Spray foam insulation in Washington, DC: get up to 3 quotes from vetted local installers
Request free quotes from up to three vetted spray foam installers serving Washington and nearby District of Columbia. Below: what your climate zone means for open vs closed cell, how much insulation to ask for, District of Columbia's energy code, and the rebates we could verify.
- Climate zone: 4A (2021 IECC)
- Attic target: R-60 (ENERGY STAR, uninsulated attic)
- State code: District of Columbia Energy Conservation Code (2015 IECC base with DC amendments)
- Utility rebates we verified: DC Sustainable Energy Utility / DOEE Weatherization
- Federal 25C credit: ended for 2026 installs
Facts last checked October 16, 2026. Sources are linked in each section.
Where we match quotes from this page
Requests from Washington and ZIP codes whose center is within about 20 miles of it go to our Washington, DC partner installers (118 ZIP codes): 20001, 20002, 20003, 20004, 20005, 20006, 20008, 20009, 20010, 20011, 20012, 20015, 20017, 20018, 20019, 20020, 20024, 20036, 20037, 20045, 20052, 20059, 20064, 20204, 20220, 20230, 20240, 20245, 20250, 20260, 20317, 20319, 20373, 20388, 20390, 20408, 20415, 20418, 20422, 20427, 20431, 20510, 20515, 20520, 20530, 20535, 20540, 20542, 20551, 20560, 20565, 20566, 20591, 20701, 20705, 20706, 20707, 20708, 20710, 20712, 20715, 20716, 20720, 20721, 20722, 20723, 20724, 20737, 20740, 20742, 20743, 20746, 20747, 20748, 20755, 20759, 20762, 20763, 20769, 20770, 20771, 20772, 20774, 20777, 20781, 20782, 20783, 20784, 20785, 20814, 20815, 20832, 20851, 20852, 20853, 20855, 20860, 20861, 20862, 20866, 20868, 20879, 20880, 20889, 20892, 20894, 20895, 20896, 20901, 20902, 20903, 20904, 20905, 20906, 20910, 20912, 21113, 21114. Outside these? Send the form anyway and we'll tell you if we can't match you.
Climate zone 4A: what it means for spray foam
Washington's central point is in District of Columbia, which the 2021 IECC county map assigns to climate zone 4A (mixed-humid in DOE's Building America terms). Zone 4A is a moist ("A") zone, which drives the vapor and R-value rules below.
Other counties within our Washington service radius: Anne Arundel County (4A), Howard County (4A), Montgomery County (4A), Prince George's County (4A). All are zone 4A too.
Source: PNNL-33270, Guide to Determining Climate Zone by County (IECC 2021).
Open cell vs closed cell in Washington, DC
Attic roofline: both foams are used. The IRC (R806.5) does not require a vapor-retarder coating on open-cell foam under the roof deck in zone 4A (that requirement starts in zone 5), but for hybrid assemblies the foam layer at the deck must be at least R-15 to control condensation. Ask the installer how they manage winter moisture at the roof sheathing.
Closed cell is the usual choice for rim joists, basement and crawlspace walls, where its vapor resistance (about 1.5–2" makes it a Class II vapor retarder) matters most.
How much insulation to ask for
| Where | ENERGY STAR recommendation for zone 4A |
|---|---|
| Attic, uninsulated | R-60 |
| Attic with 3–4" of existing insulation | add R-49 |
| Floor over unconditioned crawlspace/basement | R-19 |
| Basement or crawlspace walls | R-10 continuous or R-13 cavity |
| Exterior walls (when re-siding) | add R-5 to R-10 insulative wall sheathing beneath new siding |
To reach R-60 with foam alone you'd need roughly 16.2–17.1" of open cell (about R-3.5 to R-3.7 per inch) or 8.6–12.0" of closed cell (about R-5 to R-7 per inch). Many roofline spray foam jobs are installed thinner than that and justified through the code's performance path or the unvented-attic rules, so ask every installer to write the foam type, thickness and resulting R-value on the quote and explain how it meets your local code.
Source: ENERGY STAR, Recommended Home Insulation R-Values (based on 2021 IECC). ENERGY STAR's figures are recommendations for existing homes; your local code sets the legal minimum for new work.
District of Columbia energy code
District of Columbia Energy Conservation Code (2015 IECC base with DC amendments), effective May 29, 2020. DC amendments raise several insulation requirements above the model code.
Source: NAHB, "Residential Provisions of the IECC: State Adoption Status" (current as of May 2026); official state status at DOE Building Energy Codes Program.
Homes in Washington, DC
Census figures for Washington city (ACS 2020–2024 5-year estimates): about 361,014 housing units, a median year built of 1958, 69% built before 1980 and 17% built in 2010 or later. 11% are single-family detached homes and 0% are mobile/manufactured homes. 42% of occupied homes are owner-occupied, with a median owner-reported home value of $737,100.
- With 69% of homes built before 1980, many attics here predate modern energy codes. Older attics often need old insulation removed or air-sealed first, and knob-and-tube wiring must be checked before any insulation covers it. Ask whether removal and prep are in the price.
- 48% of homes heat with utility gas. Spray foam makes a house much tighter, which changes how gas furnaces, water heaters and fireplaces draft, so ask whether the installer (or your HVAC contractor) will do combustion safety testing after the job. Some utility rebates require it.
Rebates and incentives for Washington, DC
Utility programs that may apply, depending on which utility serves your address:
DC Sustainable Energy Utility / DOEE Weatherization
DCSEU's residential rebates did not include a general insulation rebate when we checked. Income-qualified households can get insulation and air sealing through DOEE's Weatherization Assistance Program.
Read on the program's own page October 16, 2026. Programs change; confirm before you sign.
District of Columbia state Home Energy Rebates
Unclear: check official page Affordable Home Electrification Program (AHEP)
"Property owners/managers and residents are encouraged to learn more about these programs and apply directly with the DCSEU. Federally funded rebates will not be available outside of participation in AHRA or AHEP."
Official source: DC Sustainable Energy Utility (DCSEU). Status text compiled via referencesource.org, last checked by them August 25, 2026. Full District of Columbia rebate page →
What spray foam costs (national published ranges)
We don't have enough local quotes for Washington, DC to publish local prices, and we won't make them up. These national ranges are a starting point; your installers' quotes are what count.
| Example job (typical thickness) | Estimated installed range |
|---|---|
| 1,000 sq ft attic roofline, open cell (6") | $3,600–$9,600 |
| 1,000 sq ft attic roofline, closed cell (3") | $3,900–$9,300 |
| 1,500 sq ft walls, open cell (3.5") | $3,150–$8,400 |
| 1,500 sq ft walls, closed cell (2") | $3,900–$9,300 |
| 200 sq ft rim joists, closed cell (2") | $520–$1,240 |
Board feet × Angi's 2026 installed price per board foot. Angi reports a national average spray foam project of $2,888 (typical $1,455–$4,337). Check a quote you already have →
Questions to ask each installer
- Foam type, brand, thickness and resulting R-value for each area, in writing.
- Which climate zone and code edition they're designing to.
- Whether removal of old insulation, air sealing, and any required ignition/thermal barrier coating are included.
- Whether they participate in DC Sustainable Energy Utility / DOEE Weatherization, and who files the paperwork.
- Whether they'll do (or coordinate) combustion safety testing if you have gas appliances.
FAQ
What climate zone is Washington, DC in?
District of Columbia is IECC 2021 climate zone 4A, per PNNL's county list (PNNL-33270).
Should I use open-cell or closed-cell spray foam in Washington, DC?
Both work at the roofline in zone 4A; closed cell is the usual pick for rim joists and basement or crawlspace walls. In hybrid roof assemblies the foam layer must be at least R-15.
How much attic insulation do homes in Washington, DC need?
ENERGY STAR recommends R-60 for an uninsulated attic in zone 4A (or adding R-49 on top of 3–4 inches of existing insulation). District of Columbia's code: District of Columbia Energy Conservation Code (2015 IECC base with DC amendments).
Are there spray foam or insulation rebates in Washington, DC in 2026?
The federal 25C tax credit does not apply to insulation installed after December 31, 2025. Utility programs that may apply, depending on which utility serves your address: DC Sustainable Energy Utility / DOEE Weatherization. District of Columbia's state Home Energy Rebate program status: Unclear: check official page.
How much does spray foam cost in Washington, DC?
We don't publish local prices until we have enough real local quotes. National published ranges are about $0.60–$1.60 per board foot for open cell and $1.30–$3.10 for closed cell, installed (Angi, 2026), and many companies have a $1,000–$2,000 minimum.
How does requesting quotes work?
Fill in the form once. We pass your request to up to three vetted partner installers who serve Washington, DC, and they contact you to schedule an estimate. It's free and there's no obligation.