IES-VE User Forum

Running the CIBSE simulation for a Class 3 building (apartments) I have encountered negative conduction gains during the day when the HVAC (cooling) system is turned off. All rooms have one wall exposed to the corridor (set as an adjacent building at the design temperature in the model) and another wall to the exterior. The exceptions to this are the end rooms which have two walls exposed to the exterior and one to the corridor. At no time does the temperature in the room exceed outdoor temperatures.

My first thought was that the negative conduction gain was due to heat flowing from the rooms into the corridor, however this explanation also does not make sense since the two end rooms (with more exposure to the exterior) have almost identical conduction heat gain characteristics as rooms with only one wall exposed to the exterior.

Firstly does anyone have another explanation for the negative conduction heat gains observed ? And secondly does IES VE actually consider heat flows between adjacent buildings or are partitions between "active" rooms and adjacent buildings considered adiabatic?

Thank you all.

yeh - adjacent are in adiabatic condition.
what else is going on in the apartments? Eq gain, solar?

Thanks for your reply ZapBran, I have gotten an answer elsewhere in this forum actually and others have suggested that the negative conduction gains are a result of the building fabric absorbing the heat. I had heat gains from all sources into the rooms (internal, infiltration, solar and conduction).

Just again with the adiabatic condition of adjacencies, I did another test which makes me question this. Creating a room completely bounded by adjacent rooms without windows, but with infiltration and internal gains, simulations resulted in increased room temperatures when solar was "turned on". Looking at the source of these increased temperatures, the only heat gain which changed between the non-solar case and the solar case was the conduction gain. This seems to indicate that the solar is heating up the adjacent spaces - or is there another explanation?

Thanks

hi iwmech,

I also experience the same result with you, my 11th-story building have negative conduction gain. as you said, conduction gains are a result of the building fabric absorbing the heat. I want to compare the conduction gain of the bare flat roof compare with the green roof (in this case I only apply soil on top of the previous bare flat roof).

Vista result show for both type of the conduction gain result are negative although the green roof show lower conduction gain than the bare roof. but still, both are in negative value. can you please explain for me about this negative value, is it possible happen in the building simulation for negative value? what does it mean of this negative value? does it mean that I have something wrong with my simulation?

I really need some explanation regarding this matter, please help me.

thanks

Answered by Complex Potential in this other thread