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June 1, 2026
Sunroom Addition in Seattle: Design Options and 2026 Costs
A sunroom brings light and a connection to the outdoors into a Seattle home, valuable in a climate with long gray winters. Here is a guide to sunroom design and costs.
Three-Season vs. Year-Round Sunrooms
- Three-season sunroom: Not fully insulated or heated. Comfortable spring through fall. Lower cost but unusable in cold months.
- Year-round sunroom: Fully insulated, heated, and built to energy code. Functions as true living space in all seasons. This is the right choice for most Seattle homes given our climate.
Glazing Strategy for the Northwest
Seattle’s climate calls for high-performance glazing. Large windows capture limited winter light, but low-quality glass loses heat and creates condensation. A year-round sunroom needs double or triple-pane low-E glazing. South-facing orientation maximizes passive solar gain.
Permit Requirements
A sunroom is a room addition and requires a building permit with architectural drawings, energy code compliance, and structural design. A year-round sunroom must meet the same insulation and energy standards as any heated room.
Cost (2026)
- Three-season sunroom: $35,000 to $75,000
- Year-round insulated sunroom: $80,000 to $180,000
- Architect fees: $8,000 to $20,000
Design Integration
The best sunrooms feel like an integral part of the home, not a tacked-on glass box. Matching rooflines, materials, and proportions to the existing home is key. See our home additions service.
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