The engineering

Better by design, down to the material

Most of what makes a Foundation body better is what you never see — the foam in the wall, the way the panel is bonded, the extrusion at every corner, and the subframe under the floor. Here is the engineering behind it, and why every choice was made.

The four things that matter

Four choices behind every body

Cutaway render of a composite wall corner — a closed-cell foam core between composite skins, joined by a thermal-break extrusion

Structural insulated panel (SIP)

A one-piece composite panel — no wood, anywhere

The wall, roof, and floor are structural insulated panels: a rigid foam core bonded between tough composite skins into a single, monolithic piece. There is no wood frame inside to rot, no studs to telegraph cold, and no cavities to trap water. The panel carries load on its own, so the body is light, square, and stiff — a solid surface to build against instead of a hollow box you have to reinforce.

Fire-retardant, with no wood to rot, mold, or soak up water
Composite skins over a rigid foam core, bonded into one structural piece
Two thicknesses: a 1.5-inch R11 panel for vans and the E-Series, a 2.5-inch R17 panel for medium- and heavy-duty trucks
Flat, true 90° walls with integrated mounting — every inch is build-ready

The full length of a finished white composite body — bright, seamless walls, a locking entry door with window, and a glossy wipe-clean floor

Polyisocyanurate insulation

PIR foam — the best-performing core we could put in a wall

The core is closed-cell PIR (polyisocyanurate) foam. It is not the cheap, spongy foam you find in most RV walls. PIR delivers a higher R-value in less thickness, holds its performance across a much wider temperature range, absorbs very little water, and is more fire-retardant than the polystyrene foams — forming a protective char rather than melting — while still being light and genuinely structural. That combination is why our 1.5-inch van panel reaches a continuous R11, with no thermal-bridging frame cutting through it.

Higher R-value per inch than the foams used in typical campers — more insulation in a thinner wall
Closed-cell — it absorbs very little water, so it holds its R-value over time
A wide service-temperature range — steady performance from desert heat to alpine cold
Fire-retardant, rigid, and structural — not soft, squishy filler

Close-up render of the hybrid aluminum-and-PVC corner extrusion used at every edge of a Foundation body

Hybrid aluminum + PVC co-extrusion

A thermal-break AL+PVC extrusion at every edge

Aluminum is strong, but on its own it is a thermal highway — cold walks straight through it and condenses inside the wall. Our edges and corners use a hybrid aluminum-and-PVC co-extrusion that breaks that path: the PVC interrupts the metal so heat can’t bridge across it. The result is less condensation inside the wall, a higher effective R-value, and a cleaner, stronger joint than a plain pultruded edge.

Breaks the thermal bridge that lets cold and condensation through a plain aluminum edge
Raises the wall’s real-world R-value and keeps the inside of the panel dry
A stronger, more precise corner than a standard pultruded extrusion
The same engineered edge system ties the whole body together

White 6x6 truck chassis, rear three-quarter view showing the bare frame ready for a body

Torsion-reducing (Zero-Torsion) subframe

A subframe that lets the truck flex — so the body doesn’t

A truck frame twists over rough ground. Bolt a rigid box straight to it and that twist goes into the body — cracked walls, sprung doors, leaks. Our torsion-reducing subframe sits between the two and pivots, letting the chassis articulate over the terrain while it absorbs the twist, so far less of it reaches the composite body and the body stays square. On the E-Series it allows up to 22° of flex. It is built to outlast the truck: pivots on bronze bushings and chromoly pins, hot-dip galvanized and epoxy-coated against corrosion.

Why PIR

How PIR stacks up against the usual RV foams

Most campers insulate with XPS, EPS, or spray foam because it’s cheap. Here’s why we spend more on a closed-cell PIR core instead — the same reasons a commercial building uses it on the roof.

How PIR foam compares to XPS and EPS across insulation properties
Property	PIR (what we use)	XPS	EPS
R-value per inch	Highest	Moderate	Lowest
Water absorption	Very low — closed-cell	Low	Higher
Fire resistance	Chars rather than melting	Burns / melts	Burns / melts
High-temp performance	Wide range, stable	Softens sooner	Softens sooner
Structural rigidity	High	Moderate	Low

General material properties — the point is simple: PIR gives more insulation, in less thickness, that holds up to heat, water, and fire better than the foam in a typical camper wall.

Go deeper

Technical resources

In-depth answers to the engineering questions buyers actually ask — subframes, construction, insulation, and thermal performance.

What is a torsion-free subframe? Why frames twist, and how a subframe keeps the body square. 3-, 4- & 5-point subframes How each layout works and why more points isn’t automatically better. Composite vs aluminum bodies The real engineering tradeoffs between the two constructions. PIR vs XPS vs EPS insulation R-value, moisture, fire, and structure — and why we chose PIR. Thermal bridging What it is, why it causes condensation, and how we design it out.

How it’s engineered

Engineered, tested, then built

The materials only matter if the whole body is put together right. Every Foundation body is designed and validated the same way.

Simulated and stress-tested

Designs are modeled and FEA stress-tested before they’re built, then proven against real-world miles and terrain.

Bonded and sealed for redundancy

Panels are joined with integrated, redundant adhesive-sealed joints — sealed in more than one way, so a single failure point can’t let water in.

Built to tolerance

Tolerance studies and integral mounting brackets mean parts fit the first time and the same way every time — repeatable and consistent.

Corrosion-protected throughout

Structural metal is galvanized and coated so the parts you can’t see don’t quietly rust out under the body.

Final-stage manufactured

We install the body as a final-stage manufacturer to FMVSS and OEM requirements, so what leaves the shop is road-legal and titled.

Made in Golden, Colorado

Designed, built, and installed in-house on the Colorado Front Range — tested where the weather actually tests it.