Typically there is an inverse relationship between daylight and thermal resistance: the more daylight admitted, the more heat lost. By layering the dining room walls in the house with four curtains of bubble wrap, five air spaces, and a pane of glass on both the inside and outside, the walls provide both a measure of daylight and a measure of insulation. Importantly, the bubble wrap is not intended to replace the window, but rather to replace the wall. Large glass pivot doors set in steel pass-throughs provide shaded views from the room while the walls let in ambient daylight.

The resulting assembly achieves an R-value that approaches normative opaque walls (R-13.8), but glows with daylight. Visit www.fizwall.com to learn more. While the construction crew hung the dining room walls with bubble wrap assembled in the field, a North Carolina glass factory fabricated an alternative bubble wrap IGU with three layers of bubble wrap between two panes of glass. These were installed as sliding indoor thermal window and door shutters, increasing the R-2.5 windows to a value of R-10.5 when deployed on winter nights and on colder winter days.

The shutters also provide a measure of privacy while still allowing daylight to enter through the windows and front door. Night insulation, a strategy involving the regular periodic covering of windows with higher-thermal-resistance layers on winter nights, is a long-established, if under-utilized, approach to thermal control. In a house like this, 30% to 50% of the wintertime heat loss may be through window conduction and infiltration. Windows, so desired for daylight, view, and winter warmth when direct sun enters, are by far the single largest source of heat loss in skin-load-dominated buildings.

The challenge is to capture the solar heat available during the day, yet minimize the overnight loss of that captured heat. Normatively, in night insulation, the operable insulative panels are opaque. When deployed, the translucent sliding insulative panels designed here cut the windows’ heat loss by more than 75% while simultaneously allowing light to penetrate the house. Relative to normative opaque panels, where occupants wake up and come downstairs to a darkened living room, this translucent alternative allows morning daylight in the living spaces.

It has the added secondary use as a privacy shade—a privacy shade that keeps the room daylit. To avoid yellowing, tearing, furling, & melting of the plastic, a sturdy UV-stabilized bubble wrap — a product designed to be draped over a frame as a single- layer enclosure for European greenhouses — was specified. First UV-resistant glass coatings were tested on outdoor and indoor mock-ups. These 1:1 mock-up models were hung in the sun for three years prior to design and examined regularly for evidence of damage.

The shading frit layer, installed primarily to limit solar heat gain in the room, has the secondary advantage of also limiting the kinds of solar energy that would otherwise yellow, and eventually destroy, the plastic bubble wrap. Because the bubble wrap walls were not IGUs sealed in a factory under dry conditions, but rather field-hung from shop-assembled curtains, moisture was a concern. The worry was that water would become trapped in the assembly. Moisture might be found in an assembly (1) piggy-backing with air as humidity in small air seepages, (2) inadvertently left inside the cavity from construction activities, (3) penetrating the wall from rain leaks, or (4) diffusing through building materials at the molecular level as vapor migration. (Moisture analysis for this project is based on the writings of Joseph Lstiburek and those of John Straube.) The goal was not to prevent all moisture from entering the wall cavity—that goal is impossible in a field-constructed double glass enclosure.

Rather the target was to throttle the moisture inflowing via air leaks, rain leaks, and construction activities, and use vapor diffusion to (slowly) dry out any moisture that may be trapped. This was a pressing concern because both the glass on the vertical surfaces, and the aluminum tracks on the top and bottom, are Class I vapor control materials with very low perm rates, so even small amounts of water, once entered, might never leave. The assembly works: two years in, the room is warm and there has never been visible moisture inside the glass-and-bubble-wrap assembly.

Should the assembly fail, both the inside layer of glass and the bubble wrap assembly within the wall can be easily removed; the curtains are only attached to the aluminum tracks with strong magnets. The owner, who is himself the architect (and a professor of architecture at Virginia Tech), was living three-doors-down from the construction site during the entirety of the renovation. This allowed for twice-daily meetings with the builders and afforded a control over details not typically available in residential construction.

Plaster reveals, trimless fixtures, and materials that wrap around corners mark transitions. Credits: - Brian Corboy - Finish carpentry - Jingyi "Jessy" Qiu - Landscape design - Truesdell Engineering - Structural engineer - Johnson Granite - Countertops - Weber Analytics - Lighting consultant - Enchanted Lawn Service - Landscape - Andrew Montgomery - Custom furniture - Atmosphere Builders - General contractor - B&M Sheet Metal, Blue Ridge Fabricators, and Start City Erectors - Steel - Conrad Lankford - Glass fabrication - Pigeon Photography - Photography - Michael Ermann, Taylor Kuehm, Michael Mekonen, Jesse Newcomb, Alise Willis - Design team - Jim McLane and Milton Salcedo - Glass consultants - Stone From The Ground Up - Foundations - Energy Check - Insulation - Oakley Friend - Cabinets