Bill Lotz was a name that carried weight with many builders, tradespeople, engineers, and architects in New England through the 80s, 90s, and into the 2000s. Early on, he was a guiding voice to JLC readers with the “Lotz on …” column he wrote when the the Journal of Light Construction was still New England Builder, and he continued to contribute his “Case in Point” column in JLC into the 1990s. Bill recently left us this fall. This article pays tribute to some of the contributions to building science he made before building science was an established field.
More Information
Moisture Control and Insulation Systems
Bill’s book on how to deal with moisture problems in buildings and their components.
Fighting Mold, Rot & Paint Peeling with Bill Lotz
Ep. 142 pf the Tim Faller Show
William Alan Lotz was born in 1932 into a family insulation business. His father, John Lotz, and his mother owned and ran the family company, Lotz Insulation Company, which dated back to 1920 and insulated refrigeration warehouses, Air Force hangars, and homes across New England.
Bill joined the family business, Lotz Insulation Company, at just six years old, sweeping asbestos dust off the warehouse floor for five cents an hour. By fourteen he knew every phase of it, from installing and selling asbestos, mineral wool, and cork to managing the work and tackling insulation problems. He got his hands (and knees and face) dirty wrapping these latter materials around cold and hot pipes, not only to protect the pipes from the vagaries of moisture and rust but also to protect the people from scalds and burns.
The 1948 Dodge 6-ton truck Bill drove for work at age 16.
By 1950 the family’s Lotz Home Insulation Company had already insulated more than 20,000 homes in New England alone. So it was natural for Bill to become a mechanical engineer in insulation. It was no surprise, either, that within four years of his graduation in 1956 he became the Technical Service Engineer for another big American insulation company, Owens Corning. At Owens Corning, Bill was responsible for reviewing all the technical and sales literature on insulation. He was called in whenever there was a moisture or heating and cooling problem, whenever insulation wasn’t doing its job.
The Insulation System
Bill never said the word “insulation” by itself. He always said “insulation system,” because the word “system” includes an integral element: the vapor-air barrier. How is that? It’s simple: Any wall, roof, or foundation, any cold or hot pipe, any body sitting between a cold and hot interface, needs protection, and the insulation system is that protection. But insulation by itself isn’t enough. Insulation needs protection from moving air and moisture. Almost all insulation works on the same premise, holding tiny pockets of trapped air that slow the transfer of heat. Fill those air pockets with water and the trapped air stops doing its job. Or blow air through the insulation fibers and the insulation becomes useless.
How do we protect those insulation air pockets? Bill answered “with a vapor-air barrier.” These days, many make a distinction between an air barrier and a vapor retarder. But in Bill’s world, it was strictly referred to as a vapor-air, or more often as just the vapor barrier to denote an all-important ingredient that keeps the insulation dry and stops air blowing through it so those trapped air pockets can do their job.
For an insulation system to work, Bill emphasized, it has to be continuous through the whole building, wrapping the house the way a blanket wraps a body to hold in warmth. An insulation system a foot thick with air gaps will test at approximately zero R-value, because air flows through the path of least resistance and brings with it a huge amount of moisture. The gaps allow air currents to run across the building elements where they exist, compromising the insulation along the way. Bill didn’t think in terms of disparate control layers; instead, he sharpened his focus on one protective layer with air barrier, vapor retarder and insulation acting in unison. Looking for where the system breaks down, where the materials no longer function in unison, lay at the heart of his building inspections.
Humans Inside the House
Where does the moisture in buildings come from? Many places; it’s not just rain and meltwater. As Bill explains on page 9 of his book, Moisture Control and Insulation Systems in Buildings, Chilled Water Pipes and Underground Pipes, moisture in a building comes from “people breathing, bathing, humidifiers, indoor plants, washing clothes and dishes; construction water in plaster, paint, wood and concrete; pools, rain leaks, wet basements and crawl spaces and bare ground in old-house basements or crawl spaces.” His book is filled with case studies about what causes moisture in buildings and how to manage it successfully.
Bill draws attention here to something important: You always have to look at human activity and assess the head count living in a building to understand the moisture load. Of course, hospitals, swimming pools, ice rinks, and other facilities that run tons of water inside the building need a different approach than you take in homes, but the principles are similar.
Bill pauses during an inspection on the roof of Building 962 and 963 at IBM Burlington in 1979.
Roof Systems, Too
Bill Lotz often paid special attention to where the walls meet the roof, because at that transition the insulation and the vapor barrier get compromised. Anything that breaks the insulation system and stops it from running continuously, whether across the roof itself or at the junction of roof and wall, can lead to an ice dam. Something as simple as a recessed light, an inadequately insulated or sealed heating duct, or any other electrical equipment throwing off heat can send that heat up to the roof while it is cold outside. The heat thaws the snow on top of the roof, and the meltwater runs down to the overhang of the roof where it refreezes and builds up, creating a dam that causes water to back up the roof and leak into the structure.
Lotz also discovered on many jobs that some roof “leaks” are not actually from rain or meltwater. Instead, they come from heat escaping through improper insulation or discontinuous vapor-air barrier. The heat rises and sits underneath the roof surface inside the house. Now, what happens to hot air carrying tons of moisture when it suddenly hits the cold underside of the roof? The moisture condenses and drips back down into the house. The people living there think the roof is leaking, when it has nothing to do with leaks. It is excessive moisture from inside the house, coming from the many causes we listed earlier.
But before you think perfection, I hasten to say that Bill believed the perfect insulation or vapor-air barrier does not exist. What produces superior results is good workmanship, a crew (of architects, engineers, and tradespeople) that understands what they are doing, working with the right product and the right training.
The design does not have to be perfect either. It just has to be detailed enough to make good workmanship possible. It’s less about fussing over every little gap and more about spelling out how the pieces go together, and in what order, so the plan is both doable and effective.
Bill loved visiting and testing in the field. He would frequently emphasize that insulation systems, pipes, and heating or cooling systems always exist in the imperfect conditions of the field, not the “controlled,” “double-blind” conditions of a lab.
The Balanced Mechanical System
Besides the insulation system and the vapor-air barrier, Bill Lotz loved talking about common sense construction practices: sloped roofs, overhangs, ventilation in the bathrooms and kitchens, and most important of all, the right mechanical system.
The moisture inside a building is never fixed, it rises and falls as the temperature rises and falls, and since the temperature changes all the time, so does the humidity. That is why we call it relative humidity. Ideally, relative humidity should sit between 30 and 50 percent, and holding it there is exactly what the right HVAC system is for. In addition, a successful mechanical system should strive to keep an equal balance of pressure between the inside and the outside of the building.
Before Bill sailed off into the sunset this past fall, he enjoyed sailing a 50-foot sailboat in the Atlantic after retirement from his engineering practice.
Rain Screens
I would like to end with one more idea Bill championed 40 years ago, long before others in the industry: the rain screen. It is more important than ever in this age of installing continuous insulation on the outside of buildings. No one should be installing wood siding directly on top of polystyrene without wood strapping or another type of rain screen between the siding and the foam. Wood loves water. It soaks up rain and snow, and that is fine, as long as it can dry back out afterward. But polystyrene is a solid sheet that water and vapor cannot pass through, so when the siding is nailed tight against it, the back of the wood has nowhere to dry to. It stays wet, and wood that cannot dry begins to rot. The solution is wood strapping that holds the siding off the polystyrene foam and leaves an air gap between the polystyrene and the wood, so air can circulate and carry the moisture away before it does damage.
Building science is an evolved practice in the building industry, and many builders now pay close attention to the transfer of energy and moisture through the building enclosure. That evolution was greatly influenced by the systems thinking that Bill Lotz championed his entire career.
Is he missed? No. Personally, I don’t miss Bill , because he is still here among us, in his work, his articles, his books, and his laughter. I hear it loud and clear. Do you?
