We do need to mention though one very rare scenario we have seen just a couple of times over our 35 years.
Venting metal roof over shingles.
A metal roof typically does not increase nor decrease the need for ventilation.
Doesn t provide the flattest surface for the metal roofing to be installed over each course of shingles is about a 1 8 higher than the course just below it.
Metal roof over shingles condensation.
If it s slightly windy keep the steel downwind from you so a gust of wind doesn t knock you over.
One of the big reasons homeowners choose metal roofing is for the uninterrupted run of metal from the top of the roof to the gutter which reduces the risk of leaks.
Also don t go up on the roof if it s windy.
Metal roofs must be laid flat on a vapor barrier because steel will condensate if there s any air space underneath it.
A steel roof is a lifetime investment lasting 50 years or more if it s a good one.
Ventilation that meets code requirements is adequate for any type of roofing material including metal.
Cool outside air travels under the shingles to the vented ridge pulling out moisture and heat.