Tiny House Insulation – Baby, it’s cold outside!

Marc Bilodeau/ Building, Tiny House

With phase one of electricity complete, and the fact that it’s Maine and Winter, it’s time to add insulation throughout the tiny house. Although, I’m still a few steps from adding a vapor barrier and closing up every wall, it will help keep the heat inside while the inside projects continue. Compared to the last task, this one is a walk in the park.

[more photos of this process]


As with the subfloor, the walls and ceiling have ROXUL. ROXUL is what many (but not all) other tiny house projects use from what I have seen from various YouTube videos and blogs. However, after doing some more planning and research, it fits this project best.

This tiny house has 2″ x 4″ exterior walls and 2″ x 6″ ceiling construction. That being said, I chose ROXUL for a number of reasons. Primarily, ROXUL rates higher in terms of sound absorbency. This is important due to the thinner exterior walls.  Additionally, it’s made from natural and recycled materials, doesn’t rot or slump if it’s exposed to water, and it won’t burn or release harmful chemicals under high heat.

ROXUL R23 2x6 insulation
TinyHome.io uses ROXUL R23 (shown) and ROXUL R15 insulation

ROXUL cuts with little effort using a Stone Wool Insulation Knife. I find it much easier to install and less itchy then other traditional insulation.

However, the one thing I don’t like about it is that it produces a lot of dust particles. It’s important to wear a mask or you may find yourself coughing up a storm. It can also be a little bit crumbly when making some cuts. Regardless, I highly recommend ROXUL.

Windows and Wall Gaps

ROXUL insulation isn’t the only insulating material involved. Gaps and spaces must be filled first before the insulation can be installed. There are two types of spray foam for gaps and spaces. The first one fills gaps around the doors and windows. This type helps fills those spaces and avoids putting pressure between the windows and doors.

GREAT STUFF Windows and Doors Spray Insulation
Spray foam around a couple of windows in the great room.

For gaps in other areas near the framing and sheathing or between the subfloor and fenders, I use a spray foam specifically for gaps and cracks up to an inch in diameter. It’s important to cover all tops, bottoms, and corners of the interior framing, windows, and doors.

Using Great Stuff Gaps and Cracks Spray Foam
Gaps and Cracks spray foam in the wall above the fender

When applying spray foam, use gloves and eye protection. It’s messy, and it takes days to remove if it gets on your skin. Overall, it works well despite the process. Once it dries, the excess is easily removed with a knife. Two cans for windows and doors and three cans for gaps and cracks took care of everything.

Ceiling Insulation

The ceiling insulation is ROXUL R23 ComfortBatt. R23? What? The R-value measures the insulation’s resistance to conductive heat flow in terms of its thermal resistance. In layman’s terms, the higher the R-value, the more effective the insulation. Regardless of the R-value, it’s important to never pack or compress the insulation since this decreases its ability to insulate. It should snugly fit between the framing without having to force it.

Tiny House Ceiling Insulation using ROXUL R23 ComfortBatt.
ROXUL R23 ComfortBatt Insulation in the ceiling

Each package of R23 insulation includes eight pieces. Overall three packages insulate the entire ceiling.

Wall Insulation

Unlike the ceiling, the walls are 2″ x 4″ framing. Therefore, the insulation has a lower R-value since it’s not as thick as the 2″ x 6″ roof framing. For this job, ROXUL R15 ComfortBatt is used instead. Although the R-value is less, it’s within range for wall cavities in my zone.

Tiny House Wall Insulation uses ROXUL ComfortBatt R15
ROXUL R15 ComfortBatt Insulation in the walls

Each package of R15 insulation includes twelve pieces. Overall six packages insulate the walls. However, it would have required a seventh package except a few leftover pieces of the R23 were used instead. This requires cutting a couple inches of thickness to properly fit the 2″ x 4″ framing.

Tiny House Leftover Insulation
The leftover pieces of insulation fit neatly in a box.

For now, the leftovers are around in case there is a need further down the road. Of course, after the completion of this project I will properly dispose of the extras.

Vapor Barrier

A vapor barrier is a thin layer of impermeable material that prevents moisture from damaging the interior of the building. I’ll add a polyethylene sheeting to the surface of the walls that will reside underneath the interior wall.

The advantage of a tiny house is that it’s easier to use a single sheet without overlapping seams on each wall. However, there is some overlap at the corners, but those layers are joined together with clear shipping tape.

Tiny House Vapor Barrier
The progression of adding a vapor barrier to the loft

Since there are still some inlets that aren’t cut yet, not all walls have a vapor barrier. Once I’m sure that there are no wires, pipes, or other reasons a section of wall needs to be exposed, it will be wrapped and finished.


How long did this task take? 18 hours of work between two people. When looking back at all the progress, it’s amazing to see everything come together and watch as an idea transforms into reality. However, it takes a team effort. This project would be far slower if tackled alone. It’s important to take the time to reflect and celebrate the work, and treat any friends and family for their efforts.

Each step keeps me motivated for the next. The journey is a wonderful experience and part of me will be sad when it’s over. However, there will always be something exciting. This project will never truly be complete. New and exciting technologies are discovered daily for cleaner and healthier living, and more efficient and optimal ways to live life to the fullest.

Tiny House Before and After Insulation