Task 6 - Integrating Advanced Humidity Control to Reduce Energy Use

In most buildings today, indoor air quality (IAQ) equates directly to outside air quantity, as prescribed by the ventilation rates in ASHRAE Standard 62, “Ventilation for Acceptable Indoor Air Quality”. The 1989 version of the standard was adopted by building codes and, in turn, those revised model codes were accepted into state and local codes by the late 1990’s. For most building types, the nominal outdoor air intake was doubled or tripled. One consequence of the increased ventilation air requirements was that air handling units now were processing large percentages of outside air without regard to their capabilities to do so.

The moisture loads present in outside air are now readily determined with the 1997 edition of the ASHRAE Handbook of Fundamentals, which contains the design humidity ratio along with the traditional design dry bulb temperature. This design humidity ratio has been the long overlooked “other peak cooling condition”. In fact, in non-arid climates, the cooling load resulting from outside air is larger at the design humidity than the design temperature traditionally used as the basis for sizing and selection of cooling equipment. These moisture laden outside air streams require advanced air handling equipment to properly and efficiently control humidity in buildings.

The objective of Task 6 is to develop an analysis tool and evaluate improved, more energy efficient humidity control approaches. This task has been further divided in five subtasks:

In Subtask 6.1, the current state of HVAC equipment for accomplishing improved building humidity control has been determined. This has been achieved by reviewing the existing technical literature and conducting interviews with industry expert. The objectives of this subtask were:

§     To establish the moisture removal performance capabilities of conventional vapor compression, direct expansion (DX) cooling equipment

§     To identify enhanced (DX and desiccant based) dehumidification components and

§     To integrate the enhanced dehumidification components into an HVAC system for modeling and evaluation in Subtasks 6.2 through 6.4.

The results of this Subtask will be published shortly.

In Subtask 6.2, performance metrics for comparing advanced humidity control equipment are being defined.

In Subtask 6.3, a new computer-based analysis tool is being developed. It will allow the user to construct integrated HVAC equipment configurations with conventional and improved humidity control components such as enthalpy exchangers, desiccant dehumidifiers, single and dual cooling coils, wraparound heat exchangers, (condenser) reheat coils and others. The tool will calculate state points for each component, allow for side-by-side comparison of various systems and generate performance maps for individual systems. The performance metrics from Subtask 6.2 will be applied to rank the improved humidity control systems. Complete performance maps and curve fitted algorithms will then be generated for both the conventional and the highly ranked improved humidity control systems.

In Subtask 6.4, the performance maps/algorithms are being incorporated in the EnergyPLUS simulation program to determine the most energy efficient equipment approaches to improved humidity control in targeted building types and climatic locations.

In Subtask 6.5, which parallels the other subtasks, the building moisture management market is being assessed. The objectives of this subtask are:

§     To identifying the potential market for moisture management. This process is being guided by a “situation analysis” method, analyzing building data, identifying literature resources, defining key concepts, and developing a clear picture of the gaps in knowledge of market potential

§     To fill gaps in market knowledge using standard data collection techniques

§     To develop a detailed scope for an integrated solution for moisture management that simultaneously addresses the building HVAC system and the building envelope. This will be reviewed and refined further through interaction with an industry expert panel.

§     To test a refined, integrated moisture management program with building owners, asset managers, and property managers in commercial and institutional building types.

This project is being executed by the Energy Resources Center (ERC) at the University of Illinois at Chicago (UIC). The Principal Investigator is Douglas Kosar.

Subtask 6.5 is being performed by the Chelsea Group Ltd. The Principal Investigator is George Benda.

This project is scheduled to be completed by April of 2006.