How Much Does a Sunroom Cost in 2026? Three-Season Room and Porch Enclosure Pricing

A sunroom is the rare addition that pays you back every single day. It is the room people actually sit in, and it is usually cheaper per square foot than any other way of adding space to a house. The hard part is that almost nobody publishes honest numbers. So here is what a sunroom really costs in 2026, written by the crew that builds them, with the cost drivers laid out so you can tell where your project will land before anyone walks your property.

Short Answer: 2026 Sunroom Cost Ranges

• •Three-season sunroom addition: about $200 to $350 per square foot installed.
• •Four-season (insulated, heated and cooled) sunroom addition: about $350 to $600 per square foot installed.
• •Converting an existing screened porch into a three-season sunroom: about $28,000 to $55,000, the cheapest path to a finished room.
• •Screening in an existing covered porch or deck: about $6,000 to $18,000.
• •Prefab or kit patio enclosure: about $18,000 to $45,000, lower cost but shorter life and a bolted-on look.
• •Typical 2026 national average for a built-on-site sunroom addition: roughly $45,000 to $85,000.

Sunroom Cost by Size

Size is the single biggest lever. These are installed, turn-key ranges for a site-built room on a new foundation or a properly engineered deck structure, including framing, windows, roof, siding, electrical, and interior finish. Prices assume a straightforward attachment to the house with no major grading or structural surprises.

• •10x10 (100 sq ft): three-season about $20,000 to $35,000. Four-season about $35,000 to $60,000.
• •12x12 (144 sq ft): three-season about $29,000 to $50,000. Four-season about $50,000 to $86,000. This is the most searched size and the most common real-world build.
• •12x16 (192 sq ft): three-season about $38,000 to $67,000. Four-season about $67,000 to $115,000.
• •14x20 (280 sq ft): three-season about $56,000 to $98,000. Four-season about $98,000 to $168,000.
• •16x24 (384 sq ft): three-season about $77,000 to $134,000. Four-season about $134,000 to $230,000.

Notice that per-square-foot cost drops slightly as rooms get bigger. The foundation, roof tie-in, permit, and mobilization costs are close to fixed, so a 12x16 rarely costs 33 percent more than a 12x12. If you are on the fence between two sizes, the bigger one is almost always the better value.

Three-Season Room vs Four-Season Room vs Screened Porch

These three terms get used interchangeably online and they are not the same product. Choosing the wrong one is the most expensive mistake homeowners make on this project, so here is the plain-language version.

• •Screened porch: a roofed structure with screen panels instead of glass. Lowest cost, no insulation, no glass, comfortable roughly late May through September in New England. Bugs out, weather mostly in.
• •Three-season room (also called a 3 season sunroom): fully enclosed with real windows, siding, and a finished interior, but not conditioned for winter. Comfortable roughly April through November here. Costs about 40 to 50 percent less than a four-season room and permits more simply because it is not counted as heated living space.
• •Four-season room: a true insulated addition with an HVAC tie-in or a ductless mini-split, code-level insulation in the walls, floor, and roof, and year-round use. It is assessed as living space, which raises property value and property tax alike.

Our honest guidance for most New Hampshire homeowners: a three-season room delivers the large majority of the enjoyment at a much lower cost. Build it so it can be upgraded later. If we frame the walls and roof to accept insulation and leave a clean electrical path for a mini-split, converting to four-season down the road is a real project rather than a tear-apart.

The Cheapest Path In: Enclosing a Porch You Already Have

If you already have a covered porch, a screened porch, or a solid roofed deck, you are most of the way to a sunroom and you do not know it. The foundation, posts, beam, and roof are the expensive parts of any addition, and they already exist. Enclosing that structure typically runs $28,000 to $55,000 for a three-season conversion in southern New Hampshire, which is well under the price of building the same room from scratch.

We did exactly this on a project in Atkinson, NH. The homeowners had a 1990s screened porch that had weathered gray, the screens had torn away from the staples, and they told us they used it maybe eight weeks a year. We stripped it to the frame, verified and reinforced the structure, framed real window openings, set a wraparound run of white-trimmed windows, sided the knee walls in gray vinyl, ran a natural pine plank ceiling and painted beadboard wainscot inside, and rebuilt the stair with composite treads and railing. They now use it from early spring through late fall.

You can see the full before and after set, including costs and permit notes, in our Atkinson screen room to sunroom conversion showcase, and more finished work in our project gallery.

What Actually Drives the Price

Two 12x12 sunrooms can be $30,000 apart. Here is where that money goes, in roughly the order it moves the budget.

• •Foundation: a full frost-depth footing and foundation wall is the priciest option and the right one for a four-season room. Helical piers or sonotube piers cost less and suit a three-season room over a deck structure. In New Hampshire footings must reach roughly 48 inches to get below the frost line, and that depth is not optional.
• •Windows and glass: this is the largest material line by far. A budget vinyl package versus a high-performance low-E, argon-filled package on a full window wall can swing the job $8,000 to $20,000. Do not cheap out here, the glass is the entire point of the room.
• •Roof: tying a new roof into an existing roofline costs more than a simple shed roof, and if the existing roof is near end of life you should reshingle it at the same time rather than paying for staging twice.
• •Insulation and conditioning: the jump from three-season to four-season. Wall, floor, and roof insulation plus a ductless mini-split typically adds $12,000 to $25,000.
• •Electrical: outlets, switching, ceiling fan, and exterior lighting. Budget $1,500 to $4,000 for a normal package, more if the panel needs work.
• •Interior finish: a pine plank ceiling, beadboard wainscot, and real trim cost more than painted drywall and read far better in a sunroom. This is where a modest upgrade has an outsized effect.
• •Flooring: LVP and tile are the two right answers for a room with big temperature swings and wet boots.
• •Site access and grading: tight access, steep grade, or a septic field in the way all add labor days.

New Hampshire Specifics That Change the Number

National cost calculators do not account for a New England winter, and that is exactly what your sunroom has to survive. A few local realities worth knowing before you budget.

• •Permits: every sunroom and porch enclosure in New Hampshire needs a building permit because it changes the building envelope. Permit fees are typically a few hundred dollars and are usually calculated on project value. We pull permits on every project we build.
• •Frost depth: footings need to reach roughly 4 feet. This is why a proper sunroom costs more than the patio-enclosure kit advertised online.
• •Snow load: southern New Hampshire roofs are engineered for ground snow loads generally in the 50 to 70 pounds per square foot range depending on town. Roof framing and headers get sized accordingly, which is a real cost that kit enclosures often quietly skip.
• •Energy code: only a four-season room is reviewed against the insulation requirements of the state energy code, which is another reason three-season projects move faster through permitting.
• •Best build season: late spring through early fall is ideal, but a porch enclosure is a great late-fall project since the structure already exists. If you want the room for next summer, sign in the fall or winter. Booking in September through February typically means better scheduling and stable pricing.
• •Property tax: a four-season room adds finished living square footage and will be picked up at the next assessment. A three-season room is generally assessed differently. Check with your town assessor if this matters to your budget.

Is a Sunroom Worth It?

On resale, sunroom additions typically return somewhere in the 45 to 60 percent range, which is middling for a renovation on paper. But that number misses the point. A sunroom is the cheapest square footage you can add to a house, and it is the room your family will use every day from spring through fall. Compared to a full addition at $400 to $700 per square foot, a three-season room gives you real, usable space for a fraction of the cost. If you want the higher-ROI project, our home addition cost calculator will price that comparison out for you in a couple of minutes.

How to Keep Your Sunroom Project on Budget

• •Reuse existing structure wherever it is sound. A porch conversion beats a new build on cost every time.
• •Pick three-season now, framed for a four-season upgrade later.
• •Spend on the window package and the ceiling, save on the flooring and the furniture.
• •Go one size larger if you are close to the line, the incremental cost per square foot is lower.
• •Get the roof and siding done at the same time if either is near end of life.
• •Book in the off-season. Fall and winter contracts get better scheduling and firmer pricing.

Get a Real Number for Your House

Ranges are useful for planning and useless for signing. Every sunroom depends on what is already there, and the only way to price yours accurately is to walk it. Ryan & Greene Construction is a licensed, insured, veteran-owned general contractor based in Plaistow, NH, building sunrooms, three-season rooms, porch enclosures, and additions across Rockingham County and the Merrimack Valley. Estimates are free and there is no pressure. Call 603-797-9224 or request an estimate online, and see more of our deck and porch work while you are deciding.