A while back, I did a blog post about using data that ASHRAE published to project building maintenance costs.
Its turned into one of my more popular posts with about 8-10 views a day on average. I think that is because data on projecting building maintenance costs and the costs themselves can be pretty hard to come by.
For what-ever reason, over the past month or so, I have had a number of folks get in touch with me to ask questions about that topic, mostly students in classes but also a few clients. And subsequent to writing the blog post, I have also had discussions with a number of folks inside my company about this topic.
As a result, the recent flurry or questions got me curious again, especially about the details behind the factors in the equation ASHRAE developed that I used in my projection calculations. To really answer some of the questions I had been asked, I needed to look deeper at what was behind the ASHRAE data.
So, I spent a bit more time finding papers and looking into the statistics behind the data. I also spent some time looking at the publicly accessible online database that ASHRAE set up in 2005 to track building operating costs and equipment service life. What follows are my conclusions based on that effort for what they are worth; basically an update on the earlier effort.
Bear in mind that what follows is simply the result of my little research effort. Conclusions and opinions drawn are mine and you may feel differently or have different and better data. If you do, I would encourage you to share it as a comment for the benefit of others.
The links below will jump you to major topics in the post that follows. A Back to Contents link at the end of each section will bring you back here.
- ASHRAE’s Current Database
- A Few Bottom Lines on the Current ASHRAE Building Operating Cost Database
- The Research Behind the Numbers
- The 1997 Equipment Life and Maintenance Cost Survey – RP-186
- The 1986 Analysis Of Survey Data On HVAC Maintenance Costs RP-382
- The 1999 Maintenance Cost Report ASHRAE-D-RP-929
- The 2005 ASHRAE Web-based Owning Operating Cost Data Base RP-1237
- ASHRAE Applications Handbook and Pocket Guides
- ASHRAE Journal Articles
- BOMA’s Preventive Maintenance Guide Book
- Variations in How the ASHRAE Cost Equation is Written
- Assessing Maintenance Costs Using the ASHRAE Model
- Equipment Replacement Costs
- We May have “Counterfeited the Currency”
- Other General Observations
- Understanding Statistics
- Potential Limitations of the Data
- Internal Data May “Trump” ASHRAE and BOMA Data and Projections
- A Few Interesting 1986 Study Conclusions
- HVAC maintenance costs are higher for older buildings
- The costs of HVAC maintenance are higher in buildings with air and water systems
- The analysis of the data suggest that the factors causing this variation are numerous, complex and difficult to measure
- Buildings where total responsibility for HVAC maintenance, including pasts and materials, is contracted to a maintenance service firm have higher HVAC maintenance costs per square foot
- Buildings with computerized HVAC control systems also have higher HVAC maintenance costs
ASHRAE’s Current Database
Around 2004/2005, ASHRAE set up two public data bases where you could go and enter data from a facility you are associated with. One is for building maintenance costs and the other is for equipment life.
I will start out with the current ASHRAE maintenance cost data base, where maintenance cost varied from $0.000 to $7.048 per square foot based on 266 data points (a.k.a facilities of one sort or another).
If you arbitrarily eliminate the outliers (the about 8 at $0.00 and one at $7.048), then you end up with the following metrics. (Note that with the outliers eliminated, you end up with square foot costs that step up at fractions of a cent from the low end to the high end; about 199 distinct values that often vary from each other by fractions of a cent.)
A Word About Arbitrarily Eliminating Outliers
Before moving on, I wanted to make a point about what I just did when I arbitrarily eliminated the outliers. It probably makes statistician’s hair stand on end because in some ways, I said I know what building maintenance costs are in terms of dollars per square foot and its not $0.00 and not $7.048 per square foot.
I actually don’t know the answer; if I did, we probably would not be having this conversation. Its one thing to eliminate data that you know to be bad. For instance, a medical data base that had someone’s date of birth as being after their date of death likely has a problem with that particular record. But the figures I eliminated could actually be valid.
For instance, the higher figure could reflect a facility that is addressing something that I think is not directly addressed by the data in the data base, that being the cost associated with the eventual need to replace aged machinery, a very important aspect of keeping things running in top form. More on that later in the post.
And by eliminating the zero’s, I may be reflecting facilities where there is no ongoing effort to maintain things and everything is handled by repairing it when it fails. That’s usually not a great way to go in my opinion, both in practical terms and in the more holistic perspective of being mindful of the things we are blessed with. Maybe the entry of those buildings into the database was a cry for help from the facility owners.
So my point is that you have to be careful when you do what I did and be aware of the implications. In this case, I elected to narrow the field by saying There could in fact be facilities that spend $7.048 per square foot and $0.000 per square foot on maintenance in the context of how these results are stated. But clearly not many people are in that group, so I would like to see what the results say about a smaller portion of the database population.
So I filtered the data set bearing in mind that there are some facilities with costs outside of the narrower window I created and that there could be a very good reason for that, perhaps even something that should be addressed by the data base or someone using the information to inform their maintenance cost projections.
A Few Bottom Lines on the Current ASHRAE Building Maintenance Cost Database
Almost half of the buildings in the current data base are Offices, but there is representation from a number of other functions. Here is the list on that.
These two charts, which I generated by downloading a copy of the current ASHRAE HVAC Maintenance Cost Database probably are the bottom line on everything in some ways.
Basically a lot of scatter with no real pattern emerging.
There are probably a bunch of reasons for that including how folks do maintenance, how they report the costs, wages, in house vs. out of house labor, facility type, etc. Most of the reports discuss this and there is a pretty good examination of it in 1982-09 ASHRAE Journal – Availability and Validity of Maintenance Cost Data, which you can obtain from ASHRAE if you are interested (free for ASHRAE members; not sure what the charge would be for non-members).
The Research Behind the Numbers
Near as I can tell, there were three ASHRAE research projects that looked at HVAC maintenance costs and/or equipment life expectancies. There are also a number of Journal articles that probably sprung from the research.
The Building Owners and Managers Association (BOMA) has a number of resources that target equipment life expectancy and operating costs. And from what I can tell, facilities that are owned or operated by BOMA members are significant contributors to the ASHRAE research. What follows is a list of the documents I have found and referenced as I looked into this.
The 1997 Equipment Life and Maintenance Cost Survey – RP-186
This project developed a fairly detailed table of equipment life expectancies. The maintenance cost portion of the report is much more tentative for reasons that end up showing up through out the literature (differences in how people track costs, the drivers behind the costs, the fact that in-house maintenance crews do other things besides HVAC maintenance, etc.)
I think you can obtain a copy of at no charge if you are an ASHRAE member or can obtain for a modest fee if you are non-member. Note that the RP in RP-186 stands for Research Project, which is helpful to know if you are looking for it on the ASHRAE web site.
The 1986 Analysis Of Survey Data On HVAC Maintenance Costs RP-382
This project appears to be where the maintenance cost projection equation was developed. There are a lot of statistics in it that explain how the coefficients used in the equations were derived and show the data behind them. It looks at maintenance costs for facilities with in-house maintenance and also facilities that use a service agreement approach.
There are actually more equipment adjustment factors contained in it than show up in the tables in the handbooks. I’m not sure if they are not published in the Handbooks because the committee concluded they were not practically or statistically meaningful or if they simply were trying to make things a bit less complex.
This is a document you have to pay for, ASHRAE member or not. But members can obtain it at a reduced cost. If you purchase it, the file will be locked to your computer, so it’s a bit harder to share the information with others. It is possible to buy extra copies at a discount however.
The 1999 Maintenance Cost Report ASHRAE-D-RP-929
This project expands the work from the 1986 survey and seems to develop additional coefficients for the cost equation all-though they do not seem to be reflected in the ASHRAE Handbooks as I mentioned above. In addition to looking at facilities with in-house and out-of-house maintenance strategies this report also also includes a section on maintenance for chain stores.This is another report that you need to pay for if you want it, no matter if you are an ASHRAE Member or not.
The 2005 ASHRAE Web-based Owning Operating Cost Data Base RP-1237
I’m not sure why ASHRAE lets me access this report as a member for no charge when I had to buy some of the others, but I’m not complaining (probably operator error on my part). In any case, this report includes summary data from the other reports but if you want the details like the expanded set of coefficients to use with the dummy variables in the maintenance cost equation, you need the other reports. It also has some data comparing in-house with contract maintenance and predictive with preventive and unplanned maintenance strategies.
The “new ground” covered by this report is that the project behind it established the current public data base that I discussed earlier in the post. It also established a public data base for equipment life cycles and replacement costs.
The report provides the statistical analysis of the data among other things. I think one of the most interesting things in the report is the following table.
The highlights are mine from when I was reading it and point out that based on the data set that ASHRAE worked with, building age was not statistically significant in terms of the maintenance cost. And of the three items that were statistically significant, only the Building Class and the Heating Plant Type were practically significant.
That would seem to imply that a number of the factors used in the cost projection equation were not that important compared to the three factors highlighted above. Its also interesting to note that Building Region is not a factor in the cost projection equation, even thought this study said it was a significant driver of maintenance costs (which makes logical sense to me).
Since it is my understanding that sometimes, the words “statistically significant” are not used correctly in the pure technical sense, I spent some time trying to understand that and in this case, I think they were (but probably am not totally sure since I never had a statistics course).
ASHRAE Applications Handbook and Pocket Guides
The ASHRAE Applications handbook is the one that contains the Owning and Operating Cost chapter and it is where the results from the studies I mention appear. Currently, the Owning and Operating Cost chapter is Chapter 37, but it moves around over the years.
There is a gap in my handbook collection because I sometimes give one a way. But I find the cost equation all of the way back through the 1991 edition. In the 1987 edition, the 1986 study is cited along with the base cost, but the equation is not shown.
Going the other way in time, all of the ASHRAE Applications handbooks since 2007 reference the studies, eliminate the cost projection equation developed by the 1982 study, talk about what you have to consider when developing costs, and basically say it is complicated.
I have two editions of the Pocket Guide and both of them (1999 and 2005) include the cost equation.
ASHRAE Journal Articles
I found two ASHRAE Journal articles that were likely driven by the research going on at the time. Availability and Validity of Maintenance Cost Data shows up in the September 1982 issue and contains a pretty good discussion about why there is so much scatter in the data.
Determining Equipment Service Life shows up in the August 2000 issue and includes a good discussion of the difference between a scientific study of the topic vs. survey data. Both articles can be obtained for free if you are an ASHRAE member and at a nominal cost if you are not a member.
BOMA’s Preventive Maintenance Guide Book
BOMA has published information on equipment life, operating costs, and preventive maintenance for a while now in the form of their Preventive Maintenance Guide Book. I happen to have the 2010 Edition and find it to be a handy reference when the topic comes up. This is a publication you would have to purchase but you can bundle it with a couple of other BOMA publications that may come in handy in the commissioning business including:
- BOMA’s Standard Operating Procedure Manual Guide, which may provide some insight into how to develop procedures for a system manual.
- BOMA’s Guide to Exterior Maintenance, which might help with understanding envelope commissioning issues, a growing focus in our industry.
Currently, the Equipment Life Span appendix associated with the Preventive Maintenance Guide Book is available in the public domain. It contains 5 pages of tables like the one illustrated below, so pretty handy if you are trying to figure out when you might need to replace something or how long something should last.
I should point out that if you do building retrocommissioning, knowing how long something should last can be valuable information. For one thing, you don’t want to recommend making a modification to a piece of machinery that will likely fail due to age before you have recovered the cost of your investment. In situations like that, it may be better to roll you savings potential into a replacement project, allowing the savings to discount the cost and maybe even picking up additional savings due to the newer, potentially more efficiency machinery.
Going the other way, if you have identified an issue that may be reducing equipment life, like compressor short cycling or the impact of a hunting control loop on actuator life for instance. then understanding the normal life expectancy along with the cost of a premature replacement effort (probably in “emergency” mode) can bring a significant Non-Energy Befit (a.k.a. NEB) to the table, making your simple payback or ROI much more attractive than it might be if you only were looking at energy.
Variations in How the ASHRAE Cost Equation is Written
One thing I noticed over the years and revisited in my current little foray into this is as follows. From what I can tell, the original cost equation was developed based on 1983 dollars using units of dollars per square foot. And it appears in the all of the editions of the Handbook that I have looked at in that context along with instructions on how to adjust it to current dollars.
But both versions of the pocket handbook correct the base cost factor and equipment cost factors to reflect 1993 dollars instead of 1983 dollars. Actually to be more specific, the Pocket Guides use units of cents per square foot where as the the Applications Handbooks and reports all seem to be using units of dollars per square foot. So if you are flipping back and forth, you need to remember to keep the decimal place in the right location. But bottom line, if you use the equation in the Pocket Guide, you adjust the result to current dollars based on 1993 instead of 1983.
That part is fairly straight forward. But what I found puzzling is that the age cost factor is not adjusted from the 1983 value in the Pocket Guides that I have. A units analysis would say that the term is in fact of cost per square foot and it would seem like inflation would impact that term as much as the others, so I tend to think its an oversight. That said, if you do the math to adjust that factor and compare it to using the equation as published, it does not make much of a difference (illustrated below), especially given the broad range of operating costs reported in the public data base.
Assessing Maintenance Costs Using the ASHRAE Model
If you run the ASHRAE calculation using the equation developed by the 1982 ASHRAE effort for the “vanilla” facility (fire tube boilers, centrifugal chillers, and VAV systems) you get the following result for a 25 year old facility (basically in the middle of the 20-30 year useful life estimate for that type of equipment from BOMA).
If you run it for a 1 year old building with the same systems, you get this result.
So, the ASHRAE model suggests that age affects maintenance cost by about 10% over the course of 25 years.
And no matter which number you use, the model’s projection is well below the maximum reported by the current ASHRAE data set (about half of the maximum if you filter out the $7.048 point) but well above the average and median in that data set.
That result is for the entire data set which includes buildings ranging from about about 2,000 square feet to buildings with 1,800,000 gross square feet and it is based on maintaining fire tube boilers, centrifugal chillers, and VAV systems.
In most instances, it is unlikely that smaller buildings would have these systems in them. So, I filtered the data set for facilities with a gross square footage of 100,000 sq.ft. or more which tended to narrow the functions down to Class A and B office space, Labs, Healthcare, etc. Here is the result I get when I do that.
Not much different really, and apparently the facilities driving the cost towards $1.660 per square foot were smaller than what I filtered for.
So, I guess my conclusion from looking at the result predicted by the ASHRAE model vs. the data in the current ASHRAE public data base is that lacking anything else, the model will get you into the ballpark in terms of projecting costs and would give you a defensible position since you would be citing ASHRAE (and indirectly, BOMA). But compared to the average for the current database, the model may over-state the costs. And there are so many other variables (quality of the maintenance you intend to provide, in-house vs. out of house, etc.) that at most, the projection is probably just a starting point for developing a budget.
Equipment Replacement Costs
One of the things that I think the ASHRAE equation (and for that matter, the database) do not address directly is that at some point, you have to replace equipment. I’m not saying the data doesn’t include this information; in fact, I speculated earlier that it could be the reason for the $7.048 per square foot figure. I’m just saying that, near as I can tell, there is no way to understand if replacement costs are included. And, if I had to guess, I might guess that they are not since a lot of facilities would categorize the replacements as a capital expenditure vs. an operating cost.
I think (but don’t know) that the capital cost vs. operating cost categorization is an accounting principle. And I think that if the accounting department does not fully appreciate that the equipment will not last forever and as a result, have some sort of funding mechanism in place to support that need when it happens, then you could run into trouble down the road.
I have not had time to experiment with what I am about to say very much. But I think that if you took developed a budget using the maintenance cost projected by the ASHRAE equation or by using engineering judgment to select a value from the current data base, and combined it with estimates for equipment replacement costs a certain points in time, based on the ASHRAE or BOMA equipment life tables (they are very similar and probably share roots), then you would get a time vs. cost maintenance cost curve that had some of the following characteristics.
It would be very low and flat for the first couple of years because you really would only need to do the basics and major costs, if they happened, would be covered by warranty.
It would be non-linear because not everything begins to show its age at the same point nor do things necessarily wear evenly.
It would be spikey for a number of reasons including equipment replacements at the end of service life or failure and the nature of the maintenance you are doing. In other words, I suspect the costs associated with preventive maintenance are smoother than breakdown maintenance.
The baseline value would have a lot to do with the quality of maintenance you intended to perform. For instance, if you had to remove insulation from a pipe and control valve to make a repair, would you replace it completely when you finished the repair, including new insulation, vapor barriers, color coded painting, and labels? Or would you simply put the old insulation back as best you could and call it good.
The baseline value would have a lot to do with the nature of the systems you were servicing. For instance, filter maintenance on the make-up air systems at Komatsu (the wafer fab where I was a facilities engineer) included caring for MERV 7 prefilters, chemical filters that used beds of charcoal treated to absorb ammonia and nitrous oxide, MERV 15 final filters, HEPA filters at the fan discharge, and ULPA filters at the clean room ceiling. In contrast, a LEED office space may only have MERV 13 filters and may or may not use pre-filters, depending on what a life cycle cost analysis tells them about the trade-offs of leveraging different filter technologies. And the air handling systems ventilating equipment rooms may only have a MERV8 filter in either case.
The baseline value would have a lot to do with the nature of the climate you were operating in. Harsh environments are tough on equipment. For example, here is a picture of what a marine environment can do to the fins on an air cooled condenser after a while.
Amazingly enough, the equipment still ran, but the kW per ton was through the roof, even on a mild day at low load. Fortunately, that justified replacement with an all copper coil, which looks like this if you have never seen one before.
Sadly, the fins got banged up a bit during the install, as you can see.
I could elaborate more but I suspect you get my point; maintenance costs are likely very complex to assess and predict and very subject to a lot of variables. Recent versions of the ASHRAE handbooks and the BOMA literature go into this in more detail if you are interested.
We May have Counterfeited the Currency
I also suspect we have counterfeited the maintenance dollar currency a bit. In other words, what we might preach that we should do (or maybe even say we are doing) to maintain a well-run facility is different from what we might actually be doing.
It’s kind of like everyone wanting to buy a new car and being very excited about that, spending a lot of time making the decision, buying all sorts of features they want etc. But once they acquire it, they quickly loose interest in doing things like changing the oil, keeping the air filter clean, changing the coolant, etc. As a result, their financial records would understate what it cost to truly maintain the vehicle and that would not immediately be obvious by casual observation of the vehicle with out lifting the hood.
To put a building specific context on this, consider the following. If you read the NFPA codes for fire protection systems, there are requirements for periodic testing that verifies things like:
- The line feeding the facility has not become obstructed with gravel due to a repair out in the street or
- Debris in the piping inside the facility has not compromised performance, and
- Flow triggered alarm devices respond to the required flow level in the required amount of time, and
- If there is a fire pump, it responds appropriately, comes on line in the required amount of time, and delivers the required flow rate.
The frequency and specific tests required varies with the type of facility. For example, we needed to be much more rigorous in our fire protection testing at Komatsu1 for the systems serving the process equipment than we needed to be for the systems serving the office building due to the nature of the risk in the process area.
My point in bringing this up here is that I am fairly sure there are more than a few facilities that either rely on service contracts or service on failure approaches to maintenance where this type of testing is not happening, even though it is required by law. If it was happening, I’m pretty sure I would not see heavy layers of dirt and dust on the test valve handles and things like that.
Similarly, there are NFPA maintenance items related to fire and smoke dampers that require periodic visual inspection and every couple of years, actual actuation of the damper, which may involve removing and replacing the fusible link in some cases. I also believe at some point in time, you are required to replace the fusible links. But my observation of the condition of the dampers and links when I am crawling around buildings would suggest this is not happening. In fact, there are instances where the operators were not even aware that the fire damper existed because it was not well documented and/or was nearly inaccessible.
I suspect that if you were to ask the facility managers at one of these locations if they have done all testing that is required by law they would say they had, probably believing that is the case. That in turn would imply that their maintenance cost data reflected the cost of those requirements.
But if the work is not actually being done then the costs are not truly representative of what it takes to truly maintain the facility. And, while I have used life safety system maintenance as an example, I believe there are similar analogies for equipment in general in some facilities.
Other General Observations
In concluding, I thought I would list the other general thoughts and observations that came to me over the past month or so as I looked at this stuff. They are in no particular order.
Statistics play a big role in the various reports I was looking at and in the bigger picture in a lot of the things we end up involved with in building science. For me, having never had a statistics course, the topic is is pretty complex and, in some ways , obtuse and full of lingo that does not mean what you think it might mean taken at face value.
A couple of years ago, while trying to understand some statistical principle, I ran into the book Intuitive Bio-Statistics which I found to be really helpful . It was written not to try to teach you how to do the analysis. Rather, it was written to help you interpret the analysis. And while a lot of the examples in it are medical, I find that, at least for my taste, it gives some fairly understandable explanations and guidance. I have a paper copy of the 2010 edition, but just now, in looking for a link to share, I found that you can download a free .pdf version of the original 1995 edition.
Potential Limitations of the Data
There are some limitations to the data sets we have been discussing that its important to be aware of. The reports are very clear about this but unless you actually read all of them, you may not realize some of the limitations.
One is that a significant amount of the information has been derived using data from BOMA members with office buildings , or at least “seeded” with that data initially. But its more than anyone else seems to know or be willing to talk about I think, and machinery is machinery and physics is physics so at least a starting point for a discussion. And hopefully, as the public database grows, the variety of facilities it represents will grow.
Another is that when you think about how many buildings are out there, the data behind any of the reports and data bases seems extremely small; in some ways, it makes you wonder about doing any statistics with it all. The 1999 Maintenance Cost Report ASHRAE-D-RP-929 discusses this in the section on Data Collection Methodologies.
Based on that,I was surprised to learn that the random sample size required to generate data at the precision level targeted by the study was much smaller than I would have guessed. Specifically, the study targeted a 90 percent confidence level and 10 percent precision (bear in mind that these terms are used in the very specific context associated with them in a statistical analysis). To achieve that, analysis revealed that they would need to survey about 1,350 buildings to obtain the required sample size of 270 or more responses.
They in fact achieved this for facilities with in-house staff. For facilities that used an outside source for maintenance, they did not achieve it and thus, the precision of the results for that portion of the results was reduced.
Internal Data May “Trump” ASHRAE and BOMA Data and Projections
This is speculative on my part, but I suspect if you had your own internal data to work with and that the data was consistent across all of your facilities, then using that data to project maintenance costs would likely give better results than projections from the ASHRAE and BOMA data. That is not saying anything is wrong with the other data. But given some of the constraints on it, working with data that is derived from facilities that are being operated and maintained specifically as you desired is likely to more accurately reflect that reality moving forward.
Of course, the assumption is that the data does actually reflect operation as required or desired and my gut tells me that may not always be true; basically my “We May Have Counterfeited the Currency” argument.
A Few Interesting 1986 Study Conclusions
There are a couple of interesting things that showed up in the conclusions associated with the 1986 study. From what I can tell, this study has the most detail regarding maintenance cost, although the 2005 study has some interesting tables but does not draw conclusions from them beyond the table I inserted previously. Also, I have not read it as closely as the earlier studies
HVAC maintenance costs are higher for older buildings: This is probably a sort of a “well Duh” conclusion. But on the other hand (assuming you trust the statistical analysis in the reports, which I do) they have the numbers to back it up.
The costs of HVAC maintenance are higher in buildings with air and water systems: Probably another “well Duh” But I think the potential to deliver what is needed for someone who Owns Class A office space or a flagship hotel or a health care facility or production space is higher relative to heat pumps. PTACs, unitary packaged equipment, etc. might deliver, if they can deliver it at all. But the equipment has to work (also a “well Duh”, but not a given) which comes down to design and maintenance at some point.
For instance, in a hotel meeting room, I know from experience that a current technology packaged unit that is working reasonably well will probably deliver better guest satisfaction than a VAV reheat system that is making the meeting room hit the set point of 72°F …
… by cooling one half to 60°F …
… while reheating the other half to 86°F …
… because the controls and terminal units are nearly impossible to access for maintenance.
The analysis of the data suggest that the factors causing this variation are numerous, complex and difficult to measure: Probably what our guts are telling us and why this topic seems to be of so much interest to everyone and why there is so little data out there despite the interest.
Buildings where total responsibility for HVAC maintenance, including pasts and materials, is contracted to a maintenance service firm have higher HVAC maintenance costs per square foot: To me this makes logical sense because if you out-source the maintenance, you add a tier to the contracting structure. But from what I can tell, there is a perception that you can save money by doing this, which is not supported by the data.
I think what really happens is you shift cost to a different budget that perhaps can be justified more readily. But if you looked at it at the bottom line, you might have been better not outsourcing things from a number of standpoints including raw cost, keeping the expertise in house, which has some sort of intrinsic value I think, and persistence of benefits (because the people have a sense of ownership).
Incidentally, for a while, I thought one of the later reports (1999) was contradicting this because it says buildings without a maintenance staff had lower maintenance costs. But I think what the comment above is about is a facility where they still do maintenance and have a staff, its just not the Owner’s staff in contrast with a facility where at the most, there are service contracts for the basics and you call someone when something breaks.
Buildings with computerized HVAC control systems also have higher HVAC maintenance costs: I think this is the price of technology but does not capture the persistence of benefits that can be delivered by the technology (but only if it works). In other words, it probably does cost more to keep a good DDC system working that it did a pneumatic system if you maintain calibration etc. If for no other reason, even a low-end DDC system will likely have more sensors to maintain than a legacy pneumatic control system with time clocks and relay logic.
I actually have some thoughts I want to share relative to the final observation regarding the cost of maintenance for computerized control systems because while I think that may be true, I also think the value delivered by having the system will by far outweigh the added maintenance burden, assuming the system is well thought out and designed and commissioned. But I will make that a topic for a separate post rather than make this lengthily one even longer.
So that is my update. I have also placed a newer copy of the spreadsheet I use on my Google Drive if you want to use it as a starting point for building your own. As is the case with anything like that, when I share it, I am offering it at face value in the hope that it will be helpful. But you are using it at your own risk and should check the results and make sure you agree with them.
Senior Engineer – Facility Dynamics Engineering
1. Komatsu Silicon America is the company I worked for as a facilities engineer when they were building their Hillsboro wafer manufacturing facility. I was the fire protection system owner in addition to the HVAC system Owner and Co-Owner of the central chilled water plant and DDC system. As a result, I learned a lot about fire protection systems and what it took to test and maintain them. pretty interesting, but also pretty intense on occasions.