Interior shot of spray foam

How to properly insulate a tiny house

Spray-in-place polyurethane is the only commonly used solid insulation that absolutely protects itself from air infiltration. When it is properly placed between two studs or against a concrete block wall or wherever, the bonding of the spray plus the expansion of the material in place creates a total seal. It’s almost impossible to overestimate this total seal. In my opinion, most of the heat loss in the walls of a home has to do with the seal, rather than the insulation.

Heat does not conduct horizontally nearly as well as it does vertically. Therefore, if a home had no insulation in its walls, but did have an absolute airtight seal, there would not necessarily be a huge difference in heat loss. But this would not be the case if ceiling insulation was missing.

Spray-in-place polyurethane can most effectively stop air infiltration. It is the only material that properly applied fills in the corners, cripples, double studs, bottom plates, top plates, etc. The R-value of a material is of no interest or consequence if air can get past it.

Reference to additional information on foam insulation

3 inches of foam insulation is plenty

Nearly 100% of the heat loss from air infiltration is stopped with the first one-fourth of an inch of urethane foam. The second inch of spray-in-place urethane stops about 90% of heat loss, and the third inch stops about 95% and so forth.

We sprayed all sides of our substructure. Subfloor, all 4 walls, and the ceiling. This creates an airtight building envelope which will dramatically reduce heat loss.

Interior shot of spray foam

We even boxed in the wheel wells and applied 3″ of foam here too.

second shot of interior foam insulation

Our wall sheathing was applied vertically using 10′ panels to minimize the horizontal seams around the building

Loft and ceiling of tiny house insulation

We even sprayed the entire ceiling


I am the Tiny House instigator. Co-Founder of Greenmoxie and an obsessive entrepreneur, with interests in sustainability, the great outdoors, motorcycles, and carpentry.

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4 thoughts on “How to properly insulate a tiny house

  1. Amy

    This really helps as we are about to do some renovation to our home. We’ve been having problems with the insulation of the house, it can’t keep the air inside resulting into the AC working harder to keep the room at a certain temperature.

  2. EcoInsulation

    Enjoyed the photos. Very neat job by the installer. Space is always at a premium in a tiny house. Spray foam will give the best insulating value per inch of thickness…so much more efficient.

  3. Iris

    have you had any issues with off-gassing due to the spray foam? We are considering it but I am worried about the potential risk from the chemicals.

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