The B&W 105 mm KB20 Cooling Color Conversion Glass filter is the correct filter to use when the illumination is provided by 40-150 Watt household incandescent bulbs and the transparencies are to show the subject in its original colors (e.g. technical interior, architectural photographs or reproductions).
It should not, however, be used for moody interior pictures because unlike the KB15 and KB12 filters, the KB20 corrects the light to a neutral balance, eliminating the warmth that we might intuitively expect from bulbs.