[Greenbuilding] Foam installed between framing during framing

RT archilogic at yahoo.ca
Thu Jan 3 18:10:52 CST 2013


On Thu, 03 Jan 2013 11:04:14 -0500, Eli Talking  
<elitalking at rockbridge.net> wrote:

>
> I am wondering if it would be reasonable to install accurately precut  
> eps foam between joist, rafters, or top chord of truss during the framing

While not exactly the same as the above, I have done something similar  
that may be relevant:

For a ceiling in new construction, I typically install an  
agricultural-grade black poly (available in rolls up to 100 ft wide) on  
the underside of ~R-70 in parallel chord trusses to function as an air  
barrier, installed before any interior partitions are built.

Then red chalk lines are snapped onto the black poly as layout lines for  
1.5" x 1.75" (ripped from 16' long, kiln-dried/kept-dry stock) furring @  
16" o/c, perpendicular to the trusses.

Furring is clamped together side-by-side with 4-ft or longer bar clamps so  
that the truss centres can be laid out across the width of the 27-or-more  
clamped-together furring all at once.

Then holes for screws are pre-drilled on either side of each of the centre  
lines at a maximum separation, angled towards the centre, screws  
pre-started.

Then acoustical sealant is applied to the backside at fastening points  
before the furring is set in place, taking care to align with the  
hi-visibility red-on-black chalk lines.

Since the relatively skinny ~1.75"-wide furring is fastened every 24",  
they are adequately restrained to ensure that they stay straight.

The 1.5" deep channels are used to accommodate any electrical wiring and  
octagon boxes thereby ensuring that there will be no penetrations in the  
ceiling air barrier. Temporary pans made out of salvaged corrugated  
cardboard can be fitted in the channels as protection for the poly while  
the subs are poking around at this stage.

When all of the services are installed, 1.5"- thick EPS is ripped on a  
table saw, between 3/32" and 1/8" wider than the channel into which it has  
to fit and then 12"-wide drywall taping knives are used to help shoehorn  
the pieces of EPS into place.

Without the use of the drywall knives-as-shoehorns, the edges of the EPS  
would tend to get buggered up.

The slight oversizing/compression during installation ensures that the EPS  
stays in place on its own.
A non-bleeding indelible ink marker can be used to mark on the surface of  
the EPS where the wiring is beneath.

When ripping EPS the blade guard with integral splitter and anti-kickback  
pawls MUST be in place.
Without them, the EPS (and any fingers that may be holding the EPS) tends  
to get pulled back sideways into the blade ...resulting in inaccurate  
sizing of the EPS at a minimum and at worst, severed digits from the  
hand(s) of the table saw operator.

In the above application, the EPS is primarily intended to provide solid  
support for the poly air barrier, the additional ~R-5 being somewhat  
inconsequential.

"Why not just use the EPS as layout jigs for installing the furring ?" you  
might ask.
Imagine trying to hold up the EPS and furring while pulling against the  
furring to compress the EPS , all with one hand while trying to drive in  
the screws with the other.
-- 
=== * ===
Rob Tom					AOD257
Kanata, Ontario, Canada

< A r c h i L o g i c  at  Y a h o o  dot  c a  >
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