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New Advanced material for eQUEST course

Nov 29, 2011

Energy-models.com is proud to announce a new advanced section in the eQUEST online course. While there are more videos in production, we have just released these popular requests (most of them are related to LEED or to help yield more LEED points):

All lessons contain real-world demos in eQUEST. These are best lessons of the course. Thanks for adding them

Ryan P.  - eQUEST user

  • Global parameter example (change LPD quickly in parametric runs)
  • Model a Dedicated Outdoor air unit
  • Model Energy Recovery Devices
  • Daylighting 
  • Custom curves (example using a LEED fan curve)
  • Optimum Start schedules (for LEED)
  • Import custom items (import curves for LEED)
  • Calculate Loads in eQUEST (Try the free tool)

Counter-Intuitive Wall Insulation Energy Study

Oct 7, 2011

A while ago, energy-models.com published a blog, "Is insulation the best energy saver?" and illustrated the number of hours where high R-values may increase energy. People may argue, "that's what an economizer is for!"  In my opinion, that of course is a good argument, but I have talked to too many people who have asked, "Why does my energy go up with increased wall insulation?"

To test this scenario, we looked to our good friend eQUEST. We built a simple building and tested it over a range of climate zones, and a range of R-values. In order to "normalize" the data, we compared everything to R-9 insulation (which is a pretty low R-value). We also made a number of assumptions:

  • L shaped Office building (100,000 sq ft)
  • Only Wall insulation was evaluated
  • DB economizer set to 65 degrees F
  • 43 percent glass (glass stayed constant at triple low-E to minimize effect of glass)
  • Medium high internal loads (1.5 w/sq ft lights, 2 w/sq ft plug loads)
  • 12 hour occupancy per day, 7 days a week
  • 76/70 F cooling/heating setpoints (82/64 unnoccupied)
  • No change in infiltration was considered
  • Different building orientations were evaluated without change to normalized results
  • 10 cents/kw-hr and 1.00/therm were used with no demand charges
  • Only climate zones A were evaluated, though results should be similar for B
The results were very surprising given that insulation only showed an increase in savings for the extreme climates: climate zones 1, 6, 7 and 8. 
For climate zones 3A and 4A, more insulation actually yielded AN INCREASE in cost (even with the economizer). Most interestingly, for climate zone 4, an obvious "sweet spot" was displayed.


Check out the results for yourself: 


Google Visualization API Sample

Miami, FL1A
Orlando, FL2A
Dallas, TX3A
Lexington, KY4A
Chicago, IL5A
Fargo, ND7A
It should be noted that a number of other locations were tested at each climate zone and the results were surprisingly consistent. The final data comes from the listed cities.

The Real Effect of Lighting on Energy and LEED points

Aug 16, 2011

EAc1 LEED points can't fall entirely on the back of the MEP!

I've probably seen as many LEED files as most LEED reviewers. What blows my mind is that most of the files I have seen save very little in lighting, even though lighting is often 25% of the building energy costs. In my opinion, this is a result of Architects and firms who, let's face it, are too set in their ways to change their designs. (Either that, or it's just plain laziness).  Perhaps, I am being harsh and they simply don’t understand the huge impact lighting has on LEED points. So, I’m going to spell it out mathematically, but first let’s see how a typical conversation goes:

"We have a design that is going to save 30% on energy costs annually. The HVAC has an improvement of 35% over the 90.1-2007 baseline, and we are using such and such.."

…..But then, I look at the lighting and see that it is designed at 1.2 watts/sq ft compared to a baseline building at 1.3 w/sq ft .

Now if you're asking, "what's wrong with this?"-  I want to ask you, "What's wrong with you and why are you reading my blog?" Okay, maybe I'm being harsh again but it's really simple math and I shouldn't need to explain it in depth. The truth is that lights are one of the best ways to earn LEED points.

Here's a rule of thumb for LEED buildings:

 Whatever your intended net savings on LEED is, your lighting design should save that percentage against the whole building method. (for buildings where lights are the typical 15-25% of savings)

Example:  

Target savings: 30%

Whole building method lighting: 1.2 w/sq ft

Designed lighting (after 10% credit for sensors) equal or less than: 1.2 *.7  = .84 w/sq ft 

Now, I see a lot of jaws drop at this, but that's only because they have been designing buildings the same way for 30 years. The message from LEED is that things need to change. The work that will go into this design will save days and maybe weeks of backtracking in the design when you find that it’s mathematically impossible to save 30% on your project without saving more in your lighting. That said, let’s take a look at the TRUE impact of lights on LEED points

What is the true extent of designing highly efficient lighting systems?

Let's assume we are comparing to a baseline building that uses 1.3 w/sq ft on (whole building area method) and let's assume the whole building design averages to .84 w/sq ft. What is the savings on this? Well, most people will say, "that's easy, .46/1.3 or 35%"

However, most people forget about the additional savings that comes from lights, especially in a cooling and in heating when the heat is non-electric. Remember, lights give off heat and therefore increase the amount of cooling energy (compressor, fan, and heat rejection).

So, what's the real saving:

Let's assume a VAV system and that lights save on the compressor, fan, and heat rejection with an overall EER of 13.65 (~COP of 4)

.46 w/sq ft = .46 w/sq ft immediate lighting savings

.46 w/sq ft * 1/4 = .115 w/sq ft compressor/fan savings          

Total: .575 w/sq ft actual savings in cooling mode

So, a 35% savings on the lighting yields an effective savings of nearly 45%.

Yeah, but don't the lights provide "free" heat in heating mode?

Let's assume there is gas heat, electricity costs $ .10 kw-hr, and gas costs $1.00/therm (so we will do this in costs). We will also assume a 90% efficiency in heating equipment and 4000 hours of operation.

Using the energy-modeler's unit converter, we find that 1 therm = 29.3 kw-hr

.46 w/sq ft *$.00010/w-hr*4000hrs = $.184 /sq ft immediate lighting savings

.46 w/sq ft /29300 w/thm*1/.9*4000hrs =  -$.070 /sq ft addtnl heating required  

  Net savings of $.114/sq ft in heating mode

So, yes, there is an offset in heating mode but there is still substantial savings as long as the heating is provided using low cost fossil fuels (relative to electricity) or if heat pumps are used in heating mode. 

Furthermore, most commercial buildings have a significant amount of cooling required. Remember, even in economizer mode, additional cooling means more fan energy.

Several sets of data were simulated in eQUEST to see how various cities saved. As predicted, cities with greater cooling showed the greatest savings per watt of lighting saved. It was surprising that even Fairbanks, Alaska had similar savings to climates like Miami. If additional effects, such as summer demand charges are considered, the savings would further increase!


See the calculated data for yourself:

Lighting power cost savings by city
Google Visualization API Sample

LEED and Energy-Modeling

Jul 24, 2011

Are you a LEED AP? Do you know the ins and outs of energy-modeling?

If you can answer yes to both of these questions your portfolio will be on hyper-drive. Here, we are going to outline the TRUE importance of an Energy-model in LEED certification. In fact, we'll quantify it and also answer some beginner questions if you are new to the subject. We are also going to help you decide whether to do a model in house or hire a consultant (and also help you to avoid getting ripped off if you do hire a consultant).

What is LEED energy-modeling?

When someone refers to LEED energy-modeling, they are almost always referring to LEED Energy and Atmosphere credit 1, and likely Energy and Atmosphere pre-requisite 2.  Also refer to our "What is energy-modeling page".

Why is it important for a LEED AP to know energy-modeling?

Well, the answer is simple math (and as a LEED AP, you are probably pretty good at math). There are 110 possible credits for a LEED building including all bonus points. Energy and atmosphere credit 1 is the single largest credit, with up to 19 points. Just how many of the total LEED points is this? Well, let's look at a pi chart of all the LEED points by credit:

LEED Points Pie Chart

This large piece of the pie, or these 19 LEED points are what most people consider to be the LEED energy model. HOWEVER, details used in the energy-model can also be used in other credits, which will increase your piece of the LEED pie. Some of the other points an energy model can earn you include(hover to display details):

So, if we adjust the chart and subtract these aforementioned points from their current category and move them into the energy-model's portion of the pie, we get the true extent of the LEED energy-model. So, what does our adjusted chart look like now?

LEED Points Energy Modeling Pie Chart

There are as many as 41 LEED points that are directly associated with LEED energy-modeling.  Here is the beakdown of energy model LEED credits out of 41 total credits:

Pie Chart Breakdown of LEED Energy Modeling Credits and Points

Just how many LEED points is this? Well, let's compare the number of LEED points that an energy-model can directly impact to the various LEED levels:

LEED Certification levels relative to Energy-modeling

There are enough energy-modeling points to get a building LEED certified! Of course, with all the pre-requisites and complexities, we aren't recommending that anyone try this. We just wish to illustrate the importance of energy-modeling to LEED and to LEED AP's.

Why will it benefit a LEED AP to learn energy-modeling?

There are thousands of LEED AP's, but only a small percentage know how to create an energy-model in a legitimate software package such as TRACE 700 or eQUEST. An even smaller percentage are highly proficient. Why is this? Well, up until now, it has been easy to get LEED training, and difficult to get building simulation training.

What about the prescribed path for LEED Energy and Atmosphere credit 1?

Of course, you can go for the prescriptive path, but you can only get 1 point for the standard compliance path, or up to 3 points for the prescriptive advanced core performance option. If you are going for LEED silver, LEED Gold, or LEED Platinum, you NEED to complete an energy-model for LEED EAc1 (Which simultaneously meets the requirement of EAp2). You may hear that it is very expensive to complete an energy-model and therefore, you avoid these energy-modeling expenses at all costs. HOWEVER, the cost per credit can be quite low as opposed to other credits (that let's face it - other credits are bought just to meet the minimum requirements). For instance, if the company spends $5000 for bike racks and they get 1 point, it costs $5000/point. Given that energy-modeling can easily equate to 30 points or more (or a max of 41), well, you can do the math backwards

What is the cost of energy-modeling for LEED?

Now, the issue of cost for energy-modeling is highly disputed. The reason it is so expensive is that very few people can create valid models within a reasonable time frame. However, a rate of 20 cents per square foot is pretty common for high end modeling (as the buildings get larger than 120,000 square feet, this number might be 10-15 cents per square foot, but if you disagree, please comment!) The LEED energy-model is often, sub-sub-sub-consulted (and maybe more), and therefore, the price is highly inflated. I would suggest working directly with an energy-modeling firm as to complete any energy-model. Given that the model may be 60% of the total LEED consulting fees, this should be a no-brainer. Instead of having 1 consultant, you may wan to consider having 2 LEED consultants: 1 for General LEED and paperwork, and 1 for the energy-model (unless you are certain that the LEED consultant is giving you a good price on the model). A good energy-modeler can save you money on your design as well. It's easy for a good energy-modeler to cut out the "fluff" saving big dollars on design. Thus, a good modeler can save the money on the design.

Example: The team at energy-models.com recognized that a geothermal well might not be needed given consistent cooling and heating loads annually. We did some tests and found that the geothermal well, while 30% of the cost of the hydronic system, only added .5% additional savings. We reported our findings to a very happy, and suddenly under-budget design team.

Do you want to Learn LEED for energy modeling? Click here  

IF you are really into modeling, you also might want to learn how to use LEED approved software! Click here