Chapter 6

Insulation & Weatherproofing

The armor against high energy costs

Affordable and Effective Energy Saving Improvement

Man blowing insulation in an attic

The quality of your home’s insulation impacts just about every energy-saving improvement you make. If you’ve got a well-insulated home, you’ll use less energy to heat and cool—and in fact can cut annual costs by as much as 30 percent. What’s more, taking the time to seal leaks in your home’s structure keeps home comfort and energy dollars from leaking away through every nook and cranny.

Insulating and sealing are affordable, effective projects for your green home. Here are our top tips for ensuring year-round energy efficiency.


Choosing and Installing Insulation

Great insulation takes many forms, from fiberglass batt and blown-in products to rigid foam board. Selecting the right insulation depends on the space you need to insulate and the insulation performance required to achieve energy savings.

First, research the optimum insulation R-values recommended for the area in which you live. R-value is a measure of thermal resistance—that is, a product’s ability to resist heat flow. The higher the R-value, the more insulating power you get, and varying R-values are required for your home’s walls, attic, basement and crawlspace. Visit to review the Department of Energy’s “Recommended Levels of Insulation” guide, which provides region-by-region R-values to help you improve existing home insulation or plan insulation for a new build.

As for product selection, each type of insulation is made to fit in a different part of your house. Fiberglass batts and rolls are excellent for new-construction walls and ceilings, as well as attics and crawlspaces in existing homes. Blown-in insulation is available in either fiberglass or cellulose (a paper product coated with fire retardant), and can be used in attics or existing walls.


First Things First: Work from the Top Down

attic flooring

Your attic should be a top priority for insulation, as it offers the greatest potential for home energy savings and also happens to be the easiest area to tackle. The DOE recommended R-value for most attics is R-38, or about 12 to 15 inches of insulation coverage, and you’ll get even better results with levels between 19 and 22 inches. With the right protective gear (gloves, mask and full-coverage clothing) and tools, you can easily install batt or blown-in products in your attic.

If you’re using batt insulation to supplement existing attic insulation, remember to get the unfaced kind; otherwise, you run the risk of trapping moisture between the new insulation and the old. And speaking of ventilation issues, check for drafts while you’re in the attic, because it’s the one place you actually want them! Proper ventilation protects insulation from the dampness of wintertime condensation, which can cut insulating power by one third, as well as introduce a host of structure-threatening moisture problems.

If you’re not comfortable with handling insulation on your own or have to deal with hard-to-reach areas, a certified insulation contractor can help you with your insulation project. Insulating walls can be especially tricky, as old insulation tends to settle and it’s hard for the typical do-it-yourselfer to fill these insulation blanks. Installers who specialize in such applications have gear that takes thermographic pictures of insulation targets, providing helpful before-and-after comparisons of insulation improvements. To find an insulation contractor near you, visit the Insulation Contractors Association of America at

Spray Foam Both Seals and Insulates

Icynene Spray Foam Insulation

If you'd like one insulation that both seals out drafts and provides superior insulation, spray foam is the way to go.  For homes old or new, spray foam is unquestionably the single most effective way to increase comfort and reduce energy costs.

Spray foam insulation can be sprayed, poured, injected or even foamed-in-place for lightweight but intensive coverage and high R-value results. It adheres to surfaces, so it avoids many of the pitfalls of air-permeable insulation.

It’s usually available in two formulations, closed-cell and open-cell. Closed-cell foam insulation has high-density cells that are closed and filled with a gas that causes the foam to expand and fill spaces to be insulated. The blowing agent is then trapped, adding to R-value. Open-cell foam has a structure that allows air to diffuse into the cells making for a less dense, spongy texture; it has a somewhat lower R-value (comparable to batts and blankets).

The key advantage of spray foam is that both open and closed cell foam creates an effective barrier to air leakage in both new and existing homes, thereby, acting to both seal and insulate for sustained energy savings. Further, it won’t sag or compress with age, isn’t a source of food for nesting insects and rodents, and completely fills gaps around plumbing, vents and electrical openings. Spray foam insulation also helps to improve a home’s indoor air quality by minimizing the entry of outdoor allergens and pollutants.

Installed by a certified pro, spray foam insulation is an especially effective choice for new builds. An all-in-one solution, it saves time and money that would otherwise be spent on a range of weatherizing steps that are typically less effective, and noticeably reduces a home’s carbon footprint.

Most Common Sources of Leaks and How to Fix Them

caulk, window, drafts,

Any elements that link a structure’s interior and exterior are potential leaks where expensive heated or cooled air can escape.  Here are the most susceptible leak spots and how to seal them.


  • Apply acrylic-latex caulk where window moldings meet the exterior wall. For the best coverage, squirt a thin bead of caulk at the intersection of the wall and molding, and then use your finger to spread the caulk into the seam. Follow by using a sponge and warm water to finish spreading the caulk and remove excess.
  • Caulk under the sill, too, as it’s a particularly leaky area of the window, then come inside and caulk around interior window moldings.


  • Short of replacing it with one of the new, super-efficient fiberglass models, there are several things you can do to eliminate drafts around a door. Start by caulking moldings inside and out, then replace any degraded or defunct weatherstripping.
  • Loose door hinges or low-quality hardware can create air gaps, so tighten screws in existing fittings or upgrade to new brass or brushed steel components.
  • Use shims to re-level the door sill, and add a door sweep to block out drafts. A new, properly fitted lockset will also improve the seal and security of an entry door.

Outlets and Switches

  • Wall openings around outlets and switches can also let in blasts of outdoor air, so seal the gaps with specially designed foam gaskets. Available at your local home center or hardware store, these gaskets are made to fit between the outlet or switch device and metal cover plate. They’re easy to install—just remember to turn off the electricity first to avoid electric shocks!
  • Bigger gaps around such receptacles can be filled with a quick application of expandable foam.


  • Can ceiling lighting is another well-disguised source of household drafts. If you need to insulate around these or other ceiling fixtures, be sure to follow manufacturer and National Electric Code guidelines, which typically require three inches of clearance in order to prevent overheating. IC (insulation contact)-rated light fixtures are ideal for energy savings, as they’re designed to be covered with insulation and are the most airtight.


  • If you’ve got a forced-air heating and cooling system, the ductwork that distributes home comfort can lose about 20 percent of its payload through faulty connections and other leaks. Stop ductwork drafts with duct sealant (a.k.a. duct mastic) or UL 181 tape, a tape that looks like silver foil but, unlike mis-named duct tape, doesn’t degrade, crack or lose its bond with age.

All of these draft-deterring efforts make for easy weekend projects, and raise your home’s energy efficiency profile in the process. Plan your own “home tour” to hunt for possible air leaks, and take simple steps to stop them before the next season begins.

Trick of the Trade: Attic Stair Insulation

A folding attic stair may make for handy access to your upstairs storage, but it can also serve as a major escape hatch for conditioned indoor air. In fact, an uninsulated attic stair is the energy-wasting equivalent of leaving a window open all winter long!

How do you seal in warmth without blocking your attic entrance? Add one of the effective, ingenious attic stair insulators now on the market. Easy to install, these lightweight yet airtight additions fit through the attic opening from below, covering the opening and retractable ladder to greatly reduce heat loss. The next time you need to access storage, the insulator’s integrated hatch may be opened for easy entrance to your attic space.