One of the questions we hear quite a bit relates to whether a metal roof "catches" more heat than a non-metal roof. In other words, does a metal roof make a house too hot?
Hotter than a Regular Roof?
To answer this, we need two address two issues - the roof covering material (the metal roof) and the roof assembly construction.
Here's what to consider when you're asking about the heat absorbency of metal.
- Color and finish. Both will affect a metal's heat absorbancy. Metal exposed directly to the sun will definitely heat up, but color and finish will impact whether or not it heats up more or less than other roofing materials. Most of our metal roof products have Energy Star finishes that are certified to be reflective of sunlight, making them cooler than the older finishes. And, as you may have guessed, a lighter color will absorb less heat than a dark color.
- Absorption. It is true that a metal roof will absorb heat when directly exposed to the sun. But so does any roof covering material. Darker roofs in materials like asphalt, ceramic, slate or any other material absorb heat at roughly the same rate. It's unlikely that using the same color in a different material will mean a significant different in roof-top temperature.
- Ability to cool. When the sun stops shining on a roof directly, the lightest material will lose its heat the fastest. The lightest roof available is metal, which means it cools quickest. Once the sun stops beating down on a metal roof, it quickly reverts to the same temperature as the surrounding air. Heavier materials like slate or concrete have denser mass, and so they retain heat much longer. And be clear about this - the longer these roofs stay hot, the more heat they'll transfer to the building beneath.
Construction of the Roof Assembly
Yes, roof color and material affect the amount of heat collected by the roof. But the bigger contributor to that heat being conducted into a room below isn't the roof. It's the construction between the roof and the space below.
If a room beneath a roof has an attic, then controlling the temperature of the attic with a "cool" roof like metal is important. Even more important? Properly ventilating the attic to keep it within a few degrees of ambient air temperature. This gives the insulation in the ceiling the greatest chance of keeping heat from seeping into a room. Once you're sure your attic is properly ventilated, the second biggest consideration should be the ceiling insulation. The better the quality and quantity, the less heat from the attic will be conducted into the room below during the summer (and the less heat conducted the other way over the winter!).
Try This Test
To see if the heat in a room is coming from the ceiling (or just accumulating by convection from other areas of the house, use a digital thermometer. You can use it to take the temperature of the ceiling, walls and floors in different rooms of your house to see where heat seems to be highest. It's an easy way to quickly learn a lot.