This spreadsheet tables each room of the property, in each room each external surface is listed including surface area. Further to the right is the U value of each surface and the calculation sheet behind that showing the make up of the surface. DRG refers to specific area on the correct sketch to aid understanding. The column UNIQUE SHEET refers to one of the 40 or so special surface makeup calculations found elsewhere on this website.
For each external area of the room the AREA and the U value are multiplied together and are summed to the top of the column in cell Q9 which is repeated in Q3. In cell R3 the Delta T (red number) is multiplied by the sum in Q3 to indicate the heat loss S3, the ventilation is also taken into account N4 (red number) volume of property O4 to achieve S4. S3 and S4 are summed kW in U3.
In this way by selecting all relevant rooms by a filter to 2 in column C, the heat loss for the considered portion of the property under the selected conditions results in cell U3 HEAT LOSS.