The decision to replace a chiller, air handling unit, or cooling tower is one of the largest capital expenditure decisions a Saudi building owner or facility manager makes. Equipment costs for commercial-scale HVAC machinery run to hundreds of thousands of riyals per unit. Project management, installation labour, testing, commissioning, and the inevitable disruption to building operations during works add further to the total cost. The decision is made, in most cases, because the existing equipment is perceived to be undersized, inefficient, or unreliable — it is not keeping the building cool, or it is running continuously at full capacity and still failing to meet setpoints.
What is rarely tested before this decision is made is whether the equipment itself is actually the problem. The assumption — almost universally — is that the HVAC equipment is to blame. The alternative explanation, supported by technical evidence from building performance assessments across Saudi Arabia, is that the equipment is performing adequately but is being asked to do far more than it was designed for — because the building is leaking conditioned air at a rate that was never accounted for in the original design. In these cases, replacing the equipment solves nothing. The new, more powerful chiller is immediately burdened by the same uncontrolled loads that overwhelmed the old one, and the capital investment delivers a fraction of the expected performance improvement.
How Leakage Increases Apparent Cooling Demand
A building’s cooling system is designed to handle a specific cooling load — the combination of heat gain through the building fabric, solar radiation, internal heat gains from occupants and equipment, and the ventilation load from introducing outdoor air at the design outdoor temperature. This load is calculated at design stage using assumptions about the building’s airtightness and duct system integrity.
When the building leaks — when the envelope is more porous than assumed and the duct system loses conditioned air to ceiling voids and plant areas — the effective cooling load is substantially higher than the design calculation predicted. The envelope leakage continuously imports hot outdoor air that must be cooled. The duct leakage means that supply air is lost before it reaches occupied spaces, so the occupied spaces receive less cooling than designed and the system must run harder and longer to compensate. The result is a system that appears undersized and inefficient — because it is fighting loads it was never designed to manage.
How Leakage Contributes to Equipment Oversizing
The maintenance of a building with persistent cooling problems frequently involves progressively increasing the cooling capacity — adding supplementary split units, increasing chilled water flow rates, lowering supply air temperatures — in an attempt to overcome the performance deficit. This creates a secondary problem: when the building eventually has its leakage addressed, the oversized system then operates at part-load for much of the year, with poor efficiency and increased wear on start-stop cycling.
A new chiller specified to handle a building’s apparent cooling load — including the load contribution from envelope and duct leakage — will be oversized relative to the load that would exist if the leakage were first addressed. Correctly sequencing the intervention avoids this waste: seal the building, establish the true cooling load, then specify equipment sized for that load.
What to Test Before Replacing Chillers or AHUs
Before any capital expenditure decision on HVAC equipment replacement, Aeroseal Arabia recommends a building performance assessment covering the following:
- Envelope airtightness test: Establishes the current envelope leakage rate and compares it to the design specification. In Saudi commercial buildings, pre-assessment leakage rates of 8 to 12 ACH50 against design targets of 3 to 4 ACH50 are common — representing a two-to-four times increase in infiltration load above design.
- Duct pressure leakage test: Establishes total duct system leakage as a percentage of design supply airflow. Leakage of 20% to 30% means that 20% to 30% of the conditioned air the AHU produces never reaches the occupied spaces — the equivalent of running the system with 20% to 30% less cooling capacity than its nameplate rating.
- HVAC commissioning review: Reviews current fan speeds, coil performance data, refrigerant pressures, and chilled water supply and return temperatures against design values. A well-maintained system running outside its design parameters is a system that has been tuned to compensate for something — and that something is frequently leakage.
- Energy consumption analysis: Compares actual energy consumption against design benchmarks and against comparable buildings without leakage problems. A building consuming 40% more HVAC energy than its peers with similar occupancy and use is a strong candidate for leakage assessment rather than equipment replacement.
Establishing a Performance Baseline
Once the assessment is complete, the building has a documented performance baseline: actual envelope leakage rate, actual duct leakage rate, actual HVAC operating parameters, and actual energy consumption. This baseline serves two purposes. First, it quantifies the gap between current and design performance, which in turn estimates the improvement achievable through sealing rather than equipment replacement. Second, it provides the verified starting point against which post-intervention performance can be measured.
Comparing Repair, Sealing and Replacement Costs
In the majority of Saudi buildings assessed by Aeroseal Arabia before equipment replacement decisions are finalised, the cost of AeroBarrier envelope sealing and Aeroseal duct sealing combined is 15% to 25% of the cost of the equipment replacement being contemplated. The energy saving from sealing — typically 15% to 30% of total HVAC energy — produces a payback period of one to three years. The equipment, if replaced after sealing, can be correctly sized for the actual post-sealing load rather than the inflated apparent load including leakage.
Verifying Savings After the Intervention
Post-sealing performance verification — repeating the airtightness test, duct leakage test, and energy monitoring after the sealing programme is complete — provides the documented evidence of improvement. This evidence serves as the basis for updating the facility’s energy performance baseline, for sustainability reporting, and for the informed decision about whether any equipment upgrade is still necessary after leakage has been addressed.
Conclusion
A chiller replacement that addresses the symptom rather than the cause is capital misspent. Before committing to HVAC equipment replacement in any Saudi commercial building, test the envelope and duct system. The investment in assessment is a fraction of the equipment cost and the evidence it produces either confirms the equipment decision or reveals a far cheaper, faster, and more effective path to the performance outcome the owner is seeking. Aeroseal Arabia provides comprehensive pre-investment building performance assessments across Saudi Arabia. Contact our team before your next capital expenditure decision.
