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Why a high tickness wall generates more discomfort?

asked 2017-01-26 04:29:44 -0500

poppo92's avatar

updated 2020-08-24 13:50:23 -0500

I ran 2 simulations of the same building in openstudio, but with 2 different brick external walls (massive wall). These 2 walls have the same thermal properties (I used the same brick material), the only difference is the thickness: the 1st one has a thick of 80 cm, and the 2nd of 10 cm. My question is: how is it possible that during the summer time, it is cooler in the building with the external wall of 10 cm? PS. NO HVAC, just natural ventilation. And I want to repeat : the 2 buildings are exactly the same, only the thickness of the external walls changes. The 10 cm thick-wall has 15800 hours with a operative temp above 88 F, and the 80 cm thick-wall has 21000 hours above 88 F. image description

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answered 2017-01-26 13:19:19 -0500

Ricardo GAllegos's avatar

Do you have internal gains? Heat flow from internal gains going to the outside is retarded by such big thicness, as well as external heat flow does.

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yes I have internal gains. But I guess this doesn't make sense. I can't understand how a 10cm thickness- wall can be better that a 80-thick one during the summer time. I understand that when heat comes in the building it is difficult to get it out, but 80 centimeters should work better like this

poppo92's avatar poppo92  ( 2017-01-26 13:47:44 -0500 )edit

Per @Ricardo GAllegos comment, if the internal loads are big enough that in summer the space temperature gets higher than the outside temperature, then the 80cm wall will do a "better" job at preventing that heat from escaping the envelope to the outside air.

David Goldwasser's avatar David Goldwasser  ( 2017-01-26 14:20:12 -0500 )edit

answered 2020-08-23 20:47:31 -0500

Ruben's avatar

updated 2020-08-23 20:48:46 -0500

I agree with Ricardo Gallegos, also: If both buildings have the same openings, the heat gains through these openings are the same for both, during the night, the construction with 10 cm thick walls dissipates that energy outwards, more quickly than the 80 cm walls. In addition, the interior air volume of both buildings is not the same, due to the fact that the thickness of the walls is plowed into the construction, decreasing the interior volume of the house. That is why the behavor of de building with wall 10 cm thickness is better during the summer, and on the contrary, the construction with 80 cm wall thickness is better during the winter time.

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Are you sure that OpenStudio calculates zone volumes taking into account construction thickness? DesignBuilder can do it, but working directly with Euclid SketchUp plugin and EnergyPlus you have to do this calcs by hand and then put manually the zone volume values. I am really doubtfull about Openstudio for this aspect

Ag's avatar Ag  ( 2020-11-20 15:53:39 -0500 )edit

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Asked: 2017-01-26 04:29:44 -0500

Seen: 328 times

Last updated: Aug 23 '20