Proper Ventilation: How do I know which fan I need?

Attic ventilation is not quite as simple as just installing a fan. If you want to ensure that your attic is properly ventilated, you need to do some homework before investing in an attic fan. Many residential attics only need one 30watt fan. However, this is not always the case. It is important to properly calculate the size of your attic so you know exactly how much ventilation is required