It’s Good to Vent… The Attic

Your home should be a respite of comfort, even during the most humid months in Wisconsin. However, that can be challenging when one of the most common problems homeowners face is inadequate attic ventilation. Poor attic ventilation can make your home unbearably warm and cause damage to the roof (e.g. fatigue the sheathing) when moisture gets trapped. This will also increase your energy costs as your air conditioning is run more to dissipate the heat.NOTE:Attic insulation stores up the day’s heat and can increase the temperature of your interior ceilings to as much as 110 degrees.

winter attic ventingNot Just a Summer Issue

It’s still important to vent the attic even in the Winter.  Moisture from indoor activities will migrate from the living spaces to the attic. This can delaminate plywood, rot roof sheathing and framing or cause mold/mildew to grow.

What to Look For

Rusted nails and stained roof sheathing (boards) are the first signs of a ventilation problem.  Here’s what to look for seasonally:

  • Winter – Moisture or frost on exposed nails at the underside of the roof sheathing.  Frost can loosen and push nails out.
  • Summer – On warm and windless days, there should be a maximum 10-15 degree difference between the air in the attic and a shady spot outside.


  1. Clear any blocked soffit vents. This can often cure most ventilation problems.
  2. If you don’t have vents, install ridge and soffit vents to allow for natural airflow.  Cool air enters the soffits under the exterior roof overhangs and circulates the hot air via natural convection to a roof or gable-mounted low speed fan.
    : During Summer operation, the thermostat will automatically operate the fans as needed to force air circulation.In the Winter, the fan should be operated by a humidistat and attic should be kept cool to avoid ice dam issues.
  3. Have a Home Energy Audit performed. This will often illustrate hidden problems while providing you with a plan of what areas to address first.

Having adequate attic ventilation year round is important to the long-term health of your home, optimum interior comfort, and reduced heating and cooling costs.