# Knob and tube and attic insulation in San Francisco

> Knob and tube in an attic you want to insulate: what CEC 394.12 allows, the electrician's certification, replacing the runs first and BayREN's rebate.

URL: https://fogcitysfknobandtube.com/knob-and-tube-attic-insulation/

**Service**

Attic knob and tube surveyed, replaced or disconnected so insulation can go in, with the paperwork BayREN's rebate asks for.

Last Updated: October 30, 2026

**Where**

San Francisco and the East Bay: Berkeley, Oakland, Alameda and Piedmont.

**Local rules**

- An electrical permit from DBI before new wiring goes in, then a pre-cover and a final inspection.San Francisco Electrical Code 89.127
- A separate permit for each dwelling unit, except in single-family (R-3) buildings.DBI fee schedule
- Only owner-occupants of a single-family home may pull their own electrical permit.SF Department of Building Inspection
- No insulation around concealed knob and tube without a licensed electrical contractor's certification.California Electrical Code 394.12
- Up to $2,000 toward active knob and tube for income-qualified PG&E customers in an EASE Home project.BayREN

An insulation project can stop at the attic hatch when the installer finds porcelain knobs on the joists. [Fog City SF Knob and Tube](https://fogcitysfknobandtube.com/) clears attics with knob and tube wiring so they can be insulated, in San Francisco and the East Bay. The company tests the attic circuits, plans the work and manages it with the insulation schedule; the electrical work is carried out by licensed and insured electrical contractors. Every circuit that passes through the attic is either certified under the code’s conditions, replaced and disconnected, or confirmed inactive before insulation covers it.

The Association of Bay Area Governments, which runs BayREN, put it plainly when announcing its rebate: knob and tube can keep homeowners from moving forward with upgrades, because insulating over it or adding high-wattage appliances can lead to serious fire risks. In DBI’s electrical permit data, 22 of the 2,023 knob and tube permits filed from January 2016 to October 2026 mention an attic, and 4 mention insulation. Those are the jobs where someone wrote it down; other attic circuits are replaced under a wider [whole-house rewiring](https://fogcitysfknobandtube.com/whole-house-rewiring/) or [partial replacement](https://fogcitysfknobandtube.com/partial-knob-and-tube-replacement/) permit.

## Why insulation and knob and tube conflict

Knob and tube was designed to run in open air. Each conductor travels separately on porcelain knobs, inches from its partner, and sheds the heat it makes into the space around it. The current a wire can carry safely depends on that: a conductor in open air can carry more than the same conductor packed in a material that holds heat. Blown-in or batt insulation that surrounds the wires takes away the air the design depends on.

The heat matters because of what the wire is wearing. Original conductors are insulated with rubber under a cloth covering, and rubber hardens and cracks faster when it runs warm. A circuit that has been fused larger than its conductors can carry, an alteration some old circuits have had, makes the problem worse, because the protection no longer trips before the wire overheats. Insulation also hides the wiring, so splices, damage and rodent nests go unseen. None of this means every insulated attic is about to fail. It means the condition of the wiring has to be known before it is covered, which is the logic the California code follows. The guide to [whether knob and tube is dangerous](https://fogcitysfknobandtube.com/guide/is-knob-and-tube-wiring-dangerous/) covers the wider risk picture.

## What California’s code allows

Article 394.12 of the California Electrical Code says concealed knob and tube shall not be used in hollow spaces of walls, ceilings and attics where loose, rolled or foamed-in-place insulation envelops the conductors. California adds an exception. Insulation is permitted where:

- a California-licensed electrical contractor surveys the wiring and certifies that it is in good condition, with no deterioration, improper overcurrent protection, or improper connections or splices
- the certification is filed with the building department, and a copy goes to the owner
- accessible insulated areas are posted with a caution notice in English and Spanish
- the insulation is noncombustible and contains no electrically conductive material
- the building department may still require permits and inspection for the insulation

San Francisco’s Ordinance 228-25 adopted the 2025 California Electrical Code with local amendments, operative January 1, 2026, and those amendments make no change to the knob and tube article. No San Francisco DBI form or bulletin for the certification was found, so the code’s own steps are followed and the filing is confirmed with DBI per project. The [California legality guide](https://fogcitysfknobandtube.com/guide/is-knob-and-tube-legal-in-california/) covers the article as a whole.

## What happens on the first visit

The first visit tests every circuit in the house and follows the ones that pass through the attic. A live knob and tube run over a bedroom ceiling may feed outlets on two floors; a run that looks original may already be dead because a remodel moved its loads. The [active vs abandoned guide](https://fogcitysfknobandtube.com/guide/active-vs-abandoned-knob-and-tube/) explains why testing, not appearance, decides that.

The attic itself is looked at without disturbing the wiring: splices, cracked or missing insulation on the conductors, wires pulled off their knobs, anything already buried, and how the joists and hatch allow cable to travel. The fuses or breakers protecting each circuit are checked against the conductors they serve. The result is a written finding for each attic circuit, fit to certify, needs replacement, or inactive, and a written scope and price for the work that follows.

## Certify, replace or retire

Certification fits a short list of attics: original wiring in good condition, protected correctly, with no later splices. It keeps the circuits in service under the insulation, with the paperwork and posted notices the code requires. Any one failed condition rules it out: a later splice, an oversized fuse or cracked conductor insulation means the circuit cannot be certified as it stands.

Replacement is the answer whenever certification is not. New grounded cable is run across the open joists to the boxes below, usually the easiest wiring in the house to replace, and the old attic runs are disconnected at both ends and removed where reachable or identified and terminated. Replacing the attic circuits often also replaces the top-floor ceiling lights and the wall outlets fed from above, so the work can reach more of the house than the attic alone. Where testing shows runs are already dead, they are retired and documented, which is also what [knob and tube removal](https://fogcitysfknobandtube.com/knob-and-tube-removal/) covers.

## When insulation is already there

Some attics were insulated years ago, right over the wiring. Buried knob and tube is hard to certify, because the survey has to confirm the condition of wiring the insulation hides. The practical path is to test which buried circuits are live, route new cable for those loads, and disconnect the old runs where they leave the panel and where they reach the last device. Where the old insulation has to be pulled back to reach a box or a splice, that is coordinated with the insulation contractor, so the attic is opened once and closed once.

## BayREN EASE Home and the order of work

BayREN’s EASE Home program offers up to $2,000 reimbursed to fix active knob and tube, applied to an EASE Home weatherization project. BayREN’s announcement also listed $300 toward a licensed electrician’s certification that the knob and tube is inactive; the program page does not show that line, so confirm it with BayREN before counting on it. EASE Home covers single-family homes with four or fewer units built before 2010, served by PG&E, with household income at or under 120% of area median income. In San Francisco that limit is $162,450 for one person and $232,050 for a household of four. Participants must have insulation, duct improvements or induction cooking in their scope. Alameda homes on Alameda Municipal Power are outside it because the program requires PG&E customers.

The contractors supply the licensed electrician’s invoice or inactivity certification the rebate needs, and the company helps with the rebate paperwork. Approval is the program’s decision. The [BayREN rebate guide](https://fogcitysfknobandtube.com/guide/knob-and-tube-rebate-bayren/) covers eligibility in more detail.

## Selling, RECO and attic insulation

San Francisco’s Residential Energy Conservation Ordinance requires owners, before selling, to get an inspection, install basic energy and water conservation measures and obtain a certificate of compliance, and its energy measures may include insulating attic space. How RECO treats an attic with knob and tube is not spelled out in what the city publishes, so it is confirmed per house. A sale can be the moment the attic question arrives; the guide to [selling a house with knob and tube](https://fogcitysfknobandtube.com/guide/selling-a-house-with-knob-and-tube/) covers the rest of escrow.

## What attic work costs

No published range exists for attic knob and tube work on its own. The price depends on how many circuits run through the attic, how many are live, how easy the attic is to move in, whether insulation is already there, and whether the circuits can be replaced from above without openings in the rooms below. Current DBI fees start at $305 for a permit covering up to 10 outlets or devices, with one inspection, and step up with the device count. The [San Francisco cost guide](https://fogcitysfknobandtube.com/guide/knob-and-tube-replacement-cost-san-francisco/) explains the wider ranges, and the [cost estimator](https://fogcitysfknobandtube.com/tools/knob-and-tube-cost-estimator/) gives a first number for a whole-house job.

> An East Bay note: Berkeley Form #146
>
> Berkeley turns the state exception into a city form. Its “Knob-and-Tube Wiring Safety Report,” Form #146, says attics with knob and tube may not be insulated unless a licensed electrical contractor’s certification is submitted. The form is signed, posted in the attic before inspection with the original given to the building inspector at final, and bilingual warning signs go at every attic access where insulation conceals the wiring. The [Berkeley service area page](https://fogcitysfknobandtube.com/service-areas/berkeley/) covers the rest of the city’s rules.

**Scope**

## What's included

- A test of every circuit that passes through the attic, recording which are live knob and tube and which are later wiring or already dead
- A look at the attic runs without disturbing them: splices, damaged insulation, loose conductors and anything already covered
- A written finding for each attic circuit: fit to certify, needs replacement, or inactive
- New grounded cable for the circuits being replaced, routed through the attic before the insulation goes in
- Old attic runs disconnected at both ends, removed where reachable, otherwise identified and terminated
- The licensed electrician's invoice or inactivity certification BayREN asks for, and help with the rebate paperwork
- DBI permit, pre-cover and final inspections, a written circuit record and a labeled panel directory

**Choosing the scope**

## Certify, replace or retire attic knob and tube before insulating

| Compare | Certify and insulate over it | Replace the circuits, then insulate | Retire runs that are already dead |
| --- | --- | --- | --- |
| What happens | A licensed electrical contractor surveys the wiring and certifies its condition | New cable replaces the attic circuits; the old runs are disconnected | Runs proven inactive are disconnected at both ends and removed or terminated |
| When it fits | Wiring in good condition: no deterioration, proper overcurrent protection, no improper splices | Splices, damaged insulation, oversized fuses, or an owner who wants it gone | Earlier work already moved the loads to new circuits |
| Knob and tube left live under insulation | Yes, under the code's conditions | No | No |
| Paperwork | Certification filed with the building department, copy to the owner, bilingual notices posted | DBI permit and inspections | Electrician's certification of inactivity if a rebate needs it |
| BayREN EASE Home | Check with the program | Up to $2,000 toward fixing active knob and tube, for eligible households | $300 toward the inactivity certification, as announced; confirm with BayREN |

**Read next**

## Related resources

- [Cost GuideIs there a knob and tube rebate in the Bay Area?One regional program pays toward knob and tube work, and only as part of an energy upgrade. Here is what it pays, who qualifies and what the paperwork needs.](https://fogcitysfknobandtube.com/guide/knob-and-tube-rebate-bayren/)
- [LearnHow can you tell active knob and tube wiring from abandoned runs?Live and dead knob and tube look identical. Insurers, the insulation rule, the BayREN rebate and the real hazard all turn on which one you have.](https://fogcitysfknobandtube.com/guide/active-vs-abandoned-knob-and-tube/)
- [LearnIs knob and tube wiring legal in California?Existing knob and tube is allowed. Extending it, burying it in insulation and leaving dead runs unmarked are not. Here is where the lines fall, statewide and city by city.](https://fogcitysfknobandtube.com/guide/is-knob-and-tube-legal-in-california/)
- [LearnWhat is knob and tube wiring?How the original electrical system in older San Francisco houses works, what it did well, where it falls short and what the rules say now.](https://fogcitysfknobandtube.com/guide/knob-and-tube-wiring/)

**How a job runs**

## From the first call to the Green Tag.

### First call

Tell us what started this: an insurer's letter, an inspection report, a remodel, an attic you want to insulate.

The age of the house, the number of units and any deadline shape the next step.

### Walk-through

Circuits are tested to separate live knob and tube from abandoned runs, and attic, basement and garage access is checked.

Plaster, trim and finishes are noted, and you get a written scope and price.

### The work

The permit is filed with DBI. New cable is fished along the planned routes and openings are kept small.

The pre-cover inspection happens before anything is closed.

### Patching, inspection and the Green Tag

Once the pre-cover inspection passes, the openings are patched. Plaster patching is included and shown as its own line in the quote.

After the final inspection and the Green Tag, old runs are removed or terminated and the panel directory is updated.

**On the job**

## What this work looks like

Fresh blown insulation leveled between attic joists with a new cable stapled along a joist

Cloth-covered wires on porcelain knobs along a post and rafters above old loose-fill insulation in an attic

An open attic hatch in an upstairs ceiling, its cover on the floor, with a stepladder on a drop cloth

Rolls of insulation stacked on plywood boards near the hatch of an older San Francisco attic

**Questions**

## Attic insulation and knob and tube: questions

### What does an electrician have to certify before insulation can cover knob and tube?

That the wiring is in good condition, with no deterioration, improper overcurrent protection, or improper connections or splices. A California-licensed electrical contractor does the survey, the certification is filed with the building department with a copy to the owner, bilingual caution notices are posted, and the insulation must be noncombustible and non-conductive.

### What if insulation was already blown over knob and tube years ago?

Then the wiring's condition is hidden, and nobody can certify what they cannot see. The usual path is to test which buried circuits are still live, move those loads onto new cable routed through the attic, and disconnect the old runs. Insulation may need to be pulled back first, which the insulation contractor schedules with the electrical work.

### Does San Francisco have its own form for insulating over knob and tube?

No San Francisco DBI form or bulletin for it was found, and San Francisco's local electrical code amendments make no change to the knob and tube article. The state code's own steps apply: the electrician's survey and certification, filing with the building department, a copy to the owner and posted notices.

### Who handles the BayREN paperwork for attic knob and tube work?

The contractors supply the licensed electrician's invoice or certification of inactivity that BayREN's knob and tube offer asks for, and the company helps with the rebate paperwork. The rebate belongs to an EASE Home weatherization project, so it is filed alongside that project, and approval is BayREN's decision.

### Should the electrician or the insulation installer go first?

The electrician. Attic wiring is tested, replaced or certified while the joists are open and easy to reach, the DBI inspections happen, and then the insulation goes in. Reversing the order means working through fresh insulation, or pulling it back, to reach wiring that should have been dealt with first.

**Related services**

## Other work on the same wiring

### Knob and tube inspection

Every circuit traced and tested, live runs separated from dead ones, and findings that say plainly what was tested and what was only seen.

### Partial knob and tube replacement

The circuits still running on knob and tube replaced from the panel out, with a written record of exactly what remains.

### Knob and tube removal

Dead and abandoned runs verified, disconnected at both ends, taken out where reachable and recorded, so nobody mistakes them for live wiring later.