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Attic Ventilation

Proper Ventilation 

One of the most important and misunderstood components of a residential roof is the ventilation system.  Proper ventilation is the key to lowering home energy costs, preventing attic mold and increasing the comfort of living in your home.

Traditional asphalt roofers use can vents or passive ridge vents which are ineffective. Their design allows air to move back into the attic pushing the moisture, which is trying to escape, back into your insulation.

Hi-Flow Ridge Vents, which move large volumes of excess heat and moisture out of your attic. This keeps your attic dry and reduces the chances of growing mold. According to the U.S.Department of Energy, for each 1% of moisture in the attic insulation the customer loses 2.5% of their energy efficiency. Some homes are 10% high in moisture and are wasting 25% of their energy dollars.

The Hi-Flow Ridge Vent can decrease moisture levels in an attic by 10% and increases the R-Value of your insulation by 25%.

Hi-Flow Ridge Vent Cross Section with Airflow

But, beware! Not all ridge vents are created the same.  Improperly designed ridge vents can actually reverse the proper airflow in your attic causing heat build-up and wetting your insulation which can lead to attic mold and higher home energy bills.  Rest assured that Attic Renew representatives are trained and utilize equipment to determine what venting will be most effective for your home.

Properly Venting Kitchens and Bathrooms


Bathroom and kitchen exhaust fans are extremely important and should be used every time you cook or bathe. They remove excess moisture from your home. All bathroom and kitchen exhaust fans must be vented to the outside and never into an attic.  Venting a bathroom or kitchen fan into an attic will cause wet insulation and mold to form.

Exhaust fans should be vented:

  1. Through the roof 

  2. Through an exterior gable wall

  3. Behind a gable vent.

  4. Never into a soffit vent. Soffits are intake vents and the moisture will get pulled back into the attic.

To improve venting:  

  • The run should be the most direct route possible

  • Metal pipe is better than flexible plastic pipe

  • Avoid loops or u-shaped bends that will trap water

Properly ventilating your kitchen and bath will keep your insulation dry. According to the Department of Energy, for each 1% moisture you have in your insulation, you lose 2.5% of its effective R- value. 

People think they are saving money by not running the vent pipes through the roof only to find out they are adding moisture to their attics. This will cause moisture levels to rise at least 10%. The net result is they lose 25% of their insulating dollars and fill their homes with mold.

Ventilation Testing​

To avoid voiding asphalt shingle warranties, moldy attics, rotted wood, and clumping insulation, your attic needs proper ventilation. 


Proper venting is described as:

  • Building codes call for 1 square foot of venting for every 150 square feet of attic floor space.

  • A balanced ventilation system between intake and exhaust venting

To test if the attic is actually venting:

  • Make sure the vent openings are open not plugged or covered

  • Measure the soffit venting temperatures and make sure they are consistent along the entire opening

  • Measure the exhaust vents and ridge vent temperatures to see that they are consistent

  • Utilize a smoke pen to make sure air is flowing in the right direction from eave to ridge and not stagnate or working backwards

A good indicator of attic ventilation performance is to:

  • Test the insulation for the correct moisture content

  • Monitor attic temperatures - Poorly ventilated attics will reach temperatures as high as 140 degrees Fahrenheit or higher. This is a strong indicator the attic is poorly ventilated and costing you a lot of money to cool your home in the summer. 

How Can We Help?

Minimum attic access opening size is 22 inches by 22 inches. Minimum 4/12 roof pitch for adequate space to access the mold and use equipment.


Main Office

Flint Office

6140 Taylor Dr

Flint, MI 48507

Charlotte Office

1875 Lansing Rd

Charlotte, MI 48813


Monday - Friday 

9:00 am to 5:00 pm


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