attic ventilation

Where should you vent a bath fan?

Bath fans, or bathroom fans, are important pieces of equipment to remove moisture from your attic. Not long ago we watched a video online that was nicely edited - and the host spoke with confidence on how to vent the bathroom fan to the outside. In the first 30 seconds, he told us 3 wrong ways of doing it, thought he was convinced he was doing it right. Make sure you make the right choice for your home.

Why vent the bathroom fan to the outside? 

  • You want to remove moisture from your home. 
  • Taking hot showers can put a lot of moisture in your home. If the moisture is not removed properly from the home, you may have a mold problem on your hands. 

What happens if you do not vent the fan properly?

  • Strong likelihood of mold! Look below, the bath fan is vented to the soffit (not the way to do it)

The bath fan is located in the center cavity just below the eave chute. When a bathroom fan is vented into the soffit, it puts the moist are outside. Many contractors do this as it's easy and they do not have the proper knowledge. Then, due to how the attic ventilates, the moist air reenters the home right through the eave chute. As you can see on the other cavities, no mold / moisture problems!

What are the best practices of venting the bath fan to the outside, and why?

  • Vent to the outside - put the duct through the roof, air seal, install roof cap on the roof, and use tar to seal down shingles
  • Use rigid duct, not flex duct
  • Do not vent into the soffit nor in the attic
  • Use duct wrap insulation to insulate the ducting. This prevents chances of condensation in the winter

What are eave chutes?

Eave chutes, also called baffles, are a simple device used to help your attic ventilate properly. Eave chutes are very important to keep your soffit vents open so that your attic can ventilate from low to high. Typically homes use soffit vents as the low ventilation point to then ventilate to the top ridge vent (preferred) or gable vents. Attics should have ventilation, therefore we recommend installing eave chutes throughout the attic where soffit vents are located underneath. 

So what does an eave chute do?

  • Allows air to pass through the chute from the soffit vent to the top ventilation spot of the attic
  • Prevents insulation from blocking the soffit vent

What is important to remember when installing an eave chute?

  • Make sure the chute goes down into the soffit, must bend down into the soffit instead of sitting completely flush on the roof line
  • If using blown insulation, block off the eave chute at the base with batt insulation to help keep blown insulation from falling into the soffit

Any blown insulation tips with eave chutes?

  • The top of the eave chute should be above the blown insulation! If the insulation level is above the top of the eave chute, you are now blocking airflow
  • When blowing insulation, it is important to blow insulation from the base of the eave chute
    • Otherwise, an open blow may hit the middle of the eave chute, then swirl down in such a way that does not put insulation at the base. If blown improperly, a large portion of your attic could be un-insulated!

At Sellair, we review every attic to make sure it is ventilated properly. We install eave chutes to best practices, and make sure we blow insulation to fill your attic just right.