Dear Chunxiang Zhou ,

You can apply simple energy balance considering room as a control volume to get an approximate result.

Overall heat flux entering the control volume (room) + energy Source (bulb, heater, fan, humans etc) = rate of energy accumulation inside the room.

In mathematical form

K*A*delT + energy source. = m*C*dT/dt

You want to find it Experimentally or computationally....?

You can find your answer in any heat transfer book. You need to know that there is two ways to estimate the temperature using stationary or time dependent heat transfer equations. The first one is easy to calculate and for the second one, you need to use a numerical technique in order to find the temperature (use Comsol Multiphysics or simulink in Matlab).

Good topic

Understanding the essence of your question, you want to find the temperature assuming some standard conditions for a standard building. Your question is incorrect and that’s why.

Heat gets into the task and is transferred to the walls using heat conduction, radiation and convection. If you do not have sufficiently complete information about the conditions under which heat transfer, heat dissipation and heat transfer by radiation between walls and the environment occur, and also don’t know anything about heat sources inside rooms and the building as a whole, then you can hardly understand what will happen inside the building. You would have a chance to solve the stationary problem if the walls, floor and ceilings in the rooms were insulated. But this is not observed! Wind blows on the outer surfaces of the building, solar radiation falls, they are attacked by frost in winter, rain in summer, and there is always convection inside the premises due to open doors, heating and ventilation, and often because of open windows. And these are just some of the factors of nature. And there are also internal ones, inside rooms and corridors. Nevertheless, if you still want to know at least some accuracy about the temperature of the walls of the rooms, you will have to decide which initial and boundary conditions are most important for solving the heat conduction problem of a multi-room building and try to solve the problem, for example, in ANSYS or in another program. But even after receiving a solution, you must remember that you received only an assessment that will bring you closer to the answer. Therefore, it is best to try to make a full-fledged 3D model, gradually increasing the degree of coverage of the model with useful boundary conditions, than to try to find an answer using simple formulas with an unknown calculation error of your complex task.

I accept that the heat transfer process of multi-room is complex. I want to consider the wall heat transfer in order to get a solution closer to the real value with more details than the insulation room.@Alexey Romanov

If there would have been only sensible heat associated with multi-rooms, then we could have gone with only conduction & convection models. But Latent heat associated with infiltration air and ventilation standards keep a limitation of calculation using conduction models.If this would have been so easy, then there would not be Airconditioning ,ventilation standard engineering. Try good luck

But will not get approximate in 10% error.

You can use simple energy balance

Is the building air conditioned or not?

In heating/cooling loads calculations for buildings, there are standards (ASHRAE handbooks) that specify the indoor temperature for different types of occupancy (office, meeting room, class room, seating, etc.). Based on the given room temperature (from standards) and based on the outside temperature in your climate zone, and wall material thermal conductivity, thickness and area, you can calculate the heating/cooling load in winter and summer.

If your building is not air conditioned, then you can calculate the room temperature using thermal resistance network through the outside walls only because all the inside walls will be at the same temperature.