Building Simulations

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Building Simulations

Work collaboratively to find easier, more accurate and better ways to model, predict and verify a home's energy consumption.

Members: 70
Latest Activity: Jan 28

I spent many years modeling energy use in buildings using DOE2 and have modeled millions of square feet of commercial buildings and am quite familiar with that program's limitations. I'll admit up front that I am not a fan of DOE2. I much prefer continuous models that are object oriented. I do not like models that are based on discrete hourly approximations, although I understand why we sometimes need them in the short term.
Since coming to work for an electric electric utility 12 years ago, I have been analyzing commercial and residential building energy consumption by plotting average Watts/Ft2 (or Watts/m2) verses average monthly temperature that I obtain from monthly utility billing data. The resulting graphs are much more useful than the single number that is produced by EnergySTAR's Portfolio manager. The graph readily illustrates energy conservation potential, indicates which system is using the most energy (heating, building envelope, cooling, reheat or baseload), and is able to verify and quantifty improvements in energy performance after only one month of improvements being made to a facility. I'm happy to share this approach with any other building scientists that are interested.
I have also been using Matlab and Simulink to create a dynamic models of residential building's heating and cooling system. The results are quite interesting. My current model includes the effects of temperature setback on interior building materials and air temperatures. I will also be adding electric heat pumps to see how their auxilliary electric heaters respond to agressive temperature setbacks and to variations in outside air temperatures. I am trying to add mass effect of exterior surfaces to mimic those systems as well.

Discussion Forum

Transient Heat Transfer Analysis 5 Replies

I have put…Continue

Tags: element, difference, finite, transfer, heat

Started by James White. Last reply by James White Dec 10, 2013.

Trying to find %age energy saving from variety of upgrades in 10K sf multifamily house 4 Replies

I'm trying to figure out %age of energy savings from a variety of upgrades in a 10,000 sf building that has had deferred maintenance and a disfunctional heating system.I'm using Energy Pro software…Continue

Started by George M. Matthews. Last reply by Guy DuBois Mar 18, 2013.

Using Average Monthly Temperature to Model Home Energy Use 16 Replies

Discuss how monthly electric and gas billing data can be combined with average monthly temperature data to model a building's energy use, quantify energy conservation opportunities and verify…Continue

Started by James White. Last reply by James White Dec 28, 2012.

How about simulation in the multifamily context? 6 Replies

We'd like to hear from you on how the topic of this group applies in the context of multifamily buildings---> here

Started by Evan Mills. Last reply by Don Hynek Jan 23, 2012.

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Comment by James White on September 5, 2012 at 5:34pm

Sean, it might help to first model an existing building, with actual data to compare your model results against.  At least one with a year's worth of gas and electricity usage.  You mention 216345.05 of Site Energy Usage.  Is this total BTU/year? 

I simulated millions of square feet of commercail buildings with DOE2 back in the 90's, but that was many moons ago. As I recall, one of the limitations I found with DOE2 was that is didn't handle air flow between zones very well.  For example, if there was an exhaust air flow in a zone, the thermal model assumed the outside air entered that zone to be either heated or cooled, rather than drawing its air from surrounding rooms.  I also seem to recall I could not assign a schedule to how infiltration entered the spaces, or relate infiltration to outside wind speeds, and had to rely on the outside air schedules in the HVAC system.  I found that accurately modeling a residential home can be more difficult than accurately modeling a large commercial building. For these reason, your model might be more accurate if you used blocks instead of trying to accurately draw each room.

That being said, I like how SketchUp can provide a visual image of the surfaces and zones that are being modeled.

Keep us up to date on your progress.

Comment by David Williams on September 4, 2012 at 6:36pm

Can you describe your data acquisition method and sensor type/location. I just completed 24 months of hourly monitoring on a passive solar residential building and have a Very large excel file of data that has been evaluated in many different ways.  This buildings' energy use was modeled using HOT 2000, prior to construction, in 1993. We have since modeled with Eplus and Greenbuild Studio, only to find that passive solar contributions are not recognized by Eplus & GbStudio.  

Our wireless monitoring equipment measures hourly conditions for: all heating zone temps and humidy, gas to boiler & dhw, electric consumption , insolation, wind speed and direction.  We have found that the actual building axillary energy requirements were not very well represented by conventional modeling tools, but found that HOT 2000 did a respectable job of identifying the 40% solar contribution that was disregarded by the other tools.  Forty percent is a huge margin of error and I am wondering if anyone else has encountered the same issues that we have?  This building is in CZ-6 with lots of sunny days>

Comment by James White on September 4, 2012 at 12:01pm

Sounds like a fair question to me. I'd like to know more about using Sketch-Up with EnergyPlus.

Comment by James White on August 3, 2011 at 4:14pm

 

Although this is not a residential building, this graph tracks the reduction in energy consumption that we have been able to achieve for the headquarters building that I work in.  The energy savings were achieved by adjusting the settings on the building control system to reduce the minimum air flow settings on the variable air volume boxes and turn off the fans during unoccupied hours.

Comment by James White on April 4, 2011 at 4:43pm

Documented 19% overall energy savings in nine residential homes that participated in our "Reduce Your Use" contest. 

The winner reduced their January through March consumption by 35% by replacing their windows, sealing air leaks and turning off their hot tub.

Winners were determined imperically using the average monthly temperature approach described in this discussion forum. Baseline energy use was established based on a linear correlation of the home's normalized energy consumption for 2008-09 and 2009-10 winters.  The actual energy consumed during the past three months was compared to two year's of average monthly energy use when the average temperature was below 45F. 

Comment by Steve Waclo on November 23, 2010 at 1:32pm
Srikanth:

"It is not a picture, it is a video tutorial "

Forgive me. In my generation, movies, were "pictures" and now they have become videos ;-). I used the four arrows to bring the tutorial up to nearly full screen HD, and along with the excellent narrative as a guide should be able to more quickly come up to speed on the dashboard, review your content and provide some feedback.

BTW, if you listen very closely, you may hear the sound of eyeballs rolling as some folks consider the prospects of yet another "tool " for the industry :-). Looks pretty good to me so far, but I'll have a complete report on your desk after Thanksgiving.

Thanks for bringing this to our attention and have a wonderful holiday!
Comment by Srikanth Puttagunta on November 23, 2010 at 1:05pm
It is not a picture, it is a video tutorial of an Excel Spreadsheet that can be downloaded at www.carb-swa.com. You can also see the video posted on youtube. The video can be expanded to full screen by pushing the button in the lower right of the video. Might be best to download the actual dashboard and play around with it a bit. Thanks.
Comment by Steve Waclo on November 23, 2010 at 12:39pm
Hello Srikanth and welcome to HEP!

Very much want to provide input on the Dashboard Video Tutorial, but (at the risk of broadcasting my ignorance, which frankly, has never stopped me before) was unable to scale up the picture large enough to follow the narration. How can I format a full screen (or close) HD image?

BTW, how often do you get mail destined for California Air Resources Board ?

Steve
Comment by Srikanth Puttagunta on November 23, 2010 at 8:15am
I posted a video to the website called: Retrofitting America: a 1970s Home Energy Efficiency Analysis. The idea was to make a dashboard (which can be downloaded at www.carb-swa.com) with general information to guide initial decisions on packages of retrofits to pursue. The intended audience is utility programs and homeowners, focusing on utility bill savings. It doesn't replace actual energy modeling, but hopefully can steer people when making decisions. I would be very interested in the groups thoughts on a tool of this nature. The plan is to provide additional options (building orientation, window to wall ratio options, and two story option). Thanks.
Comment by James White on November 19, 2010 at 1:29pm
Hello David, (1) although Y axis is listed in kW (power), it is an average of the energy used in a month. A more accurate label would be kWh per hour, but I think that would be too confusing. If I were to be technically correct, I should also be referring to "mean monthly temperature" instead of "average monthly temperature". (2) I agree that the heating and cooling lines are best described as linear functions over their related temperature ranges, but Excel does not easily curve fit two separate linear lines to a prabolic series of data.
 

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