How do you handle performance validation and energy analysis of HVAC Systems using simulation?

[RandomUserName]

Fellow engineers,

I am a developing engineer (3 years experience) who has found himself at a 100ish person private A/E firm who consults for clients in healthcare, education, pharmaceuticals, and heavy industry. Doing HVAC / plumbing / fire protection engineering, design, and specification. Most of the commercial work is renovation or small (<10,000 sq. ft.) construction, while the sky is the limit on the heavy side.

We use Carrier HAP for basic load calculations for HVAC sizing of equipment. It seems like all clients in our area are concerned with initial capital cost. As such we typically only specify multiple packaged rooftop units on small jobs and constant volume hydronic systems with constant speed AHUs on the larger project side.

I would like to have the conversation with current long term clients about spending a little more money during design development (heck, maybe even do it pro bono the first time or two) to perform an energy analysis of different HVAC air/water systems to show different break-even periods. For a small upfront cost - that I believe should pay for itself in energy savings - we can help our client build better mechanical systems. It is a win-win: we get a larger fee based off construction costs; client saves money over the lifetime of the use of the space.
Thing is, I do not know where to start.

I am plenty familiar with all the basic engineering systems and how to design them. If not, I have the books to teach me, and I really enjoy technical reading. I am also very familiar with performing financial economic analysis (PV, FV, Annuities, NPV, etc). I need to learn the correct software and approaches to blend these two skills.

1. How do you all go about presenting this to your clients?
2. What energy modeling simulation software do you use to perform your analysis? Any preferred reading materials to go along with using it?
3. Could you give me a success story or two?

I think this could be a great new territory for us. Your thoughts are greatly appreciated!

 

[EnergyProfessional]

Glad you mind energy savings. Also add maintainability and longevity to make your case for higher quality HVAC.

You could propose 2-3 different options with ROI calcs. I usually see simple payback numbers, which is a useless number.

I'm lucky enough to work for an entity that owns the buildings I work on and keeps them for an eternity, so I can design for the long run. I'm also in charge of maintenance and replacing them later... so i never want to see RTUs and all that crap that is installed in strip malls etc.

 

[317069]

Don't go behind fancy words like energy simulation or such terms, they are only for business not for real world.
let say your energy software gave you two options, a heat pump and regular rooftop unit, if you read the product data of both units of the same manufacturer you will find both are perfect in energy saving...etc.
what if the fuel or electric power price has been changed suddenly then what would you say to your clients, sorry you will get your money back not in next 15 years as I told you before, may be in next life.
just do you project, satisfy your boss and client since you say it is small jobs, keep your job and with time you will feel better

 

[EnergyProfessional]

317069: this is terrible advice and borderline unethical. I think engineers owe it to the client (and the environment and society) to at least give some options for improvement. Of course ultimately the client is the boss, but you should give him unbiased full data on the options available. That is why he hired an engineer so that an expert with experience can advise.

When we have consultants design for us, even the worst ones mention some options and even if they do the ROI data in the least sophisticated way possible, at least they try. Obviously they hope we would not go for better options as that would mean some more work for them. teh architects usually try to steer everyone to the solution that works best for them (RTU and as little insulation as possible so that they have more money for "aesthetic features"). Don't try to be like that... we already have enough designers who don't care.

 

[317069]

Herrkaleun, sorry to say that it is just fancy words such as energy, ethical, public or such words for business commercial, if I am a real engineer I should give the right suitable solution to my client from the first time(this is what we call it as an ethic), and in order to do that I should know what the client wants exactly before I quote my service to him.
client is not an engineer to decide what solution he has to choose, otherwise he wouldn't hire me and save his money (this is also a kind of energy saving)
in my opinion, there is no energy saving, there is efficient equipment, and they use this term for business only, how can you explain that the price of 200 cfm HRV unit is about half price of a 100000 BTU/hr furnace, or rooftop with heat exchanger is four times more than regular RTU, or why they don't force bylaw that every rooftop has to has a heat exchanger, like they forced to not use R22 to protect environment as an example.
(I always use HRV in my work but not for energy saving side since I don't reduce the furnace size, I use it to ensure a good ventilation)
those software are good on paper not on real world since you can not make sure that all performance conditions in your calculation are available on real application. and as you know the HVAC calculation is not a calculation as much as it is an estimation.
Term payback give client idea that he will install his project for free, while it is not the true, and it is not an ethical term too.
it is just an idea.

 

[EnergyProfessional]

317069: so from the brief scope the owner gives ("new HVAC") you come up with the perfect design without having to use an energy simulation and to go back to owner to give him options? Wow, you just design a hospital HVAC plant on paper and weigh all the options in your head and make a decision without going back to the owner for his decision?

There also is more to it then energy. Like longevity, maintainability, reliability. Your R22 example is a good one as it shows how all the people that used R22 when 410A was available all got screwed because if they have to repair the system today they will have nightmares upon learning how much R22 cost as opposed to R410A. In addition to having outdated equipment.

Not sure if ethics covers it, but I for myself feel good when I spend the extra time to evaluate the options, to ensure what the occupants and owner actually want (most don't know what they want besides the frame "office"). Performing an energy simulation today also gives me knowledge for future designs since i already know in what situations what options would be better, or when not. And I would think most people come here because they want to make things better.

To get a suitable design it takes in-depth knowledge of owners maintenance capabilities, long term plans, occupant needs, options to expand budget (or re-prioritize), energy simulation.... I doubt all this information is available without going through multiple options and involving the owner in the design.

 

[317069]

Herrkaleun,
- yes, if you are not able to make a design option in your head as the first step then you are the wrong person for design process.
- you are mixing between subjects, we didn't mention about cost of installation or maintenance, our subject was about energy simulation, so adding words such as "Like longevity, maintainability, reliability" will not add value to our subject which is about energy simulation.
- if you came up with three options A,B, and C for a project, your simulation told you that the option A is the best and option C is the worst, and for some reason the owner insist to go with option C, then what would you do?, will you proceed with option C, or you will tell the owner to find another engineer to take care of his project?.
if you proceed with option C then why do you blame designers if they go with what architects want them to do as you mentioned before, and if you insist to go with option A then why did you offer three options from the first point.
- software does not add knowledge, otherwise we don't have to go to engineering school and work fields, we can just buy a software, learn how to use it then go and design hospitals.
- also if you look at the main post, he mentioned that his job is about 1000 sq.ft project, do you thing he need to use simulation for such system, I believe he does not has to use HAP at all for this size.

 

[Drazen]

there are many software packages that allow you to make energy simulations.

elite has energy module. cymap has own simulation ability together with link to tas dynamic simulation software.

what is important is that such simulation has to include relevant data like usage profiles/schedules, equipment efficiencies, energy prices and even multi-year price predictions.

there are no ideal simulations, but those available give more arguments and more weight to owner decisions, which is similar to any other type of business predictions as well.

for your business there are two important subjects.

firstly if you cannot convince client that such simulation has value, there is no sense to insist on it, as the price of consulting will likely double or be even higher. doing that pro-bono makes no sense at all, if client is not ready to pay adequate price, you cannot sell it, especially in situation when you cannot guarantee the outcome.

seconndly, such kind of simulations are becoming more and more meaningless if not being tied to similar architectural simulations. building physics, shape, concepts of use and spatial organization affect the things so much that there is little justification to undertake comprehensive simulation for hvac systems only.

 

[EnergyProfessional]

An energy simulation is one of the tools to make a decision. Keep in mind the simulation results are as good as the data you enter. AFAIK the elite software is bin-based. I'd recommend an hourly simulation. I'd think HAP is hourly, so is Trace.

Drazen is right, don't push an agenda, give the client 2-3 honest options and clearly state the ups and downs. Energy is only part of the equation, maintenance easily can cost more than the energy a system uses if it doesn't work right.

 

[dbill74]

Random,
What you are wanting to do is a Life Cycle Cost Analysis (LCCA) or Life Cycle Assessment (LCA), for which I am sure you can find plenty of guides on the internet.
The basic components of a LCCA/LCA are:
-Initial purchase/install cost
-yearly maintenance costs
-yearly energy use costs
-replacement costs
-Life time (years)

For the yearly energy use, Carrier HAP can do that for you. I recommend searching Carrier's help pages for guidance, there is too much to explain in a forum.
For the other items, you will need to do some research. If you want help from a forum such as this, try to develop some pointed questions so we can provide pointed answers. Vague questions will get varied answers.

Whether or not you do a LCCA/LCA is going to depend on the project. For small projects with limited budget, doing an LCCA is not going to be a sound investment of your time. Certain clients (government work) will require completing an LCCA/LCA regardless.
Sometimes client/owner requirements may limit system choices. Often times, the owner's maintenance personnel are familiar with one type of system and they do not want to retrain or stock up on different replacement parts; or if the project is on a campus, you need to match the systems that are already on the campus. Available space in a building can also affect your system choice.
Just because a system is the most LCCA/LCA cost effective or most energy efficient does not make it the "best" system for the project.

For example, in the southeast USA, gas is cheap. When comparing gas fired water heaters to solar water heaters, gas is going to come out cheaper in the long run every time. At least until the price of solar collectors drops significantly. But if you are doing a Navy job (as an example), you have to have 30% of your hot water from solar.

As for presenting the idea to look at different systems to a client, I recommend bringing up the topic of alternate systems at an early meeting, perhaps even during negotiations for your services. I've found it never hurts to ask "Have you considered using ______?" or "Is there a particular reason for using ______?" How these get answered can go a long way to understanding your client's needs.

The good engineer/businessman knows what fights are worth fighting and which are not. Learning the difference comes with time and experience.
Bill

 

[EnergyProfessional]

For the options limit it to 2 or three. Realistically there are not 10 different good HVAC options for an application

 

[urgross]

Limiting the HVAC to 3 options sounds reasonable, but then include envelope, lighting etc. Enevelpope is as big as HVAC to my mind.

Don't forget utilities and O&M escalation for the LCCA; that can be a big difference, subject to sensitivity.

If you are doing any Federal (to include Navy) the 30% solar DHW is subject to a positive 40-year LCCA, as are all renewables.

Energy rebates from the DSIRE database can be quickly verified, as well as potential A-E benefits from EPAct 2005 179D. It's difficult to make bean counters think of long term, so any advantage available is needed.

 

[EnergyProfessional]

envelope is very important. However, architects usually are in charge and in most cases HVAC engineer is sub to the architect. good luck getting paid if you tell the owner having those huge fenestration areas is very bad.

 

[urgross]

That's where the simulation and LCCA come in, as well as 179D savings for the architect.

 

[EnergyProfessional]

urgross: I've worked with so many different architects and all they care about is to squeeze HVAC into a corner and make it as cheap as possible for their "aesthetic" features. All the 179D, LEED etc. "saving "results can be easily achieved by tweaking the energy simulation regardless of how bad the enclosure is. I'm sure the EPact buildings use exactly as much energy as the other randomly designed ones.
Some entertainment proving my point You only need to watch 5 minutes to get the statistics.

 

[urgross]

179D has nothing to do with LEED, it's a tax credit for the designer of record for meeting/exceeding energy standards.

I have the same issue with architects, none ever read 90.1 or the insulation equivalency for 16" OC and 24" OC studs. That's why I do that on every project. None give a crap that their schemes neglected to include a mechanical room. More than once I've been asked to recommend an HVAC system that will fit budget when the LCCA has already een completed, the Owner has approved the system, then been told that it no longer fits budget. That's good news for VRF vendors. I usually try to get ASHRAE 189.1 included in the contract for new construction, and 90.1-2010 for renovation.

On the plus side, the architect pretty much always depends on the MEP firm for the load simulation.

Depending on location, the State incentives might also be a carrot for the Owner. All States are listed on the DSIRE web site.

 

[cry22]

"As such we typically only specify multiple packaged rooftop units on small jobs and constant volume hydronic systems with constant speed AHUs on the larger project side"

Nothing wrong with CV systems if they are ASHRAE 90.1 compliant (understand small enough) - propose ASHRAE 90.1-2010 compliant design and you're done.

We also need to stop this rant about architects - sometimes it is the engineer's fault not communicating in time.
ASHRAE 901.1 states minimum R values and I have yet to see an architect that refuses to provide minimum R values, actually, they always provide a better envelope when you ask them.

Same with Mechanical space, you need to give the architect a Size and location for the mechanical space (and shaft space) ahead of time so he can accommodate, if you wait till late, he gets mad and tells you to use ceiling mounted FCU's and RTU's.

 

[cry22]

Random

Forgot to include this in my earlier post
I usually use Trace 700 for energy calculations and report the values to BLCC for the economics analysis, much more reliable numbers than Trace.
BLCC is a very user friendly software.

http://www.energy.gov/eere/femp/building-life-cycle-cost-programs

 

[EnergyProfessional]

cry22: sure some engineers are at fault. but it is hard to speak up if the architect is the one who can and will delay your payment.

On CV systems, i wouldn't say 90.1. is a standard to aspire to. It is pretty low standard. After all, it is just the code in some jurisdictions and just designing to code isn't going above and beyond
It is also better humidity control etc. that you get with VAV systems over CV (unless you reheat the crap put). i think in nowadays world there isn't much of a reason for CV except soem very few applications. Just less wear on the system starting up makes VFD useful.

 

[cry22]

Herr
Sorry to disagree,
ASHRAE 90.1 requires VAV on most systems nowadays, only small systems are allowed with CV.
when you have say a 4000 CFM, 3 HP or less AHU. Just what kind of savings are you getting in going from 3 HP down to 2 HP or 1 1/2 HP? the cost to run few light bulbs?. and for that, you have spent money for VFD's, VAV boxes, pressure sensors, Testing and balancing, more maintenance and calibration, etc.. You will never get your money back, and the energy savings are meaningless.

You better off spending the money on PV panels to power the CV for free than spending it on VAV equipment and controls.