Blown-In Insulation Cost - Same-Day Service, Done Right the First Time

How Much Does Blown-In Insulation Cost in San Francisco?

Blown-in insulation in San Francisco typically costs between $1,800 and $4,200 for an average 1,500-square-foot attic, with most homeowners paying around $2,800. For a full attic air-seal plus insulation package, expect $3,500 to $6,500 depending on attic accessibility and the current depth of existing insulation. We give every customer a written price before any work begins, so you’ll know your exact number before we touch a rafter.

Blown-In Insulation Cost Breakdown (2026)

San Francisco pricing runs higher than the national average because of the city’s older housing stock, narrow attic access, and strict building code requirements for energy compliance. Here’s what we’re seeing across the Bay Area market this year.

What pushes a job to the higher end: a steep roof pitch, no attic floorboards to work from, knob-and-tube wiring that needs an electrician consult, or an attic that’s never been insulated and needs full air sealing first. What helps: a simple rectangular attic with an existing access ladder and good headroom.

What Affects Blown-In Insulation Pricing in San Francisco

No two attics in this city are alike. A Victorian in Noe Valley presents different challenges than a 1950s Sunset District row house. Here’s what moves the number.

• Attic square footage and current insulation depth. If your attic only has R-11 (about 3.5 inches), we’re topping up. If it’s bare, we’re starting from scratch. Most San Francisco homes built before 1978 have under-insulated attics, often with compressed fiberglass batts that have lost their loft.
• Attic accessibility. Many older San Francisco homes have scuttle holes instead of pull-down stairs. Jobs that require us to bring a ladder through a bedroom closet and up into a tight hatch take longer, and labor is a real portion of the bill. We lay drop cloths across your hallway and wear shoe covers from the front door to the attic hatch either way.
• Air sealing scope. The number of recessed lights, bathroom fan vents, and wall-top gaps varies wildly by house. A 1908 Edwardian with original plaster and a dozen unsealed penetrations needs more sealing work than a 2010 build. Air sealing is where the real energy savings come from in San Francisco, because our fog-heavy air finds every gap.
• Material choice. Fiberglass is the budget-friendly workhorse. Cellulose costs slightly more but performs better in San Francisco’s damp air because it’s denser and doesn’t lose R-value when temperatures swing. Mineral wool is at the premium end and we often recommend it for homes close to busy streets, where its sound-damping properties matter in addition to temperature control.
• Old insulation removal. If we find rodent nests in the attic, water-stained fiberglass, or material that tests positive for asbestos, removal adds real cost. We don’t remove old insulation unless it’s genuinely failing or hazardous, because layering on top often works fine and saves you money.
• Building code compliance. San Francisco requires R-38 minimum for new attic insulation work under Title 24. If your attic currently has R-19, you’re not legally required to top it up just because we’re in the attic, but if you’re doing a permitted remodel, the inspector will want to see the full depth.

Blown-In Fiberglass vs. Cellulose vs. Mineral Wool: San Francisco Pricing

We install eight brands, including Owens Corning, Johns Manville, Knauf, Rockwool, CertainTeed, Icynene, Demilec, and GreenFiber, because different attics call for different products. Here’s how the three main blown-in material types compare in San Francisco specifically.

Fiberglass (Owens Corning AttiCat, Johns Manville Climate Pro)

$1.20 – $2.00 per square foot installed. Lightweight, non-absorbent, and the most budget-friendly option. It settles slightly over time, so we always blow to about 10% above target depth. Fiberglass loses some R-value when it gets damp, which matters in San Francisco’s marine layer climate, but proper attic ventilation handles that.

Cellulose (GreenFiber, CertainTeed InsulSafe)

$1.40 – $2.30 per square foot installed. Made from recycled paper with a borate treatment that resists fire, mold, and pests. Cellulose is denser than fiberglass and does a better job of blocking air movement, which is why it’s a strong choice for drafty older San Francisco homes. We choose pet-safe products where a choice exists, so the dog can be home during the job.

Mineral Wool (Rockwool ComfortBatt or loose-fill)

$2.00 – $3.20 per square foot installed. The premium option. Rockwool doesn’t absorb water, doesn’t burn, and dramatically cuts street noise, which is a real consideration for families near the 101 corridor or Muni lines. It’s the heaviest product we blow, and some older San Francisco attic floors need a structural check before we add the full weight.

How to Save on Blown-In Insulation

You don’t have to overspend to get a properly insulated attic. Here are the practical ways we help families keep the number reasonable.

• Layer on top rather than removing. If your existing insulation is dry, pest-free, and not compressed beyond usefulness, blowing new material over it is often the right move. Removal adds $900 to $2,000 that you may not need to spend.
• Ask about bay area rebate programs. BayREN and PG&E occasionally offer incentives for attic insulation upgrades in San Francisco, though program availability changes. We can tell you what’s active when we quote your job.
• Bundle air sealing with insulation. Doing both in one visit saves a separate mobilization fee and the energy savings compound. An air-sealed attic with R-38 insulation typically performs better than an unsealed attic with R-49.
• Get a written quote before committing. You should never take a bid that says “somewhere between.” Call us at (341) 247-0222 and we’ll give you a written price before any work starts, always included, never conditional.
• Don’t over-insulate for the sake of it. Beyond about R-49, you’re chasing diminishing returns in San Francisco’s mild climate. We’ll tell you if your attic is already at the point where extra depth won’t pay for itself.

Is Blown-In Insulation Worth It in San Francisco?

Yes, and the reason isn’t just heating bills. San Francisco’s problem is rarely freezing winters. It’s fog, temperature swings, and the fact that many homes have no real thermal boundary between the living space and the attic. On a typical July afternoon, a Sunset District attic can hit 120°F while the living room below struggles to stay at 68°F. That heat is pouring into your home through the ceiling, and the right blown-in insulation stops that transfer.

Most San Francisco homeowners see a 15% to 25% reduction in heating and cooling energy use after an attic insulation and air sealing job, with the best results in older homes with minimal existing insulation. The comfort difference is immediate, especially in bedrooms directly below the attic.

Beyond energy, blown-in insulation helps with the city’s noise problem. Cellulose and mineral wool both dampen street noise noticeably, which matters if you’re near a bus route or a busy corner.

What to Expect When We Install Blown-In Insulation

We don’t start until you have your written price in hand. When the crew arrives, here’s what happens.

Our technicians are background-checked and uniformed, and they’ll introduce themselves at the door. We lay drop cloths from the front door to the attic access, and we wear shoe covers the entire time we’re inside your home. The blowing machine stays outside with a long hose running through an open window or the attic hatch. We use quiet tools when children are sleeping, and we’ll ask before we move or touch anything in closets or halls.

The actual blowing takes two to five hours for a typical San Francisco attic. Air sealing happens first, then the insulation goes in to the target depth. We take photos of the attic before and after, including the clean-up, and we leave you with the photos before the van pulls away. The 365-Day Done Right Promise covers the work: if it’s not done right, we make it right, no debate, no fine print.

Thistledown is the soft fluff of the thistle, one of nature’s lightest insulators. The name is a promise about how carefully we work. We are part of the Cedarwell family of independently owned insulation companies, founded in 2003 and held to the Cedarwell Care Promise on every visit: clean up like it is our own home, ask before we move or touch anything, respect the family’s time and quiet hours, and explain the price before the work.

FAQs – Blown-In Insulation Cost

How much does blown-in insulation cost per square foot in San Francisco?

Blown-in insulation in San Francisco runs $1.20 to $3.20 per square foot installed, depending on the material. Fiberglass is the lowest at $1.20 to $2.00 per square foot, cellulose lands around $1.40 to $2.30, and Rockwool mineral wool runs $2.00 to $3.20. The square foot price includes labor, equipment, and cleanup. Call (341) 247-0222 and we’ll give you an exact written number for your attic.

How much does it cost to insulate a 1,500 sq ft attic in San Francisco?

A 1,500-square-foot attic in San Francisco typically costs $1,800 to $4,200 for blown-in insulation alone, or $3,500 to $6,500 with air sealing included. Older homes with lots of ceiling penetrations land at the higher end. We’ll tell you exactly what your attic needs and what it costs, in writing, before any work starts.

Is blown-in insulation cheaper than spray foam in San Francisco?

Yes. Blown-in insulation runs $1.20 to $3.20 per square foot installed, while spray foam insulation in San Francisco typically costs $3.50 to $7.00 per square foot. Spray foam makes sense for certain rim joist and crawlspace applications where air sealing and insulation need to happen in one step, but for attics, blown-in insulation is the better value in almost every case.

How long does blown-in insulation last?

Blown-in fiberglass and cellulose insulation last 20 to 30 years, and Rockwool effectively lasts the life of the home. The things that shorten insulation life in San Francisco are roof leaks, rodent activity, and moisture from poor ventilation. We check for all three during the inspection, and we take photos so you can see what we see.

Does blown-in insulation reduce noise in San Francisco homes?

Yes, blown-in cellulose and mineral wool both meaningfully reduce street noise, with mineral wool offering the best sound damping. If you’re near Muni, the 101, or a busy commercial street, we’d typically recommend Rockwool. Fiberglass helps less with noise reduction but still offers some benefit compared to an empty attic.

Can blown-in insulation be done in one day?

Yes. Most San Francisco attic insulation jobs are completed in a single visit, typically two to five hours on site. Air sealing adds time, so plan for a full day if you’re doing both. We can usually schedule within one to two weeks of your quote, and we’ll give you a window so you’re not waiting around all day.

Is it cheaper to repair or replace existing attic insulation?

Layering new blown-in insulation over existing material is almost always cheaper than removal and replacement. We only recommend removal when the existing insulation is water-damaged, pest-infested, or compressed beyond recovery. A typical removal in San Francisco adds $900 to $2,000, so we don’t suggest it unless the existing material is genuinely failing.

Get Your Written Price Before You Decide

You don’t have to guess. Call us at (341) 247-0222 and we’ll schedule an attic inspection. We’ll measure your insulation depth, check for air leaks and moisture issues, and give you a written price before any work begins. The estimate is free. The advice is honest. And when the crew arrives, they’ll treat your home the way we’d treat our own: shoe covers on, drop cloths down, and a photo of the clean-up before we leave.

Read more about blown-in insulation in San Francisco or return to our home page to see everything we do.

Pricing reflects the San Francisco market as of 2026. Thistledown Insulation San Francisco offers free estimates – call (341) 247-0222.

Written by Neil Barron, Owner at Thistledown Insulation San Francisco, serving San Francisco since 2003.