Signs of moisture and air flow in fiberglass insulation
When you climb into an attic and see this, you know something is seriously wrong. In fact, if your home isn’t very old, your insulation should be clean like when it was installed. The reason you get black insulation like this is because air and moisture are moving through the insulation, and it’s acting like an air filter.
The reason I’m showing you this picture is because it’s an example of the wrong insulation being used for a job. I feel pretty strongly about this because I’ve seen numerous homes where fiberglass has been installed in open walls like this and in almost every case, the insulation was seriously compromised – it was buckling under its own weight or simply falling out of the wall cavity. Or, in cases like this, it was hiding a big hole in the wall that should have been air sealed.
Let’s walk through the different insulation types and compare their main attributes: R-value, ability to reduce air movement, suitability for retrofit applications, and other characteristics.
In part 1 of this series, I gave you an overview of the different insulation materials and the various forms they come in. This article covers where insulation goes and why. Knowing this helps you understand why you’d want to use a particular type of insulation for specific applications in your home.
Where do you use insulation?
- On the attic floor
- In attic cavities
- On an attic knee wall
- On the attic ceiling
- In the walls
- Around the windows and doors
- Around pipes and other holes in the wall
- In the basement and crawlspace ceilings
- On the basement and crawlspace walls
- Under the slab
- Outside the foundations
Each of these areas really deserves an article of its own. In fact, if you look on the Building Science website, you’ll find highly detailed articles doing exactly that. If you want to go straight to the source, consult these references.
Let’s look at some photos to get an idea of several of these cases…
Bonded Logic Denim Insulation
When you insulate your house, you’re going to be confronted by a dizzying array of choices. How do you know which one to use? How much do they cost? Are some better than others or is it all hype? In this article, I’m going to do my best to sort through the options and help you make sense of them. Be warned – there’s a LOT of material here, so I’m going to have to break this into several articles.
First, let’s survey the types of insulation that you’re likely to encounter. I’m also going to provide links where appropriate.
- Fiberglass – batts
- Fiberglass – dense batts
- Fiberglass – compressed
- Fiberglass – shredded / loose fill
- Fiberglass – Johns Manville Spider – sprayed in
- Cellulose – loose fill
- Cellulose – damp sprayed in
- Cellulose – dense packed
- Spray foam – open-cell, Icynene
- Spray foam – open-cell, soy based
- Spray foam – high-density closed-cell
- Spray foam – high-density closed-cell, soy based
- Board foam – expanded polystyrene
- Board foam – extruded polystyrene
- Board foam – polyisocyanurate
- Board foam – foil faced polyisocyanurate
- Denim – Bonded Logic batts
This list is long enough. There are other insulation materials that have been used over the years, from vermiculite to horse hair to rice hulls to straw bales, but I’m not going to touch on anything that isn’t commonly available in the United States. Sorry!
Before we go into analyzing all the details of insulation materials, let’s spend a moment defining the basic characteristic of insulation – the R-value.