Types of Insulation: Part 2 – Where does insulation go?

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…

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Q&A – Types of Insulation

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!

Insulation Characteristics

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.

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Retrofit your attic hatch for improved comfort and energy efficiency

Link: Retrofit your attic hatch for improved comfort and energy efficiency

Thermal image of leaky attic hatch

The typical attic hatch is drafty and improperly insulated. Fixing it can reduce the energy loss of a room by half. This afternoon project is simple and cost effective providing results you can enjoy year-round.

If you’re looking for the best commercial product on the market, check out the Energy Guardian attic hatch covers from ESS Energy Products. They’re by far the nicest product I’ve seen for this application.


Why Attic Insulation is a Big Deal A properly insulated attic is supposed to have about R-

Why Attic Insulation is a Big Deal

A properly insulated attic is supposed to have about R-40 insulation everywhere. This means that the insulation reduces heat loss by a factor of 40 – pretty simple eh? That also means, R-20 roughly equals twice the heat loss as R-40. R-10 is four times the heat loss and so on.

So what’s the R-value of an area of ceiling with no insulation? As it turns out, bare sheetrock on the ceiling has an R-value of about R-1. This means that every square foot of uninsulated ceiling loses about forty times as much energy as a square foot of properly insulated ceiling! 

Put another way, if you have one square foot of uninsulated ceiling, it’s losing as much energy as forty square feet of normally insulated ceiling. So what happens when you have a hundred square feet that are uninsulated, like in this photo? Well, the energy loss from this section of attic are about what the energy loss of a 4,000 SF attic would be!

The take home message is – details matter! Every square inch of your attic should be fully insulated. And if you’re an electrician, take the time to put insulation back carefully after you’re done running wires in the attic. If you don’t you’re basically robbing your customers.

Find insulation problems this winter

The winter snow can be your best friend – at least when it comes to finding where your home is losing energy.

Take a look at this house. Half the roof is covered with snow, while on the other half, the snow is all melted. What’s going on here?

There’s a serious problem with heat leaking out of the living space and into the attic. It takes a lot of energy to melt snow, so undoubtedly, these people are spending lots more on their heating bills than they should.

The first thing to do is to go up to the attic and check the insulation. Is it missing in this area or is there some other reason why the heat is leaking out? Maybe there are heating ducts running through the attic and they’re leaking badly. If your ducts are leaking, you’ll often find that the insulation around the ducts has turned black. Once you learn what to look for, it’s pretty easy to find problems. You might also find mold growing on the underside of the roof.

Another big problem that might be happening is there may be a bathroom vent that is blowing into the attic. You never want this because it can rot out your roof! Usually, you’ll find that the roof sheathing is black or discolored. If you see that in your attic, you know you’ve got a big air leak from the house into the attic.

The main thing is this – if you see something strange like this, you know that there’s a problem. Go find it!