raw · notes · ingested 2026-07-02
PCM window retrofit / frame-insert landscape — patents & secondary glazing (research note)
confidence: high
Source: https://patents.google.com/patent/US4813203A/en
Purpose: close gap #2 — is there a genuine way to add translucent PCM to an existing window frame? Bottom line: No frame-insert translucent-PCM retrofit product or dedicated patent exists. The space is occupied by non-PCM retrofit glazing on one side and full PCM-IGU replacements on the other; only automotive attachables and standalone interior PCM devices bridge toward the concept.
Sources reviewed
- US 4,813,203 “Retrofit glazing system” (Newman/Palacios/Hogan, NPH Partnership; filed 1987, issued 1989-03-21). Retrieved in full. Purely mechanical: extruded aluminum sub-frame fastened to the existing framework + a factory “miniframe” silicone-bonded to the glass that interlocks with the sub-frame; exterior-install. Contains NO PCM. Settles the prior round’s open question. https://patents.google.com/patent/US4813203A/en
- US 9,797,187 B2 “Devices for modulation of temperature and light based on PCMs” (Carnegie Mellon). Transparent hollow vessels (PP/PC/acrylic/glass) holding PCM with internal conductive mesh; deliberately transparent; modular and relocatable, NOT a frame insert — louvers, honeycomb networks, venturi-tube-with-fan, cable-hung containers. Closest patented “translucent PCM added at a window without replacing the IGU.” https://patents.google.com/patent/US9797187B2/en
- US 2010/0244495 A1 “Phase change material usage in window treatments” (GM). PCM (paraffin, salt hydrate, poly-alcohols, eutectics) contained three ways: between two films, self-encapsulated beads, or beads embedded in glass/plastic. Explicitly attachable — roller shades, removable suction-cup housings on existing windows, pivoting visors. Automotive, abandoned. Clearest “attach PCM to already-installed glass” pattern. https://patents.google.com/patent/US20100244495A1/en
- Fang et al. (2013), Energy & Buildings “Thermal performance of secondary glazing as a retrofit alternative for single-glazed windows.” Tests real retrofit secondary glazing (plastic film, magnetically attached sheet, plain glass, low-E) for existing single-glazed frames; R improves 0.15 → 0.34–0.57 m²K/W. No PCM — documents the attachment methods a PCM version would reuse, and shows the field stops short of PCM. https://www.sciencedirect.com/science/article/abs/pii/S0378778812003830
Implication for a retrofit
The realistic retrofit path is a sealed PCM secondary-glazing panel added behind the existing sash (method 2 of the transparent-PCM taxonomy), borrowing the magnetic/clip/suction attachment of non-PCM secondary glazing and the film-enclosed or encapsulated-bead containment of the GM patent. Containment (leak-proof sealing, freeze-thaw durability) is the design problem, not the PCM.