IES-VE User Forum

I did some 11-story building model for my thesis and run apachesim , I found the electricity consumption, energy consumption, room cooling load and heating load, but when I try to look at external conduction gain and roof conduction gain, the value is all negative. What does it mean?did I do something wrong with my model? is it possible to have negative conduction gain in a building?

Please give me some enlightenment or suggestion regarding this matter. I don't know if i did something wrong with my model or not.

note for my building information:

for Building template manager, i set default for "construction" and "general". I only edit (use provided template from ies-ve) to "thermal" as shown below
room condition


roof project construction


green roof layer


main system


internal gain room type 1


internal gain for room type 2


air exchange


for Vista result analysis
room cooling plant sens load


as for the result for external conduction gain (i just show it in my Ms.excel )
part1
http://imagizer.imageshack.us/v2/640x48 ... 6/d74y.jpg
Part 2
http://imagizer.imageshack.us/v2/640x48 ... 2/odxp.jpg

so the result is negative value, conduction gain is how much heat the building material absorbed, isnt it? so does this negative state that this building cannot absorbed heat from outside and it is a good sign?

oh please tell me if i did something wrong. i really need some explanation about this.

A negative external conduction gain is just a conduction loss and specifically means that the external fabric is absorbing heat from the room. This could be because the ambient temperature is lower than the room temperature or because the mass of the internal layer of the roof construction is heavyweight enough to create a lag cooling effect.

In any event, just seeing a negative external conduction gain is not a cause for concern. If the building is in a cold climate you would actually expect to see negative gains all the time.

CP

Dear CP,

thank you for your reply. really appreciate it I understand now about the negative conduction gain and its role in building thermal analysis.

I will further do my research now.

arumdaum

I understand that there can be negative conduction gain (losses) when it's winter and the inside is warmer. However I would be interested in hearing other opinions about getting negative conduction gains when you're doing CIBSE cooling loads and the inside temperature is lower than the outdoor temperature. I appreciate that fabric absorbs heat gain, but wouldn't it be clearer if the Vista variables can split between this heat absorbed by the fabric and actual external conduction within the CIBSE loads option?