955, for your application I'd go with flue cap damper. It has a cable that runs down the flue so you can open or close it from inside the house.
Here's one:
Chimney Damper Source...large selection of chimney dampers & downdraft solutions...lyemance & lock top chimney flue damper.
My application will be more difficult. I have searched and so far not found what I need, so most likely I will have to build them. I am thinking of welding up a box with a steel shutter in it that has flue collars on each side. If I am not using the Soapstone it is also fairly easy to make plugs to close off the primary cold air intake and secondary intake. It's the stove or fireplace upstairs that will be more of a challenge.
I haven't decided on which yet...stove or fireplace. The wife wants a fireplace, me, I'm a stove guy. However, I was at a buddies house last Christmas and his Dad built their house in the late 50's. It had a gigantic fireplace that heated the house like nothing I had ever seen. It was a double wall steel 4' wide and 3' tall, with the space being 10" all the way around, cold air intakes down low below the fire pit and hot air exit vents up top by the mantle. It worked by convection and it was by far the most impressive fireplace I have ever seen as far as heat output. Most fireplaces require you to sit inside of them if you want to get warm. I'm not kidding, it was below freezing outside, the house was cold when we arrived. His brother had already stacked kindling and wood on the grate. We lit the thing off and in 5 min I was pushing my chair back, 5 more min and I was peeling off layers of clothing and pushing the chair back further. I googled for hours and the closest thing to that design was the old old Heatalator, but I think his was custom built. Unfortunately his Dad is no longer around to tell me the story on the design.
Next time I am down there I am taking measurements and pictures....I sense another welding project in my future:thumbsup:
Mo, that is a good idea, even a 1/2" double foil under the foam would help. Reflective R value is elusive and I think underestimated. Last time I checked the 1/2" was around $8 a sheet. If I stagger the seams I can eliminate taping.....hmmmm.
Hook, I have read many accounts similar to yours which is why I want to give it a whirl.