RE: [EnergyPlus_Support] Decrease in Cooling after Increasing WWR

Hi,

Can anyone suggest pointers that could point me to the problem? I have a decrease in cooling load after including a window ot 50% WWR.

The quick summary of the exterior wall and window constructions are:

U-Factor [W/m2-K] SHGC

Exterior Wall 0.459

Exterior Window 2.131 0.125

Is there anything that I could have missed out?

Thanks and Best Regards,

Poh Khai

To: energyplus_support@xxxxxxxxxxxxxxx
From: ng_khai@xxxxxxxxxxx
Date: Fri, 17 Aug 2012 00:17:12 +0800
Subject: RE: [EnergyPlus_Support] Decrease in Cooling after Increasing WWR

Hi

I have checked for the ZONE WINDOW HEAT GAIN ENERGY and ZONE WINDOW HEAT LOSS ENERGY...

in all four orientations, the heat gains are more than the heat loss energy in an annual simulation.

my climate is in singapore which is a tropical region near the equator with high solar radiation on the east/west orientations and slightly lower solar radiation (due to diffuse radiation as the cloud cover in Singapore is very high).

Is there anything i should be aware of?

Thanks all!

Regards,
Poh Khai

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jcrossett@xxxxxxxxxxxxxxx
Date: Thu, 16 Aug 2012 01:53:00 -0700
Subject: Re: [EnergyPlus_Support] Decrease in Cooling after Increasing WWR

Here is an idea- are your losses higher than your gains?

What are your window orientations? In my climate zone 4c north windows would let much more heat out than they would let in.

Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions

120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com

On Thu, Aug 16, 2012 at 1:44 AM, Ng Poh Khai <ng_khai@xxxxxxxxxxx> wrote:

Hi Jeremiah,

Thanks for your reply... I have checked the solar gains and the ZONE TRANSMITTED SOLAR ENERGY is higher with larger WWRs... However, the cooling load is lower!!! I am using the idealloads model... Is there anything that I could have missed out?

Thanks and Best Regards,
Poh Khai

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jcrossett@xxxxxxxxxxxxxxx
Date: Thu, 16 Aug 2012 01:28:57 -0700
Subject: Re: [EnergyPlus_Support] Decrease in Cooling after Increasing WWR

I was recently schooled on this subject- due to a comment I made on the eQuest forums- the modeler was having a similar issue to yours and the chiller objects in Energy Plus are the same so the problem may also be: Check your part load chiller curve- it may be possible that the curve causes your system to run more efficiently with the higher load. Another way to check your model would be to check your solar gains and make sure they are higher with larger WWR.

Jeremiah D. Crossett  | Senior Analyst  | Phase Change Energy Solutions
120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com



On Thu, Aug 16, 2012 at 1:09 AM, Ng Poh Khai <ng_khai@xxxxxxxxxxx> wrote:

Dear All,

I have a problem here. I compared the cooling loads of a building with 0%WWR, 50%WWR and 100%WWR and got the results that the cooling load decreases sa the WWR increase. I am located in a tropical country and this should actually not happen. I have checked the constructions but it does not seem that anything is wrong.

The construction details are:

External Wall (default construction from sketchup):

! <Construction>,Construction Name,#Layers,#CTFs,Time Step {hours},ThermalConductance {w/m2-K},OuterThermalAbsorptance,InnerThermalAbsorptance,OuterSolarAbsorptance,InnerSolarAbsorptance,Roughness
! <Material>,Material Name,Thickness {m},Conductivity {w/m-K},Density {kg/m3},Specific Heat {J/kg-K},ThermalResistance {m2-K/w}
! <Material:Air>,Material Name,ThermalResistance {m2-K/w}
Construction,EXTERIOR WALL,   5, 16,   0.167,     0.4586    ,   0.900,   0.900,   0.700,   0.700,MediumRough
Material,M01 100MM BRICK, 0.1016,         0.890,   1920.000,      790.000, 0.1142
Material,M15 200MM HEAVYWEIGHT CONCRETE, 0.2032,         1.950,   2240.000,      900.000, 0.1042
Material,I02 50MM INSULATION BOARD, 0.0508,         0.030,     43.000,     1210.000,   1.693
Material:Air,F04 WALL AIR SPACE RESISTANCE, 0.1500
Material,G01A 19MM GYPSUM BOARD, 0.0190,         0.160,    800.000,     1090.000, 0.1187

Window Glazing:

! <WindowConstruction>,Construction Name,#Layers,Roughness,Conductance {W/m2-K},SHGC,Solar Transmittance at Normal Incidence,Visible Transmittance at Normal Incidence
! <WindowMaterial:Glazing>, Material Name, Optical Data Type, Spectral Data Set Name, Thickness {m}, Solar Transmittance,Front Solar Reflectance, Back Solar Reflectance, Visible Transmittance, Front Visible Reflectance,Back Visible Reflectance,Infrared Transmittance, Front Thermal Emissivity, Back Thermal Emissivity,Conductivity {W/m-K},Dirt Factor,Solar Diffusing
! <WindowMaterial:Gas>,Material Name,GasType,Thickness {m}
WindowConstruction,EXTERIOR WINDOW,   1,VerySmooth,   2.141,   0.125,   0.051,   0.074
WindowMaterial:Glazing,SPEAR TECHONOLOGY,SpectralAverage,, 0.03491, 0.05048, 0.77453, 0.77453, 0.07340, 0.21158, 0.37284,

Can anyone help me with this? I have been stuck with this for a week now... I do not mind sending my idf files over if someone is able to take a quick look for me.

Any help or advice will be kindly appreciated.

Best Regards,
Poh Khai

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