Envelope & Glazing — Cutting the Load Before the Machine

The cheapest cooling is the cooling you never have to make. Before any adsorption chiller, heat pump, or free-cooling handoff, the building envelope sets the load every machine downstream has to meet. This theme collects the envelope and transparent-material sources from the library — structural insulation, dynamic façades, and specialty glazing — under one idea: reduce the conductive and solar gain first, then size the cooling to what’s left.

This is the same envelope-first sequencing the 601 Delaware energy strategy insists on: improve the envelope, then size the mechanical system to the improved load — never the bare-building load.

Insulation — structural insulated panels (SIPs)

SIPs (a rigid foam core bonded between two structural facings) deliver structure and continuous insulation in one panel — high R-value with minimal thermal bridging, and fast, airtight assembly. The collection’s sources are Michael Morley’s Building with Structural Insulated Panels (Taunton Press) and a Geofaze SIP presentation. The cooling relevance is direct: continuous insulation + low air leakage cut the sensible conductive load and the infiltration load, which is the largest lever on a hot-climate cooling bill before you touch a chiller.

Insulation — aircrete (foamed cement)

Aircrete (aerocrete / cellular concrete) is cement foamed with air — a lightweight, insulating, fireproof, mineral material that sits in the resist column alongside SIPs but from the opposite material family: a monolithic cementitious envelope rather than a foam-cored panel. Two sources frame it from different ends.

DomeGaia (vendor/educational) builds the DIY-aircrete-dome ecosystem — courses, manuals, workshops, design services (claimed 150+ buildings across 7+ countries). Its envelope argument combines the material (foamed cement: insulating, fire/pest-resistant, low resource use per volume) with dome geometry, which minimizes the surface-area-to-volume ratio — less envelope area to gain heat through for a given enclosed space. The vendor’s insulation/durability claims are marketing and carry no independent data.

NightHawkInLight supplies the harder numbers and a notable process innovation: a self-foaming recipe that needs no foam generator or compressor. Pre-hydrating xanthan gum (with detergent, in water) before mixing 1:2 by volume into Portland cement lets bubbles form and survive the cement’s hostile alkalinity during ordinary stirring; stir time sets density (more stirring → lower density → more insulation, less strength), with a closed-cell → open-cell transition at the point surface bubbles begin to pop. A crude comparative thermal test put a 1-inch sample at R ≈ 6.3 — slightly beating an R6 foam board of equal thickness, with the author explicitly cautioning that his DIY measurement setup may be unreliable. Treat R6.3 as suggestive, not validated; the directionally useful claim is “foamed cement reaches foam-board-class insulation in a fireproof, microplastic-free mineral.”

Cooling relevance: like SIPs, aircrete is a resist material — it cuts the sensible conductive load at the envelope before any machine is sized, and uniquely does so with thermal mass and fire resistance a foam panel lacks. The trade-off is lower mechanical strength at insulating densities and (for the DIY route) unproven, batch-variable performance. Worth tracking as a low-cost, owner-buildable envelope option rather than a specified assembly.

Dynamic façades — the double-skin façade

A double-skin façade is two envelope layers (usually glass) with an air cavity between them that air flows through (How Do Double-Skin Façades Work?, ArchDaily). The cavity is the active element: in cooling mode it is ventilated to carry away absorbed solar heat by the stack effect before it reaches the interior, turning the outer skin into a buffer rather than a direct heat path. It’s an envelope that manages solar gain dynamically instead of just resisting it — the architectural-scale cousin of the radiative/selective-surface approach, and conceptually adjacent to the CoolSkin adsorption façade (where the skin itself does the cooling).

Specialty glazing — UV-transmitting double-skin acrylic

ACRYLITE® Alltop (Röhm) is a UV-transmitting, double-skin acrylic glazing. Most glazing blocks UV; Alltop passes it — which matters for solar-collector covers, daylighting, and growth/process applications where the full solar spectrum (or specifically UV) is wanted. In a cooling/energy envelope it sits at the intersection of the solar-thermal thread (a transparent cover that admits the full solar band to an absorber) and the double-skin idea (the multi-wall geometry gives some insulating cavity while staying transparent). It’s a specialty material to reach for when the design wants light or solar in (a collector, a daylit hall) rather than kept out.

Specialty glazing — translucent phase-change glazing

A translucent window can also store heat, not just admit or resist it. A phase-change material (PCM) sealed into a glazing cavity absorbs solar/room heat as latent heat during the day (melting) and releases it at night (freezing), flattening the indoor temperature swing while staying see-through. The clarity question is delicate: salt hydrates (CaCl₂·6H₂O) are translucent as both solid and liquid, while paraffins are clear only when molten and go milky-white when frozen — which doubles as automatic solar shading. The one mature commercial product, GlassX Crystal, seals a salt hydrate in polycarbonate channels behind a prismatic filter. Note these ship as full IGU replacements, not slot-in retrofits for existing frames — the retrofit path is a sealed PCM secondary-glazing panel behind the existing sash. This is the store option that complements resist/manage/transmit, and it links the envelope to latent thermal storage. Full treatment: Translucent PCM Glazing.

How the envelope fits the strategy

The three sit on a spectrum from resist → manage → transmit:

SIPs and aircrete — resist heat flow (continuous insulation, airtightness; foamed-cement mass + fire resistance) → lowers the firm load.
Double-skin façade — manage solar gain (ventilated buffer cavity) → sheds gain before it’s a load.
UV-transmitting acrylic — transmit deliberately (collector covers, daylighting) → admits solar where the design wants it (e.g. to drive solar-thermal cooling).
Translucent PCM glazing — store (and self-shade): a see-through cavity that buffers heat as latent storage and, with paraffins, auto-dims when hot → see Translucent PCM Glazing.

Load reduction here multiplies everything downstream: a smaller load means a smaller adsorption/heat-pump array, more hours covered by free cooling, and less hydronic capacity to install.

Scope note: these sources are envelope/daylighting material science rather than refrigeration cycles — compiled here as the load-reduction layer that the cooling technologies depend on, not as cooling machines themselves.