This article will present a rigorous, site-specific decision framework that goes beyond “wood vs. composite” to quantify how Colorado Front Range exposures (high UV at altitude, wide diurnal temperature swings, freeze–thaw cycles, low humidity and variable snow loads) interact with material properties (thermal-expansion coefficients, moisture uptake, photodegradation resistance, slip-resistance, and fastener compatibility). It will show a reproducible life‑cycle cost model (NPV over 20–30 years) that factors upfront cost, scheduled maintenance labor and materials, likely mid-life repairs, and replacement timing, alongside sustainability metrics (embodied carbon, recycled content, recyclability and end‑of‑life disposal). The guide will include a climate-exposure matrix tuned to local microclimates (Littleton/Centennial vs. Highlands Ranch/Parker vs. Castle Rock/Golden), a structural-compatibility checklist (joist spans, ledger attachment, hidden fasteners, thermal movement allowances), and clear decision pathways that map homeowner priorities—lowest total cost, lowest maintenance, highest traditional aesthetic, or maximum longevity—to specific material choices (pressure-treated wood, cedar/redwood, composite, capped PVC, and aluminum) with trade-offs and practical installation/maintenance prescriptions.