Bad Indoor Air Quality For Attic Ventilation

Roof and attic ventilation is one of the most important and over-looked items that most roofing companies do. When it is done improperly, it is dangerous to the health and safety of your home and family.

Poor ventilation can affect indoor air quality within the home, as well as the structural integrity of the roof framing. The attic air needs to move freely throughout the attic, with the natural flow from hot air rising for exhaust. When the attic is not vented properly, the attic air will smell musty. Below I will talk about the different types of causes and what can happen if it is not taken seriously.

When the musty smell from attic air travels into the living area of the home, it directly affects people inside the home with allergies or respiratory health problem. When Vesel Services started to do attic inspections, the first one we ever did was really hard to get the appointment scheduled. Until we finally met, they apologized, they started talking about how their oldest of three kids had asthma bad and they are in and out of the hospital. So, we went about the roof and attic inspection, the roof shingles were in good shape, but the roof sheathing felt soft walking around on it. When sticking a head into the attic it was obvious there was BLACK MOLD everywhere, including the musty smell. Needless to say, we got the job we replaced every square inch of roof decking attic insulation. We sprayed moldacide on everything and to date, it was definitely the worst roof job we have ever done. The home owners even had a drywall contractor come out to replace the drywall on the ceilings in the house. (the cause of the problem was a combination of 2 bathroom vents and no intake (soffit) vents.)

An improper attic ventilation system can cause moisture spots on ceilings, down from the top exterior walls. It is amazing how many times we go out to see home owners that have these problems. We see over and over when home owners see the problem hire a roofing contractor to fix the problems, what do they not do an ATTIC Inspection prior to doing the project! That is why here at Vesel Services we make it mandatory for ever roof job to include an attic inspection. The first time our Sales Specialist visits the home we do an attic inspection so there are no surprises during the project. This allows us to inspect the roof decking, bathroom ventilation, kitchen ventilation, insulation of baffles (if applicable) and attic insulation. Here at Vesel Services we take every part of the comfort and safety of your home seriously.  It’s a simple way for the home owner and contractor to know how the attic’s ventilation system is performing. Quite often in the past the attic ventilation systems have been over looked.

Winters can lead to ice dam problems that wreak havoc on your home caused by poor attic insulation, leaking, or drafty air from below. This, in turn, allows warm air to the attic. This then causes the under side of the roof decking to warm up enough to melt the snow on your roof, then it freezes day after day. The ice then starts to crawl under the shingles. If there is not a layer of protection (ice & water shield)  under the shingles, the ice will slowly melt and start to drip water on to the insulation. Once that is wet, then next area compromised is the drywall.  Properly installed ice and water shield will prevent the damage to the interior.

Another very overlooked problem is the actual installation of the ice and water shield. The number of feet covered from the eve (gutter apron) is very important and depends on the amount of soffit and pitch of the roof. The coverage needs to be a minimum of 18 inches past the exterior wall. 

Improper attic ventilation can cause premature shingle failure as well. Too much heat will cook the shingles from the inside out. Shingles need air to flow in the attic to keep the roof decking cool.

When moisture gets into the attic, it condenses on the roof sheathing in the form of frost. Frost itself doesn’t do any damage, but once it melts, things get wet, and then damage occurs. Melting frost can lead to deteriorated roof sheathing, mold on the roof sheathing, wet insulation, and water stains on the ceilings.  These are all bad occurrences, so you definitely don’t want frost in your attic. Frost gets into the attic from air leaks, or attic bypasses. Of course, any type of exhaust (bathroom or kitchen) fan needs to be exhausted directly to the exterior, and never into the attic. Even if the exhaust fan is aimed at a roof vent, this isn’t good enough. A lot of moist air will still find its way back into the attic. This will add to the moisture in the attic.

Ventilation of attic spaces is required by most building codes as well as by roofing material manufacturers and the National Roofing Contractors Association (NRCA).


Owner, Eric Vesel


Author: Eric Vesel

COMPANY: Vesel Services Today

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Vesel Services Today are experts in roofing, siding, window installation, home remodeling, and home construction, and so much more! We are the neighbors you see walking the block, and we’re the friends you see in the carpool lane. It’s that kind of intimate market knowledge which makes us the #1 contractor in Southeastern Wisconsin.

Categories: Roofing.