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Can you help provide insights on the batch of building energy efficiency questions below?

Doug Houseman's picture
Visionary and innovator in the utility industry and grid modernization Burns & McDonnell

I have a broad background in utilities and energy. I worked for Capgemini in the Energy Practice for more than 15 years. During that time I rose to the position of CTO of the 12,000 person...

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A set of questions for the Energy Efficiency Gurus here.

1) If one is building a new building how does one measure in KWH the improved efficiency based on the design?

2) Once the building is built, how does one prove the building meets the design standards?

3) In 5 to 10 years after it is built, how does one verify the efficiency still exists?

4) If the building is now 20 years old, and requirements have changed to make it just a “normal” building, should it still be classed as energy efficient?

5) The building is now 50 years old, and the standards call for better energy efficiency, should the building be classed as energy efficient?

6) In the real world how do you make sure that repairs and expansions maintain the efficiency of the building?

7) If the HVAC is replaced with a less efficient unit, how do you know?

8) If I am going to award a 20-year contract for energy efficiency to a building, what if anything should be done to make sure it remains efficient?

9) Is there a seasonal difference in energy efficiency of a typical building?

10) If peak shifts from summer evening to winter night, does that make a difference to the value of an energy efficient building?

I would appreciate thoughtful answers to these questions.
 

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Hello Doug,
I read the answers of Jennifer, Fabrice, ICF and Deb and think these are very complete. If I add to it, it is because I have a specific view on how to boost the Energy Transition. Maybe it is because I am in Europe but doubt that it is not applicable in other parts of the world.

I repeat for example to everyone that more Energy Managers are necessary to do the job, including addressing your questions. Energy Efficiency questions are very specific to each situation (your 10 questions prove it) and it needs a professional in each organisation with more than half a million USD of energy expenses (just to put the bar at some point), which knows not only the local situation but also Energy Efficiency. This combination is difficult to find, at least in Europe, certainly in Switzerland and Italy, which I know better.

Building commissioning and recommissioning is very important as Fabrice says. I agree also fully with Deb about IPMVP. Monitoring, for example with an Energy Management System, will deliver the raw data for Key Performance Indicators (KPI) like kWh/sqm/year. This can be the parameter to answer the questions 2 - 8. None of the issues in those questions can escape the control that is possible with KPIs.

I have a patent pending on the Energy Consumption Graph (ECG™), which is a mobile set of meters, which can measure distant consumers in a building and send the time function to a cloud based Energy Management System. It is not very different from a regular Energy Management System but I didn’t find a practical MOBILE solution for the Energy Audit on the market so I made one myself, based on radio transmission, passing also through the walls of big buildings.

I think there are so many (big) enterprises, where nobody knows where the energy is going after entering the main meter (Energy Transparency), that I have the impression it is just made too difficult to obtain it. We have to start there.

Lower the hurdle for Energy Transparency and the number of sheep passing it will increase exponentially. Then the Energy Transition will have a great victory.

1) If one is building a new building how does one measure in KWH the improved efficiency based on the design?
The most common method is an energy modeling comparison between the proposed design and a baseline design using the methodology in ASHRAE Standard 90.1 Appendix G. This is well documented if you're intersted in following it. There are a number of other protocols that have been created too, but they are similar and often reference 90.1. One issue to be aware of with this approach is that elements like schedules, HVAC operation, and other items are often idealized in the model. Which is not a significant problem in this comparison, because those same assumptions exist in both baseline and proposed models and somewhat cancel out.

 However, it does make it challenging to compare these modeled results against the ACTUAL building usage, or against benchmarks. As a result we've been urging designers and modelers to also consider more realistic modeled cases, with results that compare to reasonably similar actual building benchmarks. This also allows the team to set a specific energy target, which can then be used to keep the entire team focused on a measurable goal, and can even be included in RFPs for the project (see Performance-based procurement best practices).

 

2) Once the building is built, how does one prove the building meets the design standards?
This is a really important question that many who are focused on building design do not think enough about! This stage is typically called measurement and verification (M&V).

First off, the buildings energy usage should be tracked in as much detail as available. Then, following from the first answer above, if we've set a realistic energy target for our building, at this stage we simply compare the actual energy usage of the building to our target (after any adjustments due to unexpected building usage, like COVID!). 

Alternatively, if a realistic target was never set, then a model calibration exercise can be used to make this determination (see IPMVP Option D).

 

3) In 5 to 10 years after it is built, how does one verify the efficiency still exists?
As the building continues to be operated after occupancy, the core elements of M&V should also continue. Today's building systems make this relatively simple. Energy information is now easy to store in the cloud for a long period, and software such as Energy Information Systems makes it easy to continually track and compare usage year over year. Certain elements of the building may degrade, such as equipment like heat exchangers. Retrofits must also be accounted for. The key is that any major changes in energy usage should be explainable. Building performance doesn't degrade in a major way without a cause.

 

4) If the building is now 20 years old, and requirements have changed to make it just a "normal" building, should it still be classed as energy efficient?

At that point, regardless of the methods used for M&V early in the building's life, benchmarking against similar regional buildings is now the preferred method for determining whether the building is still “classed as energy efficient.” How it was classed after its construction is not as relevant. Changes in technology and other context outside the building, as well as any changes in operation or use inside the building, make these direct comparisons critical. Benchmarking ordinances in most major metropolitan areas make this much easier. If your metro area doesn't benchmark, there are still tools like ENERGY STAR Portfolio Manager that make this relatively easy.

 

5) The building is now 50 years old, and the standards call for better energy efficiency, should the building be classed as energy efficient?

 See #4

 

6) In the real world how do you make sure that repairs and expansions maintain the efficiency of the building?

Just as in the years immediately following construction, the building should continue to be monitored and tracked, and any significant changes in energy usage understood or investigated. If renovation or other known changes to the building occur, then tools may be needed to predict what the impact of that change should be. Energy Information Systems may also be used for this purpose, though engineer's or consultant's calculations may also be an option.

9) Is there a seasonal difference in energy efficiency of a typical building?
Certainly. Energy efficiency is seasonal dependent, and time dependent. Some building improvements have more of an impact during the day (efficient cooling systems) while others act at night (optimized scheduling). These differences are actually becoming much more important as more intermittent renewable energy comes online. It is increasingly more important that our buildings respond to the timing of those cleaner energy sources (see all the recent guidance from ASHRAE and the DOE on this topic).

 

10) If peak shifts from summer evening to winter night, does that make a difference to the value of an energy efficient building?
Great point! As discussed in #9, we need to understand the time of day that our energy performance improvements or strategies like renewable energy or electrification have an impact. The value of the energy efficiency in the building to its owner can be significantly impacted depending on how the building's peak or timing of energy demand compare to their utility rate structure. And the value of energy efficiency to the local grid, utility, and community can be similarly affected by its timing. We need to begin striving for energy efficiency improvements and building design that reduce electric demand when it is most needed on the grid. For example, in a grid region with significant solar photovoltaic penetration, energy efficiency measures that save energy in the middle of the day but not the evening (e.g. daylighting control) become less useful, whereas those that save energy in the evening as the sun goes down (occupancy-based HVAC control) become more useful. And in your example, as we electrify heating sources and (in cold climates) the peak changes to the early morning hours of winter, energy efficiency measures that reduce our heating peak may become the most valuable of all.

Note that ASHRAE’s new net zero energy standard (Standard 228, open for public review through May 17) actually includes an hourly path to recognize that source energy and carbon impacts vary with time of day. Also, LEED just announced a new pilot credit called GridOptimal meant to encourage design to consider all of these issues.

Answers to these questions provided by ICF:

1) If one is building a new building how does one measure in KWH the improved efficiency based on the design? Energy modeling or savings calculations would be done to compare a code building to the one being built. This can be done at a building level or equipment level depending on the jurisdiction. To verify/measure these, you could measure whole building energy consumption or individual key variables (set points, operational schedule, equipment/material efficiency) used in energy models or calculations to confirm performance.

 

2) Once the building is built, how does one prove the building meets the design standards? Commissioning should be performed to ensure building is built and operated as designed

 

3) In 5 to 10 years after it is built, how does one verify the efficiency still exists? You could verify the same parameters as was done after construction or compare energy consumption normalized for weather and other inputs to determine how the building is performing compared to the first year after construction. If it is performing worse than expected you could retro-commission your building to identify areas that aren’t operating as designed.

 

4) If the building is now 20 years old, and requirements have changed to make it just a “normal” building, should it still be classed as energy efficient? Any certifications for energy efficiency LEED, ENERGY STAR, etc will vary in how long they are valid. Regardless of age of building, people should consider when it was certified to draw conclusions on if it is currently energy efficient or not.

 

5) The building is now 50 years old, and the standards call for better energy efficiency, should the building be classed as energy efficient? Same answer as number 4

 

6) In the real world how do you make sure that repairs and expansions maintain the efficiency of the building? Repairs should be made with efficiency in mind to either bring that component of the building back to the original design efficiency or to a level better than the design. Any expansions should meet or exceed the efficiency of the building.

 

7) If the HVAC is replaced with a less efficient unit, how do you know? Nameplate efficiency (full load and/or part load) is the best indicator for this and equipment should be selected to not install less efficient equipment when replacing HVAC.

 

8) If I am going to award a 20-year contract for energy efficiency to a building, what if anything should be done to make sure it remains efficient? Monitor energy consumption or key data points at a building level (or at an equipment level for large energy using systems) to more quickly be alerted to decreased efficiency. Outside of energy, key data points could be setpoints and schedules within a controls system to ensure that any intended or unintended temporary changes aren’t left in permanently.

 

9) Is there a seasonal difference in energy efficiency of a typical building? Efficiency will vary with season based on changes in operation or changes in HVAC efficiency. Your heating system and cooling system will not have the same efficiency in most cases.

 

10) If peak shifts from summer evening to winter night, does that make a difference to the value of an energy efficient building? If you are asking about utility peak times, this could effect cost but not building efficiency as your charges could be based on time of use. You may pay more based on when you use energy but your building will (all things being equal) still use the same amount of BTUs. If you are talking about load shifting to non-peak hours using energy storage systems, this may change your building efficiency as there will be some inherent inefficiencies from storing energy when you weren’t before.

Hi Doug,

To estimate the energy efficiency of a new building you have to compare it to a fictional baseline. That baseline is an almost equivalent building, that would look the same and with the same usage, only its enveloppe performance and HVAC equipment would be different. We would pull those baseline performances out of local or international energy codes, ASHRAE 90.1 being the most used.

And typically, all of that is done by building an energy model, and simulate the performances for a typical meteorological year for the building location. During the design phase, a model for the building following ashrae 90.1 standard would be elaborated, as well as a model for the actual design case. That means that before construction started, you could have an idea how efficient your building would be. To get its "real" performance, you would then compare your energy bills to the baseline ashrae 90.1 model. Of course that last step would be after a year of standard operation, and the comparison would need to be weather adjusted to match the real meteorological year that just passed.

Now, you have to ensure you have your performance and your expected savings, and this is the critical part that is almost always missed in a project. Why ? Because energy efficiency requires system thinking and making sure interactions between all the components are 1) possible 2)controlled 3)optimized. A regular engineering firm is focused on équipements, not systems interaction and they do not stay involved much after they issue IFC drawings and are not involved in operations. They also have a limited understanding of control systems ans BAS/BMS logic. And it is not their job to a degree. To bridge that gap, and make sure your o&m staff are properly trained, a Commisionning agent is needed. It is an engineer that would be involved from design to year 1 or 2 that integrates all the energy efficiency needs from the beginning and across disciplines. Often they can also write the co trol sequence and will correct engineering mistake or improve the project during the design phase. Energy efficiency is just hard enough that you need another engineer in the team to make it work. And contrary to the design consultant, Commissioning people make their money at the end of construction mostly, so they stay engaged in that critical delivery phase by testing every system, in every conditions. Expect a between 2% and 3% of the HVAC conatruction cost for a Commissioning engineer. That is the only assurance you can have against a project where architects and engineer would receive a energy efficiency prize but having your o&m staff telling you the geothermal system keeps breaking/faulting.

And along the life of a project, hiring such people for Re-Commissioning will help you stay on track after 5+ years on any major interior redesign.

Regarding your other question, you are right in 50 years, a building should not be considered efficient anymore without having been upgraded.

I would add that LEED is a waste of money if you are after energy performance mainly. It does not ensure that at all. Also, enveloppe is important but a dollar invested in efficient enveloppe does not leverage as much saving than in your mechanical system.

Happy to discuss more if you have any questions.

Hi Doug!

The FSEC Energy Research Center in Florida has a ton of great resources to help answer these questions.  You can visit their home energy ratings section here: https://energyresearch.ucf.edu/consumer/buildings/home-energy-ratings/

The Home Energy Ratings System (HERS) helps you compare a new or existing home to a home build to code.  As you've mentioned, codes are always being updated, so the reference model home would also be updated over time allowing you to compare your home's current performance to the latest code.  Construction industry trends can also affect the performance of your home.  For instance, average homes built 30 years ago were often smaller from a square footage standpoint compared with the average home size today meaning the average energy bill today might still be higher even with better design practices. (although tiny houses are all the rage right now).  Placement of the HVAC equipment and technology upgrades like lighting systems can also play a role in how efficient a home is.  Over time, some measures beyond the building envelope also degrade or need replacement, so the performance of these measures will be reduced as time goes on.  Foam insulation, window caulking and reflective roofing materials are good examples. Nearly all energy efficiency measures have a useful life  and performance expectations that degrade over time, so be sure to ask what the useful life of a particular investment is, so that you can take replacement or repair costs over time into account.

The good news is, you can have an energy auditor that specializes in HERS ratings measure the performance of your home at any time to see it's doing.  They will compare your home in its current state against the latest performance benchmarks to see how it's doing.  There are also many excellent simulation tools available from the USDOE and others.  Check out https://www.energy.gov/eere/buildings/building-energy-modeling.  

Hope that helps!

 

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