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 3 reasons why good ventilation is important with ANY home – regardless of the roof covering.
3 Reasons Why Good Ventilation is Important for Any Hom
- 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.
- Ice Dams. For homes in our northern climate, good attic ventilation can help minimize the potential for winter ice dams. Ice dams occur when warm air from the living space reaches the roof deck and causes the snow to melt. The melted snow then runs down the roof and refreezes over the home’s cold overhangs, creating damaging and dangerous ice dams which can force melted snow into the home. Proper attic ventilation ideally keeps the attic the same as outside temperatures, helping to prevent the snow load on the roof from melting due to interior heat and then forming ice dams as it reaches cold areas of the roof.
With traditional roofing choices, there is a 4th 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.
We’re ventilation experts and can provide you with an attic inspection and expert advice on your home’s roofing and ventilation needs. Please don’t hesitate to call or contact us for more, no-obligation, information.