We purchased a rumford 42 kit last summer and my Mason installed it. Fantastic!!!!!!!! We get the feeling of a campfire that never blows smoke in your direction. We also installed a Thermolec brand 6 kw make up air u it at the same time. It makes our house a positive pressure plus we get about half to three quarter of an air change per hour. If you burn wood,there are times when for whatever reason you will get a little smoke in the house. The air change seems to clear it out in about 15 minutes. The 42 takes about 180 cfm to operate properly. The extra air keeps the house fresh so you don't even realize there is a fireplace. We leave the make up air unit on 24 hours a day.
Very happy with rumford, great support from the website.