Four wiki pages, written between 1999 and 2004, form a single argument: removing the glass cover from a solar collector is not a compromise — it is a design choice that unlocks cooling, simplifies construction, and changes how performance varies across geography and season.
| Page | Contribution |
|---|---|
| Unglazed solar collectors | Baer's 2003 SunPaper article: warm showers through "icy clear January weather" from unglazed Skymat™ panels. "Unglazed collectors are more efficient than glazed, at temperatures close to ambient." |
| Geographical variation in unglazed solar performance | Shows that performance depends on climate, wind, sky IR, and load type — not just latitude. |
| Roof integrated solar absorbers | Demonstrates that an unglazed collector can be invisible — part of the roof, not bolted on. |
| Consider perihelion | Baer's January 2004 essay: Earth is 3½% closer to the sun in early January, making winter sunlight 7% stronger than aphelion. "In perihelion time the atom bomb was invented a day ago, the steam engine a week ago." |
| Heated vs unheated plates | Stickney & Baer's matched-plate experiments: a horizontal plate with 9.5 W/ft² electric heat cannot reach ambient on a clear NM night — the sky pulls heat away faster. |
| Di-thermal roofs | Shows the endpoint: the unglazed surface becomes a dual-function roof that heats and cools. |
Conventional solar collectors use a glass cover to trap heat. Baer's SunPaper article makes the counterintuitive case: "unglazed collectors are more efficient than glazed, at temperatures close to ambient." Glazing blocks airflow and sky radiation, but it also reduces the sun reaching the absorber. Energie Solaire's own performance charts show the unglazed selective-surface collector outperforms the glazed version up to 36°F above ambient in New Mexico sun.
Practical benefits of removing the glass: no fire risk (can't overheat enough to ignite), can lay directly on composition shingles, no collector box needed, much cheaper. And critically — the surface can radiate freely to the sky at night, which is essential for cooling. Baer also makes the IR-education argument: a $30 Radio Shack infrared thermometer turns a parking lot into "a lesson in the effect of colors and orientations on stagnation temperatures."
The tradeoff is wind and convection loss. Whether that tradeoff is acceptable depends on the climate and the load.
The geographical variation study shows that unglazed collectors are not one-size-fits-all. Performance for domestic hot water, space heating, and space cooling varies by region. Wind exposure, sky infrared conditions, and building load all shift the result. The paper argues for an integrated view: unglazed collectors can be attractive because they are cheaper and look like ordinary roofs, but their value is site-specific.
Roof-integrated solar absorbers take the next step: if the collector has no glass and no frame, it can be built into the roof surface itself. The building preserves its visual shape while harvesting energy. Measured performance backs this up — it is an engineering claim, not just an aesthetic one.
This matters for adoption. Visible bolt-on panels face resistance from homeowners, architects, and planning boards. An invisible collector faces none of those barriers.
The perihelion observation adds a second-order correction that the other pages miss. Earth is ~3.3% closer to the sun in early January than in early July, which means winter insolation is ~7% stronger than aphelion values. For an unglazed collector operating at small temperature differences, this orbital boost is not negligible — it makes winter collection better than latitude-only models predict. Baer frames perihelion as a slow timekeeper: it drifts later by about one day every 57 years. "In perihelion time the atom bomb was invented a day ago, the steam engine a week ago, and fire a year or two ago."
The Tribal Messenger serialization noted this orbital effect in 1973. The 2004 page sharpens the observation three decades later. The practical takeaway is that Baer's shower worked through "icy January weather" partly because January sunlight is stronger than anyone without an ephemeris would expect.
The di-thermal roof is where the lineage converges. An unglazed roof surface that collects heat by day and radiates it to the sky at night is both a solar collector and a radiative cooler. The same hardware heats in winter and cools in summer. That dual function is only possible because the collector is unglazed — a glazed collector cannot radiate efficiently to the sky.
remove glass → map climate → integrate into roof → correct for orbit → dual-function surface
The lineage reveals that "unglazed" is not a cost-cutting shortcut. It is the enabling condition for the archive's central thermal idea: a building skin that exchanges heat with the sky in both directions. Glazing blocks that exchange. Removing the glass is what makes the di-thermal roof — and by extension Cool Cell — possible.
The practical implication is that performance evaluation for unglazed systems requires different inputs than for glazed systems: sky IR, wind, perihelion correction, and nighttime radiative capacity all matter more than they do under glass.