High Airflow Pressure Loading Actuator


Post-storm investigations conducted by FEMA [12,13], NIST [14], and others [15-17] have found that building envelope failures are a leading cause of wind and water damage to building envelopes. Unmanaged water ingress [18-20] damages or destroys the building’s interior and its contents. The economic losses can be high (greater than 40% of the value of the structure) even if major structural damage is avoided. The High Airflow Pressure Loading Actuator (HAPLA) simultaneously applies time-varying wind pressure and simulated effects of wind-driven rain on the horizontal building facade. The research on wind-driven rain deposition on building façades [21-25] has been largely based on physical testing using a combination of simulated rain and application of steady, uniform pressures. These tests lack the temporal changes in surface pressures of the incident wind, and the wetting rates used were never experimentally validated. The HAPLA is ideally designed to conduct testing on wall materials, and construction in wood, masonry, and aluminum-glass curtain walls and fenestration.

1.2. Capabilities and Principle of Operation

Conceptually based upon the UWO-designed pressure-loading actuators [8], the HAPLA was designed to test highly air-porous systems and wall systems that progressively fail during testing. The HAPLA itself consists of two 75 HP Centrifugal fans that may be configured to operate in series or parallel; the former is ideal for minimal air leakage. The ducting connects to a five-port air valve: that controls chamber pressure by modulating the amount of air traveling from the test chamber to the exhaust port. The valve disk is connected to a rotary actuation system comprised of a Metronix ARS2340 servo positioning controller, a Sumimoto Drive Technologies CHF 6135 Y-11 11:1 drive reduction and a Motor Technology Ltd. SBL-T6-2900 brushless servo motor. A two-pole resolver in the motor provides positioning feedback. This design enables the HAPLA to test components under simultaneous fluctuating pressure and wind-driven rain conditions, up to a 3 Hz waveform at pressures up to 6 kPa. Using two fans operable in parallel or in series enables the HAPLA to operate on specimens while maintaining relatively high air through-flow (leakage) rates (up to 51 m3/min or 1,800 CFM).

A variable intensity water spray system (VIWSS) was developed to simulate wind-driven rain effects on building envelope systems. The VIWSS is installed within steel chamber and it consists of two separate spray racks with 25 nozzles (Figure 50b). The spray rack is controlled by two Bray Control Series 70 Electric actuators that regulate wetting rate over a range of 50 mm/hr to 550 mm/hr [28]. This large wetting range is required because rain deposition on a building façade is a function of the (nominal) product of the horizontal rainfall intensity (i.e. the flux of rain toward to the ground) and the wind speed. The rack wetting uniformity across the chamber has been independently verified by Certified Testing Laboratories in Orlando, FL.

1.3. Equipment Specifications

A National Instruments PXI system controls the pressure in the chamber through a 50 Hz PID controller that receives feedback from a pressure transducer attached to the test chamber, which can follow rapidly varying pressures traces, with high fidelity.

1.4. Current Status and Planned Upgrades

The design of the HAPLA was purposeful for allowing a wide variety of test setups and protocols. The size of the test chamber can be modified for any component size. Users will be able to choose from a library of pre-configured test types, such as air permeability or pressure. The facility is set up to evaluate durability issues by testing newly built wall systems against weathered building components. Users will then be able to choose from a library of test protocols, such as static, sinusoidal or realistic wind pressure trace for pressure tests, and acquire the test data for load and response via standard data acquisition interfaces. All test protocols and acquisition algorithms are customizable to ensure optimal experimental conditions. Control of the test protocol and data acquisition will be handled within a common LabVIEW interface so that a common trigger can initiate both testing and data acquisition, ensuring time compatibility of the load and response data. All data will be archived to the CI and will be immediately available to the user for interpretation and analysis.

The HAPLA is suited for the following experimental investigations:

  • Through-soffit wind-driven rain effects in residential attics
  • Effects of weathering and aging on structural performance
  • Structural load path at residential building corner walls
  • Validation of standard test protocols against realistic simulations of wind and wind-driven rain.
  • Fenestration performance tests


Chamber Size 2.4 m x 2.4 m (8 ft x 8 ft)
Chamber Depth 0.1 m (1 ft)
Variable Frequency Drive Power Range 1 – 550 Hp
Peak rated pressure 5.98 kPA (125 psf)
Peak rated air flow 51 m3/min (1,800 CFM)
Frequency Response 3 Hz
Pressure Transducer Ashcroft XLdp transducer
Pressure Transducer Range +/- 17.2 kPa (359 psf)
Pressure Transducer Accuracy +/- 6.2 Pa ( 0.129 psf)
Wetting Rate 240 mm/h
Compliance with Industry Standards ASTM E-1592, UL 580, FM 4470, ASTM E331
Performance data View [pdf]
Drawings View [dwg]
Hardware Specifications View [pdf]
Standard Test Protocol View [pdf]
Calibration Certificates View [pdf]
Video of Experimental Test View [mp4]
Photo Gallery View [jpg]


  • The HAPLA can simulate up to a 3 Hz waveform at pressures up to 6 kPa.
  • Variable speed motor controller with pressure feedback
  • Large open working area
  • Can be used to test windows, sofits, walls, etc.
  • Variable rain wetting rates
  • The HAPLA can run in multiple modes
    • Pressure Set Point – Run at a constant pressure
    • Sine Wave – The pressure will follow a sine wave
    • Follow Trace – A pressure trace file can be inputted

Related Test Facilities

  • BRERWULF (Building Research Establishment, Clemson University)
  • Three Little Pigs Project (University of Western Ontario)
  • Dynamic Wall Testing Facility (National Research Council of Canada)


  • Kopp, G. A., Morrison, M. J., Gavanski, E., Henderson, D. J., and Hong, H. P. (2010). ““Three little pigs” project: hurricane risk mitigation by integrated wind tunnel and full-scale laboratory tests.” Natural Hazards Review, 11(4), 151-161.
  • Lopez, C., Masters, F. J., and Bolton, S. (2011). “Water penetration resistance of residential window and wall systems subjected to steady and unsteady wind loading.” Building and Environment, 46(7), 1329-1342.