When people ask about ‘green roofing’, they generally mean an energy efficient roof system. ‘Green roofing’ originally referred to a type of roof where dirt and plants were installed over a regular roof, also called garden roofs or vegetative roofs. This type of roof creates problems when a leak occurs and the dirt and plants have to be moved to find and repair it. Firestone has a reasonable solution where the dirt and plants are left in moveable planters.
Generally speaking, the term ‘green’ refers to the earth-friendly green movement. In response to global warming, manufacturers have created energy efficient products generally referred to as ‘cool roofs.’ While manufacturers promote their individual products for energy efficiency, as roof designers, we consider the full system along with other building issues to create a complete cool roof system.
LEED, or Leadership in Energy & Environmental Design, is a green building certification program that goes beyond roofing to ensure the whole building is energy efficient. There are five rating systems and four levels. Your project must meet prerequisites to score points in each category. Roofing qualifies with additional insulation and specific roofing materials.
Solar panels are increasingly being used across the country. With limited land space, the roof is a common place to install the panels. Solar installation is not as simple as placing panels on the roof. There must be adequate space between the panels and the roof for future re-roofing and repairs. Supports need to be properly installed to prevent leaks. There are weight considerations as well as uplift issues. When planning to have solar panels installed, find a roofing professional to ensure the process is proper from start to finish. Then, enjoy the energy savings from solar panels.
Products used in energy efficient or cool roofs include:
Insulation: Usually rated in terms of R-value per inch. Insulation is installed in various thicknesses to achieve highest rating. These are common types:
- Polyisocyanurate Insulation: Highest R-value per inch of roofing insulations at about R5.56 per inch. This product uses the LTTR or Long Term Thermal Rating because it loses some R-value over time. Using the LTTR gives the roof a true rating of what the roof will achieve during its life.
- Perlite Insulation: Usually used as a cover board over polyisocyanurate. R-value is 2.78 per inch.
- Wood Fiber Insulation: Primarily used as a coverboard in roof systems to create a rigid surface or improve attachment. R-value 2.64 per inch.
- Georgia Pacific DensDeck: Generally used as a coverboard in roof systems to create a rigid surface or improved attachment. R-value is .28 per 1/4 inch thickness.
- EPS: Commonly used to create thickness and slope in Lightweight Insulating Concrete roof deck. R-value of 3.85 per inch.
Membranes: Usually rated in SRI for Solar Reflective Index. SRI 78 is usually the minimum to be considered a cool roof. Membranes to create an energy efficient or cool roof include:
- Coatings: SRI 104
- TPO: SRI 101
- PVC: SRI 109
- Modified Bitumen (MB): SRI 30
- MB (High Reflective): SRI 93
- Built-Up Roof: SRI 9
- Metal: SRI 23-86
- Tile: SRI 29-69
- Shingles: SRI Up to 26
For more information on green roof and cool roof systems, please call us at 1-800-276-6344.