The Skylid® is Zomeworks' insulated skylight louver that opens and closes by itself in response to sunlight — no electricity, no thermostat, no motor. It is the archive's clearest example of Baer's design principle: let physics do the control work.
US Patent No. 3,884,414
A Skylid is a louver balanced on ball bearings beneath a south-facing skylight. Attached to the louver are two sealed refrigerant canisters connected by tubing — one canister on the outside near one edge, one on the inside near the opposite edge. The canisters contain only liquid refrigerant and its vapor; all other gas is purged.
Vapor pressure drives the refrigerant to whichever canister is cooler. On a sunny morning, the outside canister warms first; refrigerant transfers to the inside canister, shifting the weight balance and tipping the louver open. At night or on overcast days, the outside canister is cooler; refrigerant shifts back, closing the louver.
The key feature: the two canisters compare temperatures rather than acting at a set temperature. This makes the Skylid a relative thermostat — it responds to the difference between inside and outside, which is exactly what's needed for solar control. It works as a combination thermostat and gravity engine using no outside power.
The mechanism is the same as the Franklin pulse-glass, a novelty thermometer invented by Benjamin Franklin. Prior solar applications:
Baer's insight: modify Geer's device and the louver will follow the sun throughout the day.
Skylid work at Zomeworks began in 1971 — the same year Baer built his Corrales house, where they were installed in the zome skylights. Brought to their documented state by David Boyd, Dick Henry, and Baer. First described in detail in Sunspots (1975); still produced by Zomeworks.
The Baer House photographs show Skylid louvers seen from below, freon-actuated canisters visible at the top of the frame.
| Parameter | Value |
|---|---|
| Typical louver width | 22 inches |
| Construction | Bowed sheet aluminum C-sections over wood ribs (airfoil cross-section) |
| Weight | <2 lbs/sq ft |
| Bearing | Ball bearings; 5/16" bearings support 20-40 lbs with few foot-ounces torque |
| Fill | Fiberglass between aluminum skins |
| Standard span | 22" wide × 5" deep → 12 ft span |
| Projected span | 48" wide × 12" thick → 20 ft span |
| Refrigerant | Refrigerant 12 (Freon-12): non-flammable, non-poisonous, dense, low specific heat, low boiling point |
| Canister size | 2½" diameter × 16½" long; 80 cu in; 0.065" steel walls |
| Canister weight | 2.5 lbs; 3 lbs of R-12 |
| R factor (closed) | ~5 in practice (theoretical R-10+ with perfect seals) |
| Albuquerque open days | At least 95% of winter days |
Canister physics: Refrigerant 12 vapor pressure increases ~1.5 psi per °F rise at room temperature. The canister intercepts about ¼ sq ft of sunlight directly. On a winter morning, the outside canister must gain 40-80 BTU to pump refrigerant to the inside — taking 1-2 hours. Response can be accelerated by soldering fins to the canister.
Seals: The most critical design challenge. Warm air rising and cold air descending through cracks will defeat any insulation value. Light floppy fabrics work best — extremely flexible, with sealing force on the order of a fraction of an ounce per foot of seal.
Tests by Ron Shore and Baer (February 1974): a white or dull aluminum reflector of width equal to the skylight width increases heat gain by more than 30% during the hours the skylight faces the sun. The reflected light "gets in free" since the exposed glass area stays the same size and temperature. The reflector also acts as a windbreak, reducing convective losses. In summer, the reflector is lowered to shade the skylight.
Baer classifies the Skylid as "a very simple example of a gravity engine, one that uses the rotation of the earth or cloud cover as a kind of valve." The refrigerant redistribution is driven by the earth's position — the outside canister's exposure to the sky determines which way liquid flows. The Skylid does work (opens a louver) using gravity as the spring against which the vapor pressure acts.
The Skylid is the control layer for the DrumWall system. The drum wall stores solar heat; the Skylid admits sunlight when the outside is warm and closes when it is cold. Together they form a complete passive solar heating circuit: collect (skylight + Skylid open), store (DrumWall), release overnight (radiant heat from drums). No electricity at any step.
The same canister principle can open and close insulating doors on hot water tanks — any application requiring temperature-differential actuation.