Installing Your Own Insulation

With certain types of insulation materials, installing your own insulation is definitely doable—and you can save money not hiring a professional. Installing fiber glass or mineral wool insulation are simple DIY projects. Other insulation types, such as spray foam insulation, require the use of a professional.

Preparing for proper installation of batt insulation

Before starting your batt insulation job:

  • Make sure you have the right R-value for your home.
  • Find out if vapor retarders are required.
  • Make sure you have the combination of products needed to complete the job.
  • Make sure you have all associated tools.
  • Make sure you have right clothing and personal protective equipment Learn more.
  • Have additional resources handy. If you have internet access during installation, have this page open on a mobile device so you can check on what to do as you see specific issues. Alternatively, you can download or print the installation guide for attics & ceilings, walls & knee walls, or floors. Either approach will allow you to identify solutions to challenges you may face as you go through the installation process.
  • Consider the important safety issues detailed here.

Know the basics

There are a few things you need to keep in mind any time you are adding insulation to your home:

  • Air seal then insulate. Adding insulation without air sealing won’t get you the benefits you are after. This means making sure an air barrier is in place and leaks are sealed.
  • Make sure your insulation isn’t significantly compressed. Compressed insulation won’t give you the R-value level you see on the package, so make sure it is not too compressed—by walls or obstructions such as wires, outlet boxes, etc.
  • Large gaps and voids are not good. Attention to detail matters more than you think. For example, if you have a 1,000 square foot attic and 10 square feet, or 1%, is uninsulated (say, the attic hatch) you might assume that means your attic insulation is 99% effective. That isn’t the case—because of the way heat flows, it would be a great deal less effective. Details matter, so take the time to do it right.

Start with a Walk-Through

If you’re adding insulation to walls, inspect them to ensure all cavities where insulation will be installed will have 6 sides after the wall finish is installed.  That means there will be an exterior sheathing, such as insulation board or OSB, wood (or steel) studs on the four sides, and finally the wall finish on the interior.  Because loose-fill or batt insulation on the attic floor and batts installed under floors are not exposed to significant air movement, they do not need to be covered on the exterior side.  If you are installing attic insulation, make sure air baffles are installed at the eaves to minimize the amount of air entering the edges of the insulation in the attics. Regardless of where you are adding insulation, always check for safety issues  before getting started.

Air sealing an existing home

Minimizing air infiltration is dependent on the air barrier system and not the insulation type. Like any system, it is composed of multiple parts, but these parts can basically be categorized as air barriers and air gap sealants. An air barrier is anything that blocks air from moving—which includes exterior sheathing and interior gypsum board sealed at the edges. For an air barrier system to be effective, air gaps, including all gaps, seams, and penetrations (think plumbing and electrical entries) where air could get in need to be sealed properly.

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Achieving an effective air barrier

An effective air barrier system can be accomplished using numerous techniques and materials. During construction, homes are outfitted with housewrap, over the exterior sheathing, in a continuous manner to act as an air barrier. Unless you are fully re-siding your home, adding housewrap to an existing house is impractical. However, all homes have exterior sheathing and interior barriers such as gypsum board. So, when you are trying to air seal an existing home, the focus is really the gaps, seams and other areas you can address. Having a second air barrier in place, such as sealing the interior finish (i.e. gypsum board) may increase the air-tightness of the building and increase energy savings.

An effective air barrier system can also be accomplished using caulking or specialty sealing systems where high pressure is used to spray flexible sealants into all the joints, gaps and cracks in the building envelope.  Usually air barrier systems are a combination of housewrap and various sealants such as caulk and can spray foam applied where they are most effective to achieve a continuous air barrier.  There are limits to what you can do to air seal an existing home, but time, diligence and ample caulk or foam can take you a long way.

The basics of batt and roll installation

To get the optimum performance when using fiber glass and mineral wool batts in walls and knee walls – fill the cavity. Cut each batt so it is about ½” longer than the cavity and for non-standard cavity widths cut the batt ½” wider. (Standard batts are pre-cut to be about ½” wider than a standard wall cavity with either 16” or 24” on center framing.) Then use care to place the bat in the cavity so it fills the cavity from top to bottom, side to side and front to back.