First consider a different permitted position within the room, such as a sheltered area away from draughts, while preserving easy access. A bed with an appropriate insulating base or a compatible washable layer may help separate the sleeping surface from a cold floor. Follow the product's instructions and avoid adding materials that make it unstable or obstruct the entrance. Do not improvise a raised platform with stacked boxes or balance the bed on furniture not intended to hold it. If choosing a purpose-made raised bed, assess the route up and down, usable space and stated capacity. Keep a floor-level alternative available when that suits the cat better. Temperature is only one part of the decision: a warmer position that is noisy or difficult to reach may be less useful than a slightly cooler spot where the cat can rest undisturbed.
Check the lower edge of nearby doors and windows for a draught. Moving the same bed a short distance from that airflow can address the location before you decide a different bed or higher position is necessary.
For product comparisons alongside this advice, see Velvet Nest and Silver Velvet Nest. The details below explain their sizes and uses.
Velvet Nest
Silver Velvet Nest
AeroMat Chill Pad