Why Roof Ventilation Matters in the Winter

A well-ventilated attic seems like a great idea in the summer. After all, it should let heat escape, lowering the attic’s temperature and reducing heat transfer into your home. In the winter, however, many homeowners balk at letting heat escape through their attics. They see this as an energy efficiency killer, wasting the warm air their HVAC produces. That notion is part of a common misconception about how attic ventilation works and why it’s there. Here’s everything you need to know about why attic ventilation is vital in the winter.

How Attic Ventilation Works

The purpose of attic ventilation is twofold. One of its jobs is to lower your attic’s temperature by preventing heat accumulation. The other is to reduce moisture levels. Generally, you’ll find one of three attic ventilation methods in residential buildings.

The first method is passive ventilation. It involves a roughly equal combination of roof ridge and soffit or eave vent openings. The operating principle behind a passive ventilation system is simple. Rising heat leaves through the roof ridge openings, pulling in equal volumes of fresh, cooler air through the eaves. Ideally, that process should always keep the attic within 15 degrees of the outside temperature in the summer. It should keep it roughly equal to the outdoor temperature in the winter.

Another ventilation method you’ll find in residential buildings is active ventilation. It relies on vent designs that use wind to increase pressure differentials between the attic and the outside. When wind speeds pick up, the active vents pull more air out of the attic. That draws fresh air in through passive soffit vents. The advantage of active ventilation is that it can more efficiently lower attic temperatures, especially in the summer. That can help improve a home’s energy efficiency and lower its HVAC costs.

The final attic ventilation type you’ll find is mechanical ventilation. It relies on fans to provide extra airflow whenever necessary. Most mechanical ventilation systems use thermostat controls to turn them on automatically as needed. They offer the advantage of not relying on inconsistent wind speeds to function. As a result, they can provide more precise control over temperatures in your attic.

Won’t Attic Ventilation Waste Energy in the Winter?

In the winter, it’s essential to realize that your attic ventilation’s purpose isn’t to let conditioned air escape. That’s not the primary heat source in your attic unless you have poor insulation and plentiful air leaks. In the winter, most of the heat accumulation in your attic comes from solar radiation.

Even on cold days, the sun warms your roof all day, radiating that heat into your attic. It is that heat that your home’s attic ventilation removes. That heat plays no role in your home’s interior temperature, and there’s no efficient way to capture and use it. However, leaving it there would be problematic for a variety of reasons.

Why Attic Ventilation Matters in the Winter

Allowing your attic temperature to exceed the outdoor temperature in the winter can create significant problems. Here are a few of the most notable among them.

Condensation on Roof Decking

Any time cold air meets warm air, there’s a chance for condensation to form. With no attic ventilation, warm air would get trapped against the inside surface of your roof decking. There, it could lead to condensation on the decking and surrounding supporting structures. Eventually, that moisture might cause wood rot and shorten the lifespan of your roof.

Ice Dam Formation

One of the most damaging problems your roof can suffer in the winter is the formation of ice dams. They can develop following any accumulation of snow on your roof. An ice dam occurs when snow melts near your roof’s peak. As the resulting water moves down your roof’s slope, it can refreeze, forming a barricade. Then, subsequent water flows never reach your gutters and may find a path into your home.

Poor attic ventilation increases the temperature differential between your roof’s peak and edges. It creates the perfect environment for ice dam formation. It may also make ice dams a recurring problem you’ll get stuck dealing with all winter.

Mold Growth

All varieties of mold thrive in dark, moist environments. That’s precisely what you’ll find in an attic with inadequate ventilation. Mold growth in your attic can lead to health issues for everyone in your home. It’s also costly to remove, with attic mold abatement services frequently running into thousands of dollars.

Voided Roof Warranties

If your roof is still under warranty, you need to know that poor attic ventilation can void it. Roofing material manufacturers attach ventilation requirements to their products. Failing to meet them can lead to premature wear and tear, damaging the materials. In the winter, poor ventilation increases the odds of water damage and penetration through your roof. In those cases, the manufacturer won’t honor your warranty, and any necessary repairs will be yours to pay.

How Can You Tell if You Have Proper Attic Ventilation?

The easiest way to tell if you have proper attic ventilation is to have a qualified roofer check it. However, if you can access your attic, there are some ways to evaluate your attic ventilation. You’ll need a thermometer and a hygrometer to do it.

Ideally, the humidity in your attic should be roughly identical to the humidity outside. You can compare your hygrometer readings to the local weather report to find out if it is. The temperature should also closely mirror outside conditions. However, it’s natural for your attic to get hotter than the outdoors in the summer. If your attic’s winter temperatures are much warmer than the temperature outside, you likely have a ventilation deficiency.

Addressing Unintended Heat Loss

An attic inspection can help identify problems that lead to attic ventilation lowering your home’s energy efficiency. It will point out likely sources of air leaks that allow conditioned air to escape your home. It will also let you know if your current attic insulation is sufficient.

In our climate region, modern homes now have attic insulation with R-values of up to 60. Unless you live in a recently built house, it’s unlikely that your attic meets that specification. Thorough air sealing and insulation upgrades should eliminate any chance of your attic ventilation negatively affecting energy efficiency.

Your Roofing and Ventilation Specialists

If your attic needs ventilation adjustments, Warren Thompson & Son Roofing & Siding can help. We’ve served homeowners in Alpha, NJ since 1973. Our team of roofers has the qualifications to help you execute the perfect ventilation plan for your attic. With over 40 years of experience on staff, your attic is in good hands with us.

We also offer roofing installation, repair, and maintenance services for residential and commercial clients. And if you want to extend the life of your home’s roof, we offer Roof Maxx treatment. It can rejuvenate your roof’s shingles and restore them to like-new performance characteristics. We’re also GAF Master Elite Certified and Better Business Bureau accredited with an A+ rating.

For all your attic ventilation needs, call our roofing experts at Warren Thompson & Son Roofing & Siding today!