Hi All, I've been lurking & searching for a couple weeks and just can't sort out what I should do. I want to start off with a big THANK YOU for your generosity and shared knowledge/experience. I just pulled out an ancient BK slammer insert that the PO never connected to the flue, smokey, loud, inefficient, warped chamber with a rip connecting it to the room-air chamber. Actually cooled better than it heated and I always worried when we used it. Now have an Enviro Boston 1700, impatiently waiting to go in. I've a 19-teens farmhouse, 2 story (800ft^2 2nd, 1000ft^2 main, unheated basement); the scary, DIY'd, basement oil furnace replaced with a heatpump & central heat/air ducts. It's an external brick chimney; from basement floor to top it's probably 32', fireplace damper to top is 20', no liners, double flues (one to main floor fireplace, other to basement for oil furnace) but their separation stops about a foot below the crown. No cap, just mortar on top of the last tier of bricks (crown?). So chimney top is just an 8x19 opening "rain bucket" that widens a foot below the crown into two 10x10 flues. The fireplace damper is a 12x30 rectangular unit which has an 5x27" opening operated with a faucet handled worm-screw opener offset above the hearth. I just got an flexible SS kit: 25'x6" flex, rain-cap w/18x18 SS flashing attached and the attaching collar and want to install soon. I've talked to a mason friend of ours who'll help and a couple retailers, they all scoffed at the idea of insulating and a block-off. Insulation question: Will I need it? Will it fit? Block-off plate: Pretty sure I'll need it due to no chimney cap or separation from basement flue ie.. open from above and below. I'm thinking I'll put on a DIY'd metal cap and block-off plate to get into this season then improve when weather is better. Can you offer me advice or point to threads that'll help me out? Thanks.