How to insulate an attic

Insulating your attic is one of the best ways to cut your energy usage and utility bills. And yes, you probably already have some kind of attic insulation in your home’s attic, but it may not be enough or it may be missing in some key areas. Remember, your goal is to create a hermetically sealed (as air-tight as possible!), barrier between your living quarters and the attic itself. This is assuming that your attic is unfinished, which this article addresses. Most attics have space and gaps around pipes, vents, ducts and electrical boxes. Your attic may appear to be covered in insulation, but it’s these smaller “forgotten” spots that allow a considerable amount of air to pass between your attic and your home. Also, the batt or blown-in insulation installed might be too “weak” in terms of it’s R-value or it could be old or damaged and in need of replacement. The good news is that aside from getting a little dirty, shoring up your attic insulation doesn’t have to be too big of a burden, or cost much. Let’s take a look at the best ways to install insulation in your attic, again, assuming here that your attic is unfinished.




Types of attic insulation

For the large areas of your attic, meaning the expanse of space just above your ceilings and in between your joists, you’ll be able to use either fiberglass batt insulation or blown attic insulation. Batt insulation blankets your attic and goes in easily between ceiling joists and can offer excellent insulating qualities. Sometimes though, it’s difficult to get around trusses and other awkward spaces in your attic, so blown-in or loose fill attic insulation is used. This stuff has good insulating qualities, but not as much as batt would for your attic. It can also be a mess to install and could require a blower.

When laying fiberglass batt attic insulation, use paper-faced types when you need a vapor barrier (the paper provides this feature and should be placed against the warm part of your attic, i.e. the floor of your attic, on top of the drywall or plaster for your ceiling below). A foil-faced attic insulation should be installed the same way. The foil helps radiate heat back toward your home’s living space.

If you opt for blown or loose-fill attic insulation then you just have to decide between fiberglass, wool, or cellulose fibers for blown and polystyrene granules or mica types for loose-fill. The most common is the last one, called exfoliated vermiculite attic insulation. You can purchase this in bags and pour it in between joists and irregular spaces. If your attic is highly ventilated and/or breezy, this type of attic insulation should be avoided.

Installing attic insulation

As discussed above, you may arleady have most of your attic insulated. If not, you should seal the small gaps first before bringing in the big stuff. Otherwise, do your best to use the following tips to get all those nooks and crannies.

  • Plug up holes: Look around your attic for empty cavities that are bare. The best way to insulate these areas is to fold a piece of unfaced batting into a garbage bag and stuff it into the space.
  • Seal the gaps: In your attic, you’ll see plenty of pipes and wiring coming out through the attic floor. Using a can of expanding foam, seal all around these conduits where they come out. Electrical boxes, such as those for lights, should also be sealed. There you should use flexible caulking to cover and rid any air passages.
  • Attic access insulation: As you enter your attic, you’ll have a piece of wood or drywall covering the attic opening or hatch. Apply weatherstripping to the bottom of this where it meets the opening’s frame. Don’t forget to staple or glue a piece of cut-out batt insulation for the other side!
  • Seal flues and chimneys: If you have a fireplace or gas water heater, you’ll also want to seal around these flues. Since these pipes can get hot, install aluminum flashing around them first and then spray foam insulation on top.
  • Double-up batt insulation in cold climates: If you already have attic batt insulation installed between your joists, you can add insulation by laying in a second layer, overlapping in a criss-cross fashion.

Remember, the best attic insulation is a combination of all the above. Covering and sealing as many gaps as possible will create a solid insulated barrier between you and your attic. Sounds cozy, doesn’t it?

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