# Re: [EnergyPlus_Support] Re: wall and roof color

```EnergyPlus opaque materials require three inputs related to radiant exchange:

Absorptance:Thermal
Absorptance:Solar
Absorptance:Visible

Thermal applies to the infrared wavelengths for radiant heat transfer.  Visible
is applied to daylighting and the visible light fraction from LIGHTS.  Solar
refers to the full solar spectrum including the visible and thermal
wavelengths.  The solar absorptance is applied to incident solar radiation.

Values for these properties are available from various handbooks.  Some sources
with data for various colored roof materials are cited below.  Some handbooks
will state  emittance or reflectance data rather than absorptance.  To convert
to absorptance, use the following rules.  Emittance=Absorptance for a given
wavelength region (solar, visible, or thermal).
Absorptance+Reflectance+Transmittance=1.0.  For opaque materials, transmittance
is zero, so Absorptance = 1.0 - Reflectance.

Data sources for roof material absorptance properties:

LBL site with roofing data - http://eetd.lbl.gov/CoolRoofs/

The Florida Solar Energy Center (FSEC) has published several reports regarding
roof properties and their effect on cooling loads.  A list of publications may
be found at:
http://www.fsec.ucf.edu/bldg/resources/publications/index.htm
Two especially pertinent reports are:
http://www.fsec.ucf.edu/bldg/pubs/cr670/index.htm - Lots of measured property
data
http://www.fsec.ucf.edu/bldg/pubs/cr1336/cr1336.htm - Table 1 lists solar
reflectances for six new and weathered materials

On 24 Jul 2004, at 22:54, zhen tian wrote:

> Where can I input the "Thermal Emittance"?
>
> I only find the " Absortance: thermal", " Absorptence: solar" and " Absortance:
> visible".
>
> What is the resonable value fo these if I select the light and dark color?
>
> Thanks.
>
> Zhen
>
> chillarrahul <chillarrahul@xxxxxxxxx> wrote:
> If you want your walls to be black then
> 0.9000000 , !- Thermal Emittance
> 0.9500000 , !- Solar Absorptance
>
> if you walls are white then
> 0.9000000 , !- Thermal Emittance
> 0.2600000 , !- Solar Absorptance
> the values vary and you could look up them from any heat
> transfer book. The values i have written are at 30Deg C.
>
>
>
>
> --- In EnergyPlus_Support@xxxxxxxxxxxxxxx, Rahul Chillar
> <chillarrahul@y...> wrote:
> > hello
> > Regarding your first question, Color does have an effect but COLOR
> can be varied by changing the Emittance , absorptance of the material
> > For Example: If you want your walls to be black then
> >   0.9000000    ,   !- Thermal Emittance
> >   0.9500000    ,   !- Solar Absorptance
> >
> > These values are function of color  of material.
> > another example:
> > if you walls are white then
> >   0.9000000    ,   !- Thermal Emittance
> >   0.2600000    ,   !- Solar Absorptance
> > the values vary and you could look up them from any heat transfer
> book. The values i have written are at 30Deg C.
> >
> > Again if you wall is made of say asphalt then the E+ material
> values will have the correct values of these fields to take into
> account the effect of color of asphalt.
> >
> >  So i can is that the software E+ is taking care of it, however
> feel free to cross check the values from any data book. The values
> vary with temperature, roughness which will be very difficult to
> quantize.
> >
> > Regarding 2: a possbile reason for deviation from what you expect
> could be that in the materials you mentioned CONCRETE - 3/4 IN
> MORTAR, CEMENT SA 3 / 4 IN, A1 - 1 IN STUCCO
> >
> > These values will very with color or your concrete/ material which
> may be a little darker, or lighter basically vary from place to place
> so you may feel these are not satisfing your requirements. Then again
> the Roughness of the materials are different .
> >
> >
> >
> > Hope this helps
> >
> > Thanks
> >
> > Rahul Chillar
> >
> > Building Systems lab
> >
> >
> > Univ of Illinois Urbana Champaign
> >
> >
> > teklay Weldeabzgi <teklay1979@y...> wrote:
> >
> > hello ever body i need some help on these questions
> > 1. how does E+ considers the effect of wall and roof
> > color in cooling load. i know that color has a
> > considerable effect on cooling load of a building but
> > i can't understand how to take this effect in E+.
> >
> > 2. i have some doubt with material properties given in
> > the dataset of E+. especially on the thermal
> > emittance, solar Absorptance, and Solar Absorptance.
> > for example if u see the following three materials i
> > think they sould have the same property but it differs
> > greatly.
> >
> >      MATERIAL:Regular,CONCRETE - 3/4 IN MORTAR,  !-
> > Material Name
> > Rough,  !- Roughness
> >   1.0000000E-02,  !- Thickness {m}
> >   0.7200000    ,   !- Conductivity {w/m-K}
> >    1858.140    ,   !- Density {kg/m3}
> >    830.0000    ,   !- Specific Heat {J/kg-K}
> >   0.9000000    ,   !- Thermal Emittance
> >   0.2000000    ,   !- Solar Absorptance
> >   0.2000000    ;   !- Visible Absorptance
> >
> >   MATERIAL:Regular,PLASTER - CEMENT SA 3 / 4 IN,  !-
> > Material Name
> > Smooth,  !- Roughness
> >   9.9999998E-03,  !- Thickness {m}
> >   0.7200000    ,   !- Conductivity {w/m-K}
> >    1858.140    ,   !- Density {kg/m3}
> >    830.0000    ,   !- Specific Heat {J/kg-K}
> >   0.9000000    ,   !- Thermal Emittance
> >   0.7800000    ,   !- Solar Absorptance
> >   0.7800000    ;   !- Visible Absorptance
> >
> > MATERIAL:Regular,A1 - 1 IN STUCCO,  !- Material Name
> > Smooth,  !- Roughness
> >   2.0000000E-02,  !- Thickness {m}
> >   0.6900000    ,   !- Conductivity {w/m-K}
> >    1858.140    ,   !- Density {kg/m3}
> >    830.0000    ,   !- Specific Heat {J/kg-K}
> >   0.9000000    ,   !- Thermal Emittance
> >   0.9200000    ,   !- Solar Absorptance
> >   0.9200000    ;   !- Visible Absorptance
> >
> >   MATERIAL:Regular,CONCRETE - 3 / 4 IN STUCCO,  !-
> >                                    Material Name
> > VeryRough,  !- Roughness
> >   9.9999998E-03,  !- Thickness {m}
> >   0.7100000    ,   !- Conductivity {w/m-K}
> >    1874.160    ,   !- Density {kg/m3}
> >    830.0000    ,   !- Specific Heat {J/kg-K}
> >   0.9000000    ,   !- Thermal Emittance
> >   0.7200000    ,   !- Solar Absorptance
> >   0.7200000    ;   !- Visible Absorptance
> >
> > why is this happen ?  if these properties are not the
> > exact value can u help me how to get the exact value.
> > you can imagin that these properties varies the
> >
> > tahnks
> > tek
> >
> >
> >
> >
> > __________________________________
> > Do you Yahoo!?
> > Yahoo! Mail is new and improved - Check it out!
> > http://promotions.yahoo.com/new_mail
> >
> >
> > The primary EnergyPlus web site is found at:
> > http://www.energyplus.gov
> >
> > The group web site is:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> > Attachments are not allowed -- please post any files to the
> appropriate folder in the Files area of the Support Web Site.
> >
> >
> >
> >
> >
> > ---------------------------------
> >
> >    To visit your group on the web, go to:
> > http://groups.yahoo.com/group/EnergyPlus_Support/
> >
> >    To unsubscribe from this group, send an email to:
> > EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
> >
> >    Your use of Yahoo! Groups is subject to the Yahoo! Terms of
> Service.
> >
> >
> >
> > Thanks
> > Rahul Chillar
> > Building Systems lab
> > Univ Of Illinois Urbana Champaign
> >
> >
> > ---------------------------------
> > Do you Yahoo!?
> > Yahoo! Mail Address AutoComplete - You start. We finish.
> >
> > [Non-text portions of this message have been removed]
>
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
>
>
>
>
>
> ---------------------------------
>
>    To visit your group on the web, go to:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
>    To unsubscribe from this group, send an email to:
> EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx
>
>
>
>
> ---------------------------------
> Do you Yahoo!?
> New and Improved Yahoo! Mail - Send 10MB messages!
>
> [Non-text portions of this message have been removed]
>
>
>
>
> The primary EnergyPlus web site is found at:
> http://www.energyplus.gov
>
> The group web site is:
> http://groups.yahoo.com/group/EnergyPlus_Support/
>
> Attachments are not allowed -- please post any files to the appropriate folder
> in the Files area of the Support Web Site.
>
>
>
>
>
>
>

========================================================
Michael J. Witte, GARD Analytics, Inc.
EnergyPlus Testing and Support
EnergyPlus-Support@xxxxxxxx

Yahoo! Domains - Claim yours for only \$14.70
http://us.click.yahoo.com/Z1wmxD/DREIAA/yQLSAA/dkFolB/TM
--------------------------------------------------------------------~->

The primary EnergyPlus web site is found at:
http://www.energyplus.gov

The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/

Attachments are not allowed -- please post any files to the appropriate folder in the Files area of the Support Web Site.

<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/EnergyPlus_Support/

<*> To unsubscribe from this group, send an email to:
EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx

<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/

```