Johns Manville Attic Air Sealing: The San Francisco Owner’s Guide
Johns Manville attic air sealing in San Francisco typically costs between $900 and $2,800 installed, depending on attic size, access difficulty, and how many bypasses need sealing. We stock Johns Manville-compatible air sealing materials on our trucks and can usually complete the job same-day. Most San Francisco homeowners discover their air sealing has failed the same way: a utility bill that crept up month after month, or a bedroom that never quite holds temperature even after the insulation was topped off. The air seal is the quiet half of the attic system. When it goes, the insulation can’t do its job.
Key Takeaways
- Installed air sealing for a typical San Francisco attic runs $900 – $2,800.
- We’re an independent installer, not affiliated with Johns Manville, and we stock compatible sealing materials on the truck.
- Failed air sealing shows up as uneven room temperatures, dust, and rising heating bills, not as a visible break.
- Every job carries a 365-day written guarantee. If the seal fails in that window, we return at no charge.
Which Johns Manville Models This Applies To
Johns Manville doesn’t sell attic air sealing as a single boxed part with one model number. It’s a system approach built into their attic performance line, which includes their ComfortTherm and MR (Moisture Resistant) faced batts, their loose-fill fiberglass, and the foam sealants and gaskets specified in their attic performance guides. The compatibility question is less about a model number and more about matching the right sealing material to the existing Johns Manville insulation in your attic. Face-sealed batts need different perimeter treatment than loose-fill. A blown fiberglass attic over a 1920s lath-and-plaster ceiling in the Inner Sunset has different bypass profiles than a 1990s tract home in the Parkside.
The gotcha we see regularly: homeowners buy a case of single-component foam cans and seal the obvious gaps around the attic hatch and plumbing vents, but miss the wall top plates and electrical penetrations, which are where most air actually moves. Johns Manville’s own retrofit guidance calls out top plates as a primary bypass, and that’s the part of the job that requires pulling back existing insulation to expose the framing. If you’re trying to match something to what’s already in your attic, the label on the existing batt or the bag from the loose-fill is your best identifier. Send us a photo and we’ll tell you exactly what you’re working with before we ever schedule a visit.
Signs Your Johns Manville Attic Air Sealing Is Failing
- Upstairs rooms won’t hold temperature after the furnace kicks off. Air is moving between the conditioned space and the attic through bypasses. Insulation slows conductive heat loss, but it does almost nothing for air movement. A failed seal means your heated air is leaving through the ceiling.
- Dust accumulation on ceiling fans and light fixtures in upstairs rooms. Air moving through the attic carries fiberglass and decades of dust. When the seal is intact, that air stays put. When it isn’t, it deposits itself on anything below the ceiling plane.
- Visible daylight around the attic hatch or recessed light cans. This is the simplest one to check, and it’s almost always a contributor. If you can see light, air is moving. In San Francisco’s older Victorians, the attic hatch is frequently an uninsulated piece of plywood with no gasket at all.
- Condensation on the underside of the roof deck during fog season. The Richmond and Sunset Districts get heavy marine layer for months. Warm, moist air rising into a cold attic condenses on the sheathing. Air sealing stops the moisture at the ceiling plane before it gets up there.
- Heating bills that don’t match the house size. A 1,400-square-foot Sunset row home shouldn’t cost the same to heat as a 2,400-square-foot detached house in the Avenues. If it does, air is leaking somewhere, and the attic is the first place we look.
Replacement Cost & What’s Included
In San Francisco, full attic air sealing with Johns Manville-compatible materials runs $900 – $2,800 installed. The spread comes down to three things: attic square footage, how much existing insulation has to be moved and reset, and the number of bypasses found. A straightforward 900-square-foot attic with an accessible hatch and a handful of penetrations lands near the bottom. A 1,800-square-foot attic with recessed lights, plumbing stacks, and wall top plates buried under 18 inches of old loose-fill lands near the top.
Every air sealing job from Alden Insulation San Francisco includes the same baseline: a full bypass audit before any material goes down, writing the found bypasses into the quote, sealing with Johns Manville-compatible foam, gasket, and caulk materials, resetting all existing insulation to spec, and a written 365-day guarantee on the work. The price you approve before we start is the price on the invoice. We don’t revise at the door. If the seal fails inside the guarantee window, we return and fix it at no charge. That’s the Garrison Standard, and it applies to every job we run in San Francisco.
DIY or Call Us?
The safe line for a homeowner is inspecting and documenting, not sealing. You can check your attic hatch for a gasket, look for daylight around light fixtures, and photograph the label on your existing insulation. Those are useful, safe steps. What you shouldn’t do is crawl an unfinished attic over joists you can’t see and start pulling back insulation to expose wiring penetrations, especially in San Francisco’s older homes where knob-and-tube wiring still shows up more often than anyone wants. Air sealing isn’t high-tension like a garage door spring, but the work involves moving in tight spaces around wiring, recessed cans, and sometimes asbestos-era vermiculite. If any of that is present, the job changes. That’s a professional’s call to make, and it’s part of what our audit covers.
If you want to check the obvious spots yourself first, go ahead. If you find daylight around the hatch or around a bathroom fan housing, that’s easier to fix correctly than to redo. But if the bypasses are buried, call us at (559) 245-9792. Bryce Holloway has walked enough San Francisco attics to know which houses need a full seal and which just need a hatch gasket and some foam around a stack. He’s not going to sell you the bigger job if the smaller one is honest.
FAQs
Properly installed foam and gasket sealing lasts 15 to 25 years in a San Francisco attic, and the failure mode is almost always movement in the house structure or new penetrations added later, not material breakdown. The sealant doesn’t wear out so much as the house changes around it. We guarantee our air sealing work for 365 days in writing, and the materials themselves are rated well beyond that.
Yes, and in most San Francisco homes, repair is the right call. Air sealing isn’t typically a full replacement job because the original seal is usually incomplete rather than worn out. We find the bypasses, seal them, and verify the result. If a previous contractor sealed the hatch but missed every top plate, we’re adding, not replacing. Call (559) 245-9792 and we’ll tell you honestly whether you need an audit and touch-up or a full redo.
Most San Francisco attic air sealing jobs are done in one day, typically 4 to 6 hours depending on attic size and what’s buried under the existing insulation. Extreme cases with extensive recessed lighting or structural obstacles can stretch to a second day, and we’ll tell you that in the written quote before we start.
We do. Our trucks carry Johns Manville-compatible foam, gasket, and caulk materials, plus sealing accessories from Reflectix and other brands we stock, so there’s no parts delay between the audit and the work. We’re an independent installer, not a Johns Manville dealer, which means we stock across brands and can match the right material to your existing insulation without waiting on a distributor order.
Written by Bryce Holloway, Owner, Alden Insulation San Francisco at Alden Insulation San Francisco, serving San Francisco and nearby areas.