An Assessment of the Effects of Poor Attic Ventilation by Far West Roofing

This is Doug with Far West Roofing

Today we're going to take a look at a house that was built recently that does not have attic ventilation and we're going to look at some of the visible effects this has on the granules on the shingle roofing. 

"Gosh, 170 °F in the summer!"

Being a black roof, on a 100 degree day this roof reaches approximately 170 °F. Directly underneath these shingles is a half inch piece of plywood. If you take a look at this roof it does not have any ventilation along the ridge. Compare it to the house in the distance where you can see five of those vents close to the ridge line. In this video we show two different types of roof vents. The house shown has turtle vents and the Chapel in the background has a metal ridge vent. The purpose of those vents is to create an exhaust for the hot air in the attic that rises up and gets trapped at the top of the attic if there is no ventilation to allow it to escape. The result of this trapped hot air is that the shingle roof experiences direct sunlight from above and hot temperatures from below, causing the tar in the shingles to become very brittle. This causes premature erosion of the granules which is evident in this video. 

One turtle vent and equivalent intake vent for every 300 sq.ft. 

In the Video you can see all the granules in the gutters that have eroded off from the shingle roof. With that erosion of the granules it exposes the underlying asphalt. Eventually the asphalt breaks down, exposing the fiberglass in these shingles. The fiberglass is the silver you see in this video. This happens prematurely and happens really fast when we have no attic ventilation. You can also see that shingles have blown off on this roof in multiple locations. The vent flashing's (pipe vents) have perished and (the rubber seal) has cracked. You can see what those look like when we look in the hole straight down into this persons home. This erosion of granules, among other things, is what you can expect on your home if you do not have adequate attic ventilation. The recommended ventilation requirement is one turtle vent for every 300 sq.ft. of roof area, with the equivalent intake vent on the roof eave which in this case is accomplished by vented soffit. 

Other side effects of inadequate ventilation include delamination of plywood, pre-mature aging of shingles, moisture in the attic during the cold winter months which can cause mold, wood rot and other problems. Follow this blog for more information on these in the near future.

Once again Doug with Far West Roofing Thanks for reading and watching

3 Comments

  1. Ron Pickle on November 8, 2017 at 7:06 am

    Poor attic ventilation leads to lots of problems, specially in your most expensive investment i.e roof. Poor roof ventilation could lead to lots of moisture and this can lead to the complete destruction of the entire roofing system. Then ice dams could be created because of poor ventilation which again can cause major damage and in the absence of proper ventilation, during summers, the trapped heat inside would make air conditioners work a lot and lead to higher energy bills.

    • admin on January 9, 2018 at 5:49 pm

      Ron you bring up a great point. Poor attic ventilation can cause multiple problems to a building. In the summer months poor ventilation causes among other things, build up of heat which causes delamination of plywood, higher utility costs as you pointed out and pre-mature shingle aging. In the winter months build up of moisture can lead to wood rot and wet insulation in severe cases which can cause greater ice dams. Thanks for drawing attention to this. We will highlight several of these in posts that follow.

  2. Jane Richmond on January 31, 2018 at 8:38 am

    You have made a great point! Attic ventilation is the most cost effective way to keep the roof safer and keep the temperature moderate during extreme temperature.

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