Question: My friend installed a pellet stove(Harman P61) in her basement.. it has been working great, and I am going to be installing some hot air registers and a cold air return. Each floor of her house is 600 square feet (24 x 25) and I was wondering how many registers and what size would you recommend? I was thinking of something like 4 hot air registers, spaced 10 feet apart on 2 walls (one interior wall, one exterior), with dimensions of about 14 x 4 on those, and then a 10 x 4 cold air return. Is 4 hot ai registers sufficient? So far, the stove has kept the basement at about 78, the first floor at about 68, and barely gotten to the second floor. Of course, with the stove in the basement, the only access has been through the basement door, both hot and cold, and I can’t imagine that being too efficient. Any advice on how many registers to install? Answer: It is impossible to determine exactly how the convective air currents in the home are going to act. For instance, if you cut register directly above the stove, it may pull air down into the basement instead of allowing it out. However, in general it will take the point of least resistance.This means that if you cut a large register near the stove, air should go up it and then come back down the steps.If it were my home I'd start with just one or two near the stove and then determine the air flow....then use this information for others. Also, you may want to use fan-assisted registers or boosters(you can buy them in Home Dept and elsewhere) as these will move much more heat. Small registers without fans are unlikely to do very much good.