Lucy's story is a perfect example of the misapplication of insulation and its box-in-a-box climate control solution. Lucy's construction mishap created the world's largest terrarium -- and that caused rot.

Lucy became the world's largest terrarium.

Who is this Lucy character? Lucy is a 65 foot tall pachyderm. Lucy the Margate Elephant was built in 1881 by James Lafferty as an architectural "folly" to  promote a real estate venture. Lafferty took prospective buyers up inside Lucy through stairs in her legs. They would look out through Lucy's "Howdah," an observation deck 65 feet up in the air, to view the various lots that were for sale. At one point, a family actually lived inside Lucy. Today, she is the last of three elephants built for the project. She is an historic landmark operating as a museum on the beach in Margate, New Jersey. 

How is Lucy a terrarium? Terrariums are containers designed to trap water and Lucy's construction consists of a tightly soldered tin cover wrapped over wood, supported by internal wood trusses. Lucy underwent restoration in 1976 and again in 1984. Among other things, foil faced batting was added to the wood sheathing to improve thermal efficiency. Turns out that was a bad idea for Lucy. 

Lucy is a massive wooden structure, covered with a tight tin skin, located 50 feet from the Atlantic Ocean. When wood is heated it gives off moisture and when wood cools, it absorbs moisture from the surrounding air. In a cool, moist environment, wood can absorb up to 15 percent of its weight in water vapor. The next day when the sun is well up in the sky, it heats up Lucy's tin skin and all that wood sheathing underneath. The same wood sheathing that had spent last night absorbing moisture. And so the moisture in the wood gets driven out and into the batt insulation. Since there is air conditioning running inside Lucy for people comfort, the insulation is also cooled. As a result, all that moisture condenses inside the insulation and as the cycle repeats daily, moisture accumulates in the insulation pressed against the wood and causes dry rot.

How can we balance the needs of the museum and people inside with the need to keep Lucy dry? Understand that balance is not a compromise. In a compromise, both parties lose since neither gets what it really wants. 

The solution is a box-in-a-box. Years ago Lucy had interior walls. Replacing them and adding a ceiling creates a large enclosed space inside Lucy -- essentially a box -- completely isolated from the perimeter envelope. Insulate the interior box walls and introduce climate control inside the interior box, which is where there are people and museum collections. In the cavity space between the interior box walls and the outside box (the elephant's legs and trunk and ears and tusks and tail, and so forth) ventilate to keep it dry. Force slightly heated outside air in one end and out the other to ensure a dry condition. And take all that insulation off of Lucy's skin. It would never dry out otherwise. This is what balance is all about. Everyone is a winner when balance is achieved. 

Lesson learned: This problem will be present in any temperate climate, not just near the ocean. Many historic wood frame buildings have been compromised by well meaning people installing insulation on the underside of the wood roofing in an attic space. Think of Lucy! Put the insulation on the attic floor and ventilate the attic to the outside to keep it dry.

The box-in-a-box concept can be used almost anywhere. It is simple, reversible, and cost efficient. It only conditions the air space that needs conditioning. Many house museums can use this principle for their collections storage needs. And, it works

Ernest Conrad is a mechanical engineer with a bachelor's degree in civil engineering and a master's degree in environmental engineering from Drexel University in Philadelphia, Pennsylvania. For over 20 years, Mr. Conrad has focused on environmental issues. He developed environmental guidelines for engineers who work on museums, libraries and archives, rewriting the standards of the engineering field as it relates to collection holding facilities. This ground-breaking work contributed enormously to improved preservation environments in all collecting institutions. He is president of Landmark Facilities Group, Inc., an engineering firm specializing in environmental systems for museums, libraries, archives and historic facilities. Mr. Conrad teaches MS 211: Preservation Environments.  

Humidistatic Heating 

by Ernest Conrad  

Humidistat

Humidistatic heating is based on the hypothesis that humidity control is more important than temperature control when it comes to collections preservation. So it uses a humidistat to operate the heating system instead of a thermostat. The theory is simple: Just swap your thermostat for a humidistat. But there are rules you must follow for it to work. 

 

How does it work?

If the psychrometric chart is examined around its mid range, one will note that for each change in temperature of one degree Fahrenheit (ºF), the relative humidity (RH) will change 2 percent, so long as no water is added or taken away. Pretty neat. Thus a person could change the relative humidity in a room simply by raising or lowering the temperature. 

 

A few examples

If I am up north in the winter and it is 10 degrees Fahrenheit (-12 degrees Celsius) outdoors, and 70 degrees (21 Celsius) with 20 percent relative humidity indoors, if I lower my thermostat to 60, then the room's relative humidity will rise to 40 percent all by itself without adding moisture. If I continue to lower the thermostat to 50, then the room relative humidity will rise further to become 60 percent all by itself. So by maintaining the room between 50 and 60 degrees Fahrenheit (10 to 15.5 degrees Celsius), a reasonable relative humidity of between 40 percent and 60 percent can be maintained. Not bad, so long as you don't have to live in there. But maybe this is a collections storage room where temperature is not a concern.

 

In another example, if I get gutsy and lower that thermostat down to 40 (4 Celsius), then the room relative humidity will rise to 80 percent, right into mold territory. It is important to understand that too cold is not a good thing. For this reason, a good rule of thumb for basements is to never let them go below 50 (10 Celsius) in the winter. This will also help prevent walls from sweating in the springtime when the weather warms outside.

 

The rules 

What are the rules I need to know for humidistatic heating?

 

Rule # 1. You need a dry basement. Any active source of moisture into the building, especially a wet basement, will defeat humidistatic heating. Standing water or wet materials will try to evaporate their moisture when heated and thus the more heat is added, the more evaporation occurs and the heating just keeps spiraling up and the humidity never will go down.   

 

Rule# 2. This is a winter thing. Humidistatic heating is a technique that is intended for climate regions where winter weather goes below freezing.  It is not intended for summer use. However, in damp springtime rainy weather, it will do wonders to just bump up the heat 5 ºF as a means to ward off mold.   

 

Rule # 3. Not for occupancy (because the temperatures get too cold). Humidistatic heating is an approach largely conceived for house museums in colder regions. These buildings are usually closed down in winter and need a cost efficient preservation program. The good news is that humidistatic heating can reduce energy costs.

 

Rule #4. Not for precision climate control. This is for reasonable climate control in buildings that do not have good thermal envelopes and their energy budgets are a major concern. Outdoor weather will at times not yield the desired results indoors.  

 

Rule# 5. Computerized control is costly. Although the theory is simple, any automated controls to accomplish humidistatic heating get complex.  The "human" computer may be a better choice at times. Just set the thermostat at 60 ºF (15.5 ºC) in November and lower it to 50ºF (10 ºC) in January and back up to 60 ºF in March. There is no accurate humidistat that works on normal heating system control voltages. Generally computerized controls with electronic RH transmitters are needed.

Ernest Conrad is a mechanical engineer with over 20 years experience working with museums, libraries and archives. Mr. Conrad has focused on environmental issues in these facilities, developing environmental guidelines for engineers who work on museums, libraries and archives, rewriting the standards of the engineering field as it relates to collection holding facilities. He recently coauthored the ASHRAE Applications Handbook Chapter 20; Museums, Libraries and Archives design.

Establishing a Tribal museum - or even just expanding or enhancing one - can be daunting. It's a job that demands a clear community vision and an organized approach, which make a tremendous difference for the museum's future. Establishing a Tribal Museum will provide the facts and comprehensive advice you need to undertake this endeavor. This includes considering how your tribe's museum can get the community and financial support it needs. The course walks students through specific steps and considerations to clarify the process of establishing and maintaining a successful Tribal museum. These steps include writing a mission statement, understanding community expectations, and establishing a collections policy. Students will explore the potential role of the museum within their Native community and key considerations when establishing a tribal museum. Topics include collections care, community expectations and benefit, registration, the role of traditional culture and language within the museum setting, exhibitions, conservation, staffing and financial management.  

Course instructors Stacey Halfmoon and Claudia Nicholson  are familiar with the challenges and pitfalls involved in establishing a new museum. Ms. Halfmoon is the director of Community Outreach and Public Programs for the American Indian Cultural Center and Museum in Oklahoma City, OK. Ms. Nicholson is executive director of the North Star Museum of Boy Scouting and Girl Scouting in North St. Paul, MN.  

This course is for members of US tribes who meet NATHPO qualifications. For more information, course details and to sign up go to www.nathpo.org. This online course is part of the National Native Museum Training Program funded by the Institute for Museum and Library Services.