Circular homes are having a renaissance. From inflatable concrete shelters to earthen superadobe domes and traditional adobe roundhouses, curved structures promise strength, energy efficiency, and resilience in a hotter, stormier world. Their geometry sheds wind, holds heat, and uses fewer materials than boxy buildings. They also just feel better, as bed-“womb” builder Hassan Fathy always said.

But there’s one practical concern that consistently comes up when readers explore these climate-smart homes: How do you put flat windows into round walls?

Curved architecture may be ancient, but modern living still expects views, ventilation, and natural light. Fortunately, builders have developed elegant, low-tech solutions that work across materials and climates. Here’s a guide to the most effective ways to fit windows into round or dome-shaped homes.

Create a Flat “Window Buck” Inside the Curve

This is the most common method used in superadobe domes, monolithic domes, inflatable concrete houses, and even straw bale roundhouses. A window buck is a rigid, rectangular insert made from wood, steel, or composite. It’s placed into the wall while the dome or roundhouse is being built.

How it works: Construct a strong rectangular frame the size of your chosen window. Anchor it to rebar, mesh, or the foundation. Build your curved wall—earthbags, adobe, or sprayed concrete—snugly around the frame. Install a standard flat window once the wall cures.

Why builders use it: It interrupts the curve just enough to create a flat surface without weakening the dome. Standard windows fit perfectly, and the buck acts like a structural anchor.

Shape an Arched or Vaulted Opening (The Classic Adobe Method)

In traditional Middle Eastern and North African adobe buildings, window openings are shaped as arches carved into thick earthen walls. The windowpane stays flat, but the curved walls taper gracefully toward it.

Benefits: The arch distributes structural loads evenly. No lintels needed, reducing cracking. Creates deep, shaded window wells—excellent for cooling in desert climates. Ideal for passive solar design. This method is especially beautiful in hand-plastered homes and pairs well with natural finishes.

Add a Mini Flat Section or Buttress for the Window

Curved homes don’t need to be perfectly round. Builders often create a subtle flat segment or “mini buttress” — just wide enough for a window. This technique is common in eco-resorts in Sinai, Jordan, and Portugal that want the sculptural look of domes but the convenience of standard glazing. Why it works: It’s simple, avoids complex carpentry or brick work, and creates a stable vertical plane for installation without disrupting the overall geometry.

Install Circular or Porthole-Style Windows

Some builders embrace the curve by choosing round or oval windows. These are custom-builds, and more expensive options generally. Plastic windows, with tints, may be found in home and dome kits for a reduced fee.

Where you’ll see them: Inflatable concrete bunkers, monolithic domes, tiny eco-homes, storm-resistant shelters and in barrel sauna. They eliminate the need for a flat insert and can withstand extreme wind. Repurposed marine portholes are surprisingly popular thanks to their durability and charm.

Round homes ask us to rethink building conventions. Their curves offer comfort, efficiency, and surprising strength—but they require intentional window design. Whether you’re building in the desert, forest, or city fringe, one of these solutions will fit your climate, materials, and aesthetic.

The post How flat windows work on round and dome-shaped rooms appeared first on Green Prophet.

What is an inflatable concrete house? Robert Downey Junior owns one. And they’ve been touted as costing a mere $3500 a build. An inflatable concrete house is a home whose structural shell is formed by using an inflated form or bladder, often made of fabric or drop-stitch material – see our article on Binishells. This form is then filled or coated with concrete—sometimes sprayed—to create a permanent, self-supporting shell. After the concrete sets, the inflatable form either remains as part of the structure or is removed.

There are several versions of this method, but the classic Binishell system was invented by Italian architect Dante Bini, and uses a large inflatable bladder laid on the ground. Reinforced concrete is poured or sprayed on top, then inflated so the shell lifts itself into its final domed shape.

A newer approach developed by Automatic Construction employs inflatable flexible factory formwork—flat, lightweight drop-stitch fabric bladders that are transported easily, inflated on-site, and then filled with concrete to form both walls and roof. We can imagine that 3D printing concrete robots will be able to handle the lay-down of concrete in the future. Current designs don’t look great but are pilots in progress.

The company website states that their factory-made forms reduce on-site labour, transport cost, and job-site waste; they claim their buildings will cost “1/5th the cost” of standard cast-in-place concrete. Their website also notes that actual homes you can live in are “coming soon”.

Another experimental process, created by researchers at the Vienna University of Technology, uses pre-hardened concrete panels placed on an inflatable air cushion. When inflated, the panels lift and bend into their final curved geometry, a process known as pneumatic forming of hardened concrete. The research is coming out of  TU Wien’s Institute of Building Construction and Technology, led by Professor Benjamin Kromoser and Professor Johann Kollegger.

Instead of pouring wet concrete into a form, the concrete is already cured, and the inflation pressure deforms it elastically, forming arches, shells, or domes. Once the desired shape is reached, it’s fixed in place with steel reinforcements or stiffening ribs. This technique allows the creation of elegant curved concrete roofs and shells without traditional scaffolding, molds, or 3D-printed supports.

The appeal of these systems lies in their efficiency and simplicity. Inflation and concrete filling can take place in a few hours instead of the weeks required for conventional formwork. Builders report significant labor and material savings, and dome or shell shapes provide exceptional strength and durability, even under severe environmental conditions. The method also carries a distinctive architectural character that attracts designers seeking expressive, futuristic, or minimalist aesthetics.

As for cost, estimates vary widely depending on design, size, and finishing.

Some small Binishell prototypes have been built for around US $3,500 using sprayed concrete over an inflatable form. Automatic Construction reports shell costs of roughly $10–$30 per square foot for 100- to 200-square-foot prototypes—far below standard homebuilding prices. The Vienna method is described as “quick and cost-saving” for double-curved shell structures, but specific dollar/€ cost numbers are not given in the available sources.

More conventional dome homes, which use similar air-form techniques, typically range between US $100 to 250 per square foot once fully finished. A 1,000-square-foot monolithic dome, for example, might cost about US $60,000 for the basic shell and around US $130,000 after interior finishing.

In all cases, actual costs depend on local labor, materials, foundation, insulation, utilities, and compliance with building codes—but inflatable concrete shells remain one of the fastest and potentially most cost-efficient structural methods emerging in contemporary housing design.

The fact that cement is a non-sustainable resource (read our article here on how cement is destroying the seas), may lead prospective home owners down a different path if you are following the aesthetics of a dome.

Caltech’s Nader Kalili invented prototypes for adobe dome homes (he called superadobes), earthen homes made to breath and which are sustainable at their core from a materials point of view, but this does not give them a pass if developers destroy islands like this one, in a quest to build a sustainable resort.

These are great solutions for rebuilding Gaza and Sudan with earthen homes, and for helping back-to-the-land movements create affordable homes that are healthy and safe. If you are in the space of sustainable home building, get this book Habitat. We’ve featured the editor Sandra Piesek here. It’s currently the best and more sober resource for land-based architecture of the people for the people. Some architects refer to it as vernacular architecture.

Love the idea of an inflatable concrete house? We have some case studies for California and Canada.

The post Inflatable Concrete Houses: What Are They & How Much Do They Cost? appeared first on Green Prophet.