Carbon Taxes; it is no longer a luxury but a must, to properly insulate your attic space so you can save money on heating bills and prevent your expensive heat from escaping through the roof.
Spray foam insulation is widely recognised as the best form of insulation in achieving an airtight seal in your attic.
As well as not being able to provide an air-tight seal, traditional insulation types such as particle based fibreglass can lead to health issues such as respiratory ailments due to the inhalation of particles.
Since it is applied between the rafters rather than on the floor, you will never have to worry about burst pipes, finding cables under fibre glass, or heat escaping through the loft access hatch.