Can I Vent Bathroom & Kitchen Exhaust Through One Roof Penetration?

Best Venting for Exhaust

• The best venting for both bathroom and kitchen exhaust is actually through the sides of your home or through soffits or eave vents instead of directly through the roof. But if you have roof vents, or if the roof is the easiest outdoor access point to reach, a capped roof vent is also a potential solution. You will need one roof vent for the bathroom exhaust and one for the kitchen exhaust. There are a couple important reasons you cannot combine the two.

Venting Size

• First, you need to consider the size of your vents. Vents are designed to carry a certain load, just as blowers are designed to move a certain amount of air. If vents are too small, air will not be able to leave the house fast enough. Condensation and grease will start to collect inside your vents, leading to serious problems like leaks and mildew. Combining kitchen and bathroom vents essentially increases the necessary venting size you need, sizes that the duct work is not designed for.

Venting Length

• Venting length is also an issue. Rather than try to connect two separate venting systems to one output, channel each to the nearest exit point possible. This will ensure that the exhaust escapes as quickly as possible. Combining vents all the way up to the roof, especially for kitchen exhaust, gives the air a lot of distance to travel at a poor angle. This also leads to moisture and grease buildup.

Attic Venting

• When you do vent your bathroom and kitchen exhaust, avoid venting them into any space inside your room. Make sure your roof penetration is always fully out into the air. Even venting improperly into soffits can cause problems. Moisture will build up in enclosed spaces and continue to cause moisture and mold problems.