Insulation Properly Installing Fiberglass Batts

Insulation Properly Installing Fiberglass Batts

Insulation: Properly Installing Fiberglass Batts

The last two posts have concerned issues of properly installing Fiberglass Batt type insulation.  That discussion revolved around newly installed insulation.  Inspections were done after the insulation was there and before the drywall was installed.

In this post, I would like to address some of the problems I see after the home has been in use.  The Batts in these cases were installed anywhere from 10 years ago to 40 years ago.  We all have experienced the issues of time. What changes does time bring to a Fiberglass batt?  This leads to ‘Why proper installation is so important.”

I have audited home that were built more than 100 years ago.  My friend Bud, has discussed auditing homes that are much older, 150 250 years. A home lasts a long time.  Every month the home gets Energy Bills.  Are the Energy Efficient Features of the home keeping those bills at the level they were planned?  If a feature was improperly installed, probably not.

Best Practices for installing Fiberglass Batt type insulation include:

The insulation must be in contact with the Air Barrier.  In our Climate Zone the Inside wall is the Air Barrier.

This means the batts must be stapled to the face of the framing material; not to the side.  If you have the batts stapled that way, then they are not in contact with the air barrier.  This is illustrated in the Infared picture. Note the cooler colors near the top that are rounded and follow the framing down the wall, and the dark hole in the top of one wall cavity.

Batts not incontact with Air Barrier

A Fiberglass Batt must be covered on each of the 6 sides.

This one seems simple, in an exterior wall, the top plate, the bottom plate, the drywall, the exterior sheathing, and the framing constitute all 6 sides of the batt.  Now think about the wall that is formed between the end of the vaulted ceiling and the attic?  OK;  Drywall, Yes!; Bottom Plate, Yes; Top Plate, not usually; Framing, sort of; exterior sheathing, usually nothing.  So, we have 2.5 on these types of walls. Below is a picture of the end of two knee walls with no framing on a corner of a vaulted ceiling.

Solutions on Knee Walls:  Cover the top, back and the sides of the batts at the corners with an encapsulating material.  House wrap installed according to manufacturers directions is a good choice for an existing home.  Easy to get into the area and then apply.

A Batt should not be compressed.

OK!  Think about all the things running in walls.  Electric wires, pipes, CAT 5 cable; phone lines, cable TV, security system cables.

Insulation Properly Installing Fiberglass Batts

Poorly installed Batt Insulation

First, you have the installs that are done before the insulation is installed; typically the electric and plumbing.  The insulator can deal with these easily. The batt can be sliced, partly through, to allow the obstruction to pass through the middle, instead of stuffing the batt behind or pushing the batt into place on top the wire or pipe. It can be carefully cut to allow an electrical box.

Good Installation of Fiberglass Batts

For those tradesmen that follow the insulator, everyone else on the list above, it is not quite so easy. If they come before the drywall is up, then you may find holes in the kraft paper, and wires compressing the batt as it runs from 2x to 2x; or you may find something else. If they come after the drywall, your guess is as good as mine as to what the wall will actually be.

The infrared image below shows air infiltrating around improperly installed fiberglass batts on the other side.

If you are renovating a wall in your house, and you choose to insulate; fantastic!  It will save you money.  Lots of insulation choices available, if you choose Fiberglass Batts, follow these concepts and you will maximize the effectiveness of your insulation.

The only other item you should do, when renovating and insulating is to air seal and stop those cold drafts. That is a subject of another post!


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