ecoeficiente's profile - activity

Hi, I have observed some unexpected results when simulating a case of windows with and without frame/dividers.

I've chosen a glazing with an U-value of 3 and frame/dividers with a conductance of 9.5W/m²K. The thermal properties of the frame/dividers are worse than the glass but what I have found is that the heat loss in the case of the window without frames is higher than the heat loss of the window with frames.

And the heating load is higher too, with the extra solar gain not being enough to compensate the extra loss from the windows. I haven't been able to find the explanation for this.

If anyone wants to try, you can use this simple model: https://cloud.ecoeficiente.es/d5un21wA

It is in v22.2 and v9.4. Use Chicago weather. It has two equal zones with one window (one with frames and the other without).

Thanks!

I have finally sent an issue to E+ repository: https://github.com/NREL/EnergyPlus/issues/9714

Thanks Denis for your research and great explanation. I also did come to the issues you you link and even tried to find

Thanks Denis. My FD input may be not defining a frame in all its extension. However, according to the Engineering Ref an

Thanks Denis. I also tested it with the layer-by-layer glazing (not the simple), with similar results. With other clima

Frame and dividers unexpected behavior Hi, I have observed some unexpected results when simulating a case of windows wit

DesignBuilder can import a whole 3D model from a gbxml file. That model can be directly exported to idf. Dxf import is o

Shouldn't EnergyPlus VRF example files have a normalized curve? The default VRFTUCoolCapFT curve in is the one generatin

You cannot do it in just one step with the inclined walls option, but there are multiple ways to get to your desired des

I have never seen this problem in Results Viewer. Bear in mind that some values are translated from J to kWh depending o

Yes, that is possible. You will have to set up correctly (that is the tricky part) the diffusing properties. See at the

Yes, that's right.

Yes, it looks good to me.

It is not exactly as you have described (not sure what you mean by "how much sky can be seen") but you can find the frac

Do you actually check this when modelling for LEED? Ashrae 90.1-2007 - G3.1.1 Exception b. Hello all, I am working in a

Yes, EnergyPlus Airflow Network (Natural Ventilation) does not affect the thermal properties of operated windows. An app

You have to redraw them unless they are parametric. In last version (v5) you can scale them too (you could do this for m

My impression is that detailed technical aspects like this are totally ignored by many modelers and also by most USGBC reviewers. Quite often I wonder why I take so much effort doing things as correct as possible when I am the only one aware of it... At least, deepest knowledge allows me to take advantage of the lack of specification to get better results without breaking any Ashrae's modelling rule.

Agree with this approach. I implemented IPLV formulas in Excel so that I could reach the desired IPLV minimizing the variation in a default cuadratic curve coefficients (using Solver). I'd have to polish it to be shareable though.

Hello, for a DOAS system I've found a simple alternative (I think). You can use a SetpointManager:OutdoorAirReset with 55F at 55F or below and 75F with 75F or above. In between, it is linearly interpolated so you set the same setpoint as outdoor air, getting a deadband. You use this SM at the outlet of the AHU and use 2 SetpointManager:MixedAir to reference it from the cooling, heating and mixed air nodes.

If I am not mistaken on what your're asking, it was in my first comment. The construction is "Double clear with pleated shade".

Yes, Window 7.4, and Energyplus 8.4.

I am getting the same error. With a default Window 7 glazing (Double clear with pleated shade) and a very simple idf model. Have you found a solution?

Thanks Archmage, I agree with your second paragraph but I am not so sure about the first. I think that the flat assumption can easily lead to undersized systems and I would consider internal gain and even setpoint schedules at least in cooling design, which also assumes temperature and radiation variations along the day.

When using energy simulation (such as EnergyPlus) for load calculation, which averaging window do you choose to calculate the peak load that will determine the size of your HVAC systems?

I am specially concerned with those cases where you have thermostat schedules with night setup or setback for the design day and you'll get much higher peak values the shortest the time you average the loads. Do you design with different averaging times depending on the project? That is, you choose that one type of project can admit one hour to reach the setpoint while other may need a shorter period?

Which approach do you use? Please, share your thoughts.

According to Energyplus Engineering Reference (http://bigladdersoftware.com/epx/docs...):

Note that when the outside environment indicates that it is raining, the exterior surfaces (exposed to wind) are assumed to be wet. The convection coefficient is set to a very high number (1000) and the outside temperature used for the surface will be the wet-bulb temperature. (If you choose to report this variable, you will see 1000 as its value.)

It seems that you have rain data included in your weather file.

http://nrel.github.io/EnergyPlus/Inpu...

I recommend you to read the EMS Application Guide and take a look at the example files with EMS (or the sample programs in the Guide).

Yes, it is possible. See https://bigladdersoftware.com/epx/doc... If you generate the edd file, you will find an actuator of the kind:

EnergyManagementSystem:Actuator Available,Environment,Weather Data,Wind Speed,[m/s]

Bear in mind that environment variables are interpolated so output variable do not match epw hourly value. Could that be the reason? Take a look at http://nrel.github.io/EnergyPlus/Inpu...

Thanks LyleK. The problem is that I'd like OtherEquipment to reproduce outside air load (variable during the day). I know I could build a schedule with such variation and apply only to Design Days but I wanted something more reusable (without the need to recalculate the schedule if external or internal Design Conditions changed). The reason I cannot do it with ZoneVentilation:DesignFlowRate is because I am using Airflow Network simulation. And I need it is because Zone sizing does not account for outdoor air brought by a mechanical distribution system. I have finally achieved that with EMS.

The answer is "depending on the EMS Calling Point you use".

I was using as calling point Inside HVAC System Iteration Loop. It gave me more precise results during simulation than Begin Timestep Before Predictor.

However, it seems that ideal load calculation during sizing is not performed as an HVAC System, so the calling point Inside HVAC System Iteration Loop is not valid for sizing. I have changed to Begin Timestep Before Predictor and now the program is working for Sizing too.

Hope this findings are useful to the rest of you.

Thanks, but I am afraid it is not what I mean. I know you can change sizing results after the sizing with EMS but I need to integrate a variable thermal load during the sizing calculation. I have written some EMS code that mimics outdoor air thermal load using 2 OtherEquipment objects (one for sensible and the other for latent load). I want to add this load during sizing. It is the only way I have come to introduce outdoor air load in sizing calculations when you are using AirFlowNetwork but want a simpler outdoor air load calculation for sizing.

I am trying to add a load only during sizing calculations through EMS and although I find that something is happening during summer and winter designdays, the sizing results are exactly the same with the EMS load than without it. EMS code is working well during simulation but for sizing it seems not to affect the results despite edd file shows these lines:

PROGRAM CODE, During Warmup, Occurrence info=SUMMER DESIGN DAY IN MADRID JUL, 07/15 00:00 - 00:10 PROGRAM CODE, During Warmup, Occurrence info=SUMMER DESIGN DAY IN MIJAS JUL, 07/15 23:50 - 24:00

And the same for WINTER DESIGN DAY.

I don't understand why those lines seem to be only executed for 00:00 - 00:10 and 23:50 - 24:00 periods. Is that the expected behaviour? I think it would be better if EMS code could be taken into account during sizing calculations.

E+ with Minimal Shadowing option does not account for building self-shading. I don't think it should be very difficult to implement external shadowing to the code to cover LEED provision.

Yes, the problem is for the baseline (but affects proposed, because if you cannot have it in baseline, you have to remove it also from proposed). They forbid self-shading only for baseline. It is said in 90.1 Appendix G, table 3.1#5: "The builiding shall be modeled so that it does not shade itself".

In LEED Energy modelling for EA Credits, it is allowed (not compulsory) to include shading by adjacent structures. This can have an important effect on the results for the proposed building. However, in E+ there is no option to include only the shadowing by adjacent structures for the baseline case. If you remove all external shadowing with MinimalShadowing option, you don't account for adjacent structures. If you choose any other shadowing option, although you may remove all shadowing surfaces from the model, self-shading is always considered, which is not allowed by LEED.

Is there any solution I am not taking into account? The only option I see is to remove shading by adjacent structures, which can affect quite negatively the results from the proposed design.

You can use Airflow Network with Ideal Load Systems but you have to bear in mind that Airflow Network calculation will not take into account the effect in the pressure/flow that a real system would have if working simultaneously with natural ventilation. If you have no problem with that, you can go ahead.

For the natural ventilation not being active when the heating is on you have several options:

• The most obvious is coordinating heating and ventilation setpoints. It is quite strange that you get a higher temperature than the heating setpoint (24ºC) in a winter night (it could happen during the day, most of the times due to solar radiation). You can play with ventilation setpoint schedule but I think that the problem can be elsewhere (in the heating setpoint).
• You can play with modulation according to inside-outside temperature difference to reduce ventilation if outside temperature is too low, which may partially solve your problem.
• Finally you can use EMS, though it may be a bit scaring if you have not played with it earlier.

I am not sure which option is best because introducing those subsurfaces without thermal mass only represents the steady state behaviour of the bridge. However, degrading thermal insulation for the whole construction is also including thermal capacitance for the bridge (which will not be the same as the base construction but certainly it will not be zero either). Unfortunately there is not a totally suitable method to represent thermal briges in whole building dynamic simulation so we have to live with this sort of approximations.