If you are leaving the fiberglass insulation you may have moisture in the
wall so make sure you don't have a surface on which it will condense. (like
foil faced polyiso) With the fiberglass insulation you'd want a foam that
allows moisture through - EPS perhaps.
We did a new house with 2x6 cellulose walls, osb, Tyvek, 2" XPS (Styrofoam)
taped & foamed, 1x3 strapping (fastened with long GRK screws) plywood scraps
around windows, then Hardiboard. Relatively easy to do. Similar to
Building Science recommendations. We installed the windows outside of the
XPS, fastening them to the jamb with masonry clips as opposed to using the
nailing flange. Then did an interior sheetrock return with oak sills.
(instead of wood jambs)
Tyvek is put on as usual, carefully & taped as the drainage plane.
The 1x3 gives you a rainscreen so air gets behind the siding & lets it dry.
From: VGBN Discussion [mailto:[log in to unmask]] On Behalf Of Ben Graham
Sent: Wednesday, March 10, 2010 11:48 PM
To: [log in to unmask]
Subject: Re: Suggestions on Insulation retrofits
Not sure if you have seen the Building Science Corp. method for this deep
energy retrofit method, but I would check it out, they have it down pretty
good. Furring strips are utilized to secure the siding. I don't think they
would recommend polyiso or house wrap. Essentially, if you seal the foam
well, you don't need the wrap.
On 3/10/10 8:29 PM, "Tim Yandow" <[log in to unmask]> wrote:
> Hello all,
> On the subject of green building, I am soon beginning renovation work on a
> 1960's home in Burlington. We are adding an addition to the south and west
> sides of the house. The new envelope will be 2x6 with damp spray
> cellulose. The existing house is 2x4 with fiberglass and the owners would
> like to bottom up the house more, so we are thinking about adding a layer
> of insulation to the outside of the house since all the old vinyl siding
> is coming down and the windows all replaced (most of them have broken
> seals). I am trying to figure out the best way to insulate from the
> outside and make provisions for new corner boards and hardi-plank siding.
> With polyisocyanurate, for instance, there is the problem of not being
> able to add house wrap and needing to use longer fasteners for siding and
> to secure window flanges. Or can strapping be used over that? Then there
> is the issue of extension jams either inside or outside...I would love to
> know if anyone has worked out a good solid system to do this. What I have
> read and seen so far does not satisfy me. Thanks.
> Tim Yandow
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