you take out your fireplace,We got a fireplace company to do it as we were geting a new insert ,they put morter down on the base where the fireplace was,you let that set for a couple of days so there's a proper base for your esse and all you do then is place the stove into the opening where your open fire was.My esse 350 will not be heating rads so ask about that ,just go into one of the fireplace showrooms,you don't have to buy there but you will get your aswers?the esse will let the smoke go up the chimney like a normal fire does,its no big mystery with the esse,there great and very easy to get fix up.the company cut our insert to the size of the esse cost 500 euro but with the savings via the net it all most worked out the same.hope that helps