As expected high albedo roofs save summer cooling energy but also increase the required winter heating energy.
High albedo roof requirements.
Thermal emittance is the ability to emit absorbed heat.
Or option 2.
Install high albedo and vegetated roof surfaces that in combination meet the.
There are two properties that are used to measure the effects of cool roofs.
Or option 3.
Requirements option 1.
Natural weathering can have detrimental effects on a roof s ability to maintain high reflectance and watertightness.
Solar reflectance also known as albedo is the ability to reflect sunlight.
Single ply membranes are pre fabricated sheets rolled onto the roof and attached with mechanical fasteners adhered with chemical adhesives or held in place with ballast gravel stones or pavers.
Built up roofs consist of a base sheet fabric reinforcement layers and usually a dark protective.
It is expressed either as a decimal fraction or a percentage.
Use roofing materials having a solar reflectance index sri equal to or greater than the values in the table below for a minimum of 75 of the roof surface.
In today s market a cool roof is defined by the reflectivity and emissivity requirements set by either title 24 from the california energy commission or by the energy star program.
For example older buildings with lower roof insulation levels exhibit different savings for a high albedo roof than a new building with more roof insulation.
While conventional roofing materials warm up by an average 0 055 degrees c w m sup 2 sup the high albedo surfaces warm up by an average 0 015 degrees c w m sup 2 sup p.
Install a vegetated roof for at least 50 of the roof or install high albedo and vegetated roof in combination area of sri roof 0 75 area of veg roof 0 50 total roof area water efficiency.
Install a vegetated roof for at least 50 of the roof area.
There are different cool roof standards for commercial low slope roofs and residential steep slope roofs.
For a roof to meet albedo classifications it must emit no less than 65 measured as 65 on the solar reflectance value scale of radiant heat energy back into the atmosphere.
Reformulate or coat black membranes to make them reflective.
It is also expressed.