R- value is a measurement of the ability to prevent the transfer of heat; the larger the number, the harder that insulation is working at preventing heat conduction.

Whenever we talk about insulation, R- value inevitably enters the conversation: the wall is R- 19, a roof is    R- 30.

What does this mean?

Essentially R- value is the measure of thermal resistance (the ability to prevent the transfer of heat).  The higher the number, the better that insulation is working at preventing heat conduction. The less heat you lose, the lower your energy bills.

Say you took a piece of tin foil and held it up to a candle flame.  If you touched the other side of that foil, it would be hot. If you put a piece of wall board between the flame and tin foil, you may feel some heat, but not much.  The wall board has a higher R- value than the tin foil because it provides a better thermal break due to the material from which it is made.

How much R- value is enough in regards to homes and buildings, and what is considered energy efficient?  The  majority of American homes were constructed with 3 x 4 walls and filled with R- 13 insulation prior to 1990.  Newer, smarter standards are 2 x 6 walls (a larger cavity provides more room for a thicker thermal barrier) with R- 19 insulation. The standard R- value for roofs is R- 30 or R- 40.

Heat Transfer:  What can you do to prevent how heat transfer sabotages your home’s energy efficiency?
Heat moves in three ways: conduction, convection or radiation.

R- value addresses conduction: the transfer of heat through a material (your walls for instance).

When heat and  moisture move, it is convection and this happens when a home’s exterior- the siding, sheathing, walls, windows and doors- are not tight and there is air movement. Also, many homes have holes on the outside shell, where air can pass through the cavity to where the insulation is (such as ducts, fireplaces, fans, vents, cable lines, windows and doors). That creates two main problems: convectively moving heat in and out, which also brings moisture with it and inside the walls- which condenses and forms mildew inside wall cavities. In addition, your home becomes drafty and uncomfortable. Convection  issues are solved by sealing a home.

Radiation  is when heat flows from a hotter material to a cooler one. Black roofing attracts heat and transfers it into the attic, silver metal roofing or light colored roofing transfers less heat into the attic. If you want black roofing, you can install radiant sheathing that deflects heat from the home.

Only by air- sealing the home and improving the convection in your home, plus improving insulation and addressing radiant heat on the roof can a home  reach optimum energy efficiency.


Increasing your R- Value: Insulating your home will improve its R- value and help conserve energy, regardless of other air- sealing efforts you make. Insulation is one of the most affordable energy improvements you can make to your home.

Choosing insulation: The most common types of insulation on the market today are fiberglass batting, cellulose (paper fiber) and foam board. Foam board provides higher R- values but costs  more and is an impediment for installation of siding, brick or stone.

Go for the highest standards: Walls should minimally be R- 19 and the roof should be R- 30 or R- 40; however the standards set by the Passive House Institute (U.S.) are R- 30 walls and an R- 60 roof. Compare these numbers with your existing insulation values.

Purchase: Low/ no pollution materials. After all, you LIVE in your home, you have to LIVE with these products! Choose water- based caulks, and choose sealants that have little/ no solvents or volatile organic compounds (called VOCs).

Find the leaks:

1) Paper test: Shut a window or door on a piece of paper; if you can pull the paper out intact, you’ve got a leak that’s wasting energy.

2) Flashlight test: At night, turn off the home’s interior and exterior lights, shine a flashlight where you suspect leaks in exterior walls, windows, and doors while having a partner stand outside and make a note of where rays of light shine through.

3) Incense test: On a cold, windy day, turn off the furnace and depressurize the house by turning on any exhaust fans (kitchen and bathroom fans). Walking through your house with a lit incense stick, you hold it close to areas where there could be leaks. When smoke gets sucked away or blown around, you’ve found a leak.

Sealing leaks:

1) Seal and insulate:  Heating and air conditioning ducts that run through garages, crawl spaces, attics, and basements.

3) Caulk or spray foam: To fill cracks and gaps around  windows, pipes, and vents that pass through walls, plug leaks around plumbing and electrical conduit penetrations, joints where different parts of the building meet such as the floors and walls, at dropped ceiling areas and kitchen soffits (the lowered ceilings above wall cabinets), and in outside walls. If you see dirty spots in the attic insulation, air is being pulled through it. Move the insulation aside, find and seal the leak and replace the insulation.

5) Secure hot spots: Close gaps in the attic around chimneys and water- heater or furnace flues. These conduits require special treatment because they get hot, and building codes require that combustible materials be kept 1 to 2 inches away from them. Cut aluminum flashing to fit around them and block any gaps in the attic floor.

2) Install weather stripping: Around doors and windows.

4) Do the ducts: Heating and cooling ducts are notorious for leaking around their joints and seams- either because they were sloppily installed in the first place or got jarred during remodeling or other work on the house. Ducts can waste a lot f your money- more than 10% of a home’s heating and cooling energy when they run through uninsulated spaces.

Use duct mastic (sticky putty) but don’t use duct tape for sealing ducts since it loses stickiness after five years. Then insulate them with duct insulation, taping the seams with a high quality tape such as aluminum foil tape.

6) Weather stripping: Install felt, foam, rubber, or metal weather stripping to reduce air flow around doors and windows. Metal (copper, stainless steel, aluminum or bronze) weather stripping holds up much longer than felt or foam which tend to disintegrate quickly.

7) Electric outlets and switch plates: On exterior walls account for only about 2% of air leakage, but are a cheap and easy fix. Foam gaskets designed to fit behind an outlet or switch plate are available at any hardware store, and take just a minute or two to install.

Insulation cost:

Roofing insulation runs between $1,000 to $3,500 for the average sized home, while complete home insulation (roof and walls) runs $2,500 to $5,500 (2011 U.S. Energy).

Replacing Leaky Windows:

Triple- pane, gas- filled  windows are considered the highest value. They are windows with three layers of glass with krypton or argon gas between layers. The gas serves as insulation, reducing heat transfer between panes.

The frame material should be vinyl- framed windows, which provide better insulation than metal- clad wood frames. Additionally, the windows have a warm- edge glazing, meaning high- density foam and high- grade silicon sealant is applied between the window and frame rather than a simple metal spacer. This prevents condensation at window edges.

Replacing Leaky Doors: 

Fiberglass, foam- filled doors that will maintain the air seal he worked hard to accomplish through window replacements and insulating the wall.