In a nutshell
- 🧵 Fabric physics: towels disrupt airflow with fibre friction, forming a cushion of still, warmer air that cuts convective heat loss at the door gap.
- 🚪 Effective seal: a snug, folded roll creates a compressive seal and a tortuous path, reducing leakage by shrinking pores and slowing air permeability.
- 🧺 Choosing and folding: pick a thick cotton or microfibre towel with low air permeability, fold lengthways and roll a “double sausage” for a snug fit that conforms to floor irregularities.
- 📊 Material guide: thick cotton traps air best; microfibre seals well but can bunch; wool insulates strongly; thin tea towels leak unless layered—prioritise grip and coverage.
- 🔥 Practical gains: quick, low-cost comfort boost that stabilises room temperature, reduces boiler cycles, and proves that air control is heat control, while complementing long-term draught-proofing.
The cold creep under a door feels like a minor nuisance, yet it quietly drains heat and comfort. A folded towel, pushed tight against the gap, can be an unexpectedly effective barrier. It works not because it is heavy alone, but because fabric’s structure slows air. By crumpling the airflow and sealing irregular edges, it creates a pocket of still, warmer air at the threshold. That trapped layer cuts the wind-chill effect indoors, so rooms feel warmer even before the thermostat budges. Simple, cheap, and instantly reversible, the technique illustrates a principle used in professional draught-proofing: control the air path and you control the heat loss.
Why a Folded Towel Stops a Draught
A draught under a door is driven by pressure differences and temperature gradients. Air looks for gaps; the bottom of a door is often the largest. A towel works because fabric offers a maze of fibres that increase friction and disrupt straight-line flow. As air tries to push through the towel’s pores, velocity drops and turbulence rises, shedding energy. Once the flow slows enough, a thin cushion of still air forms on the room side and acts as insulation. This is not magic—just controlling convection at the point it starts.
Shape matters. A towel folded to fill the entire threshold creates a compressive seal against the floor and the door’s underside. The better the contact, the fewer micro-channels remain for air to sneak through. Weight helps hold position, but the key is geometry: a snug, continuous line that conforms to scuffs, uneven flags or warped boards. The result is a low-tech, high-impact blockade against infiltration.
How Fabric Traps Warm Air at the Threshold
Fabric insulates by storing many small pockets of air that are hard to circulate—sometimes called a thermal boundary layer. In towels, looped pile and tangled fibres create a tortuous path that resists flow. As outside air meets this labyrinth, its speed falls, and the tiny pockets warm quickly to room temperature. The towel becomes a buffer, lowering convective heat loss right where the pressure difference is strongest. The denser the weave and the deeper the pile, the more twists and turns the air must navigate, which raises resistance without needing plastic films or foams.
Contact also counts. Bare gaps allow a clean jet under the door; a towel turns that into distributed seepage with dramatically less momentum. Slight compression squeezes fibres together, shrinking pores and reducing air permeability. The outcome is not a perfect seal—nothing fabric-based is—but a material shift from free-flowing leakage to controlled, slow diffusion that scarcely stirs the room’s warm layer near the floor.
Choosing the Right Towel and Fold
Pick a towel that is thick, long enough to span the doorway, and textured. A medium-to-heavy cotton bath towel is ideal: the pile traps air, the mass helps it sit still, and the width covers irregularities. Fold lengthways to match the gap’s height, then roll into a gentle “double sausage” so both edges present rounded contact surfaces. Those curves seal better against tiny floor undulations than a sharp crease. Aim for a snug fit you can push under with the door slightly ajar; it should press lightly against both the floor and the door’s bottom edge.
| Material | Air Permeability | Grip on Floor | Notes |
|---|---|---|---|
| Thick Cotton Towel | Low | Good | Deep pile traps air; reliable quick fix. |
| Microfibre Cloth | Low–Medium | Very Good | Fine fibres seal well; may bunch if too thin. |
| Wool Blanket Strip | Low | Medium | Excellent insulator; needs careful folding. |
| Thin Tea Towel | High | Poor | Use only when layered; tends to leak. |
Keep fabric dry for hygiene and stability. If the door scrapes, adjust the roll rather than forcing it. For overnight use, you can secure the towel with a light ribbon or elastic band at the ends to hold the shape—and still remove it in seconds.
There’s a bigger picture behind the folded towel: air control is heat control. By slowing leakage at the threshold, you stabilise room temperature, reduce boiler cycles, and make flooring less chilly underfoot. What’s most striking is how a humble textile demonstrates the same physics as professional draught excluders—reducing convection, creating still air, and sealing irregular lines. If a towel can do this, imagine what a purpose-made brush seal or a twin-roll door snake could achieve across a winter. Which doorway in your home would benefit most from this simple tactic, and how might you combine it with longer-term draught-proofing for a warmer season ahead?
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