Selma, NC
4 miles east
Power from its own town system (Smithfield: a town system)
Attic insulation in SelmaAttic Insulation in Smithfield, NC
Blown-in attic insulation for Smithfield, NC, in Johnston County, plus removal and air sealing.
About Smithfield and Its Homes
Smithfield has been the Johnston County seat since 1771, on a bluff over the Neuse River, but it stayed a village until railroads arrived in the 1880s. Its two listed residential districts, Brooklyn and North Smithfield, hold houses from the late 1800s to about 1950, and each era left a different attic.
Smithfield, in Johnston County, grew from 11,380 people in 2020 to 13,114 in 2025 (Census Bureau estimates), on 12.7 square miles. That makes Smithfield the second-largest town in Johnston County.
Smithfield has about 5,600 housing units, 6 percent of Johnston County's; 59 percent of the town's households own their home.
Smithfield at a Glance
- County: Johnston County
- Population: 13,114 (2025), 11,380 (2020), up 15.2%
- Land area: 12.7 square miles (1,033 people each)
- Housing units: about 5,600 (±503)
- Median year built: 1973 (±3); Johnston County: 2000
- Owner-occupied: 59% (±6); Johnston County: 76%
- Detached houses: 63% (±6); Johnston County: 76%
- Attached houses: 5% (±3)
- Apartments: 26% (±9)
- Mobile homes: 5% (±3)
- Climate zone: 3 on both maps
- ENERGY STAR target for Smithfield attics: R-49 from bare, R-38 over 3 to 4 inches (R-value guide)
Census Bureau estimates for Smithfield, 2020 to 2024 (± margin of error).
Smithfield Homes and Their Attics
Brooklyn, Sold Off a Farm in the 1880s
Brooklyn began in the mid-1880s, when Seth Woodall started selling lots from his farm just south of the town center. It probably took its name from Spring Branch, the brook along its north edge. The district's 2000 nomination says the Craftsman bungalow led there from 1915 to 1930, and its inventory names one-and-a-half-story houses more than twenty times, along with a gambrel-roofed cottage from about 1939. A bungalow with a dormer puts its bedrooms up under the slope of the roof. Low triangular spaces hide behind their short side walls, and the joist bays under those walls often open into the floor. We seal and insulate those spaces too, along with the flat attic above.
Interior Chimneys in North Smithfield
North Smithfield runs from the edge of downtown to the Neuse River. Its 1999 nomination describes large houses built for an attorney, a judge and well-off merchants beside smaller middle-class bungalows and cottages, dating from about 1850 to 1950. The inventory mentions interior chimneys more than twenty times, on 1880s Italianate houses and on later bungalows alike. Where a chimney climbs through the ceiling, warm room air can slip up beside it into the attic. We close that opening with sheet aluminum bedded in high-temperature caulk, not foam, then set a metal collar so the new insulation stays about 2 inches off the masonry.
Attic Insulation in Smithfield
Some 42 percent of Smithfield's homes predate 1970; if your joists show above the insulation, ENERGY STAR says to add more insulation.
Built from 1940 to 1969, 34 percent of Smithfield homes often have little insulation.
The Local Climate
Smithfield's center sits about 150 feet above sea level, under a mile from NOAA's Smithfield station, the best match for Smithfield. The station's 1991 to 2020 normals average about 3,080 heating and 1,870 cooling degree days a year, so at Smithfield's station, heating needs outweigh cooling.
Readings change over short distances around Smithfield: NOAA's Clayton Water Plant station, 12 miles away, averages about 3,390 heating degree days.
Homes by Age: What It Means for the Attic
Some 63 percent of Smithfield housing units are detached single-family houses.
Built from 1970 to 1989, about 35 percent of Smithfield homes may hold settled fiberglass; check its depth against the joists.
About 65 percent of Smithfield's housing units predate 1980; nearly all predate the state's 1978 insulation rule too. About 26 percent of Smithfield units sit in buildings of two or more homes, where the attic is often shared.
Homes by Year Built
- Before 1940: 7% (±3), about 410 units
- 1940s: 3% (±2), about 170 units
- 1950s: 14% (±4), about 810 units
- 1960s: 17% (±4), about 960 units
- 1970s: 24% (±8), about 1,320 units
- 1980s: 10% (±5), about 580 units
- 1990s: 9% (±4), about 500 units
- 2000s: 7% (±3), about 400 units
- 2010s: 6% (±4), about 320 units
- 2020 or later: 3% (±2), about 140 units
Air Sealing and Duct Sealing in Smithfield
In Smithfield, about 64 percent of homes heat with electricity; where that heat is forced air, ducts often run through the attic.
Air sealing comes first, as the EPA advises: wire and pipe holes, wall tops and soffits.
How Homes Here Are Heated
- Electricity: 64% (±9), about 3,200 households; Johnston County: 78%
- Piped gas: 26% (±5), about 1,290 households
- Bottled or tank gas: 8% (±3), about 400 households
- Oil or kerosene: under 3%, about 65 households
Power, Gas and Rebates
Smithfield, an ElectriCities public power town, runs its own electric system. For gas, Smithfield is in the Johnston County franchise of Piedmont Natural Gas, and 26 percent of the town's homes heat with piped gas. Bottled or tank gas, bought by the delivery, heats 8 percent of homes in Smithfield.
Program to ask about in Smithfield: ElectriCities energy audits (the town's electric system), home energy audits for member-town customers; ask the town's utility office. Before a job in Smithfield, check its current terms; the Johnston County page lists every program.
Attic Insulation Removal in Smithfield
In a Smithfield attic, only wet, moldy or animal-soiled insulation is vacuumed out (ENERGY STAR's test), once the cause is fixed, and after mice that Smithfield attic is sanitized and deodorized; dry, clean insulation stays.
Also Serving Near Smithfield
Nearest to Smithfield first.
Wilson's Mills, NC
4 miles north
Median home built 1997 (Smithfield: 1973); Power from Duke Energy Progress (Smithfield: a town system)
Attic insulation in Wilson's MillsPine Level, NC
6 miles east
2,405 people, about a fifth of Smithfield's population
Attic insulation in Pine LevelFour Oaks, NC
7 miles southwest
Median home built 1985 (Smithfield: 1973); 2,978 people, about a quarter of Smithfield's population
Attic insulation in Four OaksMicro, NC
9 miles east
537 people, under a tenth of Smithfield's population
Attic insulation in Micro
Smithfield Insulation FAQs
Will Smithfield's historic commission need to approve my attic insulation?
Not for the attic itself. Brooklyn, North Smithfield and downtown are on the National Register. That listing alone, the state preservation office explains, never binds a private owner spending private funds. Smithfield also has a Historic Preservation Commission that reviews building alterations inside the town's local historic district. Under state law it rules on exterior changes, not on how the inside is arranged. Insulating and sealing the attic floor happen inside. A new roof or soffit vent is an exterior change, so talk to the commission first.
When did Smithfield houses first get electric wiring, and why does it matter?
The town's electric lights first came on in 1913. Voters approved a bond in 1911 for water works and a light plant, and the brick plant went up on the Neuse at the north end of Front Street. A house wired in the years after the plant opened can still have its first knob-and-tube runs in the attic. ENERGY STAR flags that kind of pre-1930 wiring as a fire hazard under insulation. We have an electrician check it first, and we leave any working knob-and-tube in the open.
Could the old insulation in a Smithfield attic be vermiculite?
It could: about 25 percent of Smithfield's homes predate 1960. If a Smithfield attic holds a pebble-like gray-brown or silver-gold fill, leave it undisturbed: the EPA says vermiculite may contain asbestos.
Does attic insulation in Smithfield need a permit?
Smithfield Town Hall can say whether Johnston County Building Inspections Department, the town itself or another office handles permits in Smithfield; ask before work starts.
Helpful Guides
- An energy audit program from the town's own utility: home energy audits
Sources
Census Bureau figures for Smithfield, NOAA normals for the Smithfield station, Smithfield's municipal electric system (October 2026). Compiled by Insulation Pros. How the town pages are made.
Sources for the Smithfield notes and questions (read October 20, 2026):
- Smithfield, in The North Carolina Gazetteer (William S. Powell, 2nd ed., UNC Press 2010), NCpedia
- Brooklyn Historic District, National Register nomination (NC HPO)
- North Smithfield Historic District, National Register nomination (NC HPO)
- Attic Air Sealing Project, ENERGY STAR
- Building Construction Problem Areas, Iowa Department of Health and Human Services weatherization program
- Furnace Flues Require Special Sealing Techniques, ENERGY STAR do-it-yourself guide
- What Is the National Register of Historic Places?, NC State Historic Preservation Office
- Historic Preservation Commission, Planning Department, Town of Smithfield
- N.C. Gen. Stat. 160D-947, Certificate of appropriateness required
- Attic Insulation Project, ENERGY STAR
- NC Listings in the National Register of Historic Places, NC State Historic Preservation Office
Smithfield, NC
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Insulation Pros is an insulation contractor serving North Carolina, Smithfield and the rest of Johnston County included.
Reach us
Send the square footage of your Smithfield attic, or call (336) 870-3893.