Why we walk
The deepest cold of the Pittsburgh year is between roughly December 26 and January 7. The buildings we serve see their annual peak heating load in this stretch. The chillers are off. The boilers are on. The dehumidification load is the highest it has been since the previous year’s January cold snap. The institutions that hold our retainers are mostly closed; many staff are on holiday; the buildings are the quietest they have been in twelve months. This is when the systems we built reveal what they are doing without supervision.
It is also when, statistically, the most things go wrong. We have, in the last six years, observed eleven setpoint excursions during the holiday week and three would-be stop-work events that became non-events because we caught them on a walk. The walks pay for themselves in roughly the proportion of one stop-work event avoided to four years of walks. They also pay for themselves in a less measurable way: the institutions know we are walking, the boards know we are walking, the donor letters that mention our retainer mention the walks. We have closed at least three new institutional retainers on the strength of the walk story.
I write the daybook for the binder. The form is borrowed from Aldo Leopold’s A Sand County Almanac — observed condition, time, place, weather, and an occasional reflection. It is not a service report. It is what we write while we are still in the truck.
Daybook · 2025‑12‑23 to 2025‑12‑31
2025‑12‑23 · Tuesday · −9 °C, light snow
Started at the cordage warehouse on Butler Street. Vault III, 18.0 °C / 45.1%, ribbon flat, dew-point trace 4.4 °C. Walked the second-floor vault. The 1898 brick is taking up moisture as expected; the inner shell is not condensing. Moved to North Side glass-plate. 5.0 / 30.4. The cool-storage box is quietly behaving. Visited the cellulose-nitrate vault at the iron-collection mixed-media room. The dedicated chiller had ramped up to 78% on the cold-snap forecast; perfect. Truck thermometer read −9 °C all day. The sun came out for ten minutes around noon. Drove home through the Fort Pitt Tunnel in the dusk; lights on early.
2025‑12‑24 · Wednesday · −12 °C, sun
Christmas Eve. Two sites: the Westmoreland County historical society (case 026, our oldest active retainer) and a private collector in Fox Chapel (case 049, NDA). At Westmoreland: nothing wrong, but the second-floor reading-room sensor was reading 1.4 °C low against the duct sensor. We have flagged this for the controls team for January; it is almost certainly a calibration drift on the duct probe, not a setpoint problem. At the Fox Chapel residence: the dehumidification skid was running at 92% on the load. The room held setpoint inside the band. The dog at the residence (a long-haired dachshund named Penny) accompanied me through the basement and demanded to be picked up at the chiller. I obliged.
2025‑12‑25 · Thursday · OFF
Day off. Shop closed. Mihai walked his three sites in the south-side fleet alone. He reports nothing alarming.
2025‑12‑26 · Friday · −14 °C, clear
The coldest day of the trip. The forecast had been calling for −14 since Tuesday; we had pre-warmed the dehumidifiers at four sites the previous afternoon. At the regional university library’s glass-plate vault: 5.0 °C / 30.0% on a flat ribbon. The −14 ambient pushed the cool-storage box’s air-cooled condenser to its design margin and we watched the unit approach but not exceed cycling threshold. The 320-cfm vestibule DOAS earned its keep on this day. Drove east to the historical society’s second site, then back via the parkway. The parkway was quieter than I have ever seen it.
2025‑12‑27 · Saturday · −11 °C, sun
The mill (case 041). Active construction site. We are not supposed to walk a construction site solo, so I waited at the trailer for Tania, who drove out from Mt. Lebanon to meet me. We walked the second floor. The west bay was at 4 °C ambient (the building is not yet sealed). The east bay, which has the bays of windows that the historic-preservation architect signed off on last week, was at 14 °C with the temporary heaters running. The Class B target is 18; we are close. The dust on the floor is sawdust, which is a clean dust. The columns are dark and stable.
2025‑12‑28 · Sunday · −8 °C, overcast
Two private sites: the Mt. Lebanon residence and the Squirrel Hill rowhouse. Both held setpoint within band; both walked clean. At the rowhouse, the Audubon plates have not visibly aged in eighteen months and the homeowner has stopped asking us about them on the calls. This is the quiet success.
2025‑12‑29 · Monday · −6 °C, light rain
The mixed-media room. Five zones to walk: the baseline 18/40 storage, the 5/30 walk-in, the 2/30 nitrate vault, the 20/55 humid alcove, and the 13/35 cool-storage closet. The zone walking takes about forty minutes if everything is normal. Forty minutes today: everything is normal. The nitrate vault’s vent fan was off (it cycles), which is its design behavior. The humid alcove’s humidifier was running at 14%, which is a pleasant surprise (we expected 25–30 in this weather).
2025‑12‑30 · Tuesday · −4 °C, sun
The Lawrenceville cordage vault again, on the way back from a small institutional client in Beaver Falls. Case 026, the Westmoreland society again, en route. Nothing wrong at any site. I stopped at the Cure restaurant on Butler Street for the early dinner, which is quiet between Christmas and the New Year, and which has the espresso the shop manager will not tolerate at the espresso machine.
2025‑12‑31 · Wednesday · −2 °C, snow
The last walk: two private sites in the Mexican War Streets neighborhood and one in Fox Chapel. The dachshund again. The forecast for the new year is warming. The shop reopens January 5. The walk is over.
Takeaways
What I noted, across the seven walking days, that I will tell the team about in the January 5 review:
- The Fort Pitt Tunnel takes longer than you think on snow days. Plan to leave 15 minutes earlier on a forecast snow day. We knew this; we forgot it.
- The 320-cfm vestibule DOAS at the glass-plate vault was the difference between a clean walk and an out-of-band excursion at the cool-storage condenser. Specify it standard going forward.
- The duct-probe drift at Westmoreland is the first calibration drift we have observed on a Conserv-LoRaWAN node in three years. Worth flagging in the journal as a vendor-bake-off note.
- Pre-warm the dehumidifiers two days before the forecast cold-snap peak. We did this on four sites and saw measurable margin; we did not on three sites and saw the units approach their cycling threshold.
The walks will continue every year. The form will continue to be the daybook. We will, I expect, keep doing this for as long as the practice exists.
— PA, on the way home, 2025‑12‑31