Energy Efficient Roofing

Reflectance, Emittance and the Ventilation That Matters More

A roof affects cooling load through three levers: how much solar energy the surface reflects, how quickly it releases the heat it did absorb, and whether that heat can escape the assembly before it reaches your ceiling. Colour is only the first of the three, and it is usually not the most important. A poorly ventilated attic with thin insulation will overwhelm any reflectance advantage, which is why blocked soffit vents, exhaust without matching intake and insulation crushed against the deck at the eaves are the first things to fix in every climate. This guide compares eight approaches — reflective cool roof shingles, light coloured metal, clay and concrete tile, white TPO and PVC membrane, reflective coatings on existing flat roofs, above sheathing ventilation, radiant barriers and balanced attic airflow — then maps priorities by climate zone from hot and dry through cold and snowy. It ends with six retrofits worth doing without a full re-roof.