METAL ROOFS AND INSULATION: STAYING COOL WHILE SAVING ENERGY

Typically, the effectiveness of insulation versus a cool metal roof isn't an either/or question. Most building codes require some amount of insulation - quantity and R-Value being dictated by the climate where you live. Cool metal roofs, on the other hand, are specifically designed for warm and hot weather climates, where the lion's share of undesirable heat transfer is the result of UV absorption through the roof.

Most building experts recommend using a combination of insulation and a reflective metal roofing system in order to optimize energy efficiency and interior comfort while minimizing solar heat gain since insulation and reflective roofs mitigate heat transfer differently.

INSULATION HELPS TO REDUCE THREE TYPES OF SOLAR HEAT GAIN
Insulation provides a thermal barrier, preventing heat transfer from one space to another. This heat transfer occurs in three ways:

Conduction: This occurs when heat moves through a particular material, conducting heat from one source to another. So, for example, the metal handle on a hot stove will conduct heat from the burner to your hand.
Convection: This term applies to the behavior of heat as it moves through gases or liquids. Heat circulates, and hot (lighter) air rises to the top while cool (denser) air settles at the bottom.
Radiation: Radiant heat moves in a straight line, heating anything that gets in its path. Solar radiation is a prime example of this.
An attic space is a prime example of all three of these types of heat transfer. The sun's rays are a radiant heat source, immediately warming the roofing system. Conduction continues the transfer of heat from the roof to the interior attic space. Once present, convection - both within the attic, as well as from the interior spaces below - causes the hot air to rise, further increasing attic temperatures, which can be a detriment to the rest of the home - via interior comfort issues as well as condensation problems - if it isn't kept in check.

COOL METAL ROOFS WORK TO REFLECT RADIANT HEAT
Metal roofs designed to combat solar heat gain do so implementing reflective coatings that reflect the sun's UV rays back up into the atmosphere. By default, this radiant heat source is greatly diminished, making it easier for interior layers of insulation to do its job preventing the transfer of any heat that does make it through the roof from penetrating the interior living spaces.

In addition to protecting the home from radiant solar heat, cool metal roofs are also highly emissive, getting rid of any absorbed heat much faster than traditional roofing materials. This means that once the sun sets, your metal roof will cool off faster, reducing the amount of heat that is conducted from the roof into the structure below.

INSULATION AND COOL METAL ROOFS: AN IDEAL COMBINATION
Insulation is usually a given because some amount of insulation will be required in order for your building to meet the code requirements for your location and climate. In most cases, buildings constructed in warmer climates will require less insulation than those in colder climates.

However, a cool metal roof can greatly enhance the effectiveness of the insulation. The less heat that penetrates the building in the first place, the less heat transfer becomes an issue for insulation to contend with. Plus, there are scenarios in which insulation may not be up to snuff.

For example:

R-Values aren't constant. The R-Value of a particular product is calculated under very specific and controlled conditions, but studies show that this number varies as the temperature and humidity levels fluctuate.
Compromised insulation can't perform as well. Depending on the building conditions, insulation in a roof or attic location can become compressed or shifted around, allowing for gaps or pockets where there is little to no insulation, negatively impacting overall performance.
Roof leaks and condensation are detriments. If a roof leaks or there is a lack of balance in the insulation and ventilation leading to condensation, the R-Value will be much lower, impacting interior comfort and air quality inside the building.
A weather-tight cool metal roofing system works in tandem with an adequately insulated and ventilated roof/attic to form the ideal collaboration.

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TIPS FOR ENHANCING THE PERFORMANCE OF INSULATION AND METAL ROOFING
The following tips will help you get the most from both a reflective roof as well as your building insulation:

Select a high-quality roof. Review the "potential insulation issues" and you'll note that a roof's performance is key to getting the most out of the insulation. Investing in a high-quality cool metal roof is a choice that will be rewarded decade after decade.
Choose the right coating. If you have a weather-tight roof already, you may only need to re-coat it with a light-colored, reflective coating to gain the most cost efficient benefits. Otherwise, look for lighter-colored reflective metal roofs to diminish heat absorption.
Insulate from the bottom. Make sure to insulate the bottom of your roofing material to gain the largest benefit, leaving an air space between the materials to reduce the chances of trapped moisture.
Rather than debating whether or not insulation is as effective as a cool metal roof, building owners are better off determining which insulation and roofing products will work best in tandem in order to deliver energy-efficiency and interior comfort that will last for decades.


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