A gas turbine engine , comprising: a fan section ; a compressor section comprising a low pressure compressor and a high pressure compressor ; a combustor in fluid communication with said compressor section ; a turbine section in fluid communication with said combustor , the turbine section comprising a low pressure turbine and a high pressure turbine ; an outer shaft that interconnects the high pressure compressor and the high pressure turbine ; a low speed spool including an inner shaft that interconnects the fan section , the low pressure compressor and the low pressure turbine ; a plurality of bearing structures that support said inner shaft and said outer shaft , wherein a first one of said bearing structures includes a bearing compartment (BC); a buffer system (60; 160; 260) that selectively communicates a buffer supply air (62; 162; 262A, 262B) to pressurize said bearing compartment (BC), wherein a low pressure bleed air supply (64; 164; 264A, 264B) is communicated to said bearing compartment (BC) in response to a high power condition of the gas turbine engine and a high pressure bleed supply air (66; 166; 266A, 266B) is communicated to said bearing compartment (BC) in response to a low power condition of the gas turbine engine , wherein said buffer system (60; 160; 260) includes a valve (68; 268A, 268B) that selectively modulates between said low pressure bleed air supply (64; 164; 264A, 264B) and said high pressure bleed air supply (66; 166; 266A, 266B); the gas turbine engine further comprises a controller (70; 170; 270) that selectively modulates said valve (68; 268A, 268B) in response to a power condition; and in that the fan section is driven by a geared architecture at a lower speed than the low speed spool , wherein the first bearing structure is forward of the geared architecture , and the plurality of bearing structures further comprises a bearing structure aft of the geared architecture . a fan section ; a compressor section comprising a low pressure compressor and a high pressure compressor ; a combustor in fluid communication with said compressor section ; a turbine section in fluid communication with said combustor , the turbine section comprising a low pressure turbine and a high pressure turbine ; an outer shaft that interconnects the high pressure compressor and the high pressure turbine ; a low speed spool including an inner shaft that interconnects the fan section , the low pressure compressor and the low pressure turbine ; a plurality of bearing structures that support said inner shaft and said outer shaft , wherein a first one of said bearing structures includes a bearing compartment (BC); a buffer system (60; 160; 260) that selectively communicates a buffer supply air (62; 162; 262A, 262B) to pressurize said bearing compartment (BC), wherein a low pressure bleed air supply (64; 164; 264A, 264B) is communicated to said bearing compartment (BC) in response to a high power condition of the gas turbine engine and a high pressure bleed supply air (66; 166; 266A, 266B) is communicated to said bearing compartment (BC) in response to a low power condition of the gas turbine engine , wherein said buffer system (60; 160; 260) includes a valve (68; 268A, 268B) that selectively modulates between said low pressure bleed air supply (64; 164; 264A, 264B) and said high pressure bleed air supply (66; 166; 266A, 266B); the gas turbine engine further comprises a controller (70; 170; 270) that selectively modulates said valve (68; 268A, 268B) in response to a power condition; and in that the fan section is driven by a geared architecture at a lower speed than the low speed spool , wherein the first bearing structure is forward of the geared architecture , and the plurality of bearing structures further comprises a bearing structure aft of the geared architecture . <EOS>