Progress: Installing Batt Insulation

2 min read Having passed the framing and electrical inspections, the next direct step for the basement was to finish up the insulation. For the first time ever, this task turned out to be easier than I expected.

It was unexpectedly challenging to find 23” batts of insulation (designed for more efficient 24 inch on center framing I used) which were ALSO unfaced (no place for moisture to get stuck) AND designed for a 2×4 wall (not an attic).  I scoured the internet for this unicorn of insulation objects, the 23” unfaced 3.5” batt and finally had to special order it to be delivered to Menards. 

The installation took less time than I expected.

When does that ever happen in DIY?!?

My dad and I cut and fit all the batts in a single afternoon on Friday.

Anywhere we had a 24” cavity, we just cut the batts to length and gently tucked them in.  In most cases we had horizontal runs of electrical wiring to deal with.  Rather than compress the insulation by squeezing it behind or in front of the wiring, you are supposed to split the insulation in half and run it on either side. 

Here’s an example of it tucked behind to test the length, then a wall where its been properly buried.  Dad took on the most tedious task of insulating the plumbing wall in the bathroom with continuous half thicknesses of batt behind everything and then overlaid or trimmed around the plumbing pipes that came closest to the front face.  Electric boxes also got a split bat – continuous behind and trimmed and tucked around the front.  That is a cosy wall!

A note on insulation method

/Users/shiny/Documents/Togstad Glenn/Sheets/A5-1.dwgI chose a two part method for insulating the furred out basement walls.  First, continuous, air-sealed 1” thick rigid insulation (R-5) glued to the concrete block wall.  Next, a 1” air gap.  Finally, 2×4 furring walls, cavities filled with batt insulation (R-13) resulting in a nice warm wall with minimal thermal bridging.  This is less expensive than achieving the whole R-value with rigid insulation but more effective than just relying on batts in the framing wall.

What is a thermal bridge?

A thermal bridge is a spot where an otherwise insulated bit of wall has some area that is more conductive of temperature change than the rest.  It could be a hole in insulation or a nail running through the insulating layer or simply a metal frame that goes from one side to the other as in an aluminum window.  Not only does that lower the average insulation value for the wall system as a whole, it can cause moisture problems.   If warm moist air on one side of the wall touches a cold surface, there will be condensation.  If this happens inside the wall, it can be trapped and form secret patches of mold.

A whole new basement

The end result is a totally modified space.  With the shiny pink rigid insulation covered, the basement has gone darker and quieter.  Once I have this inspected, the basement will be technically ready for drywall!  Check out these progress transitions!

Color me insulation tan, and beyond excited!