A vent hood is used as an updraft system on stove tops. These systems have fans that draw steam, smoke and other fumes into ductwork and channel it away. However, trying to channel this exhaust into your attic is a mistake and can cause serious problems. Unfortunately, contractors may forget to attach the final section of venting between the attic and the roof, or mistakenly vent the exhaust into the attic instead of into outside air.
Stove top exhaust includes oils, burnt particles of food and traces of gas exhaust. These elements can to coat your attic area with grease and dirt. Not only will this make your attic filthy, but they will also attract molds and pests.
A large amount of kitchen exhaust is made out of steam. While some hot air is not a problem for most attics, hot air that is very humid can create issues. The moisture can start to gather and drip down into the ceiling. This creates more incentive for molds to develop and starts to rot away at nearby wood and drywall, creating expensive damage in porous materials.
You have two primary alternatives for channeling vent hood exhaust beside the attic route. The first is through the roof itself, out into the open. This method is very common and efficient. The second method is through the wall and out the side of your house, which may be easier depending on where your oven vent is located. Downdraft vents may also be more suited to these wall-based systems, but no matter what type of venting you use for your cooktop, the exhaust must be channeled outside.