A Radiant Ventilated Cool Roof System harnesses 3 proven technologies known to create thermal resistance and reduce heat conduction within  steep slope roof deck assemblies; 

1-  Above Sheathing Ventilation (ASV) - using metal battens and counter battens to create an optimized convection and drainage plane between between the roof sheathing and roof substrate.  

2-  Radiant Barriers installed within the ASV assembly that prevent  97% of radiant energy from entering the attic space. 

3- Sheathing Vents  installed in the sub tile ventilation cavity that draw heated attic air into the sheathing ventilation system and improve attic ventilation.   

A Radiant Cool Roof Saves up to 25% in Summer Cooling Costs and 5%-10% in Winter Heating Costs  

Installing a metal roof with  'Radiant Above Sheathing Ventilation' ('RASV') can save you up to 25% in Summer Cooling Costs and 5%-10% in Winter Heating costs compared to a regular asphalt shingle roof. 

Radiant Ventilated Cool Roofs Come in 3 Styles and over half a dozen colours

• Cool roof Tiles
• Cool Roof Shakes
• Cool Roof Shingles

 
 A Radiant ASV Cool Roof complies with Title 24 California Building Standards, Section 152, and NAHB Green Building Standard, Chapter 7,  which both state that roofs installed with radiant barriers and an appropriate air gap are considered equivalent to the prescriptive definition of a cool roof (i.e cool pigment roofs)-  regardless of the roof color and it's associated solar reflectance.   

According to the CRRC ( Cool Roof Rating Council) "A cool roof is one that reflects the sun’s heat and emits absorbed radiation back into the atmosphere. The roof literally stays cooler and reduces the amount of heat transferred to the building below, keeping the building a cooler and more constant temperature."

When the sunlight strikes a rooftop, most of it gets reflected back into the sky but some of its energy is absorbed into the roof system in the form of heat. Cool roofs reflect more sunlight and absorb less heat than traditional dark-colored roofs. 

There are two properties that are used to measure the effects of cool roofs.

• Solar reflectance, also known as albedo, is the ability to reflect sunlight. It is expressed either as a decimal fraction or a percentage. A value of 0 indicates that the surface absorbs all solar radiation, and a value of 1 represents total reflectivity.
• Thermal emittance is the ability to emit absorbed heat. It is also expressed either as a decimal fraction between 0 and 1, or a percentage.

Another method of evaluating coolness is the solar reflectance index (SRI), which incorporates both solar reflectance and emittance in a single value. SRI measures the roof's ability to reject solar heat, defined such that a standard black (reflectance 0.05, emittance 0.90) is 0 and a standard white (reflectance 0.80, emittance 0.90) is 100.

DISADVANTAGES OF TRADITIONAL REFLECTIVE COOL ROOF SYSTEMS

• Roof surfaces become environmentally soiled over time and loose their reflective and emittance characteristics.
  
  
• A 2011 study  by the Dept. of Environmental and Civil Engineering  at Stanford University suggested that although a reflecting roof will decrease temperatures in a single house, it will also reduce the "heat island effect" even more, and would actually contribute to global warming, however this study did not account for the lower energy use and emission creation that would result from less energy needed for cooling houses having white roofs.  White roofs reduce summer air conditioning energy demand and change surface albedo. 
  
  
• The Stanford study concluded  that conversion of rooftops worldwide to white roofs, accounting for their albedo effect only, was calculated to cool population-weighted global temperatures by ~0.02 K but to warm the Earth overall by ~0.07 K.