Tim Padfield, a freelance consultant in preventive conservation, received his master's degree in chemistry from Oxford University and his doctorate in building physics from the Technical University of Denmark. He has worked in conservation at the Victoria and Albert Museum, the Smithsonian Institution, and the National Museum of Denmark.

Franciza Toledo earned her doctorate at the Department of Conservation, Institute of Archaeology, University College London. A former member of the GCI's Science department, she is currently a private researcher and consultant in preventive conservation in Brazil.

Ernest Conrad is president of Landmark Facilities Group, an engineering and design firm based in Connecticut that specializes in museums, libraries, historic structures and their collections. A graduate of Drexel University with a master's degree in environmental engineering, he has been involved in the design of climate control systems at a number of cultural institutions, including the National Gallery of Art, the Frick Collection, and the Library of Congress. Conrad is a licensed professional engineer and LEED Accredited Professional.

They spoke with Shin Maekawa, a senior scientist with GCI Science, and with Jeffrey Levin, editor of Conservation, The GCI Newsletter.

Jeffrey Levin: Recently, the issue of climate change and its impact on the historic environment has been the subject of study and debate. Some believe that managing the environment of a museum, library, historic house, or other cultural resource has to take into account broader environmental issues, such as climate change impacts and the need for all building owners to reduce energy use to limit increases in global carbon levels. Is there much interest in addressing these museum environments in a way that reflects a larger obligation to the global environment?

Tim Padfield: There is one museum for approximately every three hundred thousand ordinary houses. One can worry about burning up more energy in a museum, but that, in fact, has no practical influence on the world at all. We should treat museums as museums and not worry too much about the rest of the universe.

Ernest Conrad: If you compare the amount of energy a standard house consumes to what a[n HVAC environmentally controlled] museum consumes, a museum is an energy machine. It gobbles up so much power controlling temperature, humidity, and the filtration of pollutants. The total energy bill for a year of a house that has no air-conditioning is about one dollar a square foot. At museums, it is upward of about four dollars a square foot. That's a major difference. I wouldn't discount it.

Franciza Toledo: I think we have had advances because there are now many physicists, engineers, and architects conducting research on more and other ways of controlling indoor climates and reducing energy consumption. I think we have made progress.

Levin: Tim, couldn't it be said that those in the museum field have a responsibility to exercise leadership in developing systems that are more conscious of broader environmental concerns?

Padfield: What you're doing is pushing some moral idea onto straightforward management. I agree that museums use too much energy, but they're not going to destroy the planet. The planet has a good deal more resilience than we realize. Museums are simply badly designed, and that's a different point. What's significant is not the amount of energy that a museum uses but the fact that it uses skilled people who are on call at great expense because air-conditioning is complicated. Don't worry about the planet, but get on with designing a building that functions. Your conscience will clear up automatically by doing that.

Conrad: I design climate control systems at museums—and a rise of a couple of degrees centigrade worldwide won't make a lot of difference to the design of the systems. The real difference with global warming is not so much a slight increase in temperature, but in extreme weather changes. Hurricane Katrina is a perfect example. We're going to see weather extremes occur, which are going to affect buildings through floods and things of that nature. That's the major risk.

Levin: Are people in the museum field thinking about the extremes that global warming is going to create?

Conrad: One thing the museum community has done well is to develop disaster recovery plans. When a catastrophe is predicted, they can react. Before Katrina hit, the museum industry moved things to high ground. They had plans in place for disaster recovery. So that's one good thing—the planning in advance. The other thing that we’re doing is in smaller house museums. Many of these places can't afford a high electric bill, and so we have a method where instead of using a thermostat, we just have a humidistat that controls temperature; we call this humidistatic heating. For every one degree Fahrenheit I change temperature, I can change the relative humidity two percentage points just by moving the temperature around. But if global warming raises the temperature a little bit, it will make it much more difficult to use these low-cost types of solutions.

T. Patfield

Levin: Sustainability is a popular buzzword that is open to different interpretations, depending on the context of its use and perhaps the personal beliefs and biases of the user. How do each of you define it?

Padfield: Sustainability, in the museum context, is almost the same as durability. It means to devise a building that functions on its own. Sustainability is a reward for laziness. A building should function without all these electronic sensors and computer models sustainability for me, a person who has had a lifetime's experience of air-conditioning that doesn't work, is building a museum in thick mud where the climate is appropriate—a museum in the middle of the hot desert where you want to keep the temperature down. In other words, sustainability is the idea of using cunning, looking at what people did in the past, adding that to modern physics, and generally designing things that you're proud of because you didn't drag in a whole lot of electricity and energy.

Toledo: I would define sustainability as the ability to live according to the resources available. We have a saying, "not to take a step larger than the legs." But this cautious policy in a way hinders material development. Therefore, sustainability, despite being a popular word, is, in practice, not very popular. We do not see many examples. I do agree that buildings are not properly designed. It's architecture for the sake of architecture. It's easier to design without any sort of constraint and then to take care of the climate by installing an artificial system. The real challenge is for architects and building engineers to design more climate responsive buildings. Then, even if a mechanical system is necessary, much less is required because you are using a proper design and building materials.

Conrad: When people talk about sustainability and durability, they tend to mean status quo—we're not adding to the problems of the environment. But the status quo is not going to work. We're in such a disaster state now, we have to go back in the other direction. There is a program in the United States called 2030. Many mayors have bought into this program with ASHRAE, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. They have mandated in their cities that by the year 2030, we will no longer produce carbon products. We will become neutral to carbon-product generation, which is all the fossil fuel emissions. What they're saying is we have to go backwards and get the planet back to the better place where it once was.


Levin: But is that in conflict with what Tim suggested? Tim was talking about ways to minimize the use of things that are going to produce those carbon products, correct?

Padfield: Yes. I think all three of us are just saying the same thing, but from interestingly different career experience.

Levin: Franciza, you were suggesting that in your region, there aren’t many examples of passive climate control. What are the reasons for this?

Toledo: Because it's very difficult to control high temperature and relative humidity passively. We can use ventilation, which is good for the building itself and for visitors, but not for collections.

Padfield: Temperature definitely rots things faster, but many things rot very slowly in museum collections, so I'm wondering if we're being, in effect, bombarded with standards. The standard that I see is one actually based on human comfort. When you talk about the high temperature, is it because all your visitors are sweating or because you're worried about the objects?

Toledo: Because our visitors are sweating. Most of the objects are doing fine. We just have problems with chemically unstable collections. When it comes to attending to a collection’s physical needs and to human needs, we have climate control for the sake of human comfort.

Conrad: Lower humidity is a major player in preservation. We have difficulties when we get into tropical areas where you need to reduce the relative humidity to prevent things like mold and dry rot. You get into the expensive refrigeration systems, and reheat systems, and things of that nature.

Padfield: My experience is that actually there's more mold growth in cold climates, and it's caused by condensation. Most of the mold that I have seen is a consequence of temperature gradient—having a warm building in a cold climate and having condensation occur. As you move to hotter climates, you get much less difference between inside and outside temperature, and you don't get these gradients. Franciza, can you comment on that?

Toledo: We have to control just humidity, not temperature, in order to avoid mold growth. When we have air-conditioned buildings, we cannot afford running them continuously. When you turn them off at the end of the day, hot and more humid air has contact with cooler surfaces. This is when we have mold growth. But when you have a stable, naturally ventilated building, it's very rare to have mold develop.

Padfield: I think Franciza and I do agree, because what we’re saying is that mold growth is usually man-made, in the sense that for one reason or another you generate a temperature gradient or sudden temperature disparity. I live in Devon [England], a very wet area—it just rains almost continuously. But you don't notice any particular rot with anything that’s out in a barn. The RH [relative humidity] is 99 percent, but there's absolutely no temperature difference anywhere, and therefore it never gets to 100 percent. Mold growth usually in practice needs condensation before it will start.

Conrad: That's because for mold to do its best, it needs pure water—and that's what condensation is. As soon as you introduce anything that changes acidity or alkalinity, it's toxic to the mold.

Levin: Are you saying that with stable relative humidity, you're going to reduce some of these problems?

Padfield: It's not so much stable as uniform. In other words, if you have a temperature gradient, you get condensation. The temperature can go up and down, but as long as everything follows, you won't get into trouble. That's why in humid regions you need lightweight buildings so there is no thermal inertia, whereas in northern Europe we have, for various reasons, some rather heavy buildings that we value, such as churches, which are massive. It's very common to find condensation in those buildings simply because they've remembered the cold of the night. When you open the door to let people in during the day, the warm morning air comes in and condenses immediately. That's caused by a temperature gradient or a temperature difference.

Toledo: Yes, Tim, but we have some massive thick-walled buildings in the north of Brazil. In the past they were palaces, now they are museums, and they behave okay, maybe because of cross ventilation. We don't see signs of condensation in those buildings, not even when opening the doors in the morning. We have to measure it, but visually it's not occurring.

E. Conrad

Levin: What are the most promising developments in sustainable systems that are low energy and low cost—and what are the obstacles to the development of these systems?

Conrad: In storage areas and smaller spaces, we have been using this process called hot gas reheat. If you think about a window air conditioner, it blows cold air into the room and hot air out the other side. If you take that heat on the other side and heat the air back up again, you can do dehumidification by using that heat for free. We've been doing that on a smaller scale, and we're starting to do it on a larger scale. It eliminates the extra energy that you waste by adding heat to a cooled airstream. It's become a great way for people to be able to do dehumidification and have it be affordable. The other thing is geothermal systems, which are becoming all the rage. These are saving anywhere from 40 to 60 percent of heating costs during wintertime. The downside is that they’re very expensive to install. But they're becoming very popular.

Padfield: The most promising technology is to do nothing—and this we have demonstrated in archives. Consider that rather specialized aspect of museums, which is storing old things. Almost all over the world, there is no need to have any air-conditioning in archives because the air exchange rate is so small that with passive humidity buffering with materials—often the stored materials themselves and massive walls—nothing is needed. It baffles me that no one recently thought of doing nothing. I think that's because we live in a busy civilization where if you say you don't need to do anything, people lose money. Ernest would be out of work. And the architect's fee would be reduced because there is no mechanism. So that's the promising technology—do nothing.

Conrad: I need to comment on that.

Padfield: But just to finish my spiel, the obstacles are conservators. They quote standards that have such narrow bands of temperature and relative humidity that they can only be achieved by mechanical air-conditioning. There are psychological pressures on the experts, the people who sit on standards committees, to take the best available technology, regardless of whether there is any fundamental science that supports it. That's the obstacle to the lazy technology, which is doing nothing. An archive, which I won't name, has been functioning perfectly except that it has had temperature extremes that went up to 24°C and down to 13°C. The standard doesn't allow this. So now they're putting in air-conditioning—not to improve the climate by any scientific criteria, but simply to make it conform to the British standard for archives.

Conrad: In theory, Tim is absolutely correct. When you think about the influences on a room or a building, there are only six of them. Things like the heat from lights or heat passing through the walls or windows. You can make all these things go away. The only one that you can't make go away is infiltration. One item of infiltration is water. When it's in vapor form, it will pass through materials and get inside facilities. It takes a very small amount of energy to control that. So, in effect, what Tim is saying is correct. It doesn't take much to do climate control in a very well-designed archive, because all you have to deal with is infiltration. But if you try to do it in a building that has skylights and windows and all these other things, you get yourself into trouble.

Toledo: We should rely more and more on the building itself. We do try, but the examples are still few and new. I wonder why there have not been many articles published on a more passive approach to museum buildings. Passive design in the tropics is very much toward human comfort. But we haven't seen publications on museum passive design. Because you have to fulfill human needs, the collection's needs, and the building's needs.

Padfield: Museums are often designed to be prestigious buildings and to dominate their surroundings. By good fortune, museums started off in what you could call classical revival, and most of these museums are, in fact, massive buildings. So by chance, the prestige architecture of many museums is exactly climatically right. They're massive, often have relatively small openings and high ceilings. The problem now is that we’re constructing a second round of massive museums, and the architects are building as though they were designing aircraft. Take the Denver Art Museum. The walls are flying out in all directions. You can't possibly build that wall massive—it will fall down. The prevailing idiom of pompous architecture now is unsuited to the museum purpose of making a naturally calm interior climate.

Conrad: I tend to agree with Tim. It seems to me that with some new museums, people are coming to see the building, not the collections. The architect is making such a statement that they don't even know where the collections are. In fact, they can't even find a flat wall to put them on.

Levin: In terms of the design of buildings, how should the character of the local environment be factored into the process?

Padfield: Before even thinking about how it's going to look, you should think about the materials. Is it going to be mortar and brick, for example? Will that suit the climate? Look at the possibilities of the local climate and the local geology to give you a start in designing a building, and do that before you invite in the architect.

Conrad: Not too long ago I was in Beijing and was asked to help design a system to protect a historic building. In looking at the local situation in Beijing, the number-one thing for preservation is not so much temperature or relative humidity but the dust that comes off of the desert. The dust particles are like razor blades, and when they get on materials, it is very difficult to clean the materials without abrading them. So in our design strategies, the focus was on filtration to keep dust out of the building.

Toledo: We have had experience in dealing with local climate, buildings, and professionals, and the problem I see with alternative climate control systems is maintenance. All these devices or systems require an active role on the part of the users. In the short term we can rely on the maintenance or even rejuvenation of these passive buildings, but in the long run it is hard, and if people do not follow the routine of, say, opening and closing windows, changing filters, et cetera, it doesn't work. Requiring users to do things in order for these devices to be functional is an obstacle.

Shin Maekawa: There are a couple of ways of doing things. One way is to make the system complicated so that it can handle all sorts of situations. The other option is to use people to help the system run better. The latter option is really more sustainable, but then, surprisingly, people are not quite aware. They think a sustainable building doesn't require anything.

Padfield: There's also an element of shame. For instance, guards in a museum can regard it as demeaning to be asked to look after opening and closing a window. On the other hand, it's very culturally dependent. In the culture that I have known most recently, the opposite happens. As soon as the guards realize that they're playing an interesting and effective role and not just standing around waiting for something to be stolen, they perk up and take an interest. You don't have to automate everything in life. People get bored and, in a strange way, resentful.

Levin: Now we’re not even talking about mechanical systems—we're talking about psychological systems.

Toledo: Yes, because guards don't want to be opening or closing things or pushing buttons or going around doing an audit. This is maintenance, so museum sustainability doesn’t work. Not in Brazil, at least.

Levin: So the notion of a sustainable or passive system that doesn't involve some human involvement is a myth. You still have to have some human beings doing some things.

Toledo: Exactly. And this is for me the major obstacle for this alternative way of controlling climate in museum buildings.

Conrad: Because of the Internet, we are now designing climate control systems that are Web-based. That means all the parts that control the climate in the space are controlled through a computer, and the computer is hooked up to the Internet. I can sit at my desk in Connecticut, dial up any one of the museums that I have designed in the last couple of years, and see exactly what's going on. That gives you the ability to have a fast response to problems that crop up. It's a wonderful technique to minimize waste and to keep systems running in good order.

Padfield: It's always nice to be reminded of American optimism, but I get the impression that Franciza and I, belonging to older and more cynical civilizations, are actually heading towards designing buildings that can endure neglect, which is almost the opposite to what you're saying, Ernest. My feeling is that a building that can be totally ignored, certainly for a weekend, is inherently more sustainable. In effect, we should be building fail-safe buildings. If the Internet blows up because eventually spam mail goes supernova, then the building will just cruise along.

Toledo: Everything starts okay, but in the long run people tend not to do their jobs.

Padfield: You're talking about human activity. My idea of passive is that you can forget to open and close the windows and it may go bad, but it will go bad slowly. I think the biggest problem is that mechanical high-tech control actually demands a lightweight building with insulation close to the surface, so that any error can be corrected by the mechanism rather quickly. My design approach is exactly the opposite—make the building so massive that the temperature can't go wild because it has such huge inertia.

Conrad: One thing I can say is everything made by man eventually fails. Guaranteed. So I get back to the monitoring. If I'm not monitoring my building, how do I know what damage is going to start to occur? I agree with simplicity, but we still have to be able to see what's going on and catch faults, because failures will occur. A roof leak is a perfect example of the damage that can occur in a building if it goes undetected. It's massive damage.

Padfield: Yes, I entirely agree. But you can monitor the roof with some electronic device that works over the Internet, or you can build a roof that slopes instead of it being flat, so it takes a lot more deterioration before any damage occurs. I'm not arguing against what you're saying—I'm saying that the design looks at everything. Make a roof that is inherently fail-safe. You can still monitor it, but at least a weekend won’t do any damage.

Levin: Tim, earlier in our conversation you seemed to suggest that current environmental standards were not particularly useful.

Padfield: All our low-energy initiatives come up against this belief in the absolute power of standards. It's almost a religious belief in the power of a standard to somehow guarantee that something is going to be good. We as a profession should go back and look at the fundamental science of decay that underpins the standards, and see if they match. I feel they don't. Firstly, I think everything is too hot, because the first thing we know about decay of anything organic is: The cooler the better. The second thing is: Relative humidity value is overrated. The difference in decay between 75 and 40 percent relative humidity is significant, but compared to a drop in temperature, that difference means nothing. I would like to see standards that are related to and quote the underlying science on which they're based. At the moment, they don't. The standard is simply a legal document that gets fossilized in our consciousness. Finally, any standard that does not enforce measurement of whether the building complies is meaningless. Why build to a standard without also building into the contract that monitoring will be done? In my experience it is unbelievably difficult to get climate data more than six hours old.

Conrad: Well, in virtually every system that we now design for a building, we leave behind the permanent capability to measure and monitor conditions. For example, we put probes into walls to monitor the moisture migration rates and use this as an early warning device when the actual systems are running in the building. That's been going on in my firm for over ten years. We're finding people more and more consciously doing monitoring over long periods. Years of records are being created, and this wonderful world of digital makes it easy to store this stuff without a file cabinet full of hygrothermograph records.

Padfield: It's easier to lose digital storage than paper storage, in my experience.

Conrad: That is true. Make copies!

Maekawa: I think the climate standard is coming more from North America or Europe. When we deal with climates like Egypt, temperature is quite high but we don't see objects decaying quickly. For instance, in the pharaonic tombs in the Valley of the Queens, temperature is 29°C all the time, relative humidity is somewhere between 40 and 50 percent, and the mummies have survived for more than two millennia. Relative humidity is definitely a big issue, but low temperature is not that crucial. In the tomb environment, ancient material survives for a long, long time.

Levin: How much collaboration is there today between architects, engineers, and conservators in addressing some of these questions?

Conrad: The collaboration is getting better. A hundred years ago, the architect was totally in charge, and the systems that went into these buildings were fairly simple. But now because of codes, regulations, and other kinds of things, they are much more complex, and it takes three people to design a building envelope that's going to work right: the architect, who's in charge of the shape and color; the structural engineer, who's got to make the thing stand up and hold things; and the mechanical engineer, who gets involved in the performance of the building from an insulation, infiltration, and moisture migration standpoint, which is very new to a lot of people. They don't teach much of that. It's only recently that mechanical engineers have even been up to speed on how this stuff works. There's just not that much published about it.

Toledo: I think collaboration among architects, conservators, and engineers is getting better. But the lack of dialogue is due to our education. Architects deal with buildings. Conservators deal with collections. I think we should look at both. It is one whole thing. But it's getting better, yes.

Padfield: I would add that the collaboration, in terms of people's willingness, is there. But the problem is that the skills don't overlap. It's a matter of education. For instance, people don't understand the interaction of temperature and relative humidity and absolute humidity and thermal diffusivity. These concepts are necessary in order to design a sustainable building, but architects don't understand them. It's not in their syllabus. More surprising, engineers don't understand them either. My feeling is—and I hope I am not insulting Ernest's profession too much—that engineers are told an awful lot about what to do and given the formulae, but they're not really brought up as physicists. It's a trade rather than a science. And as science gets more advanced, there are fewer people who have had a truly fundamental education. What's really needed is a combination of education—education that has to be practical—and getting some demonstration buildings done. That means going for a small museum that's cheap to build and where mistakes don't matter—use it as a demonstration, and in that way build up confidence. You're not going to break the tradition of prestige buildings with prizewinning architects.

Conrad: ASHRAE produces textbooks for engineers to use in their design, and before 1999, the textbook that ASHRAE produced included a total of one paragraph talking about how to design for a museum—that was it. In 1999 a group of us created a whole chapter in ASHRAE handbooks specifically on the design of museums, libraries, and archives. So it's only seven years that engineers have had the materials available to them to help them understand moisture migration and things like that. They didn't know about it.

Padfield: Although there is much to admire in that ASHRAE chapter, it actually has nothing about not using air-conditioning. It's still not quite fundamental enough. I understand that ASHRAE is a business and its clients are, of course, air-conditioning installers. But there is, nevertheless, a simpler physics that belongs in that chapter about how far you can go in moderating the climate inside a building without doing any installation at all.

Toledo: We've had some successful approaches to climate control. We successfully reduced energy bills by one-fifth at the storage space of the Emilio Goeldi Museum in Belém [Brazil] just using intermittent ventilation and dehumidification. We reduced the energy consumption and yet we succeeded in maintaining a stable relative humidity. Of course, it's hot inside because we are not controlling temperature, just relative humidity, and people complain about this.

Maekawa: Wasn't the director of the museum especially concerned about the cost of energy?

Toledo: Yes. Seventy percent of the annual budget was spent in energy to run air-conditioning in their storage spaces.

Levin: Is reducing cost ultimately the best incentive that we have for making changes in the way that we handle these problems?

Toledo: Yes, energy saving and budget are strong reasons. But I think we should find other ways of raising awareness for new approaches to climate control.