I'm having a downdraft issue with my second fireplace, which is located 2 floors below the main fireplace. I currently have a rain cap on both but think I need a top sealing damper. I did some research and it looks possible to retro fit my existing fireplaces. I had a fireplace guy out and he recommend some kind of turbine, which doesn't seem right to me. Am I on the right track or is my fireplace guy correct? I also considered make-up air to reduce the negative pressure, but I have electric heat and cannot find something that will work in a house with no forced air.

Some fireplaces are just more prone to down drafts than others and that turbine won't fix much for you. Can you open a window or outside door just for about 20 seconds while you light your fire and get a fradt started. I roll newspaper into a tube 2' long and light one end, then shove the burning tip up inside the smoke chamber above the damper. See if this help with your issue.

I usually do those things too, except the newspaper thing, I'll give that a shot. My biggest problem is smoking out the downstairs when I have a fire upstairs.

Smoke out the downstairs when you have fire upstairs could be a whole new issue. I thought you just had a difficult time gets the draft started up your chimney. It it drafts up and then gets drawn down the other flue you got trouble. This situation tells me your house is very tight insulation and window wise. When you get a draft started that fireplace may be using the other fireplace for make up air. Individual spring loaded doors may help but you might need to leave a nearby window cracked open until a mason can do an inspection and give a recommendation.

I had a firepalce guy out, but he recommended that turbine which I don't want to put on there. I could ask him to put on the top sealing damper, but I think I will find someone else. A mason is a good idea, I'll try that. I have been keeping a window cracked when I have fires upstairs, but we got snow this week and it is cold, so I can't keep doing that much longer.

You said the 4 letter word, snow. Please don't say that any more, I haven't completely recovered yet. I'd get 2-3 maon to give me a bid.