I just put up an addition for a client and fellow FH reader; used the new John’s-Manville “Spider” brand blown fiberglas (sticky; blown into open stud cavities before drywall). The ceiling rock was put in first, then 8″ of dry ‘glas blown in there. My rep says no vapor barrier is needed or used in walls or ceiling, but what do you guys think? Is paint gonna’ do it?
The house is near Atlanta, addition is 16’X24′, 1-story on slab, 2×6 @ 24″ OC, framing techniques from the recent FH article, with the header hangers and drywall clips, 1″ of blue foam on the outside, taped and foamed TIGHT, dbl-insulated vinyl windows and doors. Part of the addition is a master bathroom with shower, but with a good (quiet)exhaust fan and a FS series skylight over the shower.
VB or no VB? I want to hang the wall rock tomorrow . . .
Forrest
Replies
In Atlanta, I'd say you should never, ever use an interior vapor barrier. Vapor barriers go on the warm side of the wall. For most of the year, which side is warm?
Andy
Never try to teach a pig to sing. It wastes your time and annoys the pig.
Hey Forrest, I would be curious to know the costs for the Johns-Manville Spider insulation, and the decision behind it to use it. What is the application of this addition?
16' X 24' addition; 8' tall, one long side against the house with no insulation, 2x6 & trusses 24" OC, (2) 48x30 windows, (1) 32x54 window, (1) 70x30 window, (1) 6'0x6'8 french door. R38 ceiling; R19 in wall. They claim a little better. I did sill seal and foamed any cracks at junctions, no stuffing required.
$400.00
The insulation inspector was happy with no vapor barrier.
Forrest
So, there is 5.5" of this stuff in the walls, and how thick in their ceiling, 11"? I would be interested in knowing if they use other products as well. Can you shoot me an email of who they are?
It's Wilson Insulation in Decatur, GA 770-981-8643 - I don't know a thing about them other than my good experience; I got their name from the JM website. I dealt with rep Connie Sanders.
Forrest McCanless
Here's a pic of the Spider - I usually work with loose old houses, and I like the void filling and draft blocking potential of blown in, but don't like cellulose from a wind-driven rain and dampness standpoint. Old houses around here have diagonal 1x with 1" gaps, if they have any sheathing at all.
I thought this new addition was a straightforward project to experiment with.
Note also the framing techniques form the recent FH.
Forrest
Wow, that's pretty interesting. Reminds me of spray-on foam insulation after trimming off the excess. You say you blew this into place? What tool was used to install it onto the wall?
Two guys did it with nothing more than a 4" blow hose and a 5" return hose to vacuum up the excess - they didn't really "trim" anything - I was surprised at that.
What you see was just built up by one guy with a hose, controlling the depth and placement. the other guy just kissed the visible high spots with the suction side. The blower and all was in a truck in the driveway - all that came in were the two hoses.
They first taped all the windows and elec boxes. Total time was about three hours.
Forrest
I would be more concerned with what the inspector had to say, than the product reps song & dance.