Install Mineral Wool Insulation in Framed Walls

A. Finished-Project Specification

Deliverable: every assigned framed wall cavity in the specified wall section filled with mineral-wool batt insulation matching the approved product, width, thickness, density, and facing orientation, installed with full-depth friction fit at top, bottom, sides, and back, fitted around wiring, boxes, pipes, and blocking without compression, with corners, headers, and intersecting-wall transitions at full thickness, inspected and photographed before concealment.

B. Cavity Schedule

Cavity Type	Cutting Approach	Inspection Focus
Standard bay	Individually measured and cut with friction-fit allowance	Top, bottom, edge, and back contact
Irregular/tapered bay	Single accurately cut piece matching the measured taper	No internal voids from stacked scraps
Service cavity (wiring, pipe)	Split or notched around the obstruction, preserving insulation behind and in front of the service	Full depth maintained on both sides of the service
Corner/header/intersection	Cut to maintain full thickness across the transition	No thinned or compressed sections at the transition

C. Material Takeoff

• Mineral-wool batts: product matching the approved width, thickness, density, and facing requirement for the assigned wall section, in quantity sufficient for the total measured cavity area plus the manufacturer-recommended waste allowance.
• Cutting consumables: serrated insulation knife blades as needed to maintain clean, square cuts.
• Documentation materials: installation worksheet, cavity measurement log, and camera or phone camera for photographs.

D. Acceptance Standards

Check	Standard
Cavity contact	Every cavity shows full contact at top, bottom, both sides, and back with no visible gap
Cut quality	Every cut edge is square and full depth through the batt thickness, with no ragged or angled edges at exposed cavity boundaries
Irregular cavities	Every irregular cavity is filled with a single accurately cut piece; no cavity contains stacked or packed loose scraps
Service fit	Every batt split or notched around wiring, boxes, or pipes maintains full depth on both sides of the service with no compression against the service
Corners and transitions	Full thickness is maintained at every corner, header, and intersecting-wall transition with no thinned section
Compression and slumping	No batt is compressed below its rated thickness and no batt has slumped or dropped from its installed position
Clearances	Required clearances from non-IC lights, flues, chimneys, and heat-producing devices are maintained; no junction box or serviceable equipment is covered
Documentation	Every completed cavity is photographed and the product, cavity count, deficiencies, and corrections are recorded before concealment

E. Preparation — Review and Verification

1. Review the approved mineral-wool product, cavity dimensions, thermal or acoustic purpose, facing, and fire-resistance conditions. Confirm the assigned wall section matches the wall-insulation schedule before staging any material.
2. Confirm that rough systems, air sealing, and inspections are complete. Verify the Chapter 3 and Chapter 4 air-sealing work and required rough inspections have been signed off for the assigned wall section before proceeding.
3. Verify that cavities are dry and free of contaminants. Visually inspect each cavity and touch-test framing for moisture; do not insulate any cavity showing wet framing, staining, or contamination.

F. Measuring and Cutting

1. Measure each cavity independently, including tapered, narrow, and blocked areas. Record width, height, and depth for each cavity on the cavity measurement log rather than assuming uniform stud spacing.
2. Mark mineral-wool batts using a straightedge and controlled allowance for friction fit. Add the friction-fit allowance specified by the approved product instructions to the measured cavity width before marking the cut line.
3. Cut on a stable surface using the approved serrated insulation knife. Fully support the batt on the cutting surface so the blade travels straight through the full thickness.
4. Keep cut edges square and full depth. Inspect each cut edge before installation and recut any edge that is angled, ragged, or under full thickness.

G. Installing Standard Cavities

1. Insert the batt without tearing edges or compressing the center. Support the full width of the batt while inserting it into the cavity opening.
2. Fit the batt tightly to the top, bottom, sides, and back of the cavity. Press gently at each edge to confirm friction-fit contact on all four sides before moving to the next cavity.

H. Services and Irregular Cavities

1. Split or notch around wiring while preserving insulation behind the cable. Cut the batt so insulation remains in full contact with the framing on both sides of the wiring, not compressed against it.
2. Cut clean openings around boxes, pipes, and supports. Size each opening to match the obstruction closely enough to avoid leaving a gap larger than necessary.
3. Fill narrow cavities with single accurately cut pieces where practical. Measure the specific narrow cavity and cut one piece to fit rather than trimming a standard batt down with excess waste packed in around it.
4. Avoid stacking loose scraps in a way that creates internal voids. Where a single piece cannot span the full cavity depth, use the manufacturer-approved layering method rather than loosely packed offcuts.

I. Corners, Transitions, and Clearances

1. Maintain full thickness at corners, intersecting walls, headers, and rim transitions. Cut and fit batts at these locations so no section is thinned to make the piece fit.
2. Preserve all required heat-source and electrical clearances. Confirm the clearance zones marked during earlier chapters remain uncovered and undisturbed by the mineral-wool installation.

J. Inspection and Correction

1. Inspect for edge gaps, slumping, proud surfaces, compression, torn corners, and hidden voids. Check each cavity by both visual inspection and hand contact along the perimeter.
2. Remove and recut failed pieces rather than forcing them. Do not compress an undersized batt to make it appear to fill the cavity; replace it with a correctly measured and cut piece.
3. Complete a hand-check and visual inspection of every assigned cavity. Record the result of each cavity's inspection on the installation worksheet.
4. Photograph and document the installation before concealment. Label each photograph with its cavity location and match it to the corresponding worksheet entry.