Ceilings that are Lofted or in Cathedral form are usually placed in between the rafters, like those in the picture above.  After the insulation usually gypsum boards covers the rafters.

A loft has many of the qualities of a cathedral ceilings. This means that part or all of the ceiling section will directly follow the roof’s slope. These are very difficult to insulate properly. This is because the insulations thickness is limited to t the width of the rafters.

Adding to the problem, if recessed lights are installed, the body or “can of each of the lights will create a gap in the insulation, allowing either heat or cold to escape or enter in the extreme months.

Areas around recessed lights should be sealed to stop loss of energy

If the area of the loft ceiling space cannot be accessed from above, it will be hard (even impossible) to be able to install more insulation in this type of ceiling. What can be done is to seal around the fixtures edges or place interior fittings that are airtight to seal them.  These fitting, however are not available in all sizes or for all makes and models of recessed fixtures.

Loft Ceiling and New Construction Insulation Options

Options vary for loft ceilings when new construction is involved. The intelligent choice would be to use surface-mount light fixtures in the ceiling to eliminate gaps in insulation and stop energy loss.

If fiberglass batts have been installed between the rafters, think about changing the R-value with a layer of rigid foam insulation placed just underneath the rafter, before finishing the ceiling. Having an uninterrupted layer of rigid foam insulation will make a large impact in energy efficiency, R-value and loss or air.