How To Heat A 55gal Tank???

Im going to move my 27in boa to a 55gal tank. and i cant find any thing that well keep the air temp above 80 degrees.I just bouht a huge heat mat 15in-23in. but i stell need somthing to heat the air what do u guys sugget??????

....how is the top covered? The more description you give concerning the enclosure....the better everyone can help out ;)

its 16in-48in and 1/3 of the top is sreen and the rest is glass.