KAAYA Case Study 01 - Shirt to Keep You Cool in Extreme Heat

A loose overshirt designed to keep your body cooler during short trips in extreme heat like commuting, running errands, riding a scooter. It works through three simple ideas working together: natural airflow through a chimney ventilation system, gel pack cooling at key body points, and modular attachments for different conditions.

This is KAAYA Case Study 01 — part of a larger inquiry into how bodies adapt to extreme climate. The garment is a starting point, not a finished answer. If you build it, change something, or find what works better for your conditions, share it. That's the point.

Note on color: The prototype shown here is black due limited material options. If you're building this to actually use in heat, make it in a light color. Light fabrics reflect radiant heat. Dark fabrics absorb it.

Before You Start

Skill level: Intermediate sewing. You should be comfortable with a sewing machine, setting in a sleeve, and inserting a zipper. This is not a beginner project, but it's also not technically complex.

Pattern: Print the attached PDF pattern at 100% scale on A4 sheets. All measurements are in inches. Tape the pages together where indicated and use a dry iron to press the creases out of the paper before cutting.

Understanding the Design Before You Build

The jacket works through three mechanisms. It helps to understand them before sewing, because several construction decisions only make sense in this context.

1. Chimney ventilation The boxy, loose silhouette creates a gap between fabric and body. Hot air from your body rises and exits through the back mesh panel and at the neck. Cooler air draws in at the hem and sleeves. This is the same principle as a traditional kurta or thobe.

2. Gel pack cooling Two pockets hold cold packs against high blood-flow zones: the upper back (between shoulder blades) and the wrist. Cold transfers into the blood and circulates. The pockets must stay pressed against the skin — an air gap even 1–2cm reduces effectiveness significantly. The drawstring at the sleeve compresses the wrist pocket; the back pocket relies on the natural pressure of sitting or leaning.

3. Eastern patternmaking Almost all pieces are rectangles or near-rectangles. This reduces fabric waste, makes alterations easier, and produces the loose drape the ventilation system needs. Cut along the grain.

Fabric

1. 3 meters of shell fabric (polyester-cotton blend, or any breathable medium-weight woven — linen, cotton poplin, khadi)
2. 0.5 meters of mesh/net fabric for the back vent and underarm gussets (cotton net, sports mesh, or hex mesh)

Hardware

1. 1 separating centre-front zipper (~60cm)
2. Velcro strip (~80cm total)
3. Drawstring cord (~2m)
4. 2-3 cord locks

Tools

1. Sewing machine
2. Zipper foot
3. Iron + pressing cloth
4. Scissors, pins, tailor's chalk

Important: Spread the fabric in a single layer. Pieces which are to be cut twice have been marked. Flip the pattern piece over for the second cut, otherwise you'll end up with two sleeves for the same side.

Cut all your fabric before you start sewing. It's much easier to work through the steps when everything is ready.

Press your fabric flat with an iron before cutting as wrinkles in the fabric produce inaccurate pieces. Similarly, press the paper pattern with a dry iron to remove fold creases before pinning.

Pin each pattern piece to the fabric along the grain line. Cut. Flip the pattern piece for the second cut of each piece.

Mark all pocket placement positions on the wrong side of your cut pieces with tailor's chalk before unpinning.

The body is four panels: two front pieces and two back pieces.

Join each front piece to its corresponding back piece, right sides together. Press the seam open — not to one side. Then join front to back at the side seams. Press open again.

Press rule for this entire build: On every seam, press the seam allowances flat first, then press them open. Pressing open (rather than to one side) keeps the boxy silhouette flat and removes bulk.

The back vent is what makes the chimney effect work. There are two parts: the mesh panel and the fabric flap.

the mesh panel is attached to the back flap. the sleeves are cut from back in two parts

The underarm gusset is a square-shaped piece of mesh. It goes at the highest point of the armhole. Pin the gusset in place first, then pin the sleeve around the armhole and stitch.

The mesh gusset allows air to move in and out when your arm is raised, and also stops the sleeve from restricting arm movement.

The hood is made from four shell fabric pieces — two for the outer layer, two for the inner layer. There is no separate lining fabric; the hood is double-layered using the same material throughout.

Sew each pair along the centre seam. Press open. Place outer and inner layers wrong-side-together and treat them as a single piece from here.

Pin the hood to the neckline, matching the centre-back seam of the hood to the centre-back of the garment. Clip the neckline seam allowance at the curved sections (snip to within 2mm of the stitch line, every 2cm) — this allows the fabric to ease around the curve without pulling. Stitch. Press the seam toward the hood. Topstitch 5mm from the seam to hold it flat.

Front pockets — utility, for phone, keys, wallet. Sew and press flat. Position at hip level on the front panels. Topstitch sides and bottom to the garment. The pocket flap sits above the opening, stitched only at its top edge, falling down over the pocket by gravity.

Back pocket — this holds the gel pack. Position it centred on the upper back, just below the mesh vent. Attach velcro along the pocket opening (hook side on the garment, loop side on the pocket). The velcro allows the pocket to be pressed firmly against the back — this compression is what makes the cooling work. Leave the top of the pocket open so the gel pack can slide in and out.

Arm pockets — these hold the wrist gel packs. Position on the inner side of the sleeve, closer to the cuff. Velcro closure. The drawstring (added in Step 7) will run through the center of the sleeve and through the pocket, compressing it against the wrist when cinched. Leave top open for gel pack access.

For any of the pockets, velcro can be replaced with buttons or magnets depending on what's available to you.

The drawstring channel runs through the center of each sleeve pocket. When you pull the drawstring, it cinches the sleeve into a bell shape at the cuff — and this same cinching compresses the arm pocket against the inner wrist, maintaining contact with the gel pack.

Make each channel from a folded strip of shell fabric, stitched into a tube approximately 3cm wide. Position at the cuff in the middle of the arm pocket. Fold the sleeve end under and stitch the channel in, leaving a 2cm gap at one seam for the cord to enter. Put a flat 5–6mm cord through and add a cord lock on the outside.

Press the centre-front edges under 1.5cm. Position the zip under each folded edge, with the teeth sitting 1–2mm inside the fold. Use a zipper foot throughout this step — a regular presser foot can't get close enough.

Topstitch close to the folded edge on both sides. Test that the zipper opens and closes fully before finishing. Bartack (a small square or zigzag stitch) at both the top and bottom stops for durability.

Turn the hem under twice: fold 1cm, then fold again 2cm. Pin. Stitch close to the inner folded edge.

Then press the entire finished garment in sections.

Snip all loose threads.

You have three options:

1. Buy commercial gel packs — any flexible freezer pack that fits the pocket works. Freeze before use. Duration: 1–2 hours.

2. DIY simple pack — 1 part isopropyl alcohol + 2 parts water, sealed in a zip-lock bag. Freeze. Works for 30–60 minutes.

3. DIY phase-change pack — uses sodium sulfate (melting point ~32°C), which provides longer, more comfortable cooling than ice because it holds at just below body temperature.

The base garment has attachment points ( the hood structure + pockets for putting gel packs) for add-ons. Two more are included in this -

Face shield / gaiter — a breathable mesh panel that attaches to the hood via velcro. Covers nose and mouth. Most important for scooter use, where hot wind hitting your face while the back is being cooled creates an uncomfortable temperature contrast. If you are going to use this jacket while riding, build the face shield.

Fingerless gloves — separate knit or woven gloves with fingers cut off. Sun protection for the hands while keeping fingers free for phone, keys, payments.

Climate is experienced by everyone, but adaptation is never universal. It is shaped by context, culture, available materials, and economy.

I tried to build a framework that gives people the principles and the room to adapt it to their own needs. The garment is one expression of that framework — Case Study 01.

If you build this, something will not work for your context. Change it. That is not a failure of the design, it is what the design intends.