Cotton Candy Under My Feet (i.e. Subfloor Insulation Process)

Sealing air gaps with spray foam before placing the fluffy stuff!

We chose fiberglass batts for our subfloor insulation.   Fiberglass appealed to us because it is:

  • Readily available
  • Won’t sag or shift when our house goes down the road
  • DIY friendly –
    • Nontoxic (though gloves & goggles recommended during installation)
    • Lightweight and simple to install
    • Few tools required
  • Inexpensive.  Let’s be real, cost was the main reason we chose fiberglass (we used 3 bags from Home Depot for about $150).

Trailblazing A New Insulation Strategy

While fiberglass is a traditional and widely used insulation material, the way we applied it was completely original and unlike most tiny house subfloors.  First off, our trailer was designed to have a wood floor framed on top of it (which is how most tiny houses are built).  We didn’t take that approach because having 2×4 floor framing on top of the trailer would take away precious inches of headroom in the lofts.  Instead, the trailer cross members themselves will support the floor, meaning we can just screw the subfloor sheathing directly into the trailer.

Screen Shot 2015-06-08 at 1.51.40 PM
We achieved R-22 in the floor & saved interior headroom by using two layers of 3″ insulation.

What the “trailer as the floor” strategy saves in headroom, it costs in terms of comfort and energy efficiency because steel conducts heat extremely well.  In winter (which feels like half the year here in MA), cold air that hits the steel from below will bypass the insulation and chill the floor.  The solution is to prevent cold air from ever coming in contact with the metal, which we accomplished by enveloping the cross members and main beams of the trailer in insulation.  We insulated 3″ between the cross members AND 3″ underneath them, resulting in a unique 2-layer approach.  Though this method was a lot of extra work, it will be worth it in this climate especially given that fiberglass isn’t the best insulator out there.  It worked well for our floor because we had 6 inches of room to work with, but in our 2×4 walls where space is limited, we’ll probably upgrade to more efficient spray foam insulation.

Up next: siding, staining, & subfloor sheathing (say that 3 times fast!)





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