A vent hood or fitting that creates excessive back pressure:
• lengthens cloths drying cycle & overheats fabric fibers
• prevents exhaust hoods from clearing air above a stove
• increases energy bills to power exhaust fans
• accelerates dangerous lint build-up from cloths dryers and grease deposition above stove tops. (fire risk)
• increases repair, cleaning, and replacements to maintain fan and filter operation under stress
• increases odors, excess humidity, mold growth, and other unhealthy air conditions of inadequate ventilation
As uninteresting as ducts seem they impact our health and our budget.
Not only the length of smooth conduit, but every change of direction, connection, or transition in duct form makes a difference.
Better duct design removes bad inside air with less effort while minimizing unavoidable heat-loss as outside air infiltrates more than is desired.
A $57 duct elbow sounds expensive until one realizes how reliably it will reduce other costs for decades more than would a more efficient fan.
The right ducts can enable a more efficient fan to meet ventilation needs for longer than standard assumptions predict.
Ratings of vents and elbows to reduce air-flow less.
This is not just for hyper-efficient green buildings. It can be crucial where old buildings require long ducts for a bathroom or stove where people need it.
Illustration of how significant fitting choice is.
Bathroom vent fans:
2E Bathroom: FV-08VKM3. ←has motion sensor. Ours does not.
WhisperGreen Select Fan _ FV-0511VK2 ←Diagram ; FV-0511VK2_en_install ;