Attic insulation · Costs & rebates

Best Attic Insulation for Phoenix Homes: R-Values, Costs & SRP Rebates (2026)

The honest version of what works in Arizona heat — how much insulation you actually need, what it costs this year, and how the SRP rebate knocks up to $600 off the price.

By the AZ Insulation crew 12 min read Updated July 2026 BPI-certified · ROC# 301682

Blowing fiberglass in around the ducts in a Mesa attic — coverage at the edges and around obstructions is where most jobs fall short.

If your upstairs bedroom is 10 degrees hotter than your living room, your AC never seems to shut off, and your July SRP bill made you say something you wouldn’t repeat in front of your kids — your attic is probably the problem.

We’ve been crawling around Valley attics since 2014. Here’s the honest version of what works in Arizona heat, how much insulation you actually need, what it costs in 2026, and how the SRP rebate can knock up to $600 off the price. No sales fluff.

What’s the best insulation for an attic in Phoenix?

Quick answer

For Phoenix-area attics, professionally installed blown-in fiberglass at R-38 or higher, combined with attic air sealing, is the best attic insulation for hot climates. It resists heat transfer without settling, doesn’t absorb moisture, isn’t attractive to pests, and it’s the option that qualifies for the SRP insulation rebate.

Three reasons blown-in fiberglass wins in the desert

It doesn’t settle or break down. Cellulose is paper-based — it compacts and degrades over the years, and the R-value goes with it. Fiberglass holds its loft permanently, which is why we back every blown-in fiberglass install with a lifetime warranty.
It fills the gaps batts miss. Blown-in flows around trusses, wiring, and odd framing angles. Batts leave voids at the edges — and voids are where your cool air escapes.
It handles monsoon humidity. Fiberglass doesn’t soak up moisture or hold it against your drywall.

Spray foam gets a lot of hype online. It performs well, but it costs three to four times as much per square foot, and for a standard Phoenix attic floor it rarely earns back the difference. We’ll tell you that in person too.

The part most contractors skip

R-value only measures resistance to heat conduction. Air leaking through your can lights, attic hatch, and top plates bypasses insulation entirely. R-60 over a leaky ceiling underperforms R-38 over a sealed one. Air seal first, then insulate. SRP requires it for the rebate, and it’s the single biggest reason two homes with identical insulation get very different bills.

An insulated and sealed attic access hatch with a dam to hold back blown-in insulation.

An AZ Insulation technician blowing loose-fill fiberglass across an attic floor, filling in around trusses and ductwork.

Best attic insulation for hot climates: why Arizona is different

Quick answer

In cold climates, insulation keeps heat in. In Phoenix, it keeps a 160°F attic from radiating down into your living space for six months a year. That means depth, complete coverage, and air sealing matter more here than almost anywhere in the country.

Phoenix sits in DOE Climate Zone 2B — hot and dry. On a 112° afternoon your attic can hit 150–160°F. That heat load presses down on your ceiling all day and keeps radiating into your rooms well after sunset, which is why your AC runs at 9 p.m. and your bedroom still feels warm at 11.

Homes built in the Valley before 2000 were typically insulated to R-19 or less. Some of the older Mesa and Phoenix housing stock we inspect comes in under R-11. That was code at the time. It is nowhere near enough for today’s summers or today’s electric rates.

How much insulation do I need in my attic?

Quick answer

Arizona code and the SRP rebate program both target R-38 for attics over living space. R-38 is the number to hit. If your attic is easy to access and you’re already paying for the crew and the equipment, going to R-49 costs relatively little more and buys you extra margin against desert heat.

The R-value ladder for Phoenix homes.
R-Value	What it means for your home
R-11 to R-19	Common in pre-2000 Valley homes. Under-insulated. Qualifies for the SRP rebate.
R-30	Better, but below current Arizona code for attics over conditioned space.
R-38	The target. Arizona code recommendation and the SRP rebate benchmark.
R-49+	Upgrade level. Worth it if access is good and you want maximum summer performance.

Do this in 60 seconds

Open your attic hatch, shine a flashlight across the floor, and look at your ceiling joists. If you can see the tops of the joists, you have roughly 6 inches or less — likely R-19 or under. If the insulation is level with the joists, you’re around R-19 to R-22. Insulation should sit several inches above the joists, not level with them.

Recommended insulation depth for attic (Phoenix R-value chart)

Quick answer

To reach R-38 you need roughly 13 to 15 inches of blown-in fiberglass, or about 10 to 12 inches of blown-in cellulose. Cellulose needs less depth for the same R-value, but it settles 10–20% over time — so its installed depth drops and the R-value drops with it.

Target R-Value	Blown Fiberglass ~R-2.5–2.9/in	Blown Cellulose ~R-3.5–3.8/in	Fiberglass Batts ~R-3.2/in
R-30	11–12 in	8–9 in	~9.5 in
R-38	13–15 in	10–12 in	~12 in
R-49	17–20 in	13–15 in	~15 in
R-60	21–24 in	16–18 in	~19 in

Same attic, before and after topping off to R-38. The joists disappear — that’s what you’re looking for.

How to calculate your own number: measure your current depth in inches, multiply by the R-per-inch of what’s up there, and subtract from your target. Example: 5 inches of old fiberglass ≈ R-13. To reach R-38 you need about R-25 more, which is roughly 9 to 10 additional inches of blown fiberglass on top.

Two things that quietly wreck real-world R-value

Compression. Batts rated R-19 only deliver R-19 at full loft. Boxes stacked on attic insulation, or batts stuffed into a shallow cavity, deliver far less than the label.
Settling. If your attic was blown to 14 inches of cellulose a decade ago, it may be 11 today. Measure what’s there now — not what the invoice said in 2015.

Free · no obligation

Not sure what’s up there? Find out for free.

We’ll measure your actual attic depth, photograph what we find, tell you your current R-value, and confirm whether you qualify for the SRP rebate — at no cost and with no obligation.

Schedule My Free Attic Inspection or call 480-662-2874

Fiberglass vs. cellulose blown insulation cost

Quick answer

Blown cellulose typically runs $0.80–$1.20 per square foot installed and blown fiberglass $1.00–$1.50 per square foot installed. Cellulose is cheaper up front and needs less depth, but it settles and breaks down over time — so the R-value you paid for isn’t the R-value you’ll have in ten years. Fiberglass costs slightly more but does not settle or break down, doesn’t absorb moisture, and isn’t a food source for pests. That’s why we install it in Arizona, and why we can back our blown-in fiberglass with a lifetime warranty.

	Blown Fiberglass	Blown Cellulose
Installed cost	$1.00–$1.50 / sq ft	$0.80–$1.20 / sq ft
R-value per inch	R-2.5–2.9	R-3.5–3.8
Depth for R-38	13–15 in	10–12 in
Settling over time	None — doesn’t settle or break down	Settles 10–20% and breaks down over time
Warranty	Lifetime no-settling warranty from us	No settling warranty available
Moisture behavior	Doesn’t absorb	Absorbs; can hold moisture
Made from	Spun glass fiber	~80% recycled paper, borate-treated
Pest appeal	None	Treated, but paper-based
Best for	Hot, dry climates; long-term stability	Tight budgets; irregular cavities

Our honest take

Cellulose isn’t a bad product. In a cold, damp climate with a well-detailed vapor strategy it performs great. But it’s paper-based, and paper settles and breaks down — a material that loses 15% of its depth over a decade means you paid for R-38 and end up living with R-32. Blown-in fiberglass is spun glass. It doesn’t settle, it doesn’t break down, and it holds the R-value you paid for. That’s exactly why we can put a lifetime warranty on every blown-in fiberglass insulation job we do — a promise no one can make on cellulose. If you want cellulose, plenty of good contractors here will install it. We’d just rather be straight with you about the tradeoff.

Blown-in insulation cost & attic insulation cost in Phoenix (2026)

Quick answer

Professionally installed blown-in attic insulation in the Phoenix area runs about $1,000 to $2,500 for a typical home, or roughly $1.10–$1.40 per square foot of attic space. SRP customers can have up to $600 of that covered by the insulation rebate.

Estimates for topping off existing insulation to R-38 with air sealing. Your actual price depends on access, existing R-value, and whether removal is needed. We give you an itemized quote before you commit.
Attic size	Typical topped-off cost to R-38	After SRP rebate (if you qualify)
1,000 sq ft	$1,100 – $1,400	$500 – $800
1,500 sq ft	$1,650 – $2,100	$1,050 – $1,500
2,000 sq ft	$2,200 – $2,800	$1,600 – $2,200

Loading the blower on site. Most Valley attics are done in two to four hours, air sealing included.

What moves the price up or down

Attic square footage — the biggest single factor.
How much R-value you’re adding — going from R-19 to R-38 costs less than starting from bare joists.
Insulation removal — required if existing insulation is water-damaged, smoke-damaged, rodent-contaminated, or in the way of air sealing. This adds cost, and we’ll tell you plainly if you need it.
Access — a tight hatch, low clearance, or a two-story split adds labor.
Air sealing scope — number of can lights, penetrations, and top plates to seal.

What it saves you: proper insulation and air sealing can cut heating and cooling costs by roughly 10%, per SRP. On a Valley home with a $400 summer electric bill, that’s real money every single month from June through September — plus a house that actually holds temperature.

SRP rebates for attic insulation: how it works

Quick answer

SRP covers up to 75% of professionally installed attic insulation, up to $600. Your existing insulation needs an effective R-value under R-19, the job has to be brought to R-38, and it must be done by a participating BPI-certified SRP contractor in combination with air sealing. We’re a participating contractor and we apply the rebate directly to your invoice — so you never front the full amount or wait weeks for a check.

You likely qualify if:

You’re a current SRP residential electric customer
You live in a single-family detached or attached home, apartment, or condo (mobile homes don’t qualify)
Your existing attic insulation is effectively below R-19 — or is above R-19 but demonstrably underperforming (we document that with photos and thermal images)
The work brings your attic to R-38
The job includes attic air sealing
The work is done by a participating, BPI-certified, Arizona-licensed contractor

APS customer instead? APS runs its own insulation incentives, and there may be additional utility and state programs worth stacking. We check every program your address qualifies for and file the paperwork ourselves. We’ve secured over $5 million in rebates for Arizona homeowners.

For the full breakdown of every Arizona rebate and credit available right now, see our Arizona insulation rebates and costs guide.

Up to $600 off

Let’s find out what SRP will cover on your home.

We’ll confirm your rebate eligibility during your free inspection, file every form for you, and apply the discount straight to your invoice. Zero paperwork on your end.

Check My Rebate Eligibility or call 480-662-2874

Best insulation company near me: what to actually check

Quick answer

In the Phoenix area, verify four things before you sign anything: a valid Arizona ROC license, BPI certification (required for the SRP rebate), a written warranty against settling, and an itemized quote that lists target R-value and air sealing as separate line items. If a contractor can’t produce all four, keep calling.

The checklist we’d hand a neighbor

Arizona ROC license. Ask for the number and look it up. Ours is ROC# 301682.
BPI certification. If they aren’t BPI-certified and a participating SRP contractor, you cannot get the SRP insulation rebate through them. Full stop.
A written warranty. Insulation settles or it doesn’t. Get the promise in writing — we warranty ours for life.
An itemized quote. It should state the target R-value, the square footage covered, and air sealing as its own line. Vague quotes hide vague work.
Photo documentation. A real contractor photographs your attic before and after. You should be able to see what you paid for.
Local reviews with volume. One or two five-star reviews mean nothing. We’re at 4.9 stars across 550+ reviews — you can read them on our testimonials page.

We’re family-owned, based in Mesa, and we’ve been doing this in the Valley since 2014. We serve Mesa, Phoenix, Gilbert, Glendale, Chandler, Tempe, Scottsdale, Queen Creek, Gold Canyon, Cave Creek, Goodyear, Surprise, and the rest of the metro.

Still hot after insulating? Here’s the usual culprit.

Attic insulation fixes whole-house heat gain. It won’t fix a converted garage, a west-facing casita, or that one back bedroom that’s always 15° hotter than the rest of the house — because those rooms usually aren’t getting enough conditioned air in the first place.

That’s a ductless mini-split problem, not an insulation problem. One indoor head, one outdoor unit, no ductwork, installed in a day. Insulation plus a mini-split is the combination that finally solves a hot garage or a converted room for good.

And if your AC is over 12 years old and struggling every August, insulating first is still the right move — it lets us size a smaller, cheaper system when you do replace it. Oversized equipment short-cycles, and short-cycling doesn’t dehumidify or last. Ask us about pairing an insulation upgrade with a system quote; SRP customers can get up to $1,200 off a new high-efficiency HVAC system.

When insulation isn’t the answer: one indoor head, one outdoor unit, no ductwork — installed in a day.

Frequently asked questions

Questions Arizona homeowners ask us

What is the best attic insulation for Phoenix homes?

Blown-in fiberglass installed to R-38 or higher with attic air sealing. It resists heat transfer without settling, doesn’t absorb monsoon moisture, isn’t a pest food source, and qualifies for the SRP insulation rebate.

How much insulation do I need in my attic in Arizona?

R-38 is the target for attics over living space in Arizona, and it’s the benchmark for the SRP rebate. R-49 is a worthwhile upgrade if attic access is good.

What is the recommended insulation depth for an attic?

About 13–15 inches of blown fiberglass or 10–12 inches of blown cellulose to reach R-38. Insulation should sit several inches above your ceiling joists, not level with them.

How much does blown-in attic insulation cost in Phoenix?

Roughly $1,000–$2,500 for a typical home, or about $1.10–$1.40 per square foot of attic space. SRP customers can have up to $600 covered by the insulation rebate.

Is fiberglass or cellulose cheaper for blown-in insulation?

Cellulose is slightly cheaper installed — about $0.80–$1.20 per square foot versus $1.00–$1.50 for fiberglass. But cellulose settles 10–20% and breaks down over time, while fiberglass does not, so fiberglass delivers better long-term value in Arizona. We back our blown-in fiberglass with a lifetime warranty.

How do I get the SRP insulation rebate?

Use a participating BPI-certified SRP contractor. SRP covers up to 75% of the installed cost, up to $600, when existing insulation is under R-19 and the attic is brought to R-38 with air sealing. We apply the rebate directly to your invoice.

Should I remove old attic insulation before adding new insulation?

Usually no — topping off is normal and cheaper. Removal is necessary when existing insulation is water-damaged, smoke-damaged, rodent-contaminated, or blocking air sealing work.

Do I need a permit to add attic insulation?

In most Arizona jurisdictions, adding blown-in insulation to an existing attic floor is treated as ordinary maintenance and does not require a permit. We’ll confirm for your city.

How long does attic insulation take to install?

Most Valley homes are done in two to four hours, including air sealing. Larger homes or jobs requiring removal take longer.

Does attic insulation really lower an electric bill in Phoenix?

Yes. Per SRP, proper insulation and air sealing can cut heating and cooling costs by about 10%, and the comfort difference in a Phoenix summer is usually noticeable within days.

Free · no pressure

Get Your Free Attic Inspection & Rebate Check

We’ll measure your current R-value, photograph what’s up there, tell you exactly what you need, and confirm what SRP will cover. Free, no obligation, no pressure — just an honest number.

$5M+ in rebates secured for AZ homeowners

BPI-certified, participating SRP contractor

4.9★ from 550+ local reviews

Lifetime no-settling warranty