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</o:shapelayout></xml><![endif]--></head><body lang=EN-CA link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'>I find it simpler as design concept to keep the structure as one element independent of what I’ve been calling the ‘sacrificial’ parts or everything subject to elements. In this way the structure is primarily protected. The sheathing forms part of that structure and moves with it. The sheathing is definitely a wrb but shouldn’t be the primary as its primary role is structural. My preference there is having the primary wrb outside of an exterior insulation layer (board insul). <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'>Windows, doors other penetrations are easily deformed by attachment to structural sheathing – they used to have big leaky gaps between them and the framing so they could float. Current nail fin attachments are overly fastened and adhesive membranes do restrict floating) – big problem for air leakage when windows get twisted – so not an ideal attachment point for those elements. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'>Window and doors and other surface elements can float nicely on exterior insul board – not as carpenter friendly but at that point the carpenter hat comes off and the ‘enveloper’ hat should be on.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'>On the subject of rock wool and cellulose. I’ve been involved lately in pre 1990 rehab projects and having to specify exposure contaminant controls for worker safety and it is getting serious and seriously expensive. At this point it is still primarily asbestos and lead concerns but dust exposures from aged friable borax laden cellulose, fiberglass, and brittle formaldehyde coated rockwool will soon be added the list. I think we need to seriously reconsider loose fill insulations of any sort.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:black'><o:p> </o:p></span></p><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> Greenbuilding [mailto:greenbuilding-bounces@lists.bioenergylists.org] <b>On Behalf Of </b>Alan Abrams<br><b>Sent:</b> March-27-14 2:29 PM<br><b>To:</b> Green Building<br><b>Cc:</b> archilogic@chaffyahoo.ca<br><b>Subject:</b> Re: [Greenbuilding] Double-stud wall (was Re: Best bang for the buck in wall insulation)<o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><Logically, the interior wall would be the one designated as load-bearing even if only because doing so shortens the spans of flexural members like joists and rafters. When we're talking about fat superinsulated walls, the difference in span can mean a difference in one joist size.></span><o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>taking off from the perspective pasted above, one could quickly arrive at a Larson type system, where you not only shorten the span of the floor system, but eliminate it altogether beyond the bearing wall.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>OTOH, if the premise is keeping the air barrier in a single vertical plane--and factoring in the current code obsession with braced wall systems--I still prefer keeping the air barrier and sheathing--and therefore the outer stud wall, in a constant plane. all the other previous points reinforce this--logical integration of windows and doors, combining air barrier and drainage plane--not to mention--keeping it low tech and carpenter friendly.</span><o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>The point about reducing joist depth is well taken: there is value in "resourcing down." But it is less significant if you're using wood I-beams. A tree that could provide a nice 2x12 is best left in the forest, but a little more OSB to take a TJI from 9 1/2" to 11 7/8" is less of an impact.<br><br>It's worth mentioning that this strategy derives from Building Science Corp's design for the NIST Net Zero Energy Test House--a sublime piece of work, IMO...<br><br>-AA</span><o:p></o:p></p></div></div><div><p class=MsoNormal><br clear=all><o:p></o:p></p><div><p class=MsoNormal><span style='color:#660000'>Alan Abrams<b><br></b></span><i><span style='color:#666666'>certified professional building designer, AIBD<br>certified passive house consultant, PHIUS</span></i><o:p></o:p></p><div><p class=MsoNormal><i><span style='color:#666666'>certified passive house builder, PHIUS<br></span></i><span style='color:#660000'>Abrams Design Build LLC</span><span style='font-size:13.5pt;color:#660000'><br><i>sustainable design for intentional living</i></span><span style='font-size:7.5pt;color:#666666'><br>cell 202-437-8583<br><a href="mailto:alan@abramsdesignbuild.com" target="_blank"><span style='color:#666666'>alan@abramsdesignbuild.com</span></a><br><a href="http://www.abramsdesignbuild.com/" target="_blank"><span style='color:#666666'>www.abramsdesignbuild.com</span></a></span><o:p></o:p></p></div></div><p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p><div><p class=MsoNormal>On Thu, Mar 27, 2014 at 9:11 AM, Clarke Olsen <<a href="mailto:prismoidal@gmail.com" target="_blank">prismoidal@gmail.com</a>> wrote:<o:p></o:p></p><p class=MsoNormal>The problem with single top headers is that, when triaging the lumber, it's hard to find something you feel can be trusted up there all alone... 2x3 sounds better then it is: most of them are crap. The other reason to make the interior studs bearing is that you can keep the foundation back, leaving a very generous overhang to drip past the foam that covers your foundation. I used to think I was a hero for putting 2" of blueboard under the slab and against the foundation, until I noticed how nice & cool it was in summer...<br><span class=hoenzb><span style='color:#888888'>Clarke Olsen</span></span><span style='color:#888888'><br><span class=hoenzb><a href="http://clarkeolsendesign.com" target="_blank">clarkeolsendesign.com</a></span><br><span class=hoenzb>373 route 203</span><br><span class=hoenzb>Spencertown, NY 12165</span><br><span class=hoenzb>USA</span><br><span class=hoenzb>518-392-4640</span><br><span class=hoenzb><a href="mailto:colsen@taconic.net">colsen@taconic.net</a></span></span><o:p></o:p></p><div><div><p class=MsoNormal><br><br><br><br>On Mar 26, 2014, at 5:55 PM, RT <<a href="mailto:archilogic@yahoo.ca">archilogic@yahoo.ca</a>> wrote:<br><br>> On Wed, 26 Mar 2014 11:42:01 -0400, AA-man wrote:<br>><br>>> here's where I'm heading ...*OVE stud wall<br>>> *a void, width determined by specific space heat demand analysis<br>>> *an inner frame wall<br>>> *the entire framing cavity filled with DP cellulose<br>><br>><br>> The above sounds very much like a double-stud wall section so one should choose which of the two frame walls is load-bearing .<br>><br>> Logically, the interior wall would be the one designated as load-bearing even if only because doing so shortens the spans of flexural members like joists and rafters. When we're talking about fat superinsulated walls, the difference in span can mean a difference in one joist size.<br>><br>> In making the interior wall loadbearing, there's no need for the exterior wall to be a 2x6 OVE stud wall -- it can be a 2x3 or 2x4 wall with studs at 24" o/c, single top plates, no lintels over openings (assuming that we're talking about low-rise residential building)<br>><br>> One just needs to ensure that one allows for eventual shrinkage of cross-grain framing members (ie sill & top plates, rim joists, lintels) in the bearing wall so that the curtain wall does not inadvertantly become loadbearing.<br>> --<br>> === * ===<br>> Rob Tom AOD257<br>> Kanata, Ontario, Canada<br>><br>> < A r c h i L o g i c at Y a h o o dot c a ><br>> (manually winnow the chaff from my edress if you hit "reply")<br>><br>> _______________________________________________<br>> Greenbuilding mailing list<br>> to Send a Message to the list, use the email address<br>> <a href="mailto:Greenbuilding@bioenergylists.org">Greenbuilding@bioenergylists.org</a><br>><br>> to UNSUBSCRIBE or Change your List Settings use the web page<br>> <a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org</a><br><br><br>_______________________________________________<br>Greenbuilding mailing list<br>to Send a Message to the list, use the email address<br><a href="mailto:Greenbuilding@bioenergylists.org">Greenbuilding@bioenergylists.org</a><br><br>to UNSUBSCRIBE or Change your List Settings use the web page<br><a href="http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org" target="_blank">http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org</a><o:p></o:p></p></div></div></div><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>