[Greenbuilding] Exterior insulation retrofit

Sam Ewbank g.l.ewbank at gmail.com
Thu Apr 28 12:16:29 PDT 2011


Rob
The curtain wall idea is intriguing.  Do you know of a source for the sheet
metal clips or similar?

This also got me thinking about a Larsen Truss style retrofit where you cut
off the roof over hang, wrap the walls and roof with trusses (offset to the
studs to stop thermal bridging but attached at the rim joist and wall
plates) and then filling the cavities with cellulose. You would likely need
some sort of sheathing on the exterior but maybe a good weather resistive
barrier would work and your horizontal nailers for the shake siding.
You could then create a continuous air/vapor thermal barrier on the exterior
of the structure.
Another idea would be to use I-joist attached similarly, this would then
allow you to use a batt product like Roxul on walls if so inclined.

Sam



On Thu, Apr 28, 2011 at 2:01 PM, RT <Archilogic at yahoo.ca> wrote:

> On Thu, 28 Apr 2011 08:45:46 -0400, <bill.allen at verizon.net> wrote:
>
>
>  Add external insulation....rigid styrofoam.
>>
>
>
> And of course, there is the non-plast-eccchhh! foam approach where one
> wraps the existing sheathing to do a first class job of air-sealing and then
> install short 2x3 or 2x4 standoffs over, using sheet metal clips and then
> hang curtain wall studs and sheathing off of the end of those stubs to
> create a new insulation cavity with the capacity to hold superinsulation
> levels of a blown-in non-plast-ecchhh!
>
> Avoiding the use of the foamed plast-eccchh! will usually more than pay for
> the cost of the wood for the curtain wall framing and higher levels of
> insulation, but at a penalty in terms of extra wall thickness which may be a
> problem in tight urban situations.
>
> But what about the thermal barrier in the roof especially if the roof
> volume is inhabited space ?
> ie One can only fill up a 2x# rafter cavity with # inches of insulation.
>
> If that's the case, then using the same stand-off idea on the roof to turn
> the existing rafters into parallel chord trusses with an insulation cavity
> of ## inches while at the same time raising the eaves line to accommodate
> the incremental wall thickness would, as Martha Stewart might say "Is a Good
> Thang".
>
>
>
> --
> === * ===
> Rob Tom
> Kanata, Ontario, Canada (where a raucous windstorm (probably blown up from
> the USA) has knocked out the hydro (aka "electricity")
> < A r c h i L o g i c  at  Y a h o o  dot  C A >
> (manually winnow the chaff from my edress if you hit REPLY)
>
>
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