Question-and-Answer Resource for the Building Energy Modeling Community
Get s tarted with the Help page

# AC Sizing for Room with Open Ceiling

Hi Fellas! I have bungalow room with open ceiling. I already simulated that model and got the highest cooling load contributor is roof. What I understand is because the solar radiation to the roof structure and heated the air temperature below. But the question is it is worthy to do AC sizing by making the zone including volume under the roof? The purposes of the AC is just to cool down the bedroom volume, don't care about the air temperature under the roof, by that reason should I just size the bedroom zone by adding air boundary or air wall as a ceiling that separate the bedroom zone and roof zone? I'm afraid it will be undersized. The image below perhaps explain clearer. Thank you.

edit retag close merge delete

Sort by » oldest newest most voted

One way would be to model it as one zone and increase your thermostat to the average of the stratification of air since the zone is considered well mixed. Another way would be to model it as two zones and use a Material:InfraredTransparent. You can find more details about its properties to the Engineering Reference document. In the second solution you should also take into consideration the circulation of air from one zone to another.

more

Thank you for your answer. Well, in the end, we need to take into account the roof zone, both options have uncertainly, do you have any suggestion how to adjust the setpoint temperature which representing average of the stratification of air since the zone is considered well mixed and how to calculate the air circulation from roof zone to bedroom zone?

( 2019-12-02 01:08:22 -0600 )edit

From the most generic solution to the most precise for the scenario of increasing the thermostat you can create a gradient of 2.0 ºC/m according to this or you can create three zones the occupied zone, the stratified zone and the zone that has heat exchange with the ceiling. The stratified zone will be the gradient between the occupied zone and the upper zone while the upper zone will result from the roof surface temperature. Lastly you can do a cfd analysis

( 2019-12-03 06:38:41 -0600 )edit