be drastically reduced. Its a healthy, comfortable and energy wise building.

  16. Natur Haus | | #16

    Who is this Chris guy anyway?
    O.K. First of all, thanks John Brooks for the questioning of the wall results. Cellulose is better. Chris, Can you historically prove your point. As far as I know, sustainability was around and successful long before you were born, and the homes built were out of everything BUT steel. There is nothing sustainable about mining, and trees can be regrown. So unless you pull a iron maker out of your ass you are just blowing steam.......which could be sustainable if harnessed......We'll see how long your steel framed, SIP, EIFS rot boxes are around for, my guess is not a thousand years, which history shows wood homes can last for easily.

  17. homedesign | | #17

    Question for Scott Harris
    Scott, you say you are building a steel stud wall with no foam and an R-38 rating.
    Can you describe your wall and insulation assembly in more detail?
    Are you using a "non-foam" outboard insulation?

    Otherwise...I can not imagine how you could be using a cavity insulation with steel framing.
    How are you dealing with thermal bridging?
    Can you post (or link to) photos of your wall assembly?

  18. user-723121 | | #18

    The Martians have landed
    It just bugs folks to no end you can take commonly used and sustainable building products and build a high performance home. To imply steel framing is anywhere near sustainable is not sustainable. Have you priced steel lately? Lumber is a bargain these days.

  19. wjrobinson | | #19

    This thread is hot! I too
    This thread is hot! I too want the merits of steel further explored.

    However technologies advance says both wood and steel are soon to be old ideas. Future homes will come out of giant onsite 3d printers is my prediction. What do ya think Martin and John?

  20. jbmoyer | | #20

    Thank you Matthew!
    Thank you Matthew for calling out this blowhard.

    Chris Foust,

    Are you serious? Steel structures pumped full of foam is a SUSTAINABLE building strategy? Will you please look at the definition of the term sustainable?

    As Matthew said, there is nothing sustainable about mining/manufacturing steel and petrochemical foams.

    You obviously don't know your head from your elbow, and your comments should be ignored.

  21. user-869687 | | #21

    Thermal Bridging
    Speaking of disadvantages to steel framing (and this may primarily respond to Scott Harris and Advanced Tek Systems): can you provide infrared imaging of your completed wall and roof assemblies in action? Your audience here includes many who work hard to remove thermal bridging from their projects.

  22. jLbSC4Sd9g | | #22

    Steel Studs
    John, We use the BIBS insulation and the steel studs are thermally decoupled which makes the wall system a high R value. It's the thermal decoupling that is the key and our secret for now and includes the way the windows are mounted, and picture can say a thousand words. We end up with a 10" wall cavity for the BIBS insulation.

    Most of the driving force for the steel stud development came from the reasons that Christoper already talked about. Non healthy cellulose based products that mold and mildew.

  23. wjrobinson | | #23

    White Paper for Advanced Tek
    White Paper for Advanced Tek Systems, Inc

  24. wjrobinson | | #24

    EcoTek - vs - Metal Framed
    EcoTek - vs - Metal Framed Panel Systems

    EcoTek - vs - Standard Wood Stud Framing

    I have to say, as of today with a bit of reading, I like.... Randolph D. Hedgebeth, Architect

  25. jbmoyer | | #25

    "It's the thermal decoupling
    "It's the thermal decoupling that is the key and our secret for now..."

    Yeah, and I have the secret to R-35 per inch building materials AND cold fusion.

    Scott, you and your "wall system" have no credibility until you produce test results and details.

  26. homedesign | | #26

    A thousand words?
    Scott, it sounds like you are not talking about conventional framing.
    As you probably know...cavity insulation in a typical steel framed wall is almost worthless.

    Did you intend to post a photograph? ... if sure to select "attach" after attaching the photo.

  27. albertrooks | | #28

    Oooh the irony...

    "I'm always amazed by the endless 2nd, or maybe even 3rd ra te building science discussions on these "Green" Building sites.
    Modern Building Energy Designs do not include wood framing, in any fashion! End of story! To delude yourselves, and especially clients otherwise drags the entire field into the moldy cesspool of dogmatic repetition of the past."

    The above statement of yours reads to me like dogma. If that's your mode... Then OK. Believe in your system and go to work and build stuff. I really don't think that your attempt at belittling others will bring you the satisfaction, or business, that you need.

    I find the irony in this thread quite deep. Not that you are... But that you name is so near to Dr Faust, who we know sold his soul to the devil in order to gain power and knowledge. That you so fervently have "special knowledge" that us wood frame guys are dumb and that the future is all styrene and ore from the ground ( along with vast amounts of energy to convert it to usable products.).

    But you couldn't just leave it there... You had to add that there must be a "Faustian like" conspiracy... and you ask if Martins got his checks from the Lumber Barons.

    Really Chris, it would make more sense for you to accuse ME instead of Martin of promoting wood at any cost! I'll even list the reasons for you: I'm a crass salesman by trade for 20 years. I sell to eat. My new scheme to profit off the unwitting is by importing and selling stuff to make the wood building shell airtight. Therefore, my motives must be impure.

    And by the way... I love wood. I started in a cabinet shop at 14. Had my own shop at 17. Built lots of stuff out of wood, will build more stuff out of wood, been a member of the Timber Framers Guild since 98, and am on the board of directors of a strong regional Passive House Association. Traveled building sites in Germany, Austria, Switzerland looking at how they build with wood, am currently putting the finishing touches on an import program to finally bring over the wood fibre insulation boards that are used in their superior wood buildings, just supplied the airsealing products to the first (or second?) commercial CLT (Cross laminated Timber) structure in America (Montana).

    So... Yeah... I really like wood... It's like your insulting my girlfriend... And dude... She's a hottie!

    That said, It really makes more sense that you level your conspiracy theory about the secret wood bribery "bags 'o cash" at me. Hell I'd take the bribe in a minute. Not because I need the money, just because I love wood!

    But you didn't aim that at me. You aimed it at Martin Halladay. Not that he needs any defense, he doesn't. it only takes him about a half a paragraph to point out what an ignorant fool that I am.

    The Irony is in that a "Faust" is suggesting that "Martin Halladay" would take a bribe. The other end that completes stage for Irony is Martins interview a couple of weeks ago where he talks about what he'd do if he "got the big check" to build a new house:

    "Martin: No, I wouldn’t. If I had that check and I hadn’t been shamed into admitting that I had forgotten about my charity obligations and my spiritual life — I'd have to rethink the answer — after I tithed, and then double-tithed — if I were hiring out the work, and I could afford something different — I’d like to see a better envelope than I have on my 1980 hippie house."

    So Chris... I'm not going to be a big fan of your steel and styrene wall system. So far you've insulted my girlfriend, called GBA contributors and readers dumb, and suggested that it's senior editor is "on the take".

    And btw... There are plenty of High Performance Wall System built of wood right now. And tomorrow, I'm going to wake up and help people find better ways of building High Performance Wall Systems out of Wood!

  28. WolfPackAlum | | #29

    Strapping = rain-screen
    If a rain-screen detail were applied to the double wall scenario, the labor/material cost comparison would tip back toward the foam, which has an inherent rains-screen (strapping). Now if we could just find a foam sheathing that is 100% recycled...
    As for Chris Faust - are you aware that there are timber-frame buildings several centuries old? During their lifespan the trees used in their construction have regrown and are now 'old growth'. I assume this person has never actually built anything himself.

  29. 8BCNZN5qeH | | #30

    Alternate Wall System
    The R38 is a hot box result and the building performances confirm these results.

    They actually perform better than R38 might suggest because of other things we do with our Building System in energy management and the lack of significant thermal bridging at any part of the envelope. Very careful detailing.

    We cannot share the detail information as we are in marketing start-up.

    Carbon footprint accounting is very good for recycled light ga. steel. Wood from forest to wall construction is anything but green, especially when you throw in the OSB. Well a lot of it is actually very green which helps the mold situation along.

    I will say that in the YEARS of development, I drew up every conceivable scenario to build a building and wood doesn't make it to level three, let-alone the top level for truly high performance. Sheathing and foam insulation just makes it ultimately worse. This is how we got into this mold nightmare in the first place and we continue to make it worse, not better. When I was a Sophomore in Architecture I developed what is now known as SIPS. After careful study I threw it away as ultimately a bad idea. This was well before Passivehaus.

    A breathable wall system is a must for a healthy building system that will be SELF SUSTAINING. Foam insulation and sheathing is antithetical to this ancient truth. Several millennia of construction is on this side of the argument.

  30. K4SH9nAKFH | | #31

    What About ICF Walls?
    We are currently building an ICF walled house in Nova Scotia . . . is this a taboo building material or what. The lack of articles and discussions about ICF in the magazine and on this website has me puzzled.
    Perhaps it's more fun to design complicated wall systems where half a dozen suppliers of everything thing from lumber, sheathing, insulation - batt, blown, or foam, vapor barriers, membranes, to foam panels, OSB versus plywood, and so on, can all get in the game and make a buck.
    For my dollar, ICF beats all in simplicity, solidity, airtightness, zero thermal bridging, speed of assembly, etc. There's been 3 houses built this way in the last 4 years in my Town alone, and our population is only 450. Let's see some recognition of the value of ICF, folks.

  31. homedesign | | #32

    Don't confuse Randolf or Scott with Christopher
    I have my doubts that "the system" will ever be Affordable.
    It IS interesting ...
    I don't think Randolf or Scott have been "out of line"

    ps Albert .. your link did not work for me
    I think the "Purdy house" that I posted a link to earlier is an example of "the system"

  32. GBA Editor
    Martin Holladay | | #33

    Response to Jeff Langstaff
    Q. "We are currently building an ICF walled house in Nova Scotia. Is this a taboo building material or what? The lack of articles and discussions about ICF in the magazine and on this website has me puzzled."

    A. The GreenBuildingAdvisor website has lots of articles about ICF homes. Here are some links to get your started:

    GBA Encyclopedia: Insulated Concrete Forms

    GBA Product Guide: Insulated Concrete Forms

    Green Homes: Foam Forms Create an Energy-Efficient Concrete House

    Q&A Spotlight: Should Insulated Concrete Forms be Air-Sealed?

    Q&A: Vapor barrier location in ICF construction?

    Q&A: ARXX ICF versus Durisol ICF in a Mixed Humid Climate?

  33. albertrooks | | #34

    Is it Green or is it mold?

    I think your issues that you present against wood are overstated. It's not hard to build a wooden wall that doesn't mold.

    "When I was a Sophomore in Architecture I developed what is now known as SIPS. After careful study I threw it away as ultimately a bad idea. This was well before Passivehaus." I'm not sure what your saying here... That you came up with SIP's but then threw it away?

    "This was well before Passivehaus." Passivhaus does not call out an envelope, it's only predicts it's load. It does it quite accurately. I suggest that you take a close look at the PHPP. It's really only concerns itself with finding and accounting for envelope gains & losses. Because it is "blind" to the methodology and only looks at performance, it shows quite readily that the worlds best envelopes can be made out of many materials... including wood.

    The statement that wood is not a green material is simply not true. Wood is natures perfect building material. It grows out of the ground while being fueled by light and water. While on the stump it provides habitat and converts co2 to o2. It's easily converted to useable forms for structure, sheeting and finished layers. Once well into the life span, a wood building can be readily re-modled and updated.

    At the end of the building life, wood can go back into the ground and the cycle can be repeated.

    While I respect your work in creating and making alternative systems available, I don't think that the best course in presentation is to rely on making wood look bad in order to make your "steel and foam" system look good. How about just relying on your systems merits?

    I understand that steel and foam can offer a lot. Just the requirements for prefabrication rather than site work is a promising trend. The problems that I see that comes with relying on steel & foam where wood can fit the application is at the beginning and end of life of the building. Harvesting steel and styrene is no simple thing. It's extremely disruptive to the environment. At the end of it's service life when the building needs to come down, what happens with all of that foam encased steel? It certainly can't go into the ground. There are no recycling practices. So what is the opportunity for re-use of the material?

    I'm assuming that your system is based on steel and foam due to the article about your work attached. I've seen many impressive walls systems based on encasing steel framing members in EPS. They are interesting and appear to show promise from a performance standpoint. However I don't feel that the materials are sustainable or green. Perhaps it's fine for a single generation but I don't think it that the essence of the materials are regenerative.

    With wood, we can grow another forest. They are certainly beautiful to look at...

  34. albertrooks | | #35

    Thanks John. I think I've got the link fixed. Try it again.

    To Jeff, Scott, & Randolph...

    Perhaps I'm painting with too large of a brush. I don't think that foam doesn't belong in light frame construction. It certainly has a place. ICF's have contributed to the overall discussion of the quality and value of envelopes. Without ICF's we'd be further behind in both alternatives and public awareness of the many paths to improved envelop efficiencies. SIPs included.

    I don't purport to have the "answers", just a personal bias. My bias is obviously wood.

    To take a step back and be clear about my rant (knowing full well that it's just a rant)... My issue is with any statement saying that it is not possible to build a high performance wall system from wood.

    It's just sad to rule out such an excellent material. Obviously it get's my Irish up...

    My goodness. Build out of whatever you want. Just make it perform well, last a long time and teach non builders (consumers) why it's important to do it.

    End of rant.
    Happy building :)

  35. wjrobinson | | #36

    Albert, Christopher Faust is
    Albert, Christopher Faust is the metal/foam wall guy. Advanced Tek Systems are the other polite gents. Once steel is made it is highly recycled. Another point, building superinsulated home in wet climates is no picnic. So coming up with a home that has no ready to mold paperfaced drywall, ready to rot OSB, or framing, and NO FOAM, no or at least less concrete is a fantastic option. The insulation is BIBS not foam. This makes the homes perfectly suited for deconstruction and therefore fully recyclable.

    My last concern like John is cost. That too can be dealt with via training and panelization possibly.

    As to Faust, Google his name and read up on a New Orleans contractor......

  36. wjrobinson | | #37

    Randolph Hedgebeth, for the
    Randolph Hedgebeth, for the wood loving crowd someday you might want to develop a frame substituting Blue Wood for the metal. You would lose the strength ideas you talk of but much of the northeast has lower code requirements for wind and earthquakes.

    Could you tell us more about costs such as what the Purdy house costs were over a wood frame that was outsulated or a cellulose filled double wall frame?

    I for one here at GBA am all for your work and wish you much success in your endeavor.

  37. albertrooks | | #38

    Thanks AJ Builder
    I found an article by googling as you suggested...

    Yes. I incorrectly grouped the Advantec guy's in with Mr. Faust. Sorry Advantec Guys... My bad, not yours...
    I get the BIBS and that steel can be recycled. If it spurred more deconstruction and separation then great.

    Wood and moisture are certainly problems. The other systems are not free from problems either. For wood it gets more challenging as the assemblies become bigger and harder to dry, once wet. One solution that is not in common practice today is prefabrication. It weather protects the assemblies from being saturated at the site, and hopefully we increasingly lower costs by gaining efficiencies in the shop. We are putting that into place out here: We're pretty young at it, but are committed. See:

    Thanks for the correction.

  38. wjrobinson | | #39

    "Advanced Tek Systems"
    "Advanced Tek Systems" Albert.... Advantec is lots of whatever companies and Advantech is Huber's special OSB sheathing that I recently watched rot in 3 years because a floor system built never went ahead to becoming a finished project. Keep up the good work Albert, I'll check out your link.

  39. 8BCNZN5qeH | | #40

    Cost, wood, foam and mold
    I spent some time in the late 70's doing R&D for a urethane foam company. I researched all forms of foam and continue to keep abreast of the technology. Foam has its appropriate applications but NOT in buildings. It is highly combustible unless you make it toxic as hell, but then it's already toxic enough.

    Putting wood and foam together is a fire bomb. Verges on total irresponsibility.

    Our houses are affordable in their basic form though not cheap. They also have a 1 to 2 hour non-combustible fire rating without any toxic elements.

    I LOVE heavy timber construction and have worked with it in the past and in a few large local historic rehabs.

    The main issue of historic wood houses that have survived all these several hundred years lies in their breath-ability. Having been raised amongst such historic buildings (Williamsburg, VA) and in a family of artisan brick masons I first appreciated these buildings and they are my model. That is why I designed for this system to survive a minimum of 50 years and most likely for several hundred. Re-cycling my buildings is not a top priority. Their health and survivability is.

    Far too little attention is paid to "Life Cycle Costs" in our designing and building today. If we did we wouldn't be zipping up our buildings and making them air tight. They will not survive on their own past two seasons. I know this from inspections I perform for Condo certifications. Among these are mold infested, new SIPS buildings.

    Mold infestation is probably the number one health problem in America AND the least diagnosed. The reason is we build it into our houses and work places.

    So as builders and designers we have the responsibility to design way past recyclability. The health, energy efficiency and Life Cycle Costs are at the top of the agenda. I found that GREEN and recycling almost take care of themselves.

  40. user-1012653 | | #41

    For what its worth, I am
    For what its worth, I am moving forward with a 12" double stud wall design for the home. Dense packing with cellulose and using ZIP sheathing. To hit high r, cost of materials is less then the foam options, and I do think the construction will be faster even with the inner frame wall.

  41. BruceAF | | #42

    My two cents....
    Let’s face it....wood framing material today sucks and is only getting worse. I have been building for over 25 yrs. and I have seen the quality for framing material go down hill fast. Wood may be “natures perfect building material” but it has a lot of drawbacks as well. A college professor of mine started off his structural engineering course by postulating that if wood was ‘invented’ as a building product it would never sell. It is not stable, it twists, warps, splits, and it is difficult to quantify its structural capability in any consistent way. We use it today because that is what we have been using for centuries was cheap and plentiful and available....not so anymore. So maybe this paradigm needs to shift. Is wood really ‘sustainable’? I am not sure that the forests can keep up with the demand. Loggers clear cut large areas of land to supply the lumber mills. They then plant new trees and grow them fast, degrading the quality of any future lumber that these fast growth trees may provide. I think it is a vicious cycle that cannot not be sustained. I am not suggesting that steel framing is the answer, but I am suggesting that we need to find new ways to build that are sustainable.

    In my opinion, Mr. Hedgebeth makes many valid points. He has certainly peaked my interest in his approach to building for the 21st Century. I hope he will be willing to share a bit more of his approach to construction in way that will still reward him for his efforts.

    And to Mr. should get off you high horse and engage in some discourse about the issue. There are seven ways to the get to the beach and yours may be one, but it is surely not the only one. So don’t be so full of yourself and share a bit of what your approach is so that might learn something....maybe even find a better way to get to the beach :)

  42. Natur Haus | | #43

    question for Bruce Friedman
    What material or manufactured building good is consistent these days? None, to my knowledge. Just because most of our lumber supply is not sustainably harvested, doesn't mean it can't be. For every one of it's negative properties, wood has two positive attributes.

  43. user-1012653 | | #44

    I did considering running the ICF from footing to roof, however they do not perform well in cold climates according to various case studies, do not have the high r I am after (unless you add more foam to the already costly system), and do cost quite a bit more as well as complicate the planning and design some what. I do like the seemingly effortless natural air sealing they provide, strength, sound and fire resistance. However I am not sold on them from an energy performance stand point.

  44. user-1021589 | | #45

    High Performance Wall
    To ICF or NOT??? I'm about to build a house that has been influenced a great deal by the Millcreek and Riverdale homes in Edmonton, Canada. These have a double-wall system with 16" cavity filled with cellulose . My double-wall is slightly less (15.5" for R54)), but then the Ottawa Valley is slightly warmer than Edmonton.

    At present, we're pouring over cost projections with the builder in an effort to shoe-horn the project into our budget. In doing so my builder has advised that the foundation and knee wall on the north (in my design the north wall is compound, with 4.5" of concrete and 4.5 feet of framing making up the 9 foot exterior portion of the double wall - the house is partially earth protected) would be cheaper in ICF . He feels that in Ottawa, the cost of forming, concrete, and the extensive application of insulation will be more costly than the simpler ICF, which he can do without sub-contracting.I am ok with this so long as it shrinks one of the numbers on the estimate!!

    Today, he called to ask me if we would consider going ICF to the roof, with an extra application of 2" of foam on one side of the wall. He thinks it will save enough labour that the cost savings over the framing would be equal to the cost of the cellulose insultation ($20,000). The ICF guys advise the wall will be R58. It will be 6" of foam and 6" of concrete.

    Leaving aside the issues of embodied energy, does anyone here believe the ICF manufacturer's Rvalue estimates when applied to a climate such as Ottawa where were regularly experience winter-time lows of -35C? I have a hard time believing and ICF wall with R36 worth of actual insulation would perform like R58, but I concede it would be very good. And it would definitely be air-tight. My plan already has a 4 inch concrete slab for passive solar performance.

    I love the double-wall approach with cellulose. I get the performance I want, using receycle content and with a very low burn rate. But if I can save $20000 it might be worth it.

    Feel free to comment on the embodied energy aspect if you like.

    John Scime
    outside OTTAWA, Canada

  45. user-1021589 | | #46

    ZIP sheathing Rvalue?
    To Jesse above or anyone - can you point me to an R value for the ZIP board? I have considered it as well. What is the Rvalue for your 12" wall with ZIP sheathing?

  46. albertrooks | | #47

    An agreement to Bruce Freidman

    "Let’s face it....wood framing material today sucks and is only getting worse. I have been building for over 25 yrs. and I have seen the quality for framing material go down hill fast. Wood may be “natures perfect building material” but it has a lot of drawbacks as well."

    I certainly have to agree with you there! It's really sad. I'm a native of the Pacific Northwest. I grew up around some fantastic forrest lands. I'm no expert, but where I live, It still looks to me that there are healthy forests in production, however, the good material is trucked to our ports and shipped over seas. I've watched these logs ship to Japan for the last 20 years. I see the trucks everyday. All that's left in our yards is the diminishing quality of so called #2 cut from the small stuff with butts barely bigger than 7", while the smallest log butt I see go out of the port of Olympia is 20".

    I'm not knocking the overseas buyers. It's just that the economics are such that they get more by selling the logs out vs milling them into framing lumber here.

    The extent of how poor the material that's in my local yard came to me by contrasting the material that I saw on job sites while on a recent trip to Switzerland. The European stick frame is built typically with something like a 2x8 (but more like a 2.5" wide). It's plantation grown with reasonable growth rings width and very small tight knots. the species looks really close to Douglas Fir. I'm not a framer but it sure looked good to me. The impression that it made on me was that superior grade framing lumber is possible from a plantation approach. Provided that the economics have the material going into framing material rather than sold out for other purposes.

    I wanted to just illustrate that the poor quality material that we see in the yards here is not necessarily the materials fault. It's just that the economics of wood today have us using the lowest grade material for framing.

    So... I know that doesn't change the situation, it just describes an aspect of the problem. I can see why other, more stable building systems would be attractive. My hope is that at some point that "the market" (whoever that is) starts turning a little more to higher quality envelopes which in turn might create some demand for higher quality framing material. I still have hopes for wood since the ingredients to make the stuff is: air, water & sunlight on a decent patch of dirt.

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