Sunroom Addition Cost Guide 2026: Screened Porches, Three-Season Rooms, and Four-Season Rooms

May 20, 2026 · Cost Guide · 6 min read

A sunroom addition costs $15,000–$100,000+ depending on whether you are building a screened porch, a three-season room, or a fully insulated four-season room. The type you choose is the single biggest cost driver—more so than size, because a four-season room requires a full thermal envelope, dedicated HVAC, and insulated framing that a screened porch does not. Here is what each type actually costs and what drives the price within each category.

Sunroom Types and Their Base Cost Ranges

There are three meaningfully different categories of sunroom, each serving a different purpose and built to a different standard:

Screened Porch or Porch Enclosure

A screened porch adds insect protection and weather-blocking screening to an existing or new covered outdoor space. It is not insulated, not heated or cooled, and not designed for year-round use in cold climates. Cost range:

• Converting an existing covered deck or patio: $4,000–$15,000 for screening, framing, and a simple roof addition
• New screened porch on a concrete slab: $12,000–$30,000 depending on size and roof complexity
• Cost per square foot: $60–$150 for a screened porch build

Three-Season Room

A three-season room is fully enclosed with glass or polycarbonate panels, provides some weather protection year-round, and is usable in most climates from spring through fall. It is not insulated to conditioned space standards and is not connected to the home's HVAC system. Cost range:

• Prefab/kit three-season room: $10,000–$30,000 installed on an existing deck or patio
• Custom three-season room with new foundation: $20,000–$55,000
• Cost per square foot: $130–$250

Four-Season Room (All-Season Sunroom)

A four-season room is built to the same thermal standards as living space—insulated walls, insulated floor, low-E double- or triple-pane glass, and a dedicated HVAC system (or extension of the home's existing HVAC). It is legally considered conditioned square footage and adds to the home's assessed living area. Cost range:

• Prefab/kit four-season sunroom: $30,000–$60,000 installed
• Custom-built four-season room: $50,000–$120,000+
• Cost per square foot: $250–$500+ depending on finish level and glazing specification

Foundation: The Cost Driver Most Homeowners Underestimate

The foundation is frequently the largest single line item in a sunroom budget after glazing—and the one most homeowners do not account for when getting initial quotes. Your options:

• Existing deck or patio: If you have a structurally sound existing deck or concrete patio, a sunroom can be built on top of it. The existing structure must be engineered to support the additional load of a roof and walls—a structural engineer review ($300–$800) is recommended before proceeding. This is the lowest-cost foundation path.
• Concrete slab-on-grade: $4–$7 per square foot, plus excavation and grading. A 200-square-foot sunroom slab costs $2,000–$4,500. Slabs work well in warm climates but can feel cold underfoot in colder regions without radiant heating.
• Concrete piers or helical piers: $8–$18 per square foot depending on depth and soil conditions. Piers allow the sunroom to float above grade, reducing frost heave risk in cold climates. Total cost for a 200 sq ft addition: $4,000–$9,000 for the pier system.
• Frost-protected shallow foundation: Required in freeze-thaw climates for a four-season room. Adds $5,000–$15,000 to the foundation cost compared to a standard slab but prevents cracking and settling over time.
• Full basement or crawl space continuation: The most expensive and structurally complex option, typically reserved for four-season rooms being treated as full home additions.

Glazing: Glass vs. Polycarbonate and Why It Matters

The glass or glazing panels are the defining material cost in any sunroom project. Your options range from functional to premium:

• Tempered single-pane glass: $8–$14 per square foot. Adequate for screened porch conversions in mild climates. Poor insulation value (U-factor ~1.0).
• Double-pane insulated glass: $15–$28 per square foot. Standard for three-season rooms and minimum specification for four-season rooms. U-factor 0.25–0.35 with low-E coating.
• Low-E double-pane glass: $20–$35 per square foot. Reduces solar heat gain in summer while retaining interior heat in winter. Recommended for four-season rooms in all climates.
• Triple-pane glass: $30–$60 per square foot. Maximum insulation value (U-factor 0.15–0.20). Justified for four-season rooms in climates with sustained below-zero winter temperatures.
• Polycarbonate panels: $5–$15 per square foot for the panel. Lighter, shatter-resistant, and less expensive than glass—but yellows over time, has lower visual clarity, and offers minimal insulation without multilayer versions. Most appropriate for screened porches and basic three-season rooms.

A 200-square-foot sunroom with 100 square feet of glazing uses roughly $1,500–$6,000 in glazing materials alone, plus installation labor. For full-perimeter glazed rooms with no knee walls, glazing costs can exceed $15,000 for a 200 sq ft space.

HVAC and Electrical: The Four-Season Room Upcharge

A four-season room requires conditioning year-round. If your home's existing HVAC system has capacity and the ductwork can be extended, adding a register and return runs $1,500–$4,500. More often, the existing system does not have the capacity to condition an additional 150–300 square feet efficiently, and a separate mini-split heat pump is the better solution:

• Single-zone mini-split heat pump: $3,000–$7,500 installed for a 9,000–18,000 BTU unit adequate for most sunroom sizes in most climates
• Extending existing ductwork: $1,500–$4,500 if system has capacity
• Electric baseboard heating (budget option): $800–$2,000 installed, but high operating cost in cold climates
• Radiant floor heating: $8–$15 per square foot installed; comfortable but adds $2,500–$5,000 to the project budget

Electrical work for a sunroom typically costs $2,000–$6,000 and includes dedicated circuits for heating/cooling, ceiling fan and lighting circuits, and outdoor-rated outlets. Four-season rooms built as part of permitted additions require all electrical work to be performed by a licensed electrician and inspected.

Permit Costs and HOA Considerations

Permits are required for virtually all sunroom additions that involve structural connections to the house. Cost ranges by jurisdiction:

• Small municipalities and rural counties: $300–$800
• Mid-size suburban jurisdictions: $800–$2,500
• Major urban areas and high-cost states (CA, NY, WA): $2,000–$6,000+

HOA restrictions are a significant issue in planned communities, townhome developments, and neighborhoods with active architectural control committees. Many HOAs prohibit sunroom additions entirely, require specific materials (no aluminum frames, must match home exterior), or require architectural review that adds 30–90 days to project timelines. Before getting contractor quotes, pull your HOA's CC&Rs and submit an architectural review application if required.

Regional Cost Variation

Labor rates account for 40–55% of total sunroom project cost, making geography a major price driver. Using a basic 200 sq ft three-season room as a benchmark:

• Midwest (Indiana, Ohio, Missouri): $25,000–$40,000
• South (Texas, Georgia, North Carolina): $22,000–$45,000
• Northeast (Massachusetts, Connecticut, New York): $35,000–$65,000
• Pacific Coast (California, Washington, Oregon): $40,000–$75,000

Our directory includes 500+ general contractors across the country who complete sunroom additions. The guide to getting and comparing contractor bids explains how to structure bid requests so you are comparing identical scopes—critical for sunroom quotes, where prefab vs. custom, foundation type, and glazing specification vary widely between contractors. For understanding what permits are required for your addition type and what the inspection process involves, the permit requirements by project type guide covers residential additions including sunrooms and screened porches. If you plan to finance the addition rather than pay cash, the home renovation financing guide compares HELOCs, home equity loans, and personal loans for additions in the $20,000–$80,000 range. Browse general contractors by city or find contractors near you with verified credentials and sunroom project experience noted in their profiles.