Paul Industries designs, builds and qualifies cleanrooms across Washington. The regional engineering fact worth building around is that Washington’s marine climate is unusually well suited to free cooling. A cleanroom’s dominant load is the heat it generates internally, which it must reject year round, and in this climate outside air is cool enough to do that job for a very large share of the year. The plants that capture that saving design for it; the plants that do not run mechanical cooling through mild weather for no reason.
Request a quote or call 201-450-8280
A cleanroom is a heat rejection problem wearing a cleanliness costume
People think of cleanroom air handling as being about particles, and the filtration certainly is. The energy, however, goes almost entirely into two things: moving a great deal of air, and removing the heat that the room’s own contents generate.
That heat does not go away in winter. Equipment, lighting, process loads and people produce it continuously, so a cleanroom needs cooling on a cold January morning just as it does in August. The only question is where the cooling comes from.
In a hot climate the answer is always mechanical refrigeration, because the outside air is warmer than the space. In Washington’s marine climate it frequently is not. For a large number of hours each year the outside air sits comfortably below the temperature the room needs to be held at, and on those hours refrigeration is doing work that the weather would do for free.
There are two ways to capture that, and they suit different situations.
Air-side economizer. Bring in more outside air and use it directly for cooling. Simple in principle, and in a cleanroom it is the more complicated of the two, because every cubic meter of outside air brought in has to be filtered to the room’s standard, and it arrives with whatever humidity and outdoor contaminants the day provides. In a marine climate the humidity is the real constraint: cool damp air introduced in quantity can push a room’s moisture load in a direction that costs more to correct than the cooling saved.
Water-side free cooling. Use the cool outside air to cool the chilled water loop instead, through a dry cooler or a cooling tower with a heat exchanger, and leave the room’s air alone. The room’s supply air quantity, filtration and pressure regime are unchanged; only the source of the cooling in the coil changes. This is usually the better answer for a cleanroom, because it captures most of the saving without touching the thing that is hard to change.
Where the rest of the energy goes, and what to do about it
| Lever | Mechanism | Caution |
|---|---|---|
| Free cooling | Weather does the heat rejection | Water-side is usually simpler than air-side here |
| Air change rate review | Fan power rises steeply with flow | Must be justified against in-operation performance |
| Setback when unoccupied | Reduced flow outside production | Recovery time must be proven, not assumed |
| Low pressure drop design | Ductwork and filter face velocity | Costs space; cheapest at design stage |
| Fan and motor selection | Efficiency across the operating range | Part-load behavior matters more than peak |
| Reducing internal gains | Less heat to reject in the first place | Often outside the HVAC budget holder’s control |
Two of those deserve care because they touch classification rather than only cost.
Air change rate review is frequently the largest single saving available, because fan power rises steeply with flow and many rooms are running rates inherited from a rule of thumb rather than derived from their actual particle load. It is also the change that can most easily compromise a room. Any reduction has to be demonstrated against in-operation performance and recovery, not just against an at-rest classification test, and it has to be documented as a change with proper justification.
Setback when unoccupied saves real money on a room that is only used part of the time, and its risk is recovery. The room has to return to its qualified condition reliably before production, and that recovery has to be proven and monitored rather than assumed. A setback regime without proven recovery is a finding waiting to happen.
| Continuous load | Per year | Over ten years |
|---|---|---|
| 50 kW | $28,952 | $289,520 |
| 100 kW | $57,904 | $579,040 |
| 200 kW | $115,808 | $1,158,080 |
At 6.61 cents per kilowatt-hour, below the 8.13 cent national average (EIA, 2024), Washington cleanroom running costs are moderate. The argument for the measures above is therefore not desperation about the electricity bill; it is that the same measures reduce mechanical plant size, which reduces capital, and reduce runtime on refrigeration, which reduces maintenance. Those two benefits survive even where the energy saving alone would not justify the work.
Building and qualifying
We build with walkable ceilings where the layout allows, coved junctions, flush glazing, sealed penetrations, and finishes selected for the cleaning and disinfection agents actually in use. Utility penetrations are sealed and detailed as part of the room rather than punched through afterwards, which is where the pressure regime is most often lost.
Qualification runs through installation, operational and performance stages, with classification to ISO 14644-1, recovery testing, filter integrity testing, airflow visualization where the grade warrants it, and pressure cascade verification under realistic door movement. ISO 14644-2 governs the ongoing monitoring plan. Where EU GMP Annex 1 applies alongside FDA expectations, the grade carries limits in both at-rest and in-operation states, and the air handling has to be sized for the harder of the two.
Standards referenced: EIA electricity price data · ISO 14644-1 · EU GMP Annex 1 (EudraLex Vol. 4) · ASME BPE · ISO 14644-2
Frequently asked questions
Do you build cleanrooms in Washington?
Yes, across Seattle, Tacoma, Spokane, Yakima, the Tri-Cities and statewide: design, construction, air handling and controls, free cooling integration, monitoring and the full qualification package including classification, recovery and pressure cascade verification.
Why does a cleanroom need cooling in winter?
Because its dominant load is internally generated. Equipment, lighting, process loads and people produce heat continuously, so the room needs cooling year round. The only question is whether that cooling comes from mechanical refrigeration or from outside air that is already cold enough to do the job.
What makes Washington suited to free cooling?
The marine climate. For a large number of hours each year the outside air sits comfortably below the temperature the room is held at, and during those hours refrigeration is doing work the weather would do for nothing. In a hot climate that opportunity barely exists.
Air-side or water-side free cooling?
Water-side, usually, for a cleanroom. It cools the chilled water loop through a dry cooler or tower and leaves the room’s air quantity, filtration and pressure regime untouched, capturing most of the saving without changing the part that is hard to change and hard to requalify.
What is wrong with an air-side economizer here?
Nothing in principle, but every cubic meter brought in must be filtered to the room’s standard and arrives with the day’s humidity. In a marine climate that humidity is the binding constraint: cool damp air introduced in quantity can push the moisture load in a direction that costs more to correct than the cooling saved.
Can we reduce our air change rate?
Often yes, and it is frequently the largest single saving available since fan power rises steeply with flow. Many rooms run rates inherited from a rule of thumb rather than derived from their particle load. Any reduction must be demonstrated against in-operation performance and recovery, not only an at-rest test, and documented as a change.
Is unoccupied setback safe?
It saves real money on a part-time room and its risk is recovery. The room must return reliably to its qualified condition before production, and that recovery has to be proven and monitored rather than assumed. A setback regime without proven recovery is a finding waiting to happen.
Where is low pressure drop design worth the money?
At design stage, almost always. Generous ductwork and lower filter face velocity cut fan power permanently, and both cost space rather than much money if they are decided early. Retrofitting either into a built room is expensive and frequently impossible.
If power is cheap here, why bother?
Because the same measures reduce mechanical plant size, which reduces capital, and reduce refrigeration runtime, which reduces maintenance. Those benefits survive even where the energy saving alone would not justify the work, which is the honest case in a state at 6.61 cents per kilowatt-hour.
How do I get a quote for a Washington cleanroom?
Use the form on this page or call 201-450-8280. Useful inputs are the class or grade required and whether Annex 1 applies, room footprint and ceiling height, internal heat loads, occupancy pattern, and whether the chilled water system is shared with other plant.
How is a cooling tower used for cleanroom free cooling in a Washington winter?
By running the tower to produce cold condenser water that is passed through a heat exchanger to the chilled water loop, bypassing the chiller compressors, whenever the outdoor wet bulb temperature is low enough. The tower and exchanger are sized for the cleanroom's winter load and the exchanger's approach temperature.
What controls keep outside air from carrying contamination into a cleanroom during economiser operation?
The outdoor air still passes through the full filter train, the make-up air unit dehumidifies and tempers it, and the control system limits outdoor air when its quality is poor, as during wildfire smoke. Free cooling on the water side avoids the question by never bringing extra outside air into the room.
How many hours a year can a Washington cleanroom free cool?
In the marine west of the state, wet-bulb temperatures allow water-side free cooling for a large part of the year, often the majority of hours. The exact figure depends on the site, the chilled water temperature and the exchanger approach, and it is calculated from local weather data in the design.
What chilled water temperature suits free cooling?
The warmer the chilled water can be, the more hours free cooling is available, so cleanroom cooling coils are selected for higher supply temperatures where the humidity control allows. Dehumidification needs colder water, which is why separate loops are sometimes used.
How does free cooling interact with humidity control?
Free cooling handles sensible heat well but does little for dehumidification, which needs cold coils. In the marine climate humidity control is a real load in some seasons, and the design provides for it separately.
How is the transition between free cooling and mechanical cooling controlled?
By controls that switch or blend modes based on outdoor wet-bulb and load, with the chilled water temperature held stable through the transition. Poorly tuned changeovers cause temperature swings in the cleanroom.
How is exhaust heat recovered?
Through run-around coils or plate exchangers between exhaust and make-up air, which reduce heating in winter. Make-up air heating is a meaningful load even in Washington's mild climate.
How does Washington's low tariff change which efficiency measures still pay?
Measures with low capital cost, such as air change rate reduction and setback, still pay back quickly; expensive equipment upgrades justified elsewhere by energy savings alone may not, and are justified here by reliability, capacity or carbon goals instead. The tariff shifts the case, not the engineering.
How does humidity in the marine climate affect the envelope?
Cool, damp outside air condenses on cold surfaces and drives moisture into any gap, so the envelope needs a continuous vapour control layer and sealed penetrations. Mould in interstitial spaces is a real risk in this climate.
What sectors need cleanrooms in Washington?
Biotech and pharmaceutical operations around Seattle and Bothell, medical device makers, aerospace and electronics, and food and beverage controlled areas. The classification follows the sector; the free cooling advantage applies to all of them.
How is a cleanroom protected from seismic events in Washington?
With bracing of ceilings, filter housings, ductwork and equipment to the seismic requirements of the building code, so that a tremor does not drop a filter or open the envelope. Cleanroom components are often overlooked in seismic design.
What about smoke from wildfire season?
Summer wildfire smoke loads outdoor air with fine particulate that blinds pre-filters and can carry into the room through any envelope leak. Pre-filtration capacity, monitoring and the ability to reduce outdoor air during smoke events are designed in.
How is a cleanroom commissioned for free cooling?
By verifying the changeover controls, measuring chilled water temperature stability through mode changes, and confirming that room conditions hold in both modes. The commissioning is timed to catch both mechanical and free cooling seasons where possible.
Can an existing cleanroom in Washington add free cooling?
Often, by adding a heat exchanger and controls to the chilled water system, provided the cooling tower has capacity and the chilled water temperature allows. It is one of the better retrofits available in the state.
What is the commonest missed opportunity in Washington cleanrooms?
Mechanical cooling running through mild weather because the plant was designed without free cooling. The room performs perfectly and costs more than it should every year.
The air you throw away was expensive to make
Free cooling addresses where the cooling comes from. There is a second and independent opportunity on the other side of the system, and it is the one most often left entirely alone: the air the room exhausts.
A cleanroom runs on a continuous supply of outside air to maintain its pressure regime and to dilute what the process generates. That air is filtered, heated or cooled, and humidity-adjusted to the room’s requirement, all of which costs money. Then an equal volume leaves the building, still carrying every bit of that conditioning, and in most installations it is simply discharged.
Recovering it is well-established engineering and the choice of device depends mainly on whether the exhaust may contact the supply.
Where cross-contamination is acceptable, as it often is on a room handling nothing hazardous, an enthalpy wheel transfers both heat and moisture between the two streams. That second part matters more than it sounds in a marine climate, because managing humidity is a significant share of the conditioning cost, and a device that recovers moisture in winter and rejects it in summer is doing useful work in both directions.
Where the streams must not mix at all, because the exhaust carries product, solvent or anything requiring containment, a plate exchanger or a run-around coil loop keeps them physically separate. A run-around loop recovers less than a wheel but it allows the supply and exhaust air handlers to sit in completely different parts of the building, which on a retrofit is frequently the deciding factor.
Three practical points decide whether these work in service.
Pressure drop is a permanent cost. Any recovery device adds resistance to both airstreams, and fan energy is continuous. A device recovering a great deal of heat through a high pressure drop can consume much of its own benefit, and the comparison should be made on net annual energy rather than on recovery effectiveness alone.
Bypass matters. There are hours when recovery is not wanted, because the outside air is already at a useful condition. A device with no bypass keeps adding pressure drop through those hours for nothing. Bypass dampers are cheap and they are regularly omitted.
Filter and maintain the exhaust side. A recovery device fouled on the exhaust side quietly loses effectiveness and gains pressure drop, and nobody notices because nothing fails. Access for cleaning, and a monitored pressure differential across the device, turn that into something the plant can see.
We design supply and exhaust air handling with recovery integrated rather than added, and on existing rooms we survey what is currently being discharged before recommending anything, because the size of the prize is entirely a function of how much conditioned air is leaving and at what condition.
Designing or reviewing a Washington cleanroom?
Tell us your internal heat load and whether the chilled water system is shared. Those decide whether water-side free cooling is straightforward or awkward. Call 201-450-8280 or use the form below.