FS Roof System Blog

Tips For Building an Energy Efficient Flat Roof

With seemingly ever rising heating and cooling costs in Ontario building, incorporating energy efficient flat roof best practices just makes sense. The common question you may ask is: which type of roofs are more energy efficient flat or pitched roofs?  The answer may surprise you: flat roofs take the cake most of the time.

When Researching Energy Efficient Roofing System, There are a Few Key Terms you Should Become Familiar With:

Cool Roofs:

  • cool roof is a broad term used for any kind of roof that is designed to reflect sunlight and heat. Standard roofing systems not classified as cool roofs only reflect 5 – 15 percent of the energy and heat from the sun. This means it will cost more to keep your house or building cool in the hotter months of the year, but will have the opposite effect in the winter.

Green Roofs:

  • Green roofs have many of the same benefits of cool roofs, just in a different package. You’ll see gardens and mini-ecosystems on these roofs. This shades the roof and prevents heat transfer thus keeping the building cooler overall. Another benefit of green roofs is that they also insulate during the winter months.

Solar Reflective Index:

  • One of the two properties that determines a roofs energy efficiency, the SRI, is the measurement index that tells you how much sun gets reflected from the roofing material. A lighter colour typically rates higher on the SRI and means that more heat is reflected, but new technology is constantly being developed that challenges this rule of thumb.

Thermal Emittance: 

  • The other criteria taken into account for rating the energy efficiency of a roof is the thermal emittance or simply how much heat is absorbed. A higher score here means the roof radiates heat outward, not allowing it into the building.

Knowing all these terms is great for when you talk to one of our technicians, but if you’re looking for recommendations of energy efficient flat roofing systems right now here are a few of the flat roofing systems that are well known for their energy efficiency.

TPO (Thermoplastic Polyolefin)

  • Depending on the climate, TPO roofs have for many years been the most energy efficient of the single-ply roofing systems partly due to the fact that the standard TPO roof is light-coloured and it’s material make up reflects heat well. In other words, the material does not drag in and store very much heat.

Garden Roof

  • A garden roof is a classic green roof. These roofs can be more complicated and expensive to build depending on the base you go for but in the end these roofs are both energy efficient and insulating. An added bonus for our cold winters.


  • Finally, we have to talk about insulation. No it’s not important for reflecting heat as much as it is for keeping heating costs down in winter. Even if you had plenty of insulation put in when your flat roof was first installed over the years that insulation will have degraded. In short, you may need a top up. In addition to natural degradation insulation standards have risen over the years so your building may not be to standard. These standards are put in place as recommendations to maximize heating savings.