A tiny home has very little wall to stand between you and the weather, so insulation is not a place to cut corners. The wrong choice means a home that is freezing in January, sweating in July, and damp all year round. The right choice depends on your climate, your budget, and how much wall thickness you can spare.

Closed-cell spray foam is the most popular choice in tiny homes for a reason. It fills every gap, seals air leaks, adds structural rigidity, and gives the highest insulation value per inch of thickness. In a wall that might only be three or four inches deep, that efficiency matters more than anywhere else. The downsides are cost and the fact that it must be installed properly, ideally by a professional, because a bad spray job traps moisture and is miserable to remove.

Open-cell spray foam is cheaper and easier to cut back, but it absorbs moisture and insulates less per inch. It suits interior walls and ceilings in dry climates, but it is a risky choice for exterior walls in damp places.

Rigid foam boards, usually XPS or polyiso, are the budget-friendly alternative. They cut cleanly, fit between studs, and work well in floors and roofs where spray foam is awkward. The weakness is the seams: every joint is a potential air leak, so tape and seal them carefully. A layer of rigid foam on the outside of the framing, under the siding, breaks the thermal bridge through the studs and is one of the best upgrades a tiny home can get.

Mineral wool is the quiet overachiever. It is fire-resistant, it handles moisture far better than fibreglass, it dampens sound, and it is easy to install yourself. It insulates slightly less per inch than foam, but in a well-sealed wall that difference barely matters. Many owner-builders choose mineral wool for walls and rigid foam for the floor and roof.

Standard fibreglass batts are the most common regret in tiny home builds. They sag in a moving home, lose performance when damp, and leave gaps around wiring and pipes that leak warm air all winter. If your budget only stretches to batts, take extra care sealing every gap with caulk and foam, and add a proper vapour barrier on the warm side of the wall.

Whatever you choose, remember that insulation only works with airtightness. Seal the gaps, vent the moisture, and insulate the floor as carefully as the walls: cold floors make a whole home feel cold. Get those three right and a tiny home stays comfortable on a fraction of the energy a normal house needs.

Insulation without air sealing is like a coat with the zipper open. Warm air escapes through gaps around windows, doors, wiring, and pipe penetrations, and cold air finds its way in through the same holes. In a tiny home, where the total volume is small, even a few leaks change the temperature noticeably. Before you insulate, seal: caulk the joints, foam the gaps around pipes, and tape the seams of any rigid boards you install.

Moisture is the other half of the equation. Warm indoor air carries water vapour, and when it hits a cold surface inside the wall it condenses. Over time that moisture feeds mould and rots timber. A vapour barrier on the warm side of the wall stops most of it, and controlled ventilation, a small fan or a vent that actually gets used, carries the rest away. A tiny home that is insulated, sealed, and ventilated stays warm and dry. Skip any one of the three and the other two cannot compensate.