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  1. #1
    Join Date
    Dec 2008
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    Milford, DE
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    Default Performance of staggered stud exterior wall

    Insulation of 2x6 walls is hindered by thermal bridging of studs. While OVE/advanced framing can help, the issue remains. I came across "staggered stud" construction and wonder how much improvement it would make.

    The only mention of staggered studs as load bearing walls I've found is here:
    http://www.theleapfroghouse.com/inde...play.learnmore
    These walls are usually non-load-bearing interior for sound deadening.

    The idea is still using 2x6 plates, but with 2x4 studs, 24"oc along the interior, and 24" along the exterior, staggered. Roof framing would align over exterior studs, trimmers would still be 2x6.

    Concerning material costs, 2 2x4s may be cheaper than 1 2x6. So, this wall would cost less in materials. Wiring could also wiggle its way between studs without drilling.

    There would be more physical wood in the wall, but less bridging.. so I'm wondering how it performs.

  2. #2
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    Dec 2008
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    Milford, DE
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    168

    Default Re: Performance of staggered stud exterior wall

    Hmm. With 2x4s on the 2x6 plate, there's a 2" gap at one end of the 2x4. A 1.5" x 8' sliver of rigid foam would insulate that space great. Fill the cavities with cellulose.

    If you're using rigid foam sheathing instead of structural sheathing, you could ditch the staggered studs and place the 2x4s all flush to the interior, with minimal oc spacing, attach rigid slivers on the exterior edge of the studs, and then attach the foam sheathing through the slivers. I'm not sure how difficult it would be to nail/screw through the outer sheathing plus the 2" thick sliver.

    If stick framing, you'd need special detailing at the top plate such that the bird's mouth was bearing over the interior-aligned studs.

    It's a few more details, but not much, and it could boost your wall R-value with only a few pennies. Anyone ever heard of such a technique?

  3. #3
    Join Date
    Sep 2004
    Location
    Rimbey, AB, Canada
    Posts
    333

    Default Re: Performance of staggered stud exterior wall

    If you are already using foam sheathing, then I dont know how much a staggered stud wall will really help you. The idea with the staggered studs is to provide a thermal break between the outside and inside. The foam sheathing already acomplishes this.
    In trade school we saw a few thermal images of houses on the same street taken the same day. It was very interesting to see that a traditionally framed 2x6 wall with foam sheathing easily outperformed a staggered stud house with standard sheathing. This was just one example of two real world houses though. There could easily have been other contributing factors.
    ____________
    Darren Dolman

  4. #4
    Join Date
    Jul 2006
    Location
    Portland, OR
    Posts
    2,460

    Default Re: Performance of staggered stud exterior wall

    A lot of work to reduce bridging. A sheet of foam over the entire exterior of the wall would do just as well or better

  5. #5
    Join Date
    Jun 2004
    Location
    Northern Vermont
    Posts
    1,381

    Default Re: Performance of staggered stud exterior wall

    Mdr999,
    To read more about staggered-stud walls, check out
    http://www.greenbuildingadvisor.com/...ble-stud-walls

  6. #6
    Join Date
    May 2007
    Location
    Duluth, Minnesota
    Posts
    245

    Default Re: Performance of staggered stud exterior wall

    Quote Originally Posted by mrd999 View Post
    Insulation of 2x6 walls is hindered by thermal bridging of studs. While OVE/advanced framing can help, the issue remains. I came across "staggered stud" construction and wonder how much improvement it would make.

    The only mention of staggered studs as load bearing walls I've found is here:
    http://www.theleapfroghouse.com/inde...play.learnmore
    These walls are usually non-load-bearing interior for sound deadening.

    The idea is still using 2x6 plates, but with 2x4 studs, 24"oc along the interior, and 24" along the exterior, staggered. Roof framing would align over exterior studs, trimmers would still be 2x6.

    Concerning material costs, 2 2x4s may be cheaper than 1 2x6. So, this wall would cost less in materials. Wiring could also wiggle its way between studs without drilling.

    There would be more physical wood in the wall, but less bridging.. so I'm wondering how it performs.
    If you are going to bother with staggered studs, I'd suggest going with 2 x 8 or wider plates.

  7. #7
    Join Date
    Feb 2008
    Location
    North Central Vermont
    Posts
    1,866

    Default Re: Performance of staggered stud exterior wall

    Quote Originally Posted by mrd999 View Post
    There would be more physical wood in the wall, but less bridging.. so I'm wondering how it performs.
    As noted, you'll get slighty better energy perfomance with an exterior foam board thermal break, but if you wanted to avoid foam - either for environmental reasons or to avoid siding nailing issues (thousands of nails penetrating exterior foam can dramatically reduce its effective R-value) - then staggered studs is a fine option.

    There's no need to rip foam strips, however, since blown cellulose will fill all the voids and offer a similar thermal break at far less effort and cost.

    But once you've taken the step to staggered 2x4s on a 2x6 plate (still with 2x6 trimmers as thermal bridging), you might consider a double-wall on separate plates to completely eliminate thermal bridging and allow an insulation cavity of any thickness. The thicker the wall, the smaller the percentage of wood.

    For comparison, a 2x6 16" oc wall with cellulose would give a whole wall R-value of 17.3. A 2x6 16" oc wall with cellulose and 1" exterior XPS would give R-23.4. A staggered stud wall with cellulose as you describe would give R-21.2.

  8. #8
    Join Date
    Jan 2006
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    upstate NY
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    1,761

    Default Re: Performance of staggered stud exterior wall

    Back around 1988 there was a wall system sold around here called the “Barrier System”. I think it came out of Vermont and the company went under. It was a 6” deep TJI with 2” foil faced foam insulation and an air space between both the drywall and sheathing.

    It peaked my interest and I wondered how a 6” wall made with TJIs would perform with standard types of insulation. You don’t get rid of all the thermal bridging but you go from 1.5” down to 7/16” on every stud, which I would say is a big reduction.

  9. #9
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    Feb 2008
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    North Central Vermont
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    Default Re: Performance of staggered stud exterior wall

    Quote Originally Posted by johnny watt View Post
    Back around 1988 there was a wall system sold around here called the “Barrier System”. I think it came out of Vermont and the company went under. It was a 6” deep TJI with 2” foil faced foam insulation and an air space between both the drywall and sheathing.

    It peaked my interest and I wondered how a 6” wall made with TJIs would perform with standard types of insulation. You don’t get rid of all the thermal bridging but you go from 1.5” down to 7/16” on every stud, which I would say is a big reduction.
    I'm not quite sure what you're describing as the "barrier system", but TJIs are being used as vertical structura members both in the US and Europe for superinsulated homes. You can also site-fabricate parallel chord trusses for an exterior insulation cavity (Larsen Truss) or consolidate them into the structural framing as I do with my modified Larsen Truss.

    The attached Larsen Truss version uses alternating plywood and foam board webs. I can attach only two pictures so I'll show the modified Larsen Truss in the next post.
    Attached Images Attached Images

  10. #10
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    Feb 2008
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    North Central Vermont
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    1,866

    Default Re: Performance of staggered stud exterior wall

    After building a number of double-wall houses and then a Larsen Truss (exterior insulation cavity) house, I developed the modified version which creates a single insulation cavity, has less thermal bridging than any other system except SIPS, and offers any depth of insulation desired (I use 12" R-45). I use rough-sawn full-dimension lumber but it can be built with KD as well.
    Attached Images Attached Images

  11. #11
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    Jan 2006
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    upstate NY
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    Default Re: Performance of staggered stud exterior wall

    I had never heard of the Larson truss until you started posting about it the last few months. You have written a lot of interesting stuff to ponder here that last few months.

    I was involved in one 12” double wall and I do not really care for walls that thick. Besides, if the home is comfy and reasonable to heat with a 6” wall, I am happy. According to this article, we should all be doing our part to keep the second law alive:
    http://www.physorg.com/news137679868.html

  12. #12
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    Feb 2008
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    North Central Vermont
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    Default Re: Performance of staggered stud exterior wall

    Quote Originally Posted by johnny watt View Post
    Besides, if the home is comfy and reasonable to heat with a 6” wall, I am happy. According to this article, we should all be doing our part to keep the second law alive
    And that is the gist of our problem: we are doing our part to accelerate entropy rather than to find the optimum sustainable balance between exergy (order) and entropy (chaos).

    What the article you linked to misses entirely, with a blindness typical of physical scientists, is that life is the anti-entropic process of the living universe: creating higher levels of order and organization, both through the biological process of evolution and through the cultural process of art and architecture.

    We can responsibly build minimally-insulated houses (and I consider anything with 6" walls minimal) only if they are powered exclusively with low-exergy energy sources like solar, wind, water and wave.

    We don't waste energy (the first law of thermodynamics says that it cannot be created or destroyed), but we waste enormous amounts of exergy (highly-concentrated energy such as fossil fuels and nuclear) by using them for low-exergy needs such as space heating and cooling.

    The challenge before us is this: are we going to contribute to an ecosystem that will, according to the article "maintain the highest rate of energy dispersal" or to an ecosystem that maintains the minimal necessary energy flow and exergy reduction (entropy increase) required for our survival and comfort. In other words, are we willing to live in such a way that future generations are compromised or will we live so that evolution (and our own progeny) can continue to weave an ever more intricate web of life?

  13. #13
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    Jan 2006
    Location
    upstate NY
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    Default Re: Performance of staggered stud exterior wall

    (and I consider anything with 6" walls minimal)
    Just curious… in forming your opinion, how did you arrive at that number?
    I am going to be building a 6000 sqft home soon for myself. Shouldn’t that have a higher standard then the guy that has 1200 sqft?

    They say that the sun will boil the water off the earth a billion years from now.
    Not that we should rush it any. But they also say that necessity is the mother of invention.
    Maybe the sooner we convert all those hydrocarbons to lower forms of energy, the sooner someone will come up with something better.

    I cannot help but to be skeptical of all those laws of science.
    E=MC^2, does it not contradict the conservation of energy?
    I agree, life contradicts the high entropy theory and I’ll add, “so do rainbows and smuggler’s notch”.

    Hawking theorizes that a black hole will boil away over time.
    So much for the universe coming to a single mass at a single temperature.
    They told Tesla the AC motor was impossible.
    I wonder what criticisms Tesla would have of Carnot’s work, had he chosen that branch of science.

    I don’t have much use for these young punks today…what with their tattoos, piercings, Ipods and texting.
    So I doubt I would have much use for posterity.
    Still the same, I can live with waste not want not.
    But then again that’s why I don’t use 2 x 4 walls.

  14. #14
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    North Central Vermont
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    Default Re: Performance of staggered stud exterior wall

    Quote Originally Posted by johnny watt View Post
    Just curious… in forming your opinion, how did you arrive at that number?
    Well, that number - 2x6 walls (R-19) - is today's energy code minimum standard, which I believe is far too low. It made sense to me 25 years ago to build to superinsulation standards. Today, as the climate deteriorates and we side down the slope of peak oil, it seems foolish and irresponsible to do anything less.

    I am going to be building a 6000 sqft home soon for myself. Shouldn’t that have a higher standard then the guy that has 1200 sqft?
    There is simply no ethical or rational justification for a 6000 sf single-family home.

    In 1950 affluent America, we thought 300 sf per person was adequate. Today the typical American home has 900-1100 sf per person, about double what Europeans think they need for a similar standard of living.

    The primary determinant of building energy consumption and resource use is size. So the first rule of conservation is to build small. In today's world, it should be criminal to build anything larger than what basic needs would require.

  15. #15
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    Jun 2004
    Location
    Friday Harbor, San Juan Island, Washington
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    Default Re: Performance of staggered stud exterior wall

    Quote Originally Posted by johnny watt View Post
    I am going to be building a 6000 sqft home soon for myself
    Are we talking upstate NY here? I would think that a house that size in a cold climate would be very expensive to heat and that you would be interested in building a well insulated house simply from a cost-of-heating perspective. If you expect to die somewhat soon and don't care what happens to the house after that, then I guess a code-minimum house might be adequate. Your comments about today's kids are somewhat strange, given that most generations were distasteful to their elders for a period in their teens and 20s, probably including you (and definitely me) unless you were one of those fabled altar boys.

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