The hot humid air belongs outdoors and you need an air barrier between the hot humid air and the interior of your house as well as your attic.
Pros and cons of unvented attic.
When properly installed unvented roofs perform well and cause no excess moisture accumulation.
This could actually penalize a house under leed h air sealing the ceiling is not necessary attic hatches do not need to be insulated and gasketed.
This air seal will help to make your home more energy efficient.
Pros of building the sealed attic.
This reduces latent air conditioning loads and provides further reductions in energy consumption.
A fundamental requirement of an unvented attic assembly is the use of air impermeable insulation on the underside of the unvented roof to prevent air infiltration and exclude airborne moisture from the attic.
The pros unventilated attics are common where roof assemblies are complex and it s difficult to create a sealed ceiling plane.
No roof venting to install complex roof are inherently difficult to vent sealing may be the solution may increase the usable area of a house.
Adding unvented attic insulation like spray foam seals the building envelope and stops airflow.
Making the attic a conditioned space means the space will be the same temperature as the rest of your home.
This is especially true if you plan to install any ducts in your attic.
If water or air ducts run through your attic space they are less likely to be affected by extreme temperatures and this can save you money on utility costs.