dee man

There is a missing part to these calculations. Yes the rocket stove will produce heat efficiently but it is still going to go up to the ceiling. The important thing is the heat at the floor level because having cold feet is the worst and people are often sitting down indoors. Warmth  at the ceiling level is no good. Such a stove is going to pull a pile of cold air into the house. Fresh air is good but chilling the floor isn't. Heating this intake air is the trick to getting rid of the cold air at floor level. You could put another pipe to bring the intake air thru the bench. You could also use these principles to bring it thru a solar collector and use thermal mass of the ground to take the chill out first. I did something like this and it worked pretty well. Having a fire during the warm part of the day would increase efficiency since your intake air is warmer at that time where as people usually burn a fire when it is cold at night. You could still do it but it is less efficient. With solar preheating the air  you could burn a fire during the day really efficiently but it might not be necessary. The steady flow of warmed air it produces could have already heated the house enough during the autumn that it can hold up over the worst of the winter and recover quick in the spring. It was a great set up. The intake air would tick upwards in temperature as soon as it started getting light and then the sun would hit the collector. With the strain taken off the pipe the thermal mass can recover temperature to the pipe and start charging back up. I think it is a better use of time to set something like this up. If you have a designated intake it is going to raise the pressure inside and less air is going to leak in thru colder ways. Air quality is the main thing to take care of.  A metal pipe inside a mass collector seems like it would be good air quality. Maybe better than the usual air vents eg. plastic pipes. You could use a normal stove and it would still work much better with the preheated intake.

I'd explore other options if your working with a standard house. It could be opening windows over night would do the job or shading out some patio area that heats the ground near the house. Find where the heat is coming from. If you have some white curtains to shut during the day it will reflect the light out. Dark curtains or any light coming in can heat a house a lot the moment it is warm enough outside for the glass to be ineffective at draining the heat.  You could paint the roof white but that will make it colder in winter. Insulating the roof and possibly walls would probably be better year round. For cooling tubes maybe using water and connecting it to existing radiators would be better.  You would just need a small pump or if there is some higher ground on the northside of the house you might not even need that. The problem is that the cool air  sinks so it could just pull warm air down the chimney into the house and flow the wrong way. The solar chimney might be good enough to cool it down without any additional cooling tubes if the problem is just lack of suction. I am more experienced with the heating tubes where the condensation issue is perhaps less. However it can cause condensation inside if the walls are cold. It is effective tho and you can put it thru a solar panel after to push it into the house and increase ventilation. My idea is to have quite a big pipe so lots of preheated ventilation can be provided. This keeps the house pressurised and cold air won't leak in so much elsewhere. If you run a fire then instead of cold air coming in everywhere to feed it the big vent pipe can provide it and you get a better gain and hopefully keeps it dry. My concern with it is more plastic smell from the pipes. If there is enough ventilation then it should reduce condensation problem. If you wanted cooled air then probably best to look if there is a prevailing wind direction in these hot periods that could be used to push it in thru the pipe. Otherwise it might flow the wrong way and bring air down the chimney (which could already be happening and causing the issue).