This could happen in warm weather if you have a relatively large slab on grade floor. EPlus will always loose room heat to the floor, so by early morning with
no solar gain and radiant heat loss to the sky, your interior temperature could drop a little below exterior ambient if you don’t have a lot of infiltration or fan ventilation. If you look at the ground temperature calculations for floors, they are always
lower than the ambient room. The calculation for floor heat loss is based on smaller buildings and doesn’t seem to properly deal with large slab on grade floors which could function as heat storage mechanisms under certain conditions.
Ned Lyon, P.E. (MA)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
781.907.9009 fax
www.sgh.com
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
On Behalf Of academicryan
Sent: Friday, August 17, 2012 3:48 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Indoor air temperature LOWER than ambient temperature
Hi
I've been doing E+ simulation for over half a year now and feel like I have a good grasp of it. But one thing I can't figure out is why I sometimes get results of indoor temperature being lower than ambient temperature. This often occurs during the early morning,
3am-9am. In reality this is impossible so I'm very confused by this result.
Can someone please explain to me why E+ produces this result?
If requested, I can attach additional information such as .idf or excel graph.
Many thanks,
Ryan
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