Q:

Temperature Sensing and board heat

My goal is to have an accurate measurement of the current temperature in my room, which I will use for a thermostat. 
The problem I have is I bought this breakout board and soldered it to about 5cm long cables and I get too high temperature values (and not only offset, but in a range of about 1.5 degrees Celsius and nonlinear over the range I saw). 
Using a laser thermometer I can see that the board is at 22 degC, while the room is at 20 degC. As a host processor I use a Raspberry Pi zero w, which I put a box on top, so it wouldn't distract the measurement. 
Is there any reason, why I can't measure the actual room temperature?  How is this done in 5$ cheap thermo-stations?  They don't have to use extremely long cables or such an extreme isolation, do they? 
So the setup looks as follows: I have used a laser thermometer, a cheap thermometer station and the sensor, all measuring right next to each other.  If i measure the floor I get good understanding of laser+station, but the sensor breakout board is 1 degC higher than what the other two devices measure. 

A:

It turns out that with a cable length of about 20cm I am able to get believable results.  And I am able to confirm these measurements with a weather station right besides the sensor.  It is to 0.05 degC exactly the same.  This is what initially I expected these measurements to be. 
I will leave this question here for reference for anyone wondering what a huge influence the circuit-board heat can have even with moderately long cables of about 7cm.