Window Design

Part of Permanent Shelter

Windows solve three competing problems — admitting daylight, allowing ventilation, and keeping out weather and intruders. Before industrial glass, every culture developed its own solutions: shutters, oiled paper, stretched membranes, even thin slabs of stone. This guide covers practical window designs you can build with basic materials, from the simplest shutter to translucent panels that let in light without opening the wall to wind and rain.

What a Window Must Do

Every window design is a tradeoff. Understanding the functions helps you choose the right solution for your climate and situation.

Function	What It Requires	Conflicts With
Light	Transparent or translucent covering	Security (large openings are entry points)
Ventilation	Operable opening	Weather protection, insulation
Weather protection	Sealed, waterproof closure	Ventilation, light
Security	Small size, strong closure	Light (less opening = less light)
Insulation	Thick, sealed closure	Light, ventilation

The Two-Layer Solution

The most practical approach in any climate: a translucent inner panel (oiled cloth, membrane, or glass) for light, plus a solid exterior shutter for weather, security, and insulation. Open the shutter during the day, close it at night and during storms.

Shutter Construction

A shutter is simply a small door for your window. The same ledge-and-brace construction used for doors works perfectly at window scale.

Basic Board Shutter

1. Measure the window opening precisely. The shutter should overlap the opening by 2–3 cm on each side.
2. Cut planks to height, 2–3 cm thick. Lay them edge to edge to cover the width.
3. Attach two horizontal battens (ledges) across the back — one near the top, one near the bottom.
4. Add a diagonal brace between the battens, rising from the hinge side.
5. Hinge the shutter to the outside of the window frame using leather straps, wooden pivot pins, or metal hinges.
6. Add a latch on the inside — a simple hook-and-eye or a wooden turn button.

Interior vs. Exterior Mounting

Mounting	Advantages	Disadvantages
Exterior	Sheds rain away from the wall; easier to open outward for ventilation	Hinges exposed to weather; cannot be barred from inside
Interior	Can be barred from inside; hinges protected from weather	Opens inward, takes up interior space; rain can blow onto shutter face

For security-conscious installations, mount shutters on the interior with a bar lock.

Oiled Paper and Cloth Panels

Before glass was common, oiled paper or cloth was the standard window covering across Europe and Asia. It admits diffused light while blocking wind and most rain.

Making Oiled Cloth

1. Select fabric — tightly woven linen or cotton works best. The tighter the weave, the better the weatherproofing.
2. Stretch the cloth over a wooden frame slightly smaller than the window opening, and tack it in place with small nails or pegs. Pull it drum-tight.
3. Apply oil — linseed oil is ideal. Brush or rub a generous coat onto both sides of the stretched fabric.
4. Dry completely — hang in shade for 2–3 days. The oil polymerizes (hardens) into a flexible, waterproof film.
5. Apply a second coat and dry again. Two coats minimum; three is better.

Making Oiled Paper

Same process, but use the thickest paper available. Traditional Chinese and Korean window paper was made from mulberry bark fibre, which is extremely tough when oiled. In a rebuilding scenario, any heavy handmade paper will work.

Fire Risk

Oiled cloth and paper are flammable — more so than plain fabric. Never place candles or oil lamps directly below or beside an oiled window. Use a shelf or table to keep flames at least 30 cm away.

Light Transmission

Material	Light Transmission	Weather Resistance	Lifespan
Oiled linen (2 coats)	~40% (diffused)	Good; sheds light rain	2–5 years, re-oil annually
Oiled paper (3 coats)	~50% (diffused)	Moderate; vulnerable to heavy rain	1–2 years
Animal membrane	~30% (diffused)	Good; naturally waterproof	3–7 years
Clear glass	~90% (clear)	Excellent	Decades if unbroken

Animal Membrane Windows

Historically common in cold climates where glass was unavailable.

Suitable Materials

• Cattle or sheep intestine — cleaned, split open, and stretched flat. Surprisingly translucent.
• Fish skin — large fish (salmon, sturgeon) yield skins that can be scraped thin and stretched over frames.
• Bladder — cattle or pig bladder, cleaned and stretched.

Preparation

1. Clean thoroughly — scrape off all fat and tissue. Soak in water for 24 hours, changing the water twice.
2. Stretch while wet — tack the membrane to a wooden frame, pulling it as tight as possible without tearing. Animal membranes shrink as they dry, so they will become drum-tight.
3. Dry in shade — direct sun can cause uneven drying and tearing. Allow 2–3 days.
4. Apply a thin coat of tallow or oil on one side to improve water resistance and extend lifespan.

The result is a translucent panel that admits soft, diffused light — similar to frosted glass. It is surprisingly strong and weatherproof when properly prepared.

Window Sizing by Climate

The size and placement of your windows should match your climate priorities.

Cold Climates (Long Winters)

• Fewer, smaller windows — every window is a point of heat loss.
• South-facing priority — maximize winter solar gain. North-facing walls should have minimal or no windows.
• Window area: 5–10% of floor area is sufficient for livable light levels.
• Deep window wells — thick walls create recessed windows that reduce wind exposure.
• Double layer: oiled cloth inner panel + solid shutter outer panel. Close shutters at night and during storms.

Hot Climates (Cooling Priority)

• Larger windows, opposite walls — cross-ventilation is your primary cooling strategy. Place windows on opposing walls so breeze flows through.
• Window area: 15–25% of floor area for adequate airflow.
• High placement — hot air rises. Windows near the ceiling let the hottest air escape.
• Overhangs — a roof overhang or awning above the window blocks direct midday sun while allowing lower-angle morning and evening light.

Temperate Climates

• Moderate sizing — 10–15% of floor area.
• Operable panels — design windows that can be fully opened in summer and fully sealed in winter.
• South and east facing — morning sun warms the structure after a cold night.

Insect Screens

In any warm or wet climate, flying insects are a major concern. A window that admits air must filter out mosquitoes.

Making a Screen

1. Weave a fine mesh from thin plant fibres — cotton, linen, or fine grass. The mesh openings must be smaller than 2 mm to stop mosquitoes.
2. Stretch the mesh over a wooden frame sized to fit inside the window opening.
3. Install behind the shutter — the screen frame sits in the window, the shutter closes over it.

If fine weaving materials are not available, a loose-woven cloth dipped in oil or tallow will slow airflow but stop most insects.

Smoke as Insect Control

In regions with severe insect pressure, a small smudge pot (smouldering green wood or dried herbs) placed upwind of an open window creates a smoke barrier that repels mosquitoes and flies more effectively than any physical screen.

Seasonal Window Management

Windows are not set-and-forget. Adjust them with the seasons for comfort and efficiency.

Season	Action
Winter	Close and seal all shutters at night. Open south-facing windows during sunny days for solar heat gain. Stuff gaps with cloth or moss.
Spring/Autumn	Open windows during warm afternoons, close at night. Check oiled panels for wear and re-oil if needed.
Summer	Open windows on opposite walls for cross-ventilation. Use screens for insect protection. Close west-facing shutters in afternoon to block direct sun.
Rainy season	Close shutters on the windward side. Keep leeward windows open for ventilation. Ensure sills slope outward for drainage.

Window Sill Details

Every window needs a properly designed sill to prevent water infiltration.

1. Slope outward — the sill should tilt at least 10 degrees toward the outside so water runs off rather than pooling.
2. Drip groove — carve a channel on the underside of the sill, 2 cm from the outer edge. Water following the underside hits this groove and drops off.
3. Overhang — the sill should project 3–5 cm beyond the wall face to throw water clear of the wall below.
4. Material — hardwood or stone. Softwood sills rot quickly. If using softwood, char the surface with a torch (shou sugi ban technique) to improve rot resistance.

Key Takeaways

• Use a two-layer system: a translucent inner panel for light, and a solid exterior shutter for weather, security, and insulation.
• Oiled linen is the best pre-glass window covering — stretch it over a frame, apply 2–3 coats of linseed oil, and re-oil annually.
• Animal membranes (intestine, bladder, fish skin) are a durable translucent option in cold climates where fabric is scarce.
• Size windows to your climate: 5–10% of floor area in cold regions, 15–25% in hot regions, with cross-ventilation as the priority for cooling.
• Every window sill must slope outward, have a drip groove, and overhang the wall to prevent water damage.
• Adjust window openings seasonally — solar gain in winter, cross-ventilation in summer, sealed tight during storms.