Why Is Windows and Home Sealing Important?

One-third of a home’s heat loss occurs through poorly sealed doors and windows, costing the typical homeowner hundreds of dollars a year.

How to Seal Your Existing Windows

Make sure that your windows are double-glazed (or triple-glazed in very cold climates) and airtight. Weatherstripping and caulking are easy ways to eliminate drafts and heat loss through existing windows. New windows can conserve so much energy that they pay for themselves in just a few years.

How to Test For Drafts

Figuring out where drafts are coming from can be challenging—the most likely culprits are the spaces around doors and windows. To locate the source of a draft:

  1. On a windy day, light an incense stick, a smoke pencil (sold at hardware stores), or even just a candle, and move it slowly around your door and window frames.
  2. Any specific spots where the thick smoke wavers or the candle flame moves indicate where your leaks are.

You can use spray foam to seal up larger holes, and silicone caulk for smaller spaces. If your windows are more than 20 years old, or you notice significant drafts from your windows even if they’re sealed well, it’s time to replace them.

How to Choose the Right Windows

Windows are rated primarily by their U-values, which are a measure of the rate at which heat passes through the material. Another factor used (less commonly) to rate a window is by its R-value. In contrast to a U-value, an R-value is a measure of the window’s resistance to heat. The lower the U-value and the higher the R-value, the more energy-efficient the window is. Look for a U-value of 0.25 or lower, and an R-value of 4 or higher. It’s particularly smart to choose ENERGY STAR–qualified windows, which save you money in energy bills (about $450 per year per window) and qualify you for a tax rebate. Other features to look for are:

  • Glazing: Windows with double or triple glazing (which refers to the number of layers of glass used) have higher R-values.
  • Low-e coatings: Made of thin semiconductor film, low-e coatings reduce incoming heat and keep your house cool, making them ideal if you live in a warm climate.

Several types of home windows are available on the market. If you want to be truly energy-efficient, casement windows are the way to go. Casements open outward on a side hinge and are the best-sealed and most energy efficient windows available. Awning windows, which open outward on a top hinge, and sliding windows, which slide open horizontally, are moderately efficient. Double-hung windows, which slide open and closed vertically, are the least efficient type of window because they don’t seal well. Replacing double-hung windows with casements will save you a significant amount of energy.

Window Installation

New windows won’t help you save energy if they’re installed incorrectly. Make sure to have a professional glazier install your new windows, and after the work has been completed, check each window yourself with the draft test explained above. No matter how efficient the windows are, they won’t be able to do their job of keeping your house airtight if there are cracks and spaces between the windows and the walls.

How to Understand Insulation

Keeping your home’s temperature as even as possible will reduce the amount of energy needed to heat or cool it. Insulation, a protective material that’s usually installed between walls and ceilings, keeps a house’s temperature from varying too much. Proper insulation will save you money and make your home more comfortable.

  • n an existing home, it’s important to know the location and amount of insulation you already have, and then add insulation from there.
  • In a new home or a remodel, install as much insulation as you can, using the newest insulating materials available. (Be sure to speak with your builder about this; many builders simply stick to the recommended amount of insulation in the walls and ceilings, when in fact you may be able to add more.)

Most old homes have far less insulation than new homes—an energy audit will help you determine this. If you don’t want to pay for an audit, your home’s original builder may still have records about the kind of insulation you have. If not, you can check your insulation yourself. Start in the attic and any spaces that adjoin unheated spaces, such as basements and garages, to see the types (and thicknesses) of insulation they have. To check your insulation:

  1. Use your circuit breaker to turn off the power to the room you’re checking.
  2. Locate an electrical socket on the wall.
  3. Remove the faceplate and use a flashlight to see into the space behind the wall.
  4. Determine the type of material there and use a ruler to measure its thickness.

Types of Insulation

There are plenty of types of insulation, including fiberglass, wool, plastic, spray foam, and natural materials. Knowing which one to use means understanding the level of insulation you’ll need and the R-value (ability of the insulating material to restrict the flow of heat) you’re looking to achieve. This table lists the most common types of insulation.

Type of Insulation
Typical Materials
Method of Installation
Typical Uses
Blankets (batts or rolls)
  • Fiberglass
  • Rock wool
Fitted between studs, joints, and beams
  • Unfinished walls
  • Unfinished floors
  • Unfinished ceilings
Loose fill (blown-in or spray-applied)
  • Rock wool
  • Fiberglass
  • Cellulose
Blown into place or spray-applied using special equipment
  • Enclosed existing wall cavities or open new wall cavities
  • Unfinished attic floors and hard-to-reach places
Rigid insulation
  • Extruded polyesterene foam (XPS)
  • Expanded polyesterene foam (EPS or beadboard)
  • Polyurethane foam
  • Polyisocyanurate foam
For interior applications, must be covered with 1/2″ gypsum board or other building-code approved material for fire safety; for exterior applications, must be covered with weatherproof facing
  • Basement walls
  • Exterior walls under finishing (some foam boards include a foil facing that acts as a vapor retardant)
  • Unvented, low-slope roofs
Reflective systems
  • Foil-faced paper
  • Foil-faced polyethylene bubbles
  • Foil-faced plastic film
  • Foil-faced cardboard
Fitted between wood-frame studs, joists, and beams
  • Unfinished ceilings
  • Unfinished walls
  • Unfinished floors

After you’ve determined what kind of insulation you have, go to the Department of Energy’s online insulation calculator at ornl.gov to learn how much insulation you might need for your specific region.

How to Seal Your Home

New homes are built to be much more tightly sealed than older homes, which develop gaps throughout years of settling. After insulating and sealing windows and doors, make sure you aren’t losing warm or cool air through holes and spaces in other parts of your home.

How to Seal Attics and Basements

To make sure your attic and basement are sealed properly, first do a detailed survey to find out where air leaks might be costing you money. Then, starting in the basement and using a very bright flashlight, follow the path of all plumbing pipes, HVAC tubes, chimneys, and, to a lesser extent, electric lines, starting at the point where they adjoin the furnace, septic or sewer pipe, or water heater. Do a visual inspection, following pipes and tubes through the walls and ceilings of your house, ending in the attic, where you typically lose the most heat. Look closely at electrical outlets, plumbing pipes coming from walls, fan exhausts for bathrooms, and recessed lighting for leaking holes. Seal up any cracks and holes with caulking foam.

If you can afford to add insulation to only one room in the house, make it the attic—attics often lack adequate insulation (or any insulation), especially under the roof. Get more tips from the home sealing tutorial on the EPA’s ENERGY STAR website: energystar.gov

How to Seal Attached Garages

If your garage is attached to your home, you may have noticed that the interior wall closest to the garage is cold in the winter and hot in the summer. Make sure whatever door connects your living space to an attached garage is weatherstripped and sealed tightly. Also consider insulating the garage, even if it’s just the wall that adjoins the house.

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