American Metal Roofs Asks: Do You Need to Vent?

American Metal Roofs of Wisconsin Asks: Do You Need to Vent?

You may have more reasons to vent, but in this article…we’re talking about your roof. Good ventilation of your Wisconsin roof does 2 things very well: prevent mold and and prevent ice damming.

Nobody wants mold.

Mold is caused by a combination of moisture, warmth and stillness.  When water leaks from the roof into the attic and sits, microscopic organisms in the water begin to feed off of any organic material they can find.  Eventually they grow into overpowering colonies of black mold that affect your health as well as your living space. Nobody wants mold.

Mold is a major concern to be taken seriously.  We create a lot of moisture in our homes—laundry, dishwashing, house plants, bathing, fireplaces and other appliances add microscopic water droplets that need to escape out of the house and back into the atmosphere.  Unfortunately, in attempting to build more energy efficient houses over the past 30 years, the building industry has been constructing homes that are that are “tighter” than ever before.  As a result, they have inadvertently “captured” all that moisture in your home.  All of that moisture gravitates upward into the attic and if not vented out, it will condense on cool surfaces. If the back side of the metal roof is exposed in the attic, it creates an ideal situation for severe condensation. However, condensation can also occur on the back side of solid decking if moisture is not properly vented out.  All this condensation can become a potential haven for mold. 

Ice Damming Anyone?

Another problem resulting from the lack of attic ventilation occurs in our northern climate when warm air reaches the roof system and melts wintertime snow loads.  This can result in damaging ice dams on the roof especially over the eaves where re-freezing can occur. This problem can be made even worse by a lack of insulation in the ceiling floor.  Keeping the attic very cool in the winter through good ventilation will eliminate this possibility.

Proper Venting for a Lifetime

Proper attic ventilation requires intake and exhaust air. Usually intake air is achieved through eave soffit vents. Exhaust venting is done through vents higher on the roof such as ridge vents, turbine vents, or various types of “can” vents. A good way of thinking about ventilation is to understand that your desire is to continually and consistently “bathe” the underside of the roof deck with fresh air.  This prevents condensation, keeping your decking dry and preventing the growth of mold. 

If you choose a product that needs to be installed over battens or “strapping” and you do not have solid decking in place, you will need to pay exceptionally close attention to proper ventilation in order to avoid condensation problems. In fact, because of this, you will often find that the most credible manufacturers of metal roofing products that can technically be installed over battens will advise always having solid decking in place for residential applications.

If your home’s construction does not allow for ventilation, then you need to check whether a vapor barrier is in place in the roof assembly to prevent moisture from migrating to the decking or roofing. This vapor barrier can be a sealed sheet of polyethylene (usually directly behind the ceiling drywall) or certain types of insulation such as sprayed-on polyurethane. If these things are not in place, then having a vented “cold roof” constructed on top of your current roof may be wise.

We Know About Ventilation

The critical thing to keep in mind about ventilation when buying a metal roof is that a professional contractor who cares about more than just selling you a roof will understand ventilation.  That’s us: American Metal Roofs of Northern Wisconsin. We will discuss it with you, evaluate your needs, and either approve of your home’s existing ventilation, or offer a better solution.

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