Attic Ventilation - keep cool and improve insulation effectiveness
The idea of attic ventilation doesn't appear to make sense in light of all this talk about keeping things sealed and insulated, but it truly helps.
It helps in two ways. First, it vents excess heat from the roof. Second, it reduces moisture accumulation, and that improves the effectiveness of your insulation.
Let's look at both of these factors so we understand how ventilation of the attic works in our favor during the heat of summer and the cold of the winter months.
Venting excess heat. This should be intuitive. The roof of your home gets hot from the sun beating down on it. This heat migrates quickly through the roofing boards and radiates towards the insulation that sits on your ceiling.
Without ventilation, heat in the attic will build up and create a difference in temperature that will increasingly force more warmth into your home through the ceiling. The higher the temperature differential, the faster the heat will migrate from the attic to your living space beneath the layer of attic insulation.
It's important to note that insulation doesn't stop energy transfer, it only slows it down. More insulation means slower transfer of energy. Higher energy levels means it takes more insulation to slow down the energy transfer.
If we assume that you have all the insulation that you possibly can get into your attic space, then ventilation is the only reasonable option to lower the energy levels in your attic during the heat of the summer.
Attic ventilation also helps reduce moisture accumulation. Moisture is an enemy of insulation because all forms of insulation rely on air space between the fibers to trap air and keep it from moving. If moisture is present, it replaces air space with water and that encourages matting of the fibers, thus reducing the effectiveness of the insulation.
Therefore, attic ventilation must be established to allow moisture to dissipate, without causing turbulence inside the attic. Turbulent air will help transfer energy, and that is just the opposite of what we want our insulation to do in the winter.
So, vents in the attic must discourage drafts, but still allow moisture a way to escape.
Done with Attic Ventilation, back to Ways to Save Energy