Modelling area space with Glass walls in HAP

[woshialvin]

I have modeled an area space with glass walls with a southern exposure in Carrier HAP, but whenever I run the hourly load reports, it says that I still require cooling even during at night in the middle of the winter (I understand if it is during the day, since that area space does get hot due to the solar gains as a result of the walls being completely glass). I understand that this is true to some extent due to to the area space acting as a big thermal heat sink (essentially accepting the solar gains during the day and re-radiating it back to the space during the hours when the sun has set). However, I find it hard to believe that the space still requires cooling in the late hours when the space is being cooled to maintain setpoint during the day. Is there a particular option in HAP I may have missed when creating the model? (I also tried reducing the building weight and it improved the results a bit but does not completely eliminate night time cooling).

 

[EnergyProfessional]

i don't know HAP. but it may try to actively cool down to setback temp, instead of just drifting down? i assume you talk about winter, not summer? In summer it could cool at night if your setback cooling temp is 80°F, and you have internal load, or it is above 80°F outside.

Obviously calling HAP support could help.

 

[woshialvin]

Yes, it is during the winter. Essentially, the area space gets too hot due to the solar gains during the day (walls are made of glass). But my model of the area space shows that I still have to provide cooling during the night time when it should be heating since the sun has already set. The summer data is fine and what you would expect. It is also worth noting that there are no internal loads in this space except lights, which are off during night time.

The only explanation I have with this is the thermal mass of the building causing the heat to re-radiate during night time, but it shoudn't be this severe that it causes it to need cooling at around 11PM to 4AM in the morning. I have been told that the actual space cools back down during night time so I know there is something wrong with this model. I have double checked my parameters and still can't find the reason. Unless it has to do with the alrgorithm that HAP calculates its solar gain loads.

 

[EnergyProfessional]

not sure what options HAP has, did you use heat balance, or RTS?

Assuming the adjacent spaces have same setpoints, they shouldn't radiant heat back. and if that space in questions keeps at setpoint during day, it itself shouldn't have heat stored in the structure. the glass should make it cool down rather quickly. You probably already checked all the U-values, infiltration etc. so that you correctly simulate heat losses at night.

i find it hard to believe HAP is wrong, in most cases the problem is in front of the PC Call them, sure some mundane error you made. I use Trace and find odd things in my models all the time.

 

[Drazen]

have you looked at hourly report? are night-time envelope figures negative?

 

[Light9]

I would love if you can upload the reports to take a look at it.

 

[cry22]

usually, such things are input problems

May be you have put the total Number of people and you used people/SF as a unit, or total Watts and then you picked watts/Sf as a unit.
That kind of things you should look into.

 

[EnergyProfessional]

assuming HAP has the subscription model like Trace, call HAP support and they also can look at your model.

On occasion I forgot some mundane detail and had Trace support help me. It is really hard for us without seeing the file to tell what you may have entered wrong.

 

[jostorres]

Verify the design temperatures, may be that is the problem.