[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: [EnergyPlus_Support] Use of radiant barrier systems in walls/roofs
I don't think using the Regular-R material will work for you. The heat transfer equations used in energy programs like this are predicated on constant R-Value. Radiant barriers are highly temperature sensitive, the work best when there is a large temperature difference across the space and they act like an ordinary air space when the difference is small. There is an ability to use added insulation in EnergyPlus based on a schedule. If you first run a model to develop some surface temperatures, you may be able to use the schedule to increase the insulation value to match the performance of the radiant barrier. Unfortunately, I don't think you can link the insulation increase directly to the roof temperature, so you are stuck with a pre-calc guess and fixed schedule.
Ned Lyon, Senior Project Manager
Simpson Gumpertz & Heger Inc.
41 Seyon Street, Bldg 1 Suite 500
Waltham, Massachusetts 02453
781-907-9350
________________________________
From: Scott and Roxanne Munns [mailto:munns@xxxxxxxxxxxx]
Sent: Tue 3/15/2005 11:36 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Use of radiant barrier systems in walls/roofs
Hello,
I am doing analysis on a steel-roofed building in Guatemala. Typical
construction there is just a simple corrugated steel roof, with no other
insulation, etc. Ventilation only, no air conditioning.
I am investigating whether using a radiant barrier (aluminum foil facing on
a 4mm thick plastic bubble sheet) is appropriate. Sources have recommended
a 25mm gap between the roof and the radiant barrier.
Can EnergyPlus correctly model the effect of the radiant barrier on the roof
heat transfer? I dug around the documentation quite a bit and couldn't find
the answer. For now, I have created a construction containing:
1. Steel roof (Material:Regular)
2. Air gap (Material:Air)
3. Radiant barrier (Material:Regular-R)
Will radiation cross the air gap, or is the air gap just acting as a thermal
resistance (conductivity only)? If there is a better way to do this, I
would appreciate any pointers!
Thanks,
Scott
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.
Yahoo! Groups Sponsor
ADVERTISEMENT
click here <http://us.ard.yahoo.com/SIG=129stet21/M=298184.6018725.7038619.3001176/D=groups/S=1705007389:HM/EXP=1111034183/A=2593423/R=0/SIG=11el9gslf/*http://www.netflix.com/Default?mqso=60190075>
________________________________
Yahoo! Groups Links
* 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 <mailto:EnergyPlus_Support-unsubscribe@xxxxxxxxxxxxxxx?subject=Unsubscribe>
* Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service <http://docs.yahoo.com/info/terms/> .
[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.
Yahoo! Groups Links
<*> 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/