Proper attic or roof ventilation is an important part of the roofing system. Adequate roof venting pulls fresh air into the attic and pushes out heat and moisture. This in turn reduces the temperature difference between the air outside and in the attic. When the done correctly proper roof ventilation will reduce the risk of potential problems and extend the life of the roofing system.
However, poor roof ventilation can cause a variety of problems that can cause damage and lead to expensive repairs. If you’ve ever been in an attic, mid-day on a hot summer afternoon, you are well aware of how unpleasant it can get. If not, suffice to say that temperatures inside can climb to over 150 degrees Fahrenheit and feel like a sauna.
The most common problems caused by poor roof ventilation are due to two factors, heat and moisture. Every time we run a load of laundry, take a shower or wash dishes it increases the moisture level in the home and, unless properly vented, in the attic. Trapped moisture and heat can lead to the following common problems:
1. Mold & Mildew: A humid environment is the perfect place for mold or mildew to form. Mold can ruin stored items in the attic and cause health problems.
2. Rust: Rust can begin to form on metal components like nails or other critical fasteners. Overtime it can rust the heads off of nails or cause plumbing or venting straps to fail.
3. Sagging or Spongy Decking: When excessive moisture begins seep into the roof decking it can begin to dissolve the adhesives which hold them together and cause it to warp, sag between rafters or feel spongy when walked on. This can become a danger for anyone on the roof.
4. Roofing System Deterioration: Not only can excessive heat and moisture ruin roof decking, it can also reduce the life of the underlayment and shingles themselves. Cracking shingles or premature loss of granules can be signs of improper roof ventilation.
5. Air Conditioner Replacement & Expenses: As heat builds in the attic, air conditioners must work extra hard to keep the air inside the home cool. This undue stress on the unit can reduce its life and increase energy costs.
6. Frost: Similar to how sitting in a cold car on a winter day will cause frost to form on the windows, the same can occur in a poorly vented attic. As the attic cools and warms with the day, frost formed inside the attic can melt and drip onto the ceiling.
7. Ice Dams: Ice dams can form at the edge of a roof where trapped warm air can melt snow on the roof that then freezes as it cools. As the snow continues to freeze, melt and refreeze it creates a barrier, or dam preventing water from running off the roof. Once dammed, water and ice can creep back up under the shingles and underlayment resulting in leaks. Proper ventilation and the use of added insulation can help mitigate this melting and freezing process and eliminate ice dams.
3 comments
Dinah says:
September 11, 2010 at 6:43 am (UTC -5)
We have quite a lot of older-style houses in Sydney, where the space between the ceiling and roof is just like your picture. Sydney can get very humid in summer and mold and mildew can be a real problem – especially for people with allergies.( I bookmarked this post – thanks ).
Michael says:
September 14, 2010 at 12:44 am (UTC -5)
@Dinah, Unfortunately many folks are not aware of the importance of proper roof ventilation, or the negative effects it can have on a household if poorly vented. Thanks for the comment.
Problems Caused By Poor Roof Ventilation | Orbit Roofing says:
September 11, 2010 at 6:59 am (UTC -5)
[...] Roof ventilation is really important from a number of viewpoints. Here in Sydney, it can get really muggy in summer and mold and damp can cause structural beams to weaken over time. Spores from the mildew can also get into the air inside the house and encourage breathing and chest difficulties. Here’s a list of 7 common problems caused by poor roof ventilation at http://www.trinityexteriorsinc.com [...]