Installing insulation in your attic is a great way to reduce heat transfer and save energy, but it's essential to make sure that your attic is properly ventilated after installation. Blocking air flow in the eaves is a common mistake that homeowners make, so it's important to avoid covering attic roof vents with insulation. Instead, use beamed vents and ceiling vents to maintain airflow. Mark the roof vents from the attic, where you can see the beams, and separate them evenly on the same side of the roof.
Wear a dust mask when working in the attic and place boards or plywood on the beams so as not to pierce the drywall ceiling underneath. Never cover the ventilation grilles of attic ceilings with insulating material; use ventilation grilles on the beams and on the ceilings to keep air flow. This will allow air to circulate freely and easily leave the attic. If you have a finished attic or attic space that you plan to finish, gable wall vents and roof vents are not the best option. Electric attic fans (thermostatically controlled fans that blow air out of the attic when it's hot) can increase infiltration (and therefore increase cooling loads).If you have trouble insulating the attic floor without covering the ventilation grilles, consider investing in ventilation grilles for insulating beams or baffles.
Proper insulation and sealing also keeps attics cold in winter by blocking heat and humid air from below. Doors or hatches that separate conditioned and unconditioned spaces (such as attics and mezzanines) must be waterproofed and insulated at a level equivalent to that of the surrounding complexes. It may seem counterproductive to add insulation to increase heat and then deliberately let cold air into the attic through ventilation grilles in winter, but in winter, allowing a natural flow of outside air to ventilate the attic reduces the chance of ice buildup (snow that melts from a too-warm attic roof and then refreezes in the gutters, causing an ice buildup that can damage the roof). To successfully execute this option, sufficient insulation on the outside (on top) of the floor is required to control condensation and a solid connection must be established to control air from the top of the exterior walls to the perimeter of the attic floor. For roofs with attic spaces, it's important that R-30 meets R-38 requirement and R-38 meets R-49 requirement provided that total height of uncompressed insulation at lower R value extends over upper wall plate in eaves. You can also invest in gable or shingle ventilation systems to increase air flow inside the attic and improve ventilation. A clogged ventilation grill in ceiling is almost as useless as not having any intake vents, so if you are going to insulate your attic, make sure to avoid placing insulation on top of these ventilation grilles.
This will ensure that your attic is properly ventilated after installation.