Retro-commissioning existing buildings field guide

Retro-commissioning, and why you tune what is already there

Retro-commissioning, RCx, is the process of commissioning an existing building that was never commissioned at construction or has drifted out of tune over years of operation. The work gets the equipment already installed to run the way it was meant to, rather than replacing it. Most of what RCx finds is operational, not mechanical. A schedule that no longer matches when people are in the building, a setpoint someone overrode during a complaint call and never reset, a damper stuck part open, a control loop left in hand. None of that needs a capital project to fix.

That is the reason RCx pays better than almost any other energy measure. The building already has the hardware. What it lost is the tuning, and tuning is mostly labor and controls work, not a purchase order for new chillers. Studies on commercial buildings commonly report whole-building energy savings in the range of 5 to 20 percent from RCx, with simple paybacks often under two years, though the number depends on the building, the climate, and how far it had drifted.

The work breaks into four moves: screen the building to confirm it is a candidate, investigate it with trend data and functional tests, fix the findings low-cost first, and keep the savings with ongoing monitoring. For new-construction commissioning, which proves a building before anyone occupies it, see the data center commissioning levels guide. For the continuous analytics layer that catches drift as it happens, see the building automation fault detection and diagnostics guide. This guide is about the existing building that nobody ever tuned, or that has quietly fallen out of tune since they did.

Tune the building, do not replace the equipment

The single idea behind RCx is that you tune what is already installed to work as intended before you spend a dollar on new equipment. Most buildings are running gear that is mechanically fine and operationally wrong. The air handler works. The chiller works. The valves and dampers move. They are just being told to do the wrong thing by schedules, setpoints, and sequences that have drifted away from what the building needs.

This is where RCx parts ways with a capital retrofit, and where the money is. Replacing a working rooftop unit because the building runs hot is treating the symptom and paying capital prices for it. The unit may be running hot because the economizer is stuck shut and it never gets the free cooling it was designed to use, or because a stuck reheat valve is fighting the cooling all day. Fix the economizer or the valve and the existing unit does the job it was always able to do, for the cost of a service call instead of a replacement.

Treat the new equipment as the last resort, not the first move. The discipline is to exhaust the operational fixes, prove they did not get you there, and only then make the capital case. A building that gets a new chiller while its sequence is still broken keeps wasting energy, now with a bigger invoice attached. ASHRAE frames RCx as restoring intended performance through the commissioning process, and a commissioning authority runs it so the call to tune rather than replace is made by someone independent of the contractor selling the replacement.

Why buildings drift out of tune

RCx works because buildings drift, and they drift in predictable ways. A building leaves the contractor running close to design, and from that day it slides. Operators override setpoints to settle a complaint. Schedules get bypassed for an after-hours event and never get put back. Dampers and valves stick from age and dirt. A control loop gets switched to hand for a service call and is forgotten there. Sensors fall out of calibration a degree or two at a time. The sequence the designer wrote stops being the sequence the building runs.

None of this trips an alarm. That is what makes it dangerous to the energy bill. A building can drift for years while every space stays comfortable, because the operators keep it comfortable by brute force, heating and cooling against each other, running equipment longer than it needs to, and overriding whatever fights them. The comfort is real. The waste underneath it is invisible until somebody pulls the trends and looks.

The drift is cumulative and it is human. Every override was a reasonable fix for a real problem on the day it was made. The trouble is that the fixes pile up, nobody removes the old ones, and after a few years the building is running on a stack of patches instead of its design intent. RCx is the structured pass that finds the patches, decides which ones are still needed, and returns the rest to the sequence the building was meant to run.

What is the difference between commissioning, retro-commissioning, and re-commissioning?

The commissioning family splits by whether the building was ever commissioned and whether it is a one-time event or an ongoing service. Commissioning, Cx, proves a new building or a new system works as designed before anyone relies on it. Retro-commissioning, RCx, is the first commissioning of an existing building that never got one. Re-commissioning, ReCx, repeats commissioning on a building that was commissioned before and has since drifted. Monitoring-based commissioning, MBCx, is the continuous version that watches the building with analytics so the tuning never stops.

The line that matters most on an existing building is RCx versus ReCx, and it comes down to whether there is an original commissioning record to return to. RCx on a never-commissioned building has no design-intent baseline waiting in a binder, so the team has to reconstruct what the building should do from the drawings, the sequences, and the equipment before they can say what drifted. ReCx has that record and checks the building against it. The terms get used loosely in the field and in incentive programs, so confirm which scope a program means before you bid it.

ASHRAE Guideline 0 sets the overall commissioning process, and Guideline 0.2 adapts that process specifically to existing buildings, often called existing building commissioning, EBCx, which is the umbrella that RCx and ReCx sit under. The new-construction side of this family is covered in the data center commissioning levels guide. The continuous side, MBCx, leans on the fault detection layer covered in the building automation fault detection and diagnostics guide.

What is the retro-commissioning process?

The RCx process runs in four phases: planning, investigation, implementation, and hand-off with ongoing monitoring. Planning sets the objectives and screens the building to confirm it is worth the work. Investigation finds the drift through document review, a site assessment, BAS trend data, staff interviews, and functional tests, and rolls everything into a master list of findings. Implementation fixes the findings, low-cost first. Hand-off documents what was done and sets up the monitoring that keeps the savings from sliding back.

The phases map onto the ASHRAE commissioning process, which Guideline 0.2 adapts for existing buildings, so the structure is not something a single firm invented. The order is what protects the budget. You screen before you investigate so you spend the investigation hours on a building that can actually return them. You investigate before you implement so you fix the real findings instead of guessing. You set up monitoring before you hand off so the building has a way to tell you when it starts drifting again.

The heaviest phase is investigation, because that is where the building gives up its drift, and the cheapest phase to skip is the hand-off, which is exactly why the savings so often evaporate. A building gets investigated, gets fixed, and gets walked away from with no monitoring and no persistence plan, and within a year or two it has drifted back to where it started. The phases only pay off if you finish the last one.

Is the building a candidate? Screening

Screening decides whether a building is worth retro-commissioning before anyone spends investigation hours on it. The strongest candidates share a profile: high energy use intensity compared to similar buildings, a steady stream of comfort complaints, older controls or a BAS nobody has touched in years, a building that was never commissioned, and enough floor area that a few percent of savings is real money. A building that screens high on several of these will usually return the investigation cost many times over.

Energy use intensity is the fastest first cut. Benchmark the building against its peers, through a tool like ENERGY STAR Portfolio Manager or a utility program, and a building sitting well above the median for its type is almost certainly carrying drift. Pair that with the complaint log and the override list from the BAS, and you can usually tell within a day or two whether the building is a candidate or whether its waste is structural and would need capital, not tuning.

Size and complexity raise the ceiling on savings. Large buildings with central plants, a lot of zones, and intricate sequences have the most places to drift and the most to recover, which is why hospitals, labs, universities, and large offices tend to show the best RCx returns. A small, simple building can still benefit, but the absolute dollars are smaller, so the screening is about matching the depth of the RCx effort to what the building can give back.

The investigation: finding the drift

The investigation phase is where the team finds the drift, and it works by comparing what the building should do against what it actually does. The inputs are the document review to reconstruct design intent, a walk-through site assessment of the equipment, BAS trend data pulled over weeks, interviews with the operators who know where the bodies are buried, and functional tests that prove behavior the trends only suggest. Everything that turns up rolls into one master list of findings, ranked by cost to fix and energy to save.

The operators are the most underused source in the room. The people who run the building every day know which units never worked right, which schedules they bypass, and which loops live in hand, and a few hours of honest interviews will point the investigation straight at the worst drift faster than any data pull. Ask them what they override, and why, and you have a head start on the master list.

The trend data is where the quiet waste shows itself, because the trends record what the building did when nobody was watching. Reading BAS trends to find faults and energy waste is its own discipline, covered in the building automation fault detection and diagnostics guide, and on a data-rich building that analytics layer can do in a night what a person would spend weeks on by hand. The master list that comes out of investigation is the product the rest of the project runs on, so it has to be specific: the finding, the equipment, the evidence, the estimated savings, and the proposed fix.

What does retro-commissioning fix?

Retro-commissioning fixes operational drift, and the findings repeat from building to building. Schedules that no longer match occupancy, so equipment runs nights and weekends in empty space. Setpoints overridden and never reset. Economizers that have stopped delivering free cooling. Simultaneous heating and cooling, where reheat fights the cooling coil all day. Dampers and valves stuck or hunting. Sensors out of calibration. Control loops left in manual. Sequences that quietly stopped working as written. These are the usual suspects, and most of them are no-cost or low-cost to correct.

The reason the list repeats is that the failure modes are common to how buildings are run, not to any one building. Every commercial building has schedules, every air handler has an economizer, every reheat system can end up fighting itself, and every BAS has loops that can be switched to hand. So the master list of findings on a building nobody has tuned tends to read like the table below, with the specifics filled in. The job of the investigation is to confirm which ones are present and what each is costing.

Treat the findings table as a checklist of where to look, not a guarantee of what is wrong. A building might have a perfect economizer and a badly broken schedule, or the reverse. You confirm each finding with the trends and the functional test before you put a savings number on it, because a finding you assumed instead of proved is a savings number you cannot defend in the M&V.

Functional testing: prove it, do not trust the screen

Functional testing proves a system does what it is supposed to do by making it run through its modes and watching the result, instead of trusting the BAS graphic that says it is fine. The graphic shows the commanded state, not the physical one. A damper can read 100 percent open on the screen while the linkage is broken and the blade has not moved in a year. The only way to know is to command it and confirm the blade, the temperature, or the flow actually responded.

This is the move that separates RCx from an energy audit. You do not assume the economizer works because the sequence is in the controller. You force it into economizer mode on a mild day, watch the outdoor air damper drive open, and confirm the mixed-air temperature drops and the mechanical cooling backs off. You test the resets by driving the input and watching the output follow. You test the staging by adding load and confirming the stages come on and off in order. You test the failure modes the sequence is supposed to handle and confirm it handles them.

Trusting the BAS is the most common way an investigation misses real drift. The screen is a model of the building, and the building is the building. When the two disagree, the building wins, and the functional test is how you find the disagreement. Where the trend data shows a pattern that looks like a fault, the functional test is what confirms whether it is the equipment, the sensor, or the sequence, so you fix the right thing instead of the thing that looked wrong on the dashboard.

Reading the trend data

Trend data from the BAS is the evidence that shows the drift over time, because it records what the building actually did hour by hour while nobody was watching the screen. A week or a month of trends laid over each other tells a story a single snapshot cannot. The supply temperature that never moves, the valve that is always part open, the fan that runs at 2 a.m. in an empty building, the two zones whose heating and cooling commands rise together. Each is a fingerprint of a specific drift.

The classic patterns are worth knowing on sight. Simultaneous heating and cooling shows up as a reheat valve and a cooling valve both open at the same time. A failed economizer shows as an outdoor-air damper that sits at minimum on a mild day when it should be wide open. Short-cycling shows as equipment starting and stopping far more often than the load warrants. Equipment that never turns off shows as a status point that is high around the clock. None of these set off an alarm, which is why they hide until somebody reads the trends.

Pulling and reading trends by hand works on one building and falls apart on a portfolio, which is where data-driven RCx and the analytics layer take over. The same expected-versus-actual logic, run automatically on every point every night, is the subject of the building automation fault detection and diagnostics guide. On a building with good trends, that analytics layer turns the investigation from a manual hunt into a ranked list of findings the team can confirm with functional tests.

The economizer: the classic broken thing

The economizer is the single most common thing RCx finds broken, and it is pure free cooling left on the table when it fails. An air-side economizer brings in cool outside air to cool the building when conditions allow, so the mechanical cooling can back off or shut down. When it works, it is one of the largest energy savers in the building. When it fails, the building runs its compressors on a mild day that it could have cooled for the price of running the supply fan.

Economizers fail in a handful of ways, and all of them are low-cost to fix. The damper actuator seizes or the linkage breaks, so the damper never opens. Someone disables the economizer in the sequence to stop a comfort complaint and never re-enables it. The outdoor-air temperature or enthalpy sensor drifts out of calibration, so the controller thinks it is hot outside when it is mild and never calls for free cooling. The changeover setpoint is wrong. Each one is a service call, not a capital project, and each one is recovering energy the building was designed to save.

The economizer also illustrates why functional testing matters, because a failed economizer almost always looks fine on the BAS graphic. The screen shows the commanded damper position and the sequence in the controller, both of which can be perfect while the physical damper has not moved in months. You confirm the economizer by forcing it into free-cooling mode on a mild day and watching the mixed-air temperature actually drop. The screen will lie. The mixed-air sensor will not.

Simultaneous heating and cooling: the building fighting itself

Simultaneous heating and cooling is the building fighting itself, and it is one of the most wasteful findings in RCx because you pay twice for the same air. A reheat coil warms air the cooling coil just chilled, or one zone heats while the zone next to it cools, and the energy spent on each cancels the other while the meter runs for both. The space stays comfortable, so nobody complains, which is exactly why it can run for years unnoticed.

The usual cause is a sequence or a setpoint that drifted, not a hardware failure. The cooling coil is left holding a low supply temperature while the zone reheats it back up, when a smarter supply-air-temperature reset would let the cooling back off. Overlapping heating and cooling setpoints in a zone, with too small a deadband, leave both calls active at once. A stuck-open reheat valve dumps heat into air that does not need it. In a VAV system, a minimum airflow set too high forces reheat to offset cooling the zone never asked for.

The fix is almost always operational. Widen the deadband so heating and cooling cannot both be active in the same zone. Add or repair the supply-air-temperature reset so the plant is not making colder air than the building needs. Drop the VAV minimums to the lowest the ventilation requirement allows. Repair the stuck valve. The trend signature is unmistakable once you look for it, a heating output and a cooling output both active at the same time, and finding it is most of the work because the comfort it hides behind keeps it off the complaint log.

No-cost and low-cost fixes first

The reason RCx returns what it does is that you fix the no-cost and low-cost operational findings first, before you spend any capital. Reprogramming a schedule, resetting and locking a setpoint, recalibrating a sensor, returning a loop to auto, and correcting a sequence are mostly labor and controls time. They pay back in months, sometimes weeks, because the energy starts dropping the day the fix goes in and there was little to spend in the first place.

Order the master list by payback and the no-cost items rise to the top on their own. A schedule correction that stops a building from running nights and weekends can be the single largest saver on the list and cost nothing but the time to reprogram it. A setpoint reset costs nothing. A sensor recalibration costs an hour. These are the findings that make RCx the fastest-payback energy measure there is, and they should all be done and verified before anyone writes a proposal for new equipment.

Capital has its place, but its place is after the operational fixes, not before. Once the building is tuned and you have measured what it does in its corrected state, the remaining waste is the honest case for a retrofit. A building that gets a capital upgrade while its schedules and sequences are still broken is buying efficiency it will throw away on bad operation. Fix the free things, measure, and let the real capital needs show themselves against a tuned baseline.

Implementation: fixing the findings

Implementation is where the master list becomes corrected building, and the discipline is to fix in payback order and verify each fix as you go. Work the no-cost schedule and setpoint corrections first, then the low-cost economizer and sensor repairs, then the sequence rewrites, and hold any capital recommendation until the operational work is done and measured. The common fixes are the inverse of the findings: correct the schedule, reset and lock the setpoints, repair the economizer, stop the simultaneous heating and cooling, free the stuck damper, recalibrate the sensor, return the loop to auto, and restore the broken sequence.

Verify each fix individually rather than fixing a dozen things and checking the meter. If you correct a schedule, pull the trend the next week and confirm the equipment now stays off when the building is empty. If you repair an economizer, functionally test it and confirm the free cooling actually happens. Bundling fixes and reading the whole-building meter tells you the building got better but not which fix did it, and when one of them quietly fails later you will not know which one to chase.

Document each fix as it lands, including what was changed, the trend or test that confirmed it, and the savings it is credited with. That record is what the M&V is built on and what the next operator needs so the fix does not get overridden again. A fix that is made but not documented is a fix the building will undo the next time someone calls with a complaint.

How do you prove retro-commissioning savings?

You prove RCx savings with measurement and verification, M&V, which compares the building's energy use after the fixes against a baseline of what it would have used without them. The baseline is the building before RCx, adjusted for weather and occupancy so you are comparing like to like. The savings are the avoided energy, the gap between the adjusted baseline and the measured post-RCx use. Without that comparison, the savings are a claim, not a number, and an incentive program or an owner is right not to pay on a claim.

The recognized framework for this is the International Performance Measurement and Verification Protocol, IPMVP, which sets out the methods for establishing a baseline, adjusting it, and quantifying the savings credibly. Most utility RCx incentive programs and most M&V requirements trace back to IPMVP, and the protocol gives several options ranging from a whole-building meter analysis to isolating a single retrofit. The option you use depends on what you fixed and what you can meter.

Get the baseline right or the whole M&V is worthless, because the savings are only as defensible as the thing you measure against. A baseline that ignores a weather swing or a change in occupancy will either overstate or understate the savings, and either one destroys trust in the number. Set the baseline before the fixes go in, adjust it honestly, and the avoided-energy number will hold up when the owner or the program checks it.

Why do building savings drift back?

RCx savings drift back because the same forces that caused the original drift never stopped, and a one-time project does nothing to hold them off. The setpoints you reset get overridden again the next time someone is cold. The schedules you corrected get bypassed for the next after-hours event and left bypassed. The loops you returned to auto get switched back to hand for the next service call. A new operator who does not know why a setting is the way it is changes it. Studies commonly find that without ongoing monitoring, a retro-commissioned building drifts back toward its old performance within roughly one to three years.

This is the most important thing to understand about RCx, and the most often ignored. The fixes are not permanent. They are the building tuned to a moment, and the building does not stay still. Treating RCx as a one-time event, collecting the first year of savings, and walking away guarantees you will be back doing the same investigation on the same building in a few years, paying again to fix drift you already fixed once.

The way you hold the savings is to monitor for the drift and correct it as it appears, which is monitoring-based commissioning layered on a fault detection system. The continuous version is covered in the building automation fault detection and diagnostics guide, and it is the difference between RCx that pays once and RCx that keeps paying. Build the persistence plan into the hand-off, not as an afterthought. The savings you do not monitor are the savings you will lose.

Monitoring-based commissioning: keeping it tuned

Monitoring-based commissioning, MBCx, is RCx that never ends, run continuously by analytics instead of as a one-time project. It puts fault detection and diagnostics on the BAS so the building is checked every night against how it should be running, and it surfaces drift as it appears instead of years later when somebody finally pulls the trends. Where RCx is a pass through the building, MBCx is a standing watch on it.

The mechanism is the same expected-versus-actual logic the investigation phase runs by hand, automated and run on every point. When a schedule gets overridden, when an economizer fails, when a loop goes to hand, the analytics catch it within days and raise it as a finding, while the savings are still small enough to recover cheaply. That is the whole point. The drift that a one-time RCx would let accumulate for two years gets caught and corrected almost as it starts.

MBCx is how the savings persist, and it turns commissioning from an event into a service. The detect, diagnose, dispatch, and verify loop that drives it is covered in the building automation fault detection and diagnostics guide. The short version is that a building with MBCx does not drift back, because something is watching for the drift continuously and someone is fixing it before it adds up. RCx finds the drift once. MBCx keeps finding it.

Is retro-commissioning worth it?

Retro-commissioning is the fastest-payback energy measure available on most existing buildings, because the savings come from operational fixes that cost little and the energy reduction starts immediately. Reported whole-building energy savings commonly land in the range of 5 to 20 percent, with simple paybacks often under two years and the best no-cost findings paying back in months. The exact numbers vary with the building, the climate, the energy rates, and how far it had drifted, so treat published ranges as typical, not as a promise.

The economics are driven by the fact that the fixes are mostly labor, not capital. A schedule correction or a setpoint reset costs the time to make it and saves energy from that day forward, which is why RCx cost is often quoted in cents per square foot rather than dollars per ton of equipment. Reported RCx savings frequently fall in the range of roughly $0.10 to $0.75 per square foot per year, against a project cost that the savings recover quickly, though the spread depends heavily on the building.

Utility incentive programs sharpen the case further. Many utilities offer RCx or existing-building commissioning incentives that cover part of the investigation and implementation cost, because the energy savings help them defer capacity. Where an incentive is available it can cut the effective payback to under a year. Check the local utility program for what it funds and what M&V it requires before you bid the work, because the program rules often shape the scope.

The commissioning authority

The commissioning authority, CxA, is the independent expert who runs the RCx and answers to the owner, not the contractor. The role is deliberately third-party, because the value of RCx depends on someone making the call to tune rather than replace, and to credit savings honestly, without a stake in selling equipment or hiding a finding. The CxA plans the work, leads the investigation, writes the master list, oversees the implementation, and verifies that each fix did what it was supposed to.

Independence is the point of the role, not a formality. A contractor investigating their own building has an incentive to recommend the work they sell, and an operator investigating their own building has an incentive not to surface the overrides they made. The CxA has neither, which is why ASHRAE and most incentive programs build the process around an independent commissioning authority. On an existing building the CxA also has to reconstruct design intent that may never have been documented, which is its own skill.

The CxA is also who makes the persistence plan stick, because they are positioned to hand the building back with a monitoring strategy rather than just a report. A good CxA does not close out the project at the last fix. They set up the ongoing commissioning or MBCx that keeps the savings, train the operators on why the settings are what they are, and leave a record specific enough that the next person does not undo the work.

What to document

The RCx record is what makes the savings defensible and what keeps the next operator from undoing the work, so document the whole project, not just the final report. Capture the screening that justified the building, the master list of findings with the evidence behind each, the functional tests and their results, every fix with the trend or test that confirmed it, the M&V baseline and the avoided-energy number, and the persistence plan for keeping it. A finding without evidence is an opinion, and a fix without a record is a fix the building will reverse.

Keeping that record straight across an investigation, an implementation, and a hand-off is a field-data problem, and it is the kind of structured capture FieldOS is built for. Logging each finding with its photo and trend at the equipment, tracking which fixes are done and verified, and holding the M&V and persistence plan in one place means the record survives the project instead of living in someone's notebook. The point is that the document set outlives the people who made it, because the building will be retro-commissioned again someday and the next team should start from what this one found.

Common mistakes

• Replacing equipment when tuning the existing equipment would have fixed the problem at a fraction of the cost.
• Trusting the BAS graphic instead of functionally testing the system to prove what it physically does.
• Jumping to capital projects before the free and low-cost operational fixes are done and measured.
• Skipping the M&V, so the savings are a claim nobody can defend against a baseline.
• Walking away with no ongoing monitoring, so the savings drift back within one to three years.
• Screening the wrong building, spending investigation hours where the waste is structural, not operational.
• Bundling many fixes and reading only the whole-building meter, so no single fix can be verified or trusted.

Field checklist

Standards and references

ASHRAE owns the commissioning process side of this. Guideline 0 sets the overall commissioning process and its phases, and Guideline 0.2 adapts that process specifically to existing building systems and assemblies, which is the existing building commissioning, EBCx, framework that RCx and ReCx sit under. ASHRAE Standard 202 sets the commissioning process as a standard alongside the guidelines. These define the phases, the role of the commissioning authority, and the documentation, so cite them for the process, not for any specific savings number.

The savings side is governed by measurement and verification, and the recognized framework is the International Performance Measurement and Verification Protocol, IPMVP. It sets out how to build a baseline, adjust it for conditions, and quantify avoided energy credibly, and most utility RCx incentive programs require an M&V approach traceable to it. Cite IPMVP for the M&V method, and confirm the specific option and reporting the incentive program requires.

The commissioning authority is the independent party who runs the process, and the utility RCx or existing-building commissioning incentive is often what funds part of the work and sets the M&V bar. The exact guideline editions, standard versions, and program rules change over time and vary by jurisdiction and utility, so confirm the current ASHRAE editions and the local program requirements before you cite them on a proposal. The principle holds regardless of edition: tune the existing building to work as intended with mostly no-cost fixes, functionally test the drift rather than trusting the BAS, and prove the savings with M&V and monitor them or they drift back.

Terms and definitions

Retro-commissioning carries a stack of related terms that get used loosely in the field and in incentive programs, so the same building can be described several ways across a proposal, a contract, and a utility application.

The terms below are the ones that change the meaning of the scope. Get the commissioning, retro-commissioning, and re-commissioning distinction right in particular, because it decides whether there is an original baseline to return to and how the investigation has to be run.

Commissioning (Cx)

Proving a new building or system works as designed before occupancy

Retro-commissioning (RCx)

The first commissioning of an existing building that was never commissioned

Re-commissioning (ReCx)

Commissioning again a building that was commissioned before and has drifted

Monitoring-based commissioning (MBCx)

Continuous commissioning run by analytics so the tuning never stops

Building drift

The slow loss of design performance as setpoints, schedules, and sequences are overridden over time

Functional testing

Running a system through its modes to prove what it physically does, not what the graphic says

Economizer

Controls that bring in cool outside air for free cooling so mechanical cooling can back off

Simultaneous heating and cooling

The building heating and cooling the same air or adjacent zones at once, paying twice

Persistence

Holding the RCx savings over time instead of letting the building drift back

Commissioning authority (CxA)

The independent expert who runs the commissioning process for the owner

Related tools

Calculators and readiness checks for this work

Compare your options

FAQ

People also ask

• What is data center commissioning?
• What is fault detection and diagnostics?
• What is boiler commissioning?
• What is a chilled beam?
• What is a factory authorized chiller startup?