You would need to cut a hole through to the side of the existing flue.You may also want to consider a new full length s.s. liner. I have never done a tie in to the side of an existing flue. You will need a wall thimble for the piping to pass through and a "T" or elbow on the inside of the original flue, then a liner up to the top. Something I read on here all the time, but wonder if folks think about.... Many state that they don't want a fan or blower, yet many free standing stove owners do have & use them, and enjoy the benefits they bring. Some of the same folks and others state that they are better off during a power outage with a freestander &/or no fan/blower, as it will still heat their home. I am lucky I guess, because my insert will heat my place fine during a power failure, and I have cooked on it. Not a huge roast, but I can cook smaller things on it, and some larger inside. Some of these same folks use box, door, pedestal fans etc to circulate cooler air towards the stove. I highly doubt these folks have any advantage with their freestander, over me with my insert, as I will still get a very good convective loops throughout the open layout of my home, compared to some other whom need to use fans to circulate air to and from other rooms. The bottom line, is research your options, which you are doing, pick minimal 3 stoves/inserts whatever, that fit your wants and needs the best. NONE will fit the list completely, but some will fill more slots than others do. Then narrow it down from the 3 favorites to 1. House layout will dictate the most, or what you need, and how well it will or won't heat a larger area or the home. If fans are a must for circulating heat throughout the house, a freestander might not heat much better than an insert during a power failure or not, and both may heat the hell out of the room they are in, with less traveling outward with no help. With the cathedral ceiling, loft and convection loop I get here, I don't need a fan on the insert, or the ceiling fan, but I like to use them to circulate even more air and even the temps out more. If you house is a bunch of boxed off rooms, you will have a challenge heating more of the house.