Restaurant Ventilation & Air Pressure

Energy efficiency and indoor air quality can both be enhanced by modern ventilation techniques and accurate control of indoor air pressure.

Modern ventilation and air pressure control techniques have helped restaurants to:

Increase indoor air quality and thermal comfort.
Minimize energy costs.
Prevent mold problems.
Reduce air conditioning costs by reducing the entry of humid air.
Avoid strong negative indoor air pressure that would make it difficult for customers to open your doors.

Moisture Control

Mold growth has occurred within the exterior walls of some air conditioned buildings. The most frequent source of excessive moisture in exterior walls is condensation of water vapor that has been forced through openings and porous materials by the pressures created by mechanical ventilation systems.

Recommendations for restaurants without basements or crawlspaces:

Seal air leaks in the building envelope to block entry of dust, microbes, moisture, insects, drafts, etc.
Use vapor permeable materials throughout the wall structures so that any moisture that enters can escape.
Seal any ductwork air leaks that waste energy or create undesirable airflow patterns.
During the air conditioning season, keep indoor air pressure higher than outdoor air pressure to avoid drawing water vapor from the exterior through cool walls.
During the heating season, keep indoor air pressure within 1 Pascal (.004 inches of water column) of outdoor air pressure to minimize leakage of water vapor from the interior through cold walls.
Use an air pressure sensor.

Humidity Control Design Guide

As concern grows over moisture damage in commercial buildings, owners need practical advice to minimize the costs and maximize the benefits of controlling humidity.

The Humidity Control Design Guide for Commercial and Institutional Buildings, published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), provides such guidance.

"Problems related to humidity can be reduced or avoided entirely through better understanding of humidity control issues, techniques and equipment," co-author Lewis Harriman said.

He notes that in North America, building owners' concerns about mold and mildew have generated more interest in humidity control.

"The guide provides suggestions on how to get the most out of existing systems," he said. "It explains how to tweak buildings for better humidity control before spending money on new equipment."

The book suggests:

Installing a separate ventilation system to dry or humidify the incoming ventilation air.
Calculating the moisture load separately from the sensible heat load.
Sealing all ductwork, air handlers and duct connections tightly.
Never over-sizing the cooling equipment.
Calibrating humidity sensors in-place (after installation and before commissioning).

The book includes sections on humidity effects, system design, equipment and controls, applications and design references. Guidance is provided for schools, office buildings, retail buildings, hotels, restaurants, museums, libraries and archives, hospitals, eldercare buildings, dormitories, swimming pools, ice rinks, dry air storage and laboratories.

The information was developed as part of ASHRAE Research Project 1047, funded by ASHRAE, the United States Department of Energy and the Gas Technology Institute.

The cost of Design Guide for Humidity Control in Commercial Buildings is $120 for non-members ($78, special introductory price for ASHRAE members).

To order, contact ASHRAE Customer Service at 1-800-321-4723, fax 404-321-5478, by mail at 1791 Tullie Circle NE, Atlanta, GA 30329, or visit ASHRAE Online.

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