Spray Foam Insulation in Durham, NC

Spray foam insulation in Durham has a different job than it does up north. Here the hard season is summer: long stretches of heat, thick humidity, attics that bake and crawl spaces that breathe damp air. We seal and insulate Durham homes with open-cell or closed-cell spray foam where it is the right tool, and with blown-in cellulose or fiberglass where that does the job for less money. Most of our work happens in the two places central North Carolina houses lose the most comfort: the attic and the crawl space.

Durham weather, by the numbers

The 1991-2020 normals for Raleigh-Durham International Airport, published on Wikipedia's Durham page, put the July daily mean at 80.5F and the average July high at 90.8F. The average dew point in July and August sits near 68F, which is what makes a Triangle summer feel heavy. Winters are short but real: the average January low is 31.8F, the record low is -9F, and snowfall averages about 5 inches a year. Rain comes steadily, about 46 inches a year. Put those together and you get a house that runs its air conditioner for months and its heat for a few cold weeks, with moisture pressing in from outside most of the year.

What the code says for Durham County

Durham County, like the rest of the Triangle, falls in IECC Climate Zone 4A, the mixed-humid zone (OpenEI's county list). North Carolina's 2018 Energy Conservation Code, built on the 2015 IECC with state amendments, took effect January 1, 2019, and the Insulation Institute's summary lists R-38 for ceilings (or R-30 continuous). ENERGY STAR's retrofit table goes further for Zone 4A: R-60 for an attic with no insulation, R-49 added on top of 3 to 4 inches already there, and R-19 under floors. For crawl space walls it lists R-10 insulating sheathing or an R-13 batt. Those numbers set the depth or thickness we write on your quote.

Durham houses, old and new

Much of Durham's early commercial and residential building dates from roughly 1890 to 1930, when tobacco and then textiles drove the city's growth. Mill neighborhoods in what were East and West Durham were later annexed into the city. Those older houses tend to have balloon framing, open wall cavities, little or no insulation in the walls, and crawl spaces with dirt floors. Housing developments then spread south toward Research Triangle Park in the 1970s and 1980s, and most of the residential growth since 1990 has run along the I-40 corridor in southern Durham County. Those houses usually have some insulation, but the crawl space batts sag, the attic insulation has settled, and the bonus room over the garage is the hottest room in the house. The 2022 American Community Survey counted 134,423 housing units in the city, and very few of them were built tight.

Closed cell vs open cell

Open-cell foam is soft and spongy. It expands a lot, fills odd-shaped cavities and stops air movement, but it lets some water vapor pass. HomeGuide puts it at about R-3.5 to R-3.7 per inch. Closed-cell foam is dense and rigid at R-5 to R-7 per inch, and at normal thickness it slows vapor and does not soak up water. In Durham we usually reach for closed-cell on crawl space walls and rim joists, where ground moisture and humid air are the problem, and open-cell under roof decks and in bonus room walls and kneewalls, where its sound damping and lower cost help. The right choice depends on the assembly, so the quote explains why we picked each one.

Spray foam insulation contractors: questions to ask

Whether you call us or other spray foam insulation companies and insulation contractors in the Triangle, a few questions separate a careful job from a fast one. Ask what gets air sealed before insulation goes in. Ask which foam goes where, at what thickness, and what R-value that reaches. Ask how the crawl space will be dried out or vented, how ductwork in the attic will be handled, how long you need to stay out of the house after spraying (HomeGuide suggests at least 24 hours), and what happens to old insulation. A good answer is specific and comes in writing. Searching for spray foam insulation near me will turn up plenty of names; the written details are what let you compare them.

Spray foam insulation cost

HomeGuide's 2026 cost guide lists installed spray foam at $1.50 to $5.00 per square foot: about $1.50 to $3.50 for open-cell and $3.00 to $5.00 for closed-cell. For about 1,000 square feet that works out to $1,500 to $5,000, and HomeGuide puts a crawl space at $2,000 to $4,000. Fixr's guide lists $3.15 to $7.50 per square foot for existing walls. Many installers also have a job minimum of roughly $1,000 to $2,000. Those are national figures; your price depends on the space, the access and the prep, and the number on our written estimate is what you pay.

Rebates worth checking

Duke Energy's attic insulation page lists instant rebates for single-family homes that raise attic insulation to at least R-38, from $0.25 to $0.31 per square foot (up to $600 to $800 depending on how little insulation is there now). The rebate requires a free Duke Home Energy Check and work by a Duke-approved contractor, and the page does not say which of its service areas qualify, so check with Duke before you count on it.

We serve Durham and the towns around it, from Chapel Hill and Hillsborough to Cary, Apex, Creedmoor and Roxboro. Get a free estimate

Our base market is the city of Durham and Durham County, including the neighborhoods near Duke, the older streets around downtown, and the subdivisions south toward Research Triangle Park. To the west we work in Chapel Hill, Carrboro and Hillsborough in Orange County, and out to Mebane. To the southeast we cover Morrisville, Cary and Apex, and to the south Pittsboro and the new neighborhoods of northern Chatham County. North of Durham we go to Butner, Creedmoor and Oxford in Granville County, and Roxboro in Person County, plus Wake Forest and Raleigh to the east. Older mill towns, university towns and fast-growing suburbs each have their own insulation problems, and the town pages below explain what we look for in each.