Soffit and Attic Venting In Your Home
If you are considering the purchase of a solar powered attic fan, we encourage you to read this page. Get the facts before you buy any energy conservation product.
The importance of venting your attic cannot be overlooked. In cold climates, improper venting can lead to moisture buildup which causes mold to grow, wood rot in extreme cases, or even ice in the attic insulation. During the summer, stagnant, superheated attic air can dry out your trusses, increase your energy costs for air conditioning, and make your house uncomfortable.
How did we become experts on attic venting? Our patented reflective insulation products reject the infrared heat emitted by hot roofs which, in turn, makes attics even hotter. Getting rid of this waste heat then forced us to look at not only how homes are vented, but the U.S. home building codes that dictate what is needed for adequate ventilation. What we found was amazing. Codes for attic venting are the same all over the U.S., regardless of the climate, and are designed for moisture egress, not the removal of hot air. Furthermore, most homes that do have venting have vents that are plugged with insulation.
Let’s start with an understanding of basic physics: Hot air rises. But why? Heated air rises due to a differential in density (mass), which causes an upward movement of the fluid (air is a fluid). Like a lava lamp, the colored liquid is heated, rises to the top, cools off (density is increased), then falls back to the bottom.
Think of the force required to raise a hot air balloon off the ground with 10 passengers, the tanks of propane, the weight of the basket, and the balloon. Pretty impressive force if you think about it. It should be easy for hot air to rise out of your attic, right? Driven by the density differential, the exhausting of the hot air should bring in fresh air where vents are located around the base of the roof (soffit).
There is no “pressure” that drives hot air out of an attic. The pressure (atmospheric) inside your attic is the same as it is outside (based on a no-wind condition). Wind blown across a roof can create a positive pressure on the windward side and a lower pressure on the lee side. Only the differential buoyancy of heated air over the temperature of ambient air is different.
Using a tracer gas and smoke generators, we have documented all types of attic venting, the appropriate sizes that work in hot climates, and have posted our findings below. This is not a scientific study, but observations made over the study of hundreds of homes in all types of climates.
Our field-proven results and recommendations: (if using a radiant barrier and passive vents)
What Works, What Doesn’t
CONTINUOUS SOFFIT VENTING
Continuous soffit venting is typically a 2″ or 3″ slot cut into the soffit into which is placed a manufactured venting system made from plastic or metal. The plastic is typically molded with thousands of small holes (1/32″ in diameter) to keep bugs out. It’s a great idea and easy to install, but falls short of offering sufficient net-free area to allow air to move.
Another popular type is an aluminum strip with small louvers pressed into them.
BENEFITS: Easy to install and attractive.
PROBLEMS: The holes are too small (see photo below) to pass sufficient air to let the attic aspirate naturally. Most often, these are covered with insulation or partially plugged with dust, pollen, or spider webs over time.
This vinyl soffit covering is very popular because it completely eliminates the need for painting and/or maintenance on your home. Great idea! Unfortunately, it starves the attic for air and costs you money and comfort.
The best solution for a venting problem is to install InvisiVent. Cutting into the existing soffit, covering it with InvisiVent, and wrapping the existing fascia with aluminum, as you can see below, will give you the ventilation and looks you need for your home.
Proper Ventilation Is Vital…Triple 3-1/3″ InvisiVent Has the Highest Ventilation Performance
The Triple 3 1/3″ InvisiVent soffit offers at least 50% more ventilation than most standard vinyl soffits, providing more than 10″ of net-free intake area. This means that not only will Triple 3 1/3″ InvisiVent provide a balanced ventilation system, but will do so with an overhang as short as 10″. The solid panel is an ideal solution for accent areas or where a vented panel is not necessary.
The flat face design creates a straighter panel with the look of smooth painted wood.