Field Study of a Moisture and Heat Transfer Furnace Retrofit Device

Josh Quinnell, Ph.D., Dave Bohac, P.E., Dexin Wang — Jan 2015

Project update

The project team finished collecting heating-season data at the final three sites and found that all of the devices improve furnace efficiency and provide some humidification benefit. The team will complete an analysis of the TMH performance and perform a cost-effectiveness evaluation before submitting a final report later this year. 
Full project update

Why this research is needed

Few residential gas furnaces are replaced before failure; consequently the average furnace age in Minnesota single family homes is over 15 years. Most of these older systems are operating at 15 percent lower efficiency than today’s best available technology, offering a tremendous opportunity for energy efficiency. New transport membrane humidifier (TMH) technology can retrofit the standard older furnaces to make them as or more efficient than new furnaces. Transport membrane humidifiers transfer waste heat and water vapor from flue gases into the building air supply. This improves efficiency and also improves occupant comfort by adding humidity to dry winter air.


Project process and expected outcomes

This study will evaluate the actual savings, establish implementation protocols, and demonstrate non-energy benefits of transport membrane humidifier technology. Units will be installed in five single family homes currently equipped with standard efficiency (78 to 83%) furnaces that are representative of Minnesota installations. The project will extensively monitor and evaluate the units over the course of two heating seasons (2015 and 2016). Data will be used to model expected annualized and lifetime energy savings for the five sites, and extrapolated to the Minnesota market. 

These data, combined with detailed observations on design, sizing, and installation of  the retrofit units, will be analyzed to generate realistic estimates for payback and market adoption rates as well as potential contributions to Minnesota’s Conservation Improvement Program (CIP) goals.
Innovation Exchange research staff will also conduct periodic owner interviews to assess their perception of comfort and system operation. The outcome of this monitoring will be performance expectations for the new units in the Minnesota market.

*This project supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program. And with co-funding by CEE in support of its nonprofit mission to advance research, knowledge dissemination, and program design in the field of energy efficiency.

Photos courtesy of Journal of Solar Energy Engineering

Project Info


Determine the increased efficiency of existing residential furnaces with TMH technology retrofits. Establish protocol for implementation of TMH systems.

Utility Implementation
  • Determine recommended deemed savings value and estimate of contractor installation costs for market-ready devices.
  • Identify furnace type and age range for cost-effective retrofits and evaluate humidity and comfort improvements with respect to household characteristics.
Transport membrane humidifier systems will be installed in five Minnesota single family homes and monitored over two heating seasons.

Non Energy Impacts
TMH technology may improve winter comfort by adding humidity without the hassles and potential IAQ issues associated with whole house humidifiers.

Gas Technology Institute

CEE Contact
Josh Quinnell, Ph.D.

Project Description