Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Owens Corning Home Additions & ADU: The San Francisco Owner’s Guide
If you’re planning a home addition or ADU in San Francisco and you want Owens Corning insulation and building products specified throughout, a typical project runs $53,100 – $153,400 depending on square footage, foundation work, and finish level. That range includes Owens Corning insulation, sheathing, and weather-resistive barriers installed to San Francisco code, with a written line-item price before any work starts. Most homeowners reach out after an existing addition underperforms: drafts along the sill plate, moisture in the wall cavity, or a garage conversion that never held temperature because someone skipped the insulation details. We replace or upgrade those Owens Corning components and we do it with the same discipline we’d bring to a full gut-and-rebuild.
Key takeaways:
- Installed price for a San Francisco home addition or ADU with Owens Corning products runs $53,100 – $153,400
- We stock Owens Corning PINK fiberglass batts, FOAMULAR rigid board, and Thermafiber mineral wool on our trucks
- Every job gets a written price before work begins, and every completed project carries the 365-Day Done Right Promise
- Bradford Remodeling Co San Francisco is an independent contractor, not affiliated with Owens Corning
Which Owens Corning Models This Applies To
Home additions and ADUs don’t run on a single “part” the way a furnace does, but the Owens Corning products inside them have distinct spec lines that matter. The three you’ll most often see in San Francisco additions are PINK EcoTouch fiberglass batts (R-13 to R-38, sized for 2×4 and 2×6 framing), FOAMULAR NGX rigid foam insulation (R-5 per inch, common in 1-inch and 2-inch thicknesses for foundation and under-slab work), and Thermafiber mineral wool (fire-rated, R-15 in 3.5-inch depth). The compatibility gotcha: San Francisco’s energy code now requires R-21 in exterior walls for most new additions, which means R-13 batts that worked in a 2005 build no longer clear the bar on a 2026 permit. You can identify what’s in your walls by pulling a single outlet cover and checking the facing; Owens Corning prints the R-value and product name on the kraft paper. If you don’t see it, it’s worth checking with us before you assume.
On the OEM-versus-aftermarket question: Owens Corning doesn’t make a proprietary “addition kit.” Any insulation that meets the R-value spec works. But we spec Owens Corning because the manufacturer documentation is traceable, the warranties are real, and the fiber density is consistent enough that we can run a clean material takeoff and price the job honestly. When Curtis Lane reviews an addition scope, he’s checking the wall assembly, not guessing at what’s inside it. Read the structural drawings, count the stud bays, do the math. That’s how the written price stays the price.
Styles & brands we work with
Signs Your Owens Corning Home Additions & ADU Is Failing
- Drafts along the bottom of exterior walls. This usually means the sill plate was never sealed or the rim joist insulation shifted. In San Francisco’s Outer Sunset, fog-driven moisture sneaks into those gaps and condenses inside the wall cavity, which leads us to the next symptom.
- Musty smell in one corner of the addition. That’s moisture trapped against the sheathing, often because the vapor barrier was installed backward or omitted entirely. Older balloon-frame walls in San Francisco additions are notorious for this. Once mold starts in fiberglass, the batt loses R-value and needs replacement.
- Noticeably higher energy bills since the addition went in. A properly insulated San Francisco ADU should not spike your PG&E bill. If it does, someone under-insulated the ceiling or skipped the rim joist, and conditioned air is leaving through the top of the envelope.
- Hot rooms in summer, cold rooms in winter, same-side symptoms. This is a venting problem or an insulation gap around windows and door headers. Owens Corning batts can’t perform if they’re compressed, cut short, or pushed away from the sheathing.
- Visible settling or gaps in exposed insulation. In crawlspaces and unfinished garages, batts sag over time. Once fiberglass separates from the subfloor, it stops doing its job. A garage conversion in San Francisco with sagging under-floor insulation is a common find.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
A full Owens Corning insulation replacement inside an existing San Francisco addition runs $5,900 – $16,520 depending on wall area, access, and whether we’re removing old material first. That’s the price for the repair side of this. A complete home addition or ADU, built to code with Owens Corning products from footing to ridge, runs $53,100 – $153,400, and an ADU specifically lands $106,200 – $259,600 when it’s a detached unit with its own foundation, kitchen, and bath. The spread comes from three things: square footage, foundation type, and how much of the existing structure can be salvaged. A slab-on-grade ADU in the Sunset costs differently than a hillside addition with pier-and-beam work in Twin Peaks.
What’s included in our number: Owens Corning insulation, sheathing, and weather barrier; all rough framing, drywall, finishes, and trim; permit drawings; and a written line-item scope. No numbers that move at the door. The 365-Day Done Right Promise covers every piece of that work for a full year. If anything fails inside that window, we come back and correct it at no charge. That promise is in writing, signed, and in your hand at job close.
DIY or Call Us?
Insulation is one of the few parts of an addition a homeowner can safely inspect, but replacement and new construction are different animals. You can check exposed batts in a crawlspace for sagging or moisture staining. You can pull an outlet cover and read the R-value on the kraft facing. What you should not do is tear out walls in an occupied San Francisco addition, disturb fiberglass that may be holding mold, or attempt a rim joist seal from a ladder on a hillside lot. Fiberglass dust is an irritant; mold in a wall cavity is a health risk; and the California Building Code now requires specific fire-blocking and draft-stopping details at floor and ceiling intersections that most people miss. The work itself is straightforward for a trained crew. The details are what separate a tight envelope from a drafty one. If you’d rather not climb into the crawlspace at all, call (831) 610-5598 and we’ll send a background-checked, uniformed technician to look at it.
FAQs
Owens Corning fiberglass batts, when installed correctly and kept dry, perform for 40 years or more. Mineral wool effectively lasts the life of the building. The failure point in San Francisco is almost never the material; it’s moisture intrusion from fog, unsealed penetrations, or a bad vapor barrier decision. If it’s wet, it’s done. Call (831) 610-5598 and we’ll tell you whether you’re looking at spot replacement or a full re-insulation.
Yes, in most cases we can replace the damaged section without tearing into the rest of the addition. If mold is present or the R-value has collapsed across a large area, partial repair becomes false economy. We’ll give you a written scope either way, with the price for both options, and you decide. Estimates are free.
A typical insulation replacement in an existing San Francisco addition takes one to two days. A full home addition or ADU runs four to eight months depending on scope, permit review, and weather. We’ll put the timeline in writing with the price, and we’ll tell you up front which parts of the schedule are outside our control, like DBI plan review.
We keep PINK fiberglass batts, FOAMULAR rigid board, and Thermafiber mineral wool on our trucks for repairs and insulation top-ups. If your project calls for a specific Owens Corning product we don’t carry, we order it directly and confirm lead time before we finalize the price. Either way, you get a written line-item quote before work starts. Call (831) 610-5598 for an exact number.
Written by Curtis Lane, Owner, Bradford Remodeling Co – San Francisco, CA at Bradford Remodeling Co San Francisco, serving San Francisco and nearby areas.
