1.17 Energy Conservation in Museums: Skylights, Filtration, Condensation Infiltration/Pressurization, Vestibules, and Outdoor Air Control

Ayres Ezer Lau, Consulting Engineers
The Getty Conservation Institute

J. Marx Ayres
J. Carlos Haiad
Henry Lau
James R. Druzik
Neville Agnew
Period of Activity: 4/89 to 4/90

Project Abstract
This project had six main tasks:

1. Provide additional DOE-2 simulations to determine the cost sensitivity of various particulate and activated carbon filters located within the HVAC system at one location.

2. Provide additional DOE-2 simulations to determine the cost sensitivity of various sized skylights in five locations: Burbank (California), Albuquerque (New Mexico), Minneapolis (Minnesota), New York (New York), and New Orleans (Louisiana).

3. Demonstrate the use of the Dew Point Profile Method for predicting regions of condensation within a building.

4. In previous simulations, it was assumed that the building was pressurized and there was no infiltration. This assumption is valid for most buildings, but requires closer evaluation in tall buildings subject to stack effect, buildings with severe wind exposures, and buildings with high traffic rates. This topic is revisited for buildings with infiltration.

5. The main source of infiltration for newly constructed buildings is through entrance doors. What mitigation is offered by vestibules?

6. How can one assure minimum ventilation rates consistent with the latest ASHRAE standards?

The Scott Gallery of the Huntington Library and Art Gallery in San Marino, California, was the modeled building.

Primary Publications
Ayres, J. M., J. C. Haiad, and H. Lau, "Energy Conservation and Climate Control in Museums: Skylight, Filtration, Condensation, Infiltration/Pressurization, Vestibules, and Outdoor Air Control," Final Report to the Getty Conservation Institute, November 27, 1989.

ABSTRACT-The work presented here is part of an ongoing research project at the Getty Conservation Institute on energy conservation and climate control in museums. An earlier work, Energy Conservation and Climate Control in Museums, included a literature survey, a discussion of the building design and construction process, results of computer simulations of the Virginia Steele Scott Gallery in five locations, when operated at various indoor temperature and humidity set points, and a list of recommended research projects.

The present computer simulations of the Scott Gallery investigate the impact on the annual energy consumption of various skylight areas and construction (double and triple glazed units) and different filtration systems in five locations: Albuquerque, New Mexico; Burbank, California; Minneapolis, Minnesota; New Orleans, Louisiana; and New York, New York. A standard water vapor migration and condensation analysis through several typical construction layers is also investigated.

The simulation results indicated that as the skylight area was increased from zero to 711 ft2, the energy consumption decreased and then increased sharply as the area was increased beyond 1344 ft2 regardless of the skylight construction. The addition of activated carbon and/or activated alumina filters to the filtration system has a minor impact on the annual energy requirements of the Scott Gallery.

The simulation results also indicated that the total energy requirements of the Scott Gallery increased significantly in all locations when outdoor air infiltration was considered. The results also indicated that it is necessary to account for the local weather conditions to properly evaluate the impact of the outdoor air infiltration.

When entrance vestibules were added to the Gallery building, the simulation results indicated that the total energy requirements of the Scott Gallery decreased significantly in all locations. Vestibules effectively reduced the total energy requirements to levels similar to those obtained when outdoor air infiltration was not considered.

The use of (CO2) sensors to measure the occupant density and then control the amount of polluted outdoor air introduced through the HVAC system is a valid strategy. Simulation results indicated only a minor reduction in the total energy when CO2 sensors were used. The simple payback on the investment ranged from 2.2 years in New Orleans to 8.3 years in Minneapolis.

An estimate of the hourly CO2 concentrations within the Gallery building (assuming no infiltration and no CO2 absorbing filters in the HVAC system) indicated that the CO2 concentration was as much as 81% higher than the 1989 acceptable levels set by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers during open hours and on weekends, and near the maximum between 2 and 3 p.m. on weekdays.

The condensation results, using the Dew Point Profile Method, indicated that interstitial condensation would not occur at the Scott Gallery regardless of the Gallery location. However, condensation on windows and skylights would occur in all five locations.