Hello Just found this sheet on the DT conversion kit. Looks like a great way of drawing in pre-heated burn air thru a 6 or 8 inch metal chimney Or a masonary chimney! Does adding the flashing at the top of the masonary chimney keep the heat in for the Intake Air? See red arrows in pic2 Looks like a minimum 6x6 inch chimney is needed. IMPORTANT: The existing masonry flue opening needs to have an area of at least 35-square inches to insure proper intake/exhaust flow. I have an 8x8 block chimney http://www.dynamitebuys.com/store/pdf/Selkirk-Direct-Temp-Installation-Supplement-Conversion.pdf Two different types of direct vent conversion systems are described here. One is through an existing factory built metal chimney going through the ceiling. The other is through the wall of an existing masonry chimney. Follow the appropriate directions for your situation. 4DT-CCK (Factory-Built Chimney Conversion Kit) -- for metal chimneys 4DT-MCK (Masonry Chimney Conversion Kit) -- for block or masonary chimneys Pic1 & 2 - Conversion Kit used for Adapter for Masonary Chimney Pic3 - Conversion Kit used for Metal Chimney click on pics to enlarge.