What is the R-Value of my Attic Insulation?

What is the R-Value of my Attic Insulation?

Attic Insulation is crucial for energy conservation. The higher the R-value of your attic insulation, the greater the insulating effectiveness. The R-value is a measure of insulation’s resistance to heat flow.

Determining your attic’s r-value is a matter of determining what type of insulation you have, how thick the insulation is, and how well it was installed.

Also, the overall r-value of your attic may not be the same as the insulation in it, because heat flows around the insulation and through studs and joists. An infrared camera illustrates this very well.

Here are some common do-it-yourself materials used for attics and their R-values:

Insulation Type                 R-Value per inch

Blown Cellulose                          3.7

Blown Fiberglass                        2.8

Fiberglass batts                          3.0*

*The quality of the installation is extremely important with insulation.

Fiberglass batts have to be correctly installed for this R-value. If they are compressed, or if there are gaps the r-value drops substantially.

You can measure the depth of the insulation and multiply this by the r-value. The effective r-value takes into consideration how well it was installed. There are formulas to determine the degree to which these values drop, but the message is that installing batts is at least as important as the insulation itself.

What To Look For When My Attics Insulation is Installed Poorly

I’ve been doing some insulation work and the quality of other people’s work is amazing. I don’t know if the previous worker just didn’t know how to install fiberglass batt insulation or if he was just lazy and wanted to move to the next job.

In order for insulation to reach its full advertised R value, it must be installed correctly.

Actually, it must be installed perfectly. The batt must not be compressed, rounded, or laying on top of things like cables or pipes. It must be in direct and full contact with the drywall ceiling below it.

I went through an attic and concentrated on a vaulted ceiling. This room was the warmest in the house in summer, and coldest in the winter. And for good reason. The batt insulation was hardly even touching the drywall. In fact, the batts were just sitting on top of the ceiling joists with just the center touching the drywall ceiling. This is rounding and the picture above shows this condition. The full face of the batt needs to be squarely installed so that it sits nicely in the middle of the joists. With the rounding I saw, although the batt had an R value of 30 printed right on it, it probably was performing at around an R-4 or so.

Attic Insulation Surprises

attic insulationAttic insulation is extremely important for energy savings. If you have ever gone into your attic, you may not even know what you are looking for. With insulation, it is the R-value that people look for. Certainly R-value is important, but so is the way the insulation is installed.

If you have fiberglass batts installed, most people will look for a printed R-value. If they see R-30, then they think all is well. Not so.

If your insulation is compressed or worse, not even contacting the drywall ceiling below, your R-value could be virtually zero.

Take a look at the picture to the right. If you were just to pop your head up in the attic and look around, you would see a beautiful sea of fiberglass batt insulation, seemingly doing its job to perfection.

Under all that insulation lies a nasty secret: areas of that insulation aren’t doing a darn thing.

The picture shows me lifting up a batt to check out what is underneath it, and as it turns out, there is about a 4 foot drop to the ceiling below. You can see some pipes running across the uninsulated ceiling. This dropped ceiling is over a front entryway and a chandelier hangs from it. This entire area has no insulation and is approximately 6’x 12’. This large area will effectively lower the R-value of the entire ceiling.

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By |2019-11-18T20:31:02+00:00October 6th, 2019|DIY, Heating and Cooling|0 Comments

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