Architecture Student's Guide to Energy Modeling (part2)

We're back! This post continues from the previous one. Now for the less-architectural part:

1. Open EPLaunch. This comes automatically with your EnergyPlus download and may have been given a desktop shortcut. In the upper part of the window, browse to your new *.idf file.
2. Click the button that says "IDF Editor". This will open an index to the text file that contains all the model input information. The items on the list are called "objects", and as you scroll down, you'll notice the geometry you built in OpenStudio. (Note: at the time of this writing, the IDF Editor is the only element of the EnergyPlus set that is not available for Mac OS. This is expected to change, however).
3. If you like, select View --> Inch-Pound units. Otherwise, everything will be in metric units.
4. Scroll down to the section called "HVACTemplates".
5. The first item in the list is "HVACThermostat" - your zone needs a thermostat so the model knows how warm or cool to keep your zone. Click on it, then on "New Object" near the top of the IDF editor. A set of white cells will appear.
6. Give your thermostat a name, anything you like. For "Zone Name", select your zone's name from the drop-down list (click on the first cell to reveal the drop-down list).
7. For now, set the Heating and Cooling Schedules to BLANK (an option in their drop-down lists) and provide constant heating and cooling setpoints, e.g. 68F for heating and 76F for cooling.
8. The next item in the section is "HVAC:Zone:IdealAirLoadsSystem". This is the magical tool that will calculate heating and cooling loads for you, without a modeled HVAC system.
9. Click on that item, then on "New Object", and another set of white cells will appear. For "Zone Name", select your zone from the drop-down list; for "Thermostat Name", select the thermostat you just created.
10. Still in the IDF editor, select Save As and give your file a new name. You may have to add the .idf extension.

Yea!! You've just finished the part that scares most people away from EnergyPlus. You may have noticed all the objects related to materials and internal loads - you can easily learn to edit these to model the insulation, lighting, occupancy, and other characteristics of the zone. For now, though, let's accept the default values for all of those and go ahead, since we're just comparing massing options.

1. Go back to SketchUp. Within OpenStudio, open your new *.idf file.
2. Go to OpenStudio --> Run Model. There's also a button on the toolbar to do this, which looks like a red lower-case "e" with a blue "+".
3. A window will open asking you for a weather file. Browse to your favorite weather file (C:\EnergyPlusV4-0-0\WeatherData).
4. Make sure "Annual Simulation", "Report ABUPS", and "Show ABUPS" options are checked.
5. Click "Simulate" at the bottom of the window. A black DOS box with white letters will scroll by, and then your reports will appear. The total annual energy, and energy by heating and cooling load, will be the data you compare among different massing options.

Whew! The first time through this might take 2-4 hours; after that, it should only take a few minutes after you build the geometry in OpenStudio. Try opening some of the example files provided (C:\EnergyPlusV4-0-0\ExampleFiles). Those marked "Benchmark" are the most complete. Numerous tutorials for EnergyPlus are available online, and these can teach you to edit input objects directly so that you can accurately reflect internal heat gains, lighting gains, daylighting, etc. Good luck, and please post a comment if you have any problems so I can help out. I would love to hear your results!

Architecture Student's Guide to Energy Modeling

While I was an architecture student, I felt certain I was missing something in the world of energy modeling. Two courses on Environmental Control Systems taught us how to calculate simple heat gain and loss, shading, dew point position within a wall, bulk air flow, and so on. But these couldn't tell us how the earliest alternatives considered in design - massing and orientation - would compare annually in a particular climate. We were told, "Make it long and thin, and orient it east-west", but that was hardly satisfying for every site and every program!

I experimented with Ecotect, TAS, IES Virtual Environment, Demeter, Green Building Studio, eQUEST / DOE2.1, and everything else I could find at the time (2006-08). They all had their cool features - Ecotect's graphics were fabulous, even then, for example - but none delivered a simple, direct answer to the question: which form and orientation will give the lowest annual heating / cooling / lighting load on a particular site? And how much worse is the next-best option?

To be sure, several of the tools above can this question, if you have the time and inclination also to model the complete HVAC system and plant, and if you have a Windows operating system, and if you can afford the license (though student licenses are less than $100). Architecture students definitely do not have the time, even if they have the inclination and ability; they also tend to prefer Macs. The same is true for practicing architects.

So imagine my complete delight, last month, when I finally found the tool I'd been looking for all these years. It's EnergyPlus. Are you surprised? I sure was! One of the first building consultants I met, at SimBuild 2008 in Berkeley, was openly nervous about learning it. But for answering the massing-and-orientation question, it's easy. Here's what you do:

1. Download EnergyPlus (it's free)(and it works on Macs!).
2. Download some EnergyPlus weather files of interest.
3. Since you're an architecture student, you already have SketchUp. Good job.
4. Download OpenStudio (it's free too). Make sure it lands in the SketchUp plugins folder.
5. Download xEsoView (optional; also free).

Take a break. The next part might take a few tries, but it's worth it.

1. Open SketchUp. Look for the Plugins menu; if it's not there, OpenStudio didn't land in the Sketchup Plugins folder. But we'll assume it did.
2. Click on "OpenStudio" in the Plugins menu and go down to "New Zone Tool". Click there. The cursor will change to a little + sign.
3. With the + sign, click anywhere in the drawing field, placing the point, and then double-click on that point. A black dotted box will show up. This shows that you're drawing a thermal zone in OpenStudio. With the rectangle tool, draw a floor rectangle inside the black dotted box, and use the push-pull tool to extrude it into a box.
4. Draw a rectangle on one of the faces of the box - it should automatically become a transparent window. If it doesn't, you probably left the plugin - double-click on the thermal zone until the black dotted box shows up again, and keep trying.
5. Open the Outliner and watch as you create, reshape, and delete thermal zones. Practice until you can easily make, adjust, and delete thermal zones and their windows. Try right-clicking on a surface, selecting OpenStudio, and then selecting Object Info; notice that construction details appear, as well as the surface name.
6. Save a file with one thermal zone and perhaps a window as a *.idf file. Do this within the plugin, e.g. OpenStudio --> Save As --> Bauhaus.idf.
7. If you're curious, check out the Yahoo and OpenStudio support groups for their insights.

Great! Time for another break. Let's finish this up on the next post.

A Building, and a Database, to Watch

The US Department of Energy High-Performance Buildings Database is an intriguing source of information for green design. On the positive side, it presents design intents (including architectural vision) and performance strategies for 125 progressive buildings, as well as links to sources and contacts. On the other hand, many entries dwell on the acquisition of LEED points, present only modeled performance "data", gloss over any interesting prob

lems that may have arisen, and show no evidence of post-occupancy investigation.

At least two of the buildings in the list, however, present honest, detailed, useful accounts of their experiences: the Adam Joseph Lewis Center for Environmental Studies at Oberlin College and the Environmental Technology Center at Sonoma State University. Interestingly, these are both university buildings dedicated to environmental studies; with luck, more submissions will follow their ex

amples! Here is a bit about the first one.

The Adam Joseph Lewis Center for Environmental Studies at Oberlin College. With a design team led by passionately idealistic professor, David Orr, equally visionary architects at McDonough + Partners, and outstandingly generous donors in the Lewis family, this building was privileged from the beginning. Few of its contemporaries would be able to support a living machine, for example! But many of its features are widely relevant:

• elongated form to maximize permeability to light and air
• east-west orientation to simplify shading
• passive solar heating design incorporating thermal mass (not a simple choice in a cold winter climate)
• radiant heating in large open areas, such as the atrium, that have high infiltration
• a geothermal heat pump
• daylighting with photosensors to dim electric lights
• an outstanding low lighting power density of 0.9 W/sf
• automated operable windows for passive ventilation and cooling
• demand (CO2)-controlled ventilation to save fan energy
• very expensive highly-insulating glass
• a stunningly large 4,000sf photovoltaic array (an imperfect answer to the ideal of "sustainability")

All of these features have been debated in projects I've worked on in the last year: they are gradually entering the mainstream, and owners and architects are in need of solid precedent studies.

The exceptional part of the Lewis Center effort is the commitment by both Oberlin staff and students and NREL scientists to evaluate the performance of systems in their contexts, to make both big changes (e.g. replacement of the original electric boiler with a ground-source heat pump) and small ones (controls adjustments) and to track the effects of changes. An excellent real-time display is provided on the Oberlin website, and field work results by Paul Torcellini and colleagues at NREL are also now available.

So: how well does this building perform? The answer is: quite well! It has an EUI of about 32 kBtu/sf-yr, met entirely (on an annual basis) by the PV array. This is about 1/3 of the EUI of other Oberlin buildings. Is it "really" net-zero? Some purists argue persuasively that the point of a net-zero building is not to offset energy use with enormous arrays of silicon wafers, glass, and metal. We're working on a net-zero K-12 school now that's seeking the same vast-PV solution, understandably - getting heating loads down, after a point, is just really, really hard. In any case, Oberlin has taken a fantastic step forward for all of us - not only by creating this progressive building, but by sharing their experiences, good and otherwise, with all of us.