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Old 12-09-2013, 06:33 PM   #1
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Finished Basement insulation question


Hi All, I am working on finishing my basement. I have a fairly common setup -- cripple wall sitting on top of a 4 foot poured concrete foundation. I am planning on framing out all the walls (floor to ceiling) with 2x4s, and in doing so will create about 7 inches a space depthwise where the interior wall framing lays up again the framing of the cripple wall. Should all of that space get filled in with insulation?

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Old 12-10-2013, 06:57 AM   #2
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Finished Basement insulation question


Yes.

There is no point in leaving air in there.

Google around as well for insulation recommendations or read other threads on here.

Cliff notes:

Seal up the ribbon/band board areas
Put rigid foam on the poured/foundation walls

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Old 12-11-2013, 05:28 PM   #3
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Finished Basement insulation question


On pages 30, 31 is fire-blocking requirement of your City Code for that new wood wall. 302.11 read similar to this;
Fireblocking required.
Fireblocking shall be provided to cut off all concealed draft openings (both vertical and horizontal) and to form an effective fire barrier between stories, and between a top story and the roof space. Fireblocking shall be provided in wood-frame construction in the following locations.
1. In concealed spaces of stud walls and partitions, including furred spaces and parallel rows of studs or staggered studs; as follows:
1.1. Vertically at the ceiling and floor levels.
1.2. Horizontally at intervals not exceeding 10 feet (3048 mm).
2. At all interconnections between concealed vertical and horizontal spaces such as occur at soffits, drop ceilings and cove ceiling.” Found here; http://ecodes.biz/ecodes_support/fre...tial_main.html
---------------------------------------------------------------------------------------IMHO, start with caulking the rim joist (if solid wood, NA if engineered wood) both top at sheeting and bottom at mudsill- and at joists. Then add foil-faced rigid board (R-6-5 a vapor barrier and fire-rated) cut ½” smaller than cavity, canned foam (low-expanding) around perimeter after fb installed/centered by hot melt glue dabs on backside, add some fg batt next to it, done.

Walls; install the fb with foam compatible adhesive (on label) in 1’ square grid pattern to limit air movement, cut ½” smaller than area for using canned foam-- again at top/bottom and seam joints- or foil tape the seams as sheets are ½ sized- this is imperative to be air-tight. Plan the new wall, adding ¾” plywood or other code-accepted fire-stopping at/before installing new wall to joist bottoms. I would build the new wall aligning the studs with old wall studs, with bottom plate (not pt, check with AHJ) on top of fb strips left-over from rim insulation- unless a newer house with perimeter slab insulation – 2’ in for our area.

Add ½” drywall (every 10’) vertically in wide enough strips to overlap each stud/wall 1-1/2” for fastening some screws- tying the walls together as it were- notching the drywall around bottom/top plate (to fill voids), after notching/removing the fb making slot to accept the drywall. Note; add some electrician tape or window sticky wrap to edge of drywall contacting concrete-- against moisture capillarity from concrete and meet code. Install some foil-faced fb to top of concrete wall, overlap the wall fb below, tape joints.

Chapter 6 on “Walls” in (previous link) the first table shown is your foam board thickness required to prevent cavity condensation without a vapor retarder= R-2.5 (1/2” XPS unfaced). You will need asphalt paper-faced batt if using fiberglass on the whole wall toward the room side to meet code which requires a vapor retarder for our area. Remove the paper facing from existing batts if any present- as they are too deep in the wall insulation from interior to retard moisture.
I would lay the fg batt on its side in the walls space/void, add a gutter spike on top at each stud to support next batt layer after running string/cord/wire between the spikes x2 to help support batt mid-stud. Required to stop convective loops with an air space though it may be immune as both walls are insulated and concrete air tight, -- good insurance though.

As you’re a neighbor of mine here, I expanded on WoW’s answer. It saves me a long drive, lol. If my directions are not clear, just ask…if they don’t apply… just ignore.

Gary
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Last edited by Gary in WA; 12-11-2013 at 05:30 PM.
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Old 12-13-2013, 01:12 AM   #4
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Finished Basement insulation question


related question: is dense packed cellulose not a qualified fire block in the op's area, so no extra wood is required? thanks. j
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Old 12-13-2013, 07:52 PM   #5
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Finished Basement insulation question


"R602.8.1 Materials.

Except as provided in Section R602.8, Item 4, fireblocking shall consist of 2-inch (51 mm) nominal lumber, or two thicknesses of 1-inch (25.4 mm) nominal lumber with broken lap joints, or one thickness of 23/32-inch (18.3 mm) wood structural panels with joints backed by 23/32-inch (18.3 mm) wood structural panels or one thickness of ¾-inch (19.1 mm) particleboard with joints backed by ¾-inch (19.1 mm) particleboard, ½-inch (12.7 mm) gypsum board, or ¼-inch (6.4 mm) cement-based millboard. Batts or blankets of mineral wool or glass fiber or other approved materials installed in such a manner as to be securely retained in place shall be permitted as an acceptable fire block. Batts or blankets of mineral or glass fiber or other approved nonrigid materials shall be permitted for compliance with the 10 foot horizontal fireblocking in walls constructed using parallel rows of studs or staggered studs. Loose-fill insulation material shall not be used as a fire block unless specifically tested in the form and manner intended for use to demonstrate its ability to remain in place and to retard the spread of fire and hot gases" From; http://publicecodes.cyberregs.com/ic...002_par018.htm

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Old 12-13-2013, 08:39 PM   #6
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Finished Basement insulation question


gary: thanks. the question, though, is what does "specifically tested" imply? how? what was? by whom? etc. to answer that, i did some searching, because i am 99% sure i've read that dense packed cellulose is an approved fire stop. so, here are some links that support my belief, fwiw.... i could not immediately find any links to independent test labs, so i quit.

http://www.rtekinsulation.com/cellul...e-blocking.htm (a business)

this is from http://www.nationalfiber.com/docs/Ce...lities0909.pdf

"National Fiber’s cellulose insulation has been approved as a fire blocking material under Section 708.2.1,
Item 1, of the UBC, Section 716.2.1 of the IBC, and is permitted as an alternate to the fire blocking in
Section R602.8, Item 1, of the IRC by Omega Point Laboratories Report for Project No. 16094-11638.
When installed in a dry or spray application to a depth of 14.5 inches, cellulose outperforms
conventional wood fire blocking in fire blocking tests."
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Old 12-14-2013, 01:07 PM   #7
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Good job! I actually have that one link... lol. Forgot... with 300+ links on insulation alone, hard to keep track, lol.

Gary

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