Strange problem about the huge surface temperature jump ?

asked 2017-08-24 01:35:09 -0600

Richard

85 ●6

updated 2017-09-06 10:48:49 -0600

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

What is the most possible reason causing a huge outside surface temperature jump? ( over 10[C] jump within 1 hour)

Please see the picture below.
1. In the same time period the inside surface temperature jump is about 1.5[C],but the outside surface temperature jump is over 10[C] .
2.It seems that the problem always happens in outside surface temperature jump.(the inside surface temperature jump is normal)

3.Is it a inherent simulation limit ( or bug) in Energy plus? If so , is there any suggestions for the user to avoid this problem.! image description

answered 2017-08-24 10:43:29 -0600

David Goldwasser

20395 ●94 ●14 http://www.openstudio.net/

updated 2017-08-24 10:51:35 -0600

The outside of a construction is exposed to the exterior weather conditions and sun, you should expect its temperatures to be more dynamic than the inside surface of the construction. The less mass that the outside material of the construction has and the less conductive the adjacent material layer is, the quicker the temperatures of the outside surface will swing.

As an example think of concrete wall with rigid insulation and then a thin sheet of metal on the outside. It's been 50 overnight and now it is 80 and sunny. It isn't going to take long at all for the metal to heat up, but it will take a long time for the concrete to heat up, and even then, if the space is being conditioned, it is going to dampen any effect on the inside surface temperature.

This is really the goal of using insulation or thermal mass, and avoiding thermal bridging, in an envelope. To protect the inside of the building from the exterior conditions. If you are trying to lower the outside surface temperatures you could use surface finish with a high solar reflective index (SRI).