Attic Ventilation Tips

The soffit and fascia under the roof-line of our Project House add cosmetic value to the exterior, but the real value is hidden inside. This is the best opportunity a builder has to properly ventilate the attic. Without sufficient ventilation, your utility bills could soar and your roof system could actually fail. There are some new theories about venting that may surprise you too. Let's take a closer look. Louisisana-Pacific provided the Smart Sytem Soffit, Fascia & Trim for the Project House. O'Hagin's, Inc. provided the hidden Cloaked Vent Tile in the Project House roof.

Soffit, Fascia & Trim
Rafters are the parallel beams that support the roof above the top floor of the house. Fascia is the vertical board that closes off the end of the rafter tails. It's normally vertical, sometimes sloped. The Soffit is the horizontal under-hang that completes the boxing-in of the rafters and the sheathing. That box is known as the "eaves" or the "overhang" of the house. Lookouts are short pieces of 2x4s that horizontally connect the rafter tails to the top of the wall. A Closed Soffit is a closed box. An Open Soffit leaves the rafter tails exposed. "Trim" is a term used to describe soffit & fascia.

Louisiana Pacific's "Smart System"
This is trim made of Engineered Wood, designed to look like natural wood (with grain etched into it) but engineered to be stronger and more durable than natural wood. The trim is treated with an insect repellent. As Michael points out in our segment, the trim itself is a cosmetic concern; our main concern is Attic Ventilation.

Attic Ventilation
Moisture is the #1 concern. Heat is #2. We've gotten much better over the years at building houses that are energy-efficient. We're better at building "tight" Homes - that means they're designed to keep the elements outside & your energy dollars inside. But that level of homebuilding expertise can also cause some problems. Modern insulation and house-wrapping techniques create a tightly sealed envelope that blocks leaks, drafts and other unintentional paths for fresh air to enter a house. Those techniques also prevent "stale air" inside the house from finding a path to exit.

A "Sick House"
Insulation and house-wrapping create a "stale air" environment inside. The air gets stale because the same air keeps getting conditioned - you notice it inside an airplane cabin sometimes. Lots of moisture gets produced in a home (showers, boiling water, people & pets breathing, condensation when the weather changes, etc) & it floats up into the attic as water vapor in rising air. One of our biggest problems is managing the moisture. If we don't control that moisture, we can do a lot of damage to the materials that we build into your new house. A buildup of moisture will promote the growth of mold, mildew & other biological pollutants.

Moisture over time will rot the wood in the frame of your house and remove all strength from that wood. Once the frame of your house is ruined, the entire investment you've made in your new house is ruined along with it. If it's not vented away, mold can grow in the attic, decreasing the indoor air quality and making your house "sick". Mold doesn't cause decay but high moisture levels can. Moisture makes wood grow, so it decreases in structural performance (like uneven roof decking for instance). Warm air naturally rises, so it wants to pool inside the attic. If the attic is hot and improperly vented, then energy bills go up because that hot air pocket grows and works its way down into the living area. The HVAC cannot work efficiently, and you have to pay to cool that hot air out of the attic. The combination of excessive moisture & heat can make your roof shingles deteriorate & fail prematurely. Proper venting is by far the most cost-effective way to cool the attic.

Attic Ventilation
The best venting design puts vents in the soffit (for intake) and up near the ridge line (for exhaust). That way, fresh air naturally bathes the attic as hot air rises up & out of the ridge line and fresh air replaces that outgoing air through the soffit vents. Soffits will have either discrete or continuous vents. Builders usually install individual 4x16 or 8x16 vents, or else they create a continuous soffit vent with screen door material all the way around the eaves. Some designs rely solely on continuous vents around the perimeter of the soffit (with no vents up near the ridge line).

This theory depends on wind pressure to move air through the attic, so it doesn't work well at all when there's no wind. Regardless, it still does not allow for sufficient venting since it does nothing to remove hot air from the top of the attic when you need it most, on hot summer days - attic. Different styles of passive roof vents.

In our segment, Michael demonstrated a Passive Turbine Vent, a common roof vent. Most people call it a "twirler". It's circular, and it twirls when the wind blows through it - that twirling helps draw hot air out of the attic, which draws cooler air in through the soffit vents to clean out the hot air in the attic. It works best when it's mounted high on the roofline. Sometimes people like to put plastic bags over these twirlers in the wintertime to prevent cold air from moving through your attic and into the living area.

Michael warns against that, because you end up with a lot of moisture buildup in your attic in the wintertime. In cold weather, your house is hot and the air upstairs in the attic is cold, so moisture forms just like it would on the side of a glass of ice water in the summertime. So, leave those twirlers open & exposed, even in the wintertime.

Michael also demonstrated a ridge vent; another very common system. It goes along the top of your roof line - right on the ridge itself - so it sits at the absolute highest point on a roof for ventilation. It's a simple and efficient design; a long slot that runs the length of the ridge to let hot air escape. It has no moving parts, so there's not much to worry about in terms of maintenance. This is an ideal system for a roof with asphalt composition shingles.
Michael next demonstrated the Cloaked Vent Tiles that are hidden in the roof of the Project House. They're designed to provide adequate ventilation without disrupting the beauty of a Spanish Tile roof like the one on our Project House. They're made of metal, and you paint them to match the look of any tile, so they're essentially invisible from the ground. Since the metal may have oil left over from the manufacturing process, we washed the vents first with a vinegar & water solution, then we applied a metal primer & metal paint. We were smart though, because we painted them on the ground. We used the back-side to test until we found the right color. Once we painted the vents on the ground, we gave them to the roofer to install.

Consumer Tips - When you install attic insulation, pay attention to where the insulation hits the roof decking. If it's improperly or carelessly installed, it can block airflow (from soffit vents to roof vents) and prevent the attic from ventilating properly. Be especially careful when you install sprayed insulation. Use cardboard or plastic baffles to keep the ventilation passage clear during the insulation process.

Make sure the soffit vents have holes cut behind them to match the size of the vent when your house is built. Some framers make a big mistake by leaving a tiny hole behind the vents, so a 4x16 vent may actually only have a tiny and useless hole behind it in the soffit. That means the vent is relatively worthless for ventilation.

If you don't have proper ventilation in your attic, you could lose your warranty on your asphalt or fiberglass shingles. Shingle manufacturers won't cover the shingles if you don't have proper ventilation because the heat buildup could easily cause those shingles to delaminate.

It doesn't take much work to properly ventilate your attic, and the vents don't have to make the roof look ugly. Vent your attic correctly, so you don't have to spend a lot of money later fixing problems you can easily avoid now. If you do have proper ventilation, your family's going to sneeze a lot less, your house will be healthier & stronger, plus you're going to have lower utility bills every month in your new house.