Hi,
1. Unlike conventional Air based system, Radiant system is quite tricky to model and investigate. In my opinion, the sensible capacity is very important factor to consider in while studying Low Energy System performance. As per a research document from Berkeley it says that the slab integrated system could meet only 'sensible cooling capacity on the order of 24 Btu/hr-ft2
(~7 W/ft2
or 77 W/m2
)Â
active surface, not including associated ventilation systems or strategies'. So you need to look into the total heat load (sensible+Latent) for the space where Radiant system is being implemented. If the latent load is high enough then you might need to incorporate DOAS system in your design to handle Outdoor Load which brings most part of the latent load in the building apart from people and infiltration. Refer following link to explore more.
2. Condensation control for Radiant system is something must looked into as mentioned by Mr. Jean. Default setting in E+ is when any condensation happens the Active surface will be turned off which might be one of the issue causing high zone temp in the model.Â
3. Also check zone air temp, operative temp and Radiant temp to understand how radiant system is responding to the loads. In typical fully functional radiant system following behavior in air temperature could be realized.Â
Hope this helps!!