What is a blower door?
A blower door is a large calibrated fan that is temporarily mounted in a house door to measure the "leakiness" of the house and to assist in finding the location of the leaks. Modern blower doors have variable speed fans so that the pressure in the house can be adjusted, and they also have door mounting frames so that the fan can be sealed tightly into the door jamb. In order to measure the leakiness of the house, the blower door measures both the air flow through the fan and the pressure difference between the house inside and outside.

What does a blower door look like?

The Minneapolis Blower Door in action, manufactured by The Energy Conservatory.

Why should you care about air leakage in houses?
Everyone knows that air leakage can cause uncomfortable drafts in houses, but energy researchers have discovered that sealing air leaks is one of the simplest and least expensive way to save energy in homes. A typical house may lose about 1/3 of its heat through walls and ceilings, 1/3 through windows and doors, and 1/3 through air leakage. A few hours of air sealing with inexpensive sealants can often reduce the air leakage by about 1/4 to 1/2, resulting in a saving of 10% to 20% of the total house heating and cooling bill. Each house has different amounts and types of air leakage, and the most efficient technique is to spend the most time sealing the leakiest houses. Duct leakage is probably the worst type of house air leak. Therefore, you need a tool that can quickly identify the leaky houses and show you where the leaks are.

How can you use a blower door?
Air leaks can be simple and inexpensive to seal if you can just find them, and that is where the blower door comes in. First you use the blower door to measure the air leakage and see how the house rates on a scale of "leaky" to "tight". If it is already tight, then you can forget about air sealing and look at other ways to save energy. But if it is too leaky, then the blower door can tell you how bad it is and then it can help you to find the location of the leaks. After you seal the leaks, the blower door can tell you how well you have done.

Copyright Infiltec-Thanks to David Saum for permission to use this article.

How Insulation Works
You need insulation in your home to provide resistance to heat flow. The more heat flow resistance your insulation provides, the lower your heating and cooling costs. Heat flows naturally from a warmer to a cooler space. In the winter, this heat flow moves directly from all heated living spaces to adjacent unheated attics, garages, basements, and even to the outdoors. Heat flow can also move indirectly through interior ceilings, walls, and floors—wherever there is a difference in temperature. During the cooling season, heat flows from the outdoors to the interior of a house. To maintain comfort, the heat lost in the winter must be replaced by your heating system and the heat gained in the summer must be removed by your cooling system. Properly insulating your home will decrease this heat flow by providing an effective resistance to the flow of heat. An insulation's resistance to heat flow is measured or rated in terms of its thermal resistance or R-value.

How Moisture Moves through a Home
To help understand the principles of moisture control, you need to understand the basics of how moisture can move through your home. Moisture or water vapor moves in and out of a home in three ways:
• With air currents
• By diffusion through materials
• By heat transfer.
Of these three, air movement accounts for more than 98% of all water vapor movement in building cavities. Air naturally moves from a high pressure area to a lower one by the easiest path possible—generally through any available hole or crack in the building envelope. Moisture transfer by air currents is very fast (in the range of several hundred cubic feet of air per minute). Thus, you need to carefully and permanently air seal any unintended paths to control air movement. The other two driving forces—diffusion through materials and heat transfer—are much slower processes. Most common building materials slow moisture diffusion to a large degree, although they never stop it completely. Insulation also helps reduce heat transfer or flow. The laws of physics govern how moist air reacts within various temperature conditions. The study of moist air properties is technically referred to as "psychrometrics." A psychrometric chart is used by professionals to determine at what temperature and moisture concentration water vapor begins to condense. This is called the "dew point." By understanding how to find the dew point, you will better understand how to avoid moisture problems in your house. Relative humidity (RH) refers to the amount of moisture contained in a quantity of air compared to the maximum amount of moisture the air could hold at the same temperature. As air warms, its ability to hold water vapor increases; this capacity decreases as air cools. For example, according to the psychometric chart, air at 68ºF (20ºC) with 0.216 ounces of water (H2O) per pound of air (14.8g H2O/kg air) has a 100% RH. The same air at 59ºF (15ºC) reaches 100% RH with only 0.156 ounces of water per pound of air (10.7g H2O/kg air). The colder air holds about 28% of the moisture that the warmer air does. The moisture that the air can no longer hold condenses on the first cold surface it encounters (the dew point.) If this surface is within an exterior wall cavity, wet insulation and framing will be the result. In addition to air movement, you also can control temperature and moisture content. Since insulation reduces heat transfer or flow, it also moderates the effect of temperature across the building envelope cavity. In most U.S. climates, properly installed vapor diffusion retarders can be used to reduce the amount of moisture transfer. Except in deliberately ventilated spaces, such as attics, insulation and vapor diffusion retarders work together to reduce the opportunity for condensation in a house's ceilings, walls, and floors. To effectively control moisture in your home, you need to first consider your climate when exploring your moisture control options

The R-Value of Insulation
An R-value indicates an insulation's resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value depends on the type of insulation and includes its material, thickness, and density. When calculating the R-value of a multilayered installation, add the R-values of the individual layers. Installing more insulation in your home increases the R-value and the resistance to heat flow. The effectiveness of an insulation's resistance to heat flow also depends on how and where the insulation is installed. For example, insulation that is compressed will not provide its full rated R-value. The overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself because some heat flows around the insulation through the studs and joists. Therefore, it's important to properly install your insulation to achieve the maximum R-value. The amount of insulation or R-value you'll need depends on your climate, type of heating and cooling system, and the section of the house you plan to insulate. For more information, see our information on adding insulation to an existing house or insulating a new house.

GLOSSARY

$2000 tax credit - The Energy Policy Act of 2005 (EPACT), signed by President Bush on August 8, 2005, offers consumers and businesses federal tax credits beginning in January 2006 for purchasing fuel-efficient hybrid-electric vehicles and energy-efficient appliances and products. Most of these tax credits remain in effect through 2007. For more information click here.

Air Leaks -You may already know where some air leakage occurs in your home, such as an under-the-door draft, but you'll need to find the less obvious gaps to properly air seal your home. For a thorough and accurate measurement of air leakage in your home, hire a qualified technician to conduct an energy audit, particularly a blower door test. A blower door test, which depressurizes a home, can reveal the location of many leaks. A complete energy audit will also help determine areas in your home that need more insulation.

Air Sealing is one of the most significant energy efficiency improvements you can make to your home. Air sealing will not just reduce energy costs; it will also improve your home's comfort and durability. Air leakage, or infiltration, occurs when outside air enters a house uncontrollably through cracks and openings. Properly air sealing such cracks and openings in your home can significantly reduce heating and cooling costs, improve building durability, and create a healthier indoor environment.

Appropriate Ventilation - The process of moving air (changing) into and out of an interior space either by natural or mechanically induced (forced) means.

Approved Contractors - Contractors that are screened and recommended by Frostbusters Home Energy $avings.

Blower Door - A blower door is a large calibrated fan that is temporarily mounted in a house door to measure the "leakiness" of the house and to assist in finding the location of the leaks. Modern blower doors have variable speed fans so that the pressure in the house can be adjusted, and they also have door mounting frames so that the fan can be sealed tightly into the door jamb. In order to measure the leakiness of the house, the blower door measures both the air flow through the fan and the pressure difference between the house inside and outside.

Blower door testing and air sealing - A blower door is a large calibrated fan that is temporarily mounted in a house door to measure the "leakiness" of the house and to assist in finding the location of the leaks. Modern blower doors have variable speed fans so that the pressure in the house can be adjusted, and they also have door mounting frames so that the fan can be sealed tightly into the door jamb. In order to measure the leakiness of the house, the blower door measures both the air flow through the fan and the pressure difference between the house inside and outside.

Current Energy Code - Energy codes are beneficial beyond lowering energy use in residential and commercial buildings, and thereby utility bills, because energy use also impacts our economy and the environment. Energy Codes provide builders with minimum building standards helping assure new homeowners that their home will be to these standards. For consumers, current energy codes also provide buildings that are comfortable. Fort Collins found that the energy portion of their building code resulted in a 16% improvement in energy demand.

DIY’s - Do it Yourself-ers

Energy Analysis Software - REM/Design Home Energy Analysis Software
Developed specifically with the needs of homebuilders, remodelers, energy consultants and designers in mind, REM/Design™ calculates heating, cooling, hot water, lights and appliance loads, consumption and costs for single and multi-family designs in over 250 North American cities. This windows-based software automatically analyzes the energy and economic performance of numerous energy design features including envelope insulation, air leakage control, duct leakage control, active and passive solar systems, heating and cooling equipment, mechanical ventilation and more. In addition to calculating energy performance, REM/Design™ sizes heating and cooling equipment, and automatically determines compliance with the CABO Model Energy Code, ASHRAE 90.2, and the International Energy Conservation Code for both the prescriptive and performance compliance paths.
Two levels of input have been designed for REM/Design™ users: simplified and detailed. Simplified inputs use general building design characteristics (e.g., house type) and built-in algorithms to determine building shell areas and other characteristics. Detailed inputs provide the user greater control over calculational values. Inputs include, opaque wall construction details, window conduction and solar gain values, HVAC efficiencies, duct system characteristics, passive and active solar design features, infiltration rates (measured or estimated). REM/Design™ helps you evaluate and promote the most cost-effective energy features for new home construction. The software analyzes the energy and economic performance of traditional and innovative design features, including active and passive solar systems, infiltration and duct leakage reduction packages, high-performance windows, efficient heating and cooling equipment, and panelized construction.
REM/Design™ identifies cost-effective energy improvements to existing homes. Using economic criteria that you specify, it automatically ranks energy efficiency improvements from the list of measures you've created. Once the treatments (energy efficiency improvements) and the rule base (i.e., if existing ceiling insulation is R-11, install R-19 to achieve R-30) have been created, they can be saved and used on future projects.

Energy Audit/Energy Analysis/ Home Comfort Audits - A home energy audit is the first step to assess how much energy your home consumes, and to evaluate what measures you can take to make your home more energy efficient. An audit will show you problems that may, when corrected, save you significant amounts of money over time. During the audit, you can pinpoint where your house is losing energy. Audits also determine the efficiency of your home's heating and cooling systems. An audit may also show you ways to conserve hot water and electricity. You can perform a simple energy audit yourself, or have a professional energy auditor carry out a more thorough audit. A professional auditor uses a variety of techniques and equipment to determine the energy efficiency of a structure. Thorough audits often use equipment such as blower doors, which measure the extent of leaks in the building envelope, and infrared cameras, which reveal hard-to-detect areas of air infiltration and missing insulation.

Energy Efficient Mortgage (EEM) - A type of home mortgage that takes into account the energy savings of a home that has cost-effective energy saving improvements that will reduce energy costs thereby allowing the homeowner to more income to the mortgage payment. A borrower can qualify for a larger loan amount than otherwise would be possible.

Energy Efficiency Ratio (EER) - The measure of the instantaneous energy efficiency of room air conditioners; the cooling capacity in Btu/hr divided by the watts of power consumed at a specific outdoor temperature (usually 95 degrees Fahrenheit).

Energy Star Rating - When you see products or services with the ENERGY STAR, you know they meet strict
energy efficiency guidelines set by the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Energy (DOE). Products in more than 40 categories are eligible for the ENERGY STAR. They use less energy, save money, and help protect the environment.

Heat Loss Calculations - The heat that flows from the building interior, through the building envelope to the outside environment.

Home Energy Audits - A home energy audit is the first step to assess how much energy your home consumes, and to evaluate what measures you can take to make your home more energy efficient. An audit will show you problems that may, when corrected, save you significant amounts of money over time. During the audit, you can pinpoint where your house is losing energy. Audits also determine the efficiency of your home's heating and cooling systems. An audit may also show you ways to conserve hot water and electricity. You can perform a simple energy audit yourself, or have a professional energy auditor carry out a more thorough audit.
A professional auditor uses a variety of techniques and equipment to determine the energy efficiency of a structure. Thorough audits often use equipment such as blower doors, which measure the extent of leaks in the building envelope, and infrared cameras, which reveal hard-to-detect areas of air infiltration and missing insulation.

Indoor Air Quality - Air Quality Standards, the prescribed level of pollutants allowed in outside or indoor air as established by legislation.

Insight XST Infrared Camera™ - The IR-InSight® XST (Extra Sensitive) is a portable video rate infrared camera that sets the industry standard for combining outstanding image quality and thermal sensitivity (NETD <70mK). The camera is optimized for low contrast thermal applications encountered in building sciences applications, provides precision temperature measurements and easily shows problems that other infrared cameras cannot. The IR-InSight XS is the simplest, easiest to use infrared camera on the market. The camera includes SightView™ Pro software to easily customize and prepare professional reports of your infrared surveys.

Minneapolis Blower Door™ - A blower door is a large calibrated fan that is temporarily mounted in a house door to measure the "leakiness" of the house and to assist in finding the location of the leaks. Modern blower doors have variable speed fans so that the pressure in the house can be adjusted, and they also have door mounting frames so that the fan can be sealed tightly into the door jamb. In order to measure the leakiness of the house, the blower door measures both the air flow through the fan and the pressure difference between the house inside and outside.

Readily Available Materials - Commonly used materials found at your local hardware store.

REM Design Energy Software™ - Home Energy Analysis Software
Developed specifically with the needs of homebuilders, remodelers, energy consultants and designers in mind, REM/Design™ calculates heating, cooling, hot water, lights and appliance loads, consumption and costs for single and multi-family designs in over 250 North American cities. This windows-based software automatically analyzes the energy and economic performance of numerous energy design features including envelope insulation, air leakage control, duct leakage control, active and passive solar systems, heating and cooling equipment, mechanical ventilation and more. In addition to calculating energy performance, REM/Design™ sizes heating and cooling equipment, and automatically determines compliance with the CABO Model Energy Code, ASHRAE 90.2, and the International Energy Conservation Code for both the prescriptive and performance compliance paths.
Two levels of input have been designed for REM/Design™ users: simplified and detailed. Simplified inputs use general building design characteristics (e.g., house type) and built-in algorithms to determine building shell areas and other characteristics. Detailed inputs provide the user greater control over calculational values. Inputs include, opaque wall construction details, window conduction and solar gain values, HVAC efficiencies, duct system characteristics, passive and active solar design features, infiltration rates (measured or estimated). REM/Design™ helps you evaluate and promote the most cost-effective energy features for new home construction. The software analyzes the energy and economic performance of traditional and innovative design features, including active and passive solar systems, infiltration and duct leakage reduction packages, high-performance windows, efficient heating and cooling equipment, and panelized construction.
REM/Design™ identifies cost-effective energy improvements to existing homes. Using economic criteria that you specify, it automatically ranks energy efficiency improvements from the list of measures you've created. Once the treatments (energy efficiency improvements) and the rule base (i.e., if existing ceiling insulation is R-11, install R-19 to achieve R-30) have been created, they can be saved and used on future projects.

R-Value of Insulation - An R-value indicates an insulation's resistance to heat flow. The higher the R-value, the greater the insulating effectiveness.
The R-value depends on the type of insulation and includes its material, thickness, and density. When calculating the R-value of a multilayered installation, add the R-values of the individual layers. Installing more insulation in your home increases the R-value and the resistance to heat flow.
The effectiveness of an insulation's resistance to heat flow also depends on how and where the insulation is installed. For example, insulation that is compressed will not provide its full rated R-value. The overall R-value of a wall or ceiling will be somewhat different from the R-value of the insulation itself because some heat flows around the insulation through the studs and joists. Therefore, it's important to properly install your insulation to achieve the maximum R-value.
The amount of insulation or R-value you'll need depends on your climate, type of heating and cooling system, and the section of the house you plan to insulate. For more information, see our information on adding insulation to an existing house or insulating a new house.

Specialty Products - Products that can be ordered through Frostbusters that are not commonly found at your local hardware store.