I am looking for a heat loss calculator that works. I have downloaded two so far, and still have no calculation. The one didn't work at all, you couldn't put in any measurements. So I downloaded a different one, it seemed to work. I went around and got all the different measurements for all the room. Everything seemed to be working till I printed it out. I have two bedrooms the same, but the heat loss is over a 1000 btu's difference between the two. And I have tried reentering the information and it still comes out the same.