Plenum spaces between roof and ceiling

[raaid.aldoury]

Hello 

When I add Plenum spaces between the roof and ceiling the roof area is disappeared in calculated results of heating and cooling. I try to add a plenum to a room next to another the results were similar the area of the wall between those two rooms is disappeared as well.  

Thanks 

[Anonymous]

hello,

The following formula shows how heat loss from plenum through floor above being calculated in revit

where,

and the difference between them approximately is zero so q2 is zero which is the heat loss from plenum through floor above, Btu/h which can be translated to loads so the roof load will be zero

[raaid.aldoury]

Thank you so much for your response. 

you are right but what about the heat between the real roof and plenum space it shoud not be zero as far as I know. 

as it is explained in this image 

But to expain my problem better I am going to add those pictures that might help me to do that 

According to those picture the plenum spaces have thickness or hight and it is clear from heating and cooling load, but when I go to analytical surface from details the Air gaps which should have thickness, in fact they do not have. I think this is the main resone that the results of roof do not appear or they are not reasonable. 

I am sorry the message maybe so long.  

I am thankful again for your response. 

[Anonymous]

hello,

I think the reason revit doesn't recognize its Area is that it considers this space a Sliver space so make sure its height exceeds the Sliver Space Tolerance value shown in your first picture.

you need to decrease that value as much as possible to make revit behaves with the plenum space as an ordinary one.

If my answer helps, please Kudo me.

Thanks