Research Project Information

Research Project Summary Information

Integrated Approaches to Eliminating Air Bypass in HVAC Equipment(ST10902-1)

Taitem Engineering, P.C.


Water loop heat pumps are a popular heating and cooling system in hotels and other large buildings. While these systems have several advantages, their performance can suffer when airflow intended to pass over the inside coil is unintentionally bypassed due to poor equipment cabinet designs or careless installations. This bypass air reduces the energy performance of the heat pump because not enough cooled air is reaching the room, which causes longer run times than necessary. Bypassed air can also cause the inside coil to freeze up, resulting in the heat pump failing. Taitem Engineering has observed this occurrence in a large New York City hotel where twenty out of twenty heat pumps exhibited poor performance due to bypassed airflow. This problem has also been observed in a New York City multifamily residence.

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Project Description

Taitem Engineering will assess the scope of the air bypass problem within HVAC Systems. Five buildings throughout New York will be monitored over a period of six months to determine how much air bypass occurs per unit. Methods for reducing air bypass would be developed and tested. The results of this project shall be published in technical periodicals, and may be presented to the International Codes Council.


Bypass airflows as large as 50% have been observed in the field. In addition to energy losses, bypassed airflows can cause indoor air quality problems in buildings.

Project Results

Field testing at five different sites was performed and results show that air bypass occurred in all five installations. By sealing air bypass locations after the diagnostics, the improvement in cooling efficiencies ranged from 7% to 17% and averaged 12.8%, and the improvement in heating effciencies ranged from 16% to 19% and averaged 17.5%. Based on the locations of air bypass, it was shown that 55.1% of bypassed air was passing through the locations that were common to all types of water source heat pumps. The project estimated the time needed for a maintenance person to seal the air bypass locations to be 1.2 hours and the materials cost to be $25. Based on average energy savings measured in this project, air bypass sealing of this equipment can have a payback of less than four years.


Taitem Engineering, P.C.
110 South Albany Street
Ithaca, NY 14850

Principle Investigator

Ian Shapiro

Universities Involved


Project Type:

Product Demonstration

Technologies Types:

Building Systems
Heating, Ventilation, & Air Conditioning
Cooling & Ventilation

NYSERDA Contact Information

Robert Carver


R&D - Buildings Research

Contract Details

Start Date: 1/11/2010
Project Status: Active
Contract Number: ST10902-1

Last Updated: 3/6/2012 1