Sunroom Addition Cost: $22,000–$75,000 (Average $47,000) in 2026

Why does a sunroom addition cost so much?

A sunroom addition runs $22,000 to $75,000 on average, with a national average around $47,000 (Angi, Bob Vila). Broken down per square foot, installed cost lands around $150 to $300, though HomeGuide’s data shows a wider spread of $100 to $350 per square foot once season type and finishes are factored in. The biggest swing in price comes from how the room is built out: a three-season room, which skips full HVAC and plumbing, typically costs $10,000 to $40,000 (Angi, Bob Vila), while a four-season room wired for electricity and heating/cooling runs $25,000 to $120,000 (Angi). Labor makes up roughly 40% to 60% of the total, or about $18,800 to $28,200 on a typical job (Angi), with the rest going to framing, glazing, foundation, and finishes. A prefab kit can undercut a fully custom build significantly, running $6,000 to $40,000 for the kit alone before installation (Bob Vila).

What affects the cost?

A few factors explain most of the gap between a $22,000 job and a $75,000+ one:

• Room type. A conservatory or solarium with full glazing runs $30,000 to $150,000, well above a basic Arizona room or screened conversion at $2,000 to $22,000 (Angi, HomeGuide).
• Season rating. Four-season rooms need electrical wiring, HVAC, and sometimes plumbing, which is the single biggest driver between a three-season and four-season price tag (Angi, Bob Vila).
• Foundation. A new foundation adds $500 to $6,000 depending on whether it’s a concrete slab, pier, or raised structure (Angi, Bob Vila).
• Windows and doors. Window packages run $3,500 to $15,000 total, or about $300 to $2,000 per window; patio doors add $1,300 to $11,000 (Angi) or $1,000 to $8,000 (Bob Vila).
• HVAC and electrical. Extending climate control costs $2,300 to $20,500 overall (Angi); Bob Vila breaks this out as $2,000 to $14,500 for a ductless mini-split versus a cheaper $4,000 to $6,000 to tie into an existing central system.
• Permits. Local permitting typically runs $250 to $1,800 (Angi, Bob Vila).
• Custom-built vs. prefab. A prefabricated kit costs $6,000 to $40,000 before installation, which is often cheaper than a fully custom-framed addition (Bob Vila).

How to lower your sunroom addition cost

• Consider a three-season room if year-round use isn’t required. Skipping full HVAC and insulation for four-season comfort can cut the project cost by tens of thousands of dollars (Angi, Bob Vila, HomeGuide).
• Look at prefab kits for smaller budgets. A prefab kit runs $6,000 to $40,000 for the structure alone, which can be considerably less than a fully custom build once you add your own installation labor (Bob Vila).
• Reuse an existing deck or patio slab as the foundation when it’s structurally sound, since a new foundation alone can add $500 to $6,000 (Angi).
• Shop HVAC options carefully. Tying into an existing central system is often cheaper than installing a standalone ductless mini-split ($4,000-$6,000 versus $2,000-$14,500, per Bob Vila); Angi’s overall HVAC figures span $2,300 to $20,500 depending on the approach.
• Get multiple bids on windows and glazing, since window packages ($3,500-$15,000) and patio doors ($1,300-$11,000 per Angi, or $1,000-$8,000 per Bob Vila) are among the largest line items after labor and foundation.

Prices vary by region, room size, and how much of the build is custom versus prefab, so treat the figures above as a planning budget. Get two or three local quotes, and confirm whether the bid includes foundation, permits, and HVAC, before committing to a final number.