Unless I’m quite confused, the “temperature rise” is the difference between the intake and outlet temperatures. Take your house at 10 below and turn on the furnace. Intake air is 10 below, outlet temp is 50. After a while the intake air begins to rise in temperature and so does the outlet temp. A few hours later the ambient air temperature inside stabilizes at a nice 70 and the thermostat shuts down.
The only way you would have a stable 50 at the conditions you mention is if you were stupid enough to draw all your intake air directly from the outside.
Your results may vary depending on size and insulation of structure and size of furnace.
See post #69.
In this case, temperature rise is the temperature that the heating unit is able to raise the temperature of the house above the outside air temperature, taking into account (primarily) the amount of heat that is lost due to infiltration, such as window, doors, walls, and ceiling heat loss. That varies by the number of windows, insulation thickness, types of doors, etc. Each of these items must be individually accounted for in order to determine the total amount of heat loss for each floor. It tries to include all the things that allow the heat to escape to the outside. Naturally those are invisible to the naked eye, but are calculated from manufactures specs of all the houses components.
The only outside air that’s purposely introduced to the house is the make-up air for the furnace and water heaters.
In concept, my only objection is the heavy handed way this is being administered. There is very little ‘wiggle room’, and If I hadn’t come up with the two stage furnace idea, and if the temperature hadn’t been what was on that very day, and if I hadn’t had a guy who was sympathetic to all that, someone would be buying a cold house.
Somewhere, someone is doing just that.