Do metal roofs bring special ventilation needs or condensation concerns when installed on homes? The general answer is “no” but there is more than a simple answer.
Unless a home has been built specifically in a manner which does not require attic ventilation (such as a conditioned space or hot attic, or insulated panel construction), there are 2 reasons why good ventilation is important with ANY home – regardless of the roof covering.
2 Reasons Why Good Ventilation is Important for Any Home
- Energy Efficiency. Ventilation is used during the summer to vent heat out of the attic, reducing air conditioning costs. For many years, building science experts were focused on reflectivity as a way to keep heat out of the attic. While reflective or “cool roofs” are still a good idea, tests have shown that good ventilation which quickly removes any gained heat back out of the attic is equally if not more effective at home energy efficiency.
- Condensation. A great deal of moisture is generated inside of a home’s living space. It is generated primarily by laundry, showers and bathing, houseplants, cooking, and ventless stoves. That moisture, originating in the living space of the home, migrates upward and, if a 100% reliable vapor barrier is not in place behind the home’s ceilings, it ends up in the attic. Once it’s in the attic, if that warm, moisture-laden air reaches a cool surface, it condenses. (Think of that cool glass of lemonade sitting outside on a hot, humid day.) The resulting condensation can create a very unhealthy environment prone to support mold, mildew, and other biological growth. A well-vented attic also helps to keep your attic’s insulation dry which increases its effectiveness. As it gains moisture, insulation loses considerable R-Value and effectiveness. The general calculation for this is a 2.5% decrease in R-Value for every 1% increase in insulation moisture content
With traditional roofing choices, there is a 3rd reason why attic ventilation can be helpful: good attic ventilation can help increase shingle life. By keeping rooftop temperatures a bit cooler, shingle life can be preserved. This benefit does not really have an impact on roofing materials like metal, tile, and slate which are unaffected by high temperatures.
For help in understanding your home’s ventilation needs, we encourage you to contact us, without obligation, if we can be of any assistance. We’re North Carolina’s metal roofing experts...and we know ventilation.