Accurately modelling free-running building

[SakuraOno]

Hello,

Advance apologies for a slightly long post, but I've been getting weird results (as in I get same high internal temperature even when I drastically change the construction material, say from lightweight to heavyweight) and just couldn't figure out what I'm doing wrong so want to check with the forum to see if you have any suggestions....

I am modeling a free-running (with no mechanical system whatsoever) building. Therefore my main modes of ventilation is natural ventilation and infiltration. And I'm doing only simulation analysis via ApacheSim (i.e. no CIBSELoad or ASHRAELoad calculations)

I'm wondering if the way I set up in Apache is correct? I would really appreciate any comments and recommendations!

Apache System:
>Cooling tab: natural ventilation
>Air supply tab: external air
__Cooling air supply sizing: 0 (for no sizing)

Building Template Manager - Thermal Condition (I use this template for my Room Data)
>Building regulations tab: Room type = Heated or occupied room
>Room conditions tab: set both Heating and Cooling "Off continuously"
>System tab:
__HVAC system: should I leave this as "none" or use the new system I set up in Apache System (see above) with natural ventilation?
__heating/cooling plant radiant fraction: 0
__simulation heating/cooling capacity: what should I do with these? tick the "unlimited" box?
__system outside air supply: I don't understand what I should put here, if I have only natural ventilation, wouldn't thermodynamics determine how much and how fast outside air goes in and out (based on my settings for the windows and doors in MacroFlo)?
>Air exchange tab: I just add "infiltration" since I'm doing natural ventilation via coupled MacroFlo in ApacheSim.

Do these settings seem right? Is there something else I should be setting?

I would really appreciate any help and pointers!
Thanks so much!
Sakura

[PCully]

That setup sounds ok (I commented on your other post that if you have set up MacroFlo then you shouldn't need an Infiltration air exchange).

If you are a new user of IES VE then just take care that you have actually assigned your new Constructions to the model, if you do then you should see some change but perhaps not as extreme for this kind of building as you expected. Use Vista to investigate the buildings performance so you can see what the main contributors to the building temperatures are and then you can target these to see if they can be improved.

Phil

[SakuraOno]

That setup sounds ok (I commented on your other post that if you have set up MacroFlo then you shouldn't need an Infiltration air exchange).

If you are a new user of IES VE then just take care that you have actually assigned your new Constructions to the model, if you do then you should see some change but perhaps not as extreme for this kind of building as you expected. Use Vista to investigate the buildings performance so you can see what the main contributors to the building temperatures are and then you can target these to see if they can be improved.

Phil

Hi Phil,

thanks very much for the help! But I'm still a bit confused. Would you say I should set up a system in Apache System that uses natural ventilation, or just ignore Apache System altogether and select "None" in the System Tab in the Thermal Conditions Category of Building Management Template? And what should I do about outside supply air, radiant ratio, etc? Can I just ignore all of that? Thank you so much!

Sakura

[PCully]

If you have no HVAC in the building then setting the System to None should give what you need

Phil

[ZapBran]

Use NONE and simply handle the vent with MacroFlo if you have it.

[SakuraOno]

thank you both!