As I wandered from floor to floor in the Kastor and Pollux building, I noticed a bodacious amount of Danfoss thermostatic radiator valves. I asked about them and learned that there were 4,500 of them sprinkled throughout the place. This is so typical of European construction. In Germany, the law requires that any room larger than eight square meters must have a TRV on the radiator. I remembered a job I once visited in New York City. This was back in the mid-Seventies when the price of fuel was soaring, and TRVs looked like a neat way to keep people from opening their windows during the winter.

An engineer specified about a thousand Danfoss valves for this hydronically heated apartment building. The contractor installed the valves, but then, during that first winter, many of those valves seemed to be bypassing. It turned out that the big pumps in the basement were the culprits. Those pumps were there long before the Danfoss valves went in. They were so oversized that when the TRVs began to close, the pumps just drove them back open again. We wound up trimming the pump impellers to solve the problem.

In this German office building, they used Danfoss' ASV differential pressure regulators to avoid this problem. They piped one between each two-pipe, direct-return riser to maintain a uniform differential pressure on all the riser groups in the building. As the TRVs throttled the flow through the radiators, the differential pressure valves bypassed some of the flow across the risers. The head-pressure problems we had in New York City weren't a concern in Frankfort. You live and learn, right? Besides, the circulators in the Frankfurt building weren't that large to begin with. They don't oversize pumps in Europe, as we so often do in the US. The pumps in this building were all inline and each ran on variable speed. Grundfoss made those pumps.

We wandered some more and came to a loading dock. This space was also heated with a radiant floor. Mr. Grohal and Mr. Thaler explained that they didn't like to use unit heaters as the primary source of heat for loading docks or garages because the heated air drifts toward the ceiling and escapes whenever someone opens the large overhead doors. They sometimes use unit heaters as a secondary source of heat in these areas, but radiant is always their first choice.

They bury the tubing about eight inches deep in areas such as these because they're concerned that someone may drive anchors into the concrete at some point to support equipment. Because of the depth of the radiant tubing, they don't cycle these systems. Rather, they use a floor sensor to maintain the floor's surface temperature at a constant 68 degrees F.

"It must be expensive to build this way," I commented.

"Yes," both men agreed. "But much better for the environment. And for the owners of the building as well. It costs them less to operate the system in the long term." I made a note of that statement, and the way they ordered their priorities. It's one of the things that has helped this job live on in my memory. The environment first, and then the client.