Roof Venting - Just As Important As The Roof
Updated: Mar 2
Roofing ventilation (or attic ventilation) is a topic that is often overlooked and often misunderstood, but is just as important as the roof itself. Let me repeat, this is just as important as the roof itself.
Traditionally homes have the interior living space and the roof separated by an attic. The attic provides the space for structural members that make up the roof slope and then the roof on top protects you from the elements. The inside of the home is climate controlled, and is often vastly warmer or colder than the air outside. We’ll get back to that. Another thing to mention is that there is a lot of moisture inside the common household. This comes from running water, baths and showers, cooking, and simply exhaling our breath. The inside of your home is designed to deal with the moisture created, but the attic is not.
Moisture in an attic can lead to many issues such as mold/mildew, rust, dry rot and more. So, we need to keep the moisture out of the attic. Remember the temperature difference I mentioned? Well, when there is a vast difference in temperatures it can cause condensation where the cold and warm air meet. We often see this when warm air rises into the attic (from the living space) and meets the cold air outside, and moisture forms on the bottom of the roof deck in the form of condensation.
An additional issue that is the most common problem we see is when the bathroom and kitchen fans are vented into the attic space, but not out of the roof itself. Think of how much moisture is in the air when you take a shower, or boil a pot of noodles. Often we see a fan pushing this extremely humid air straight into the attic and causing all kinds of moisture issues. Sometimes the ducts are pointed towards a standard attic exhaust vent, but this is simply not adequate as so much of this moist air flows back into the attic.
Finally, it is critically important to maintain a reasonable attic temperature to avoid premature degradation of the roof system installed above it. Having an attic that gets too hot from a lack of air movement can create hot spots that will literally burn out the shingles from the bottom side and significantly reduce their lifespan.
Venting is not simply placing holes in a roof, but instead understanding how air flows. As air heats it rises. As air enters an attic (through intake vents located near the bottom of the roof) it warms, and exits through the exhaust (at the peak of the roof). This air flow exchanges the air in the attic, and keeps temps cooler, and the air less humid. The more we can leverage this basic principle the better and healthier your attic space will be. There are building codes that dictate specifically how much intake and exhaust a structure must have, and these are the guidelines we use when evaluating roofs. The truth is that all structures are different and that each roof requires a custom approach and some thoughtful calculations determining how much air can flow through the attic space. Yes, generally more air flow is better when possible, but the balance between intake and exhaust is just as critical. If this is not calculated accurately it is very possible to actually create worse air flow and cause more problems.
Now the most problematic issue we see in older homes are the bathroom fans. I would estimate that most homes built over 10 years ago suffer from some form of incorrect bathroom fan venting. This is why every time we replace a roof, we go into the attic and make sure that any bathroom fans are ducted and sealed to their own dedicated stem vent. A stem vent is simply a vent designed to connect directly to a bathroom (or kitchen) fan and exhaust the air to the outside, and not allow any air to leak into the attic. Additionally, these vents have a flap that opens when the fan is on and doesn’t allow air to leak in when the fan is off. This keeps the interior space more comfortable.
So, what is the solution to these issues? It’s simply proper attic venting. Well, it’s not always that simple, but balanced and strategic venting solutions for your roof and attic space can help avoid moisture causing mold/mildew, rot, ice damming, and premature failure of the roof itself. Take the time with your contractor to make sure this is done properly.
Have questions? Give us a call. We would be happy to discuss venting further with you.
Thank you for reading!