[TRNSYS-users] Radiant floor in basement - temperature too low

[Marie-Claude Hamelin]

Hi all,
I'm am having an issue with a radiant floor (active layer) in the 
basement of a house I have modelled. When adding a radiant floor in the 
basement, the temperature in this zone drops during the summer. I get 
floor temperatures from 17.5 to 20.5 degrees, and air temperatures as 
low as 17.5 degrees. The same basement without radiant floor (but same 
materials and insulation for the floor) yields summer air temperatures 
that do not go below 20 degrees.
I have tried numerous things: using an internal calculation for 
convection coefficient as well as a user-defined one, segmenting the 
active layer to lower the minimal flow rate (and using that minimal flow 
rate in the constant part of my flow rate equation), playing with the 
inlet temperature, changing the timebase to match my time step (0.5 hr). 
My floor is 9.8 cm of concrete with 5 cm of polyurethane underneath it 
(0.8 mm of concrete below the active layer and 9 cm above).
Does anybody have an idea of why my radiant floor seems to loose so much 
if the room's heat to the ground?
Thank you very much for your help,

Marie-Claude Hamelin
Concordia University