[Greenbuilding] Double Stud walls
George J. Nesbitt
geoedb at idiom.com
Sat Jul 22 22:27:29 CDT 2006
Robert,
its good to know we have an old time superinsulation builder on the list.
The double wall you described is a great system.
I am wondering why you didn't use 24" oc framing on the inside
structural wall (2 story?).
And could you use 2x3 on the exterior wall, to save lumber and cost?
Why do you not build double walls any more (cost)?
What is the state of superinsulated construction in Canada and the
United States?
I recently unpacked my books and now have acess to them, and came across
The Superinsulated Home Book, by J.D. Ned Nisson (1985).
And I am blown away by the information in it, and how little of it has
been implmented, especially here out west.
Is J.D. Ned Nisson still with us? Energy Design Update apears to still
be around, but is published by someone else.
I don't know of any more current books on superinsulation, but would
highly recomend this to anybody, available used on the internet.
Fine Homebuilding had an article a long time ago showing a wood I-joist
as a wall stud, and I was just flipping though Residental Energy, by
John Krigger and he showed a drawing of this, does anyone have any
experience with this? It seem like it would be a good method to get a
thick wall for lots of insulation without much wood use, less expensive
that a double 2x wall.
Superinsulation (and Pasive House vs. Zero Energy) is definately a
better way to go than a strictly pasive solar house.
If passive solar is considered "green" wouldn't superinsulation be
considered "greener"?
A superinsulated house does better if you don't go overly passive solar.
Solar hot water and PV get lots of attention, but the reason Zero Energy
dosn't pan out yet is they haven't paid enough attention to cutting load
first.
Clarke Olsen wrote:
>>>The reasoning behind this wall system was (1) to isolate the wiring
>>>on the warm side of the vapor barrier, the thinking being that the
>>>wires and the outlet holes compromised the insulation (especially
>>>batts), (2) that the finished wall
>>>
>>>
> was the same thickness as 2x6, allowing standard window/door trim,
>(3) the foil-faced foam was a reflective
> surface, thermal break, vapor barrier, and R-5 to boot, (good
>value from minimum foam use),(4) to enable vertical
> drywall in 8'+ ceilings. I did say that if I were to do it again,
>I would frame with 2x6. I agree that the double vertical
> wall gives a thermal break sans foam.
> Clarke Olsen
>
>
>
>>>On Tue, 11 Jul 2006 21:26:04 -0400, Clarke Olsen <colsen at taconic.net>
>>>wrote:
>>>
>>>
>>>>I have built double walls like this: 2x4 framing, filled with
>>>>insulation, then covered inside with 1/2" foil faced foam, which is
>>>>then strapped with 2x4's flat. All the wiring takes place in this
>>>>1.5"
>>>>space, using 4"x4"x1.5" boxes. Taping the foam joints will make it a
>>>>vapor barrier.
>>>>For a really well insulated house, I would frame with 2x6's @ 2' oc.
>>>>
>>>>
>
>
>
>> On 7/12/06, Robert W. Tom <ArchiLogic at yahoo.ca> wrote:
>>
>>
>>>I don't follow the reasoning for strapping a 2x4 wall with 2x4's laid
>>>flat.
>>>Those same 2x4's stood on end and flipped 90 degrees:
>>> - are capable of being a loadbearing wall
>>> - are capable of providing a cavity to hold R-12 or better
>>>insulation
>>> thereby eliminating the need for the expensive foil-faced foam
>>>insulation
>>> - are capable of providing wiring and plumbing chases
>>> (to carry any-sized electrical boxes)
>>>
>>>etc.
>>>
>>>Nor do I follow the reasoning behind going to the trouble of making a
>>>double-stud wall if all one is going to do is insulate it to less than
>>>R-30.
>>>
>>>Years ago when I was still making stick-framed/double-stud walls,
>>>(this
>>>was wa-a-a-y back in the Dark Ages, pre-Windoze OS, pre-WWW ...when
>>>people
>>>still wrote letters on paper and mailed them in envelopes and
>>>non-technerds like me were struggling with DOS, Fortran, BASIC etc.
>>>when
>>>trying to use these infernal computing boxes ) ... the minimum
>>>criteria
>>>for a double-stud wall would be a nomimal R-40.
>>>
>>>ie (from inside-> out )
>>> (i) drywall
>>> (ii) 2x4 bearing wall (studs at 16" o/c) insulated to nominal
>>>R-13
>>>(ie
>>>3.5" Roxul)
>>> (iii) vapour diffusion retarder/continuous air barrier membrane
>>> (iv) structural sheathing
>>> (iv) continuous layer of R-13 insulation, no framing in cavity
>>> (v) 2x4 curtain wall
>>> (studs @24" o/c, centres not aligned w bearing wall studs)
>>> insulated to R-13
>>> (vi) exterior sheathing
>>> (vii)AIF or housewrap
>>> (viii) 3/4" ventilation airspace
>>> (ix) rainscreen cladding
>>>
>>>Typically the stud walls were built on top of each other on the floor
>>>deck... curtain wall propped up on temp blocks until 1/2" plywood
>>>plates
>>>were applied to the top plates of the bearing and curtain walls
>>>(essentially creating a box beam out of the top plates) and the outer
>>>two
>>>thirds insulated before tipping the walls up. Once stood up, the
>>>heavy,
>>>wide walls would stand and stay straight without any temp
>>>props/bracing.
>>>
>>>Since the VDR/continuous air barrier membrane (I preferred black 6 mil
>>>poly) is on the outside of the bearing wall and backed-up by
>>>sheathing,
>>>with at least R-26-worth of insulation on the outside, the bearing
>>>wall
>>>could be left uninsulated so that services could be installed in the
>>>"normal" fashion without having to futz with air-sealing details and
>>>the
>>>shell would at that point, already be better insulated than most tract
>>>housing so that even in the middle of winter, the interior would be
>>>warm
>>>without any auxiliary heating systems in place.
>>>
>>>And since the poly was black, any accidental punctures or tears as a
>>>result of installation of services would be readilly visible against
>>>the
>>>light-coloured sheathing behind it and easily repaired.
>>>
>>>Then all services were installed, the bearing wall would be insulated
>>>and
>>>the drywall applied, again in the "normal" fashion, without any
>>>futzing
>>>with air-sealing since it was done as soon as the walls were tilted
>>>up.
>>>
>>>Another advantage to the above technique is of course that interior
>>>renovations and access to services in the bearing wall can be
>>>accomplished
>>>without any concerns about compromising the integrity of the air
>>>barrier.
>>>
>>>Back then (when trees were plentiful and dinosaurs still roamed the
>>>Earth), it was less costly to do a double stud wall in the above
>>>fashion
>>>than it was to do a 2x6 wall and slap rigid foam onto it to bring it
>>>up to
>>>superinsulation levels.
>>>
>>>
>>>
>>>=== * ===
>>>Rob Tom
>>>Kanata, Ontario, Canada
>>><ArchiLogic at yahoo.ca>
>>>
>>>
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>>
>
>
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> publisher of Environmental Building News and GreenSpec(r)
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