Building in Climate Zone 6: Cold Design Guide Building in climate zone 6 demands choices that keep a home warm, dry, and affordable to heat through long, cold winters. This guide on climate zone 6 shows targeted insulation, airtightness, foundation, window, and HVAC details that a budget-conscious DIY self-builder can apply to reduce fuel use and avoid moisture problems. You'll get specific R-value and airtightness targets, practical wall and slab assemblies, vapor-control guidance, and hands-on cost-saving moves for a 1,200–2,000 sq ft tight house in northern U.S. or high-elevation towns. TL;DR: - Aim for wall assemblies around R-23 cavity + R-5–R-10 continuous insulation, attic R-49 or better, and slab edge R-10; blower-door of 1.0–3.0 ACH50 depending on budget. - Prioritize continuous exterior insulation and airtight air-barrier continuity (top plates, rim joists, window transitions) before upsizing HVAC equipment. - Use an ERV or HRV sized per ASHRAE 62.2, choose cold-climate heat ...