A blower door test machine and reader in operation in a home

Does something give you the feeling that an externally-linked component of your home is leaking air? If your suspicions are correct, it could be causing bigger problems than just you feeling chilly, like reduced energy efficiency, or structural damage to the home. If you can feel a bit of a draft every time you pass by certain areas of your home, it may be a good decision to invest in a blower door test.

Blower doors tests are used to measure the airtightness of homes and commercial buildings, usually with the intent of quantifying components of the building envelope—the structural barrier linking the interior and exterior of the building. This includes doors, windows, walls, roof, and foundation.

Most people don’t even know what a blower door test is, but it’s increasingly becoming the go-to tool for starting off on the energy efficiency journey and solving some major home leakiness issues. In many cities and counties, a blower door test is now increasingly being required for any major renovation or new home build project.

The money spent on a blower door test could pay off fairly quickly, saving you on heating costs and paying for itself in no time.

What is the Cost of a Blower Door Test?

The cost of a blower door test will vary depending on the market in which you live, the specific location of the home or neighborhood, and the company you choose. But generally speaking, you can expect to pay between $200-$450 for a test.

In some markets, like Florida, for example, rates are a bit cheaper. Prices typically range from $150-$250, but again, the cost is contingent on the company conducting the test. 

What are Blower Door Testing Machines?

A blower door machine is a calibrated fan that is placed in a building envelope element like a door or window, and all other exterior-leading openings are closed to get the most accurate reading of airflow leakage for the component in question. The fan usually uses negative pressure to suck air from the home, pinpointing the path(s) of least resistance— many of which are unintentional and unbeknownst to the homeowner.

However, door blower machines are also commonly used to test airflow for several other aspects of a home in addition to the building barrier, like ductwork, for example. While a blower door test does not evaluate how well a structure is insulated, it can open homeowners’ eyes to walls that are drafty, or air-bypass instances that could compromise otherwise well-insulated structures.

A technician unrolling plastic to seal and test the air leakages in the HVAC duct systems
Bud Fahey of Florida Blower Door helped us to decrease air leakage in our first net-zero home renovation project by 44%! 

How Long Does a Blower Door Test Take?

A blower door test typically takes one to two hours. It is most often conducted towards the end of the building process when the home is fully constructed or renovated, and most of the installations have been made.

This has is both its benefits and drawbacks. Though it wouldn’t make much sense to do the final test before windows, doors, and weather stripping have been installed, waiting until after construction is completed to first test prevents the ability for changes to be made to the structural components of the house.

The downside to preliminary testing, however, is that any window or door opening that might not be filled yet must be sealed up, or the building won’t have sufficient pressure to pinpoint where the air leaks are coming from.

Benefits of a Blower Door Test

Optimize Energy Efficiency and Insulation

The benefit most commonly associated with a blower door test is probably energy efficiency and reduction of your home’s carbon footprint. By determining and stamping out air leakages in the building envelope of your home, you make your home more energy-efficient, saving you money on heating and cooling costs, and reducing your environmental impact.

Helps Determine What Size Furnace or Air Conditioner is Right for Your Home

An added benefit of blower door testing is that it allows homeowners to accurately access which size furnace or air conditioner is optimal for their home. How much your home leaks or doesn’t leak air can impact how much heating and cooling – and even humidification and dehumidification – is required. 

Improving the Health of Your Home and Your Family, Protection From Contaminants and Insects

In addition to gaps that can permit entry to insects and other pests, dust, and contaminants like pollen, entryway leaks in wetter climates can allow moisture into the home. This ultimately makes your home more muggy, and can result in mold buildup in structural components along the passageway and even the home’s interior.

The opposite is true in more arid climates, where leakages can result in diminished humidity, potentially leading to respiratory health implications, like dry sinuses or throat, and increase the likelihood of the spreading of viruses.

Similarly, blower door tests can be used to determine what mechanical ventilation, if any, is needed to promote fresh air flow and preserve the air quality inside your home, and ultimately your health.

You really can’t put a price on health and safety, but if the price tag of a blower door test seems like too much money for your budget, there are a number of DIY measures you can take in order to pinpoint where air leaks may be in your home:

Alternative Ways to Detect Air Leaks in Your Home

First, Use the “Hand Test” Method

Though not the most precise, the hand test is useful to determine large leaks and is an excellent starting point for detecting areas where heat is escaping.

On a cold, wintery day, place your hand on openings of all windows, doors, and kitchen and bathroom air vents and fans. When you can feel cold air, this typically means you have a leak.

You can also use this technique to inspect electrical outlets.

Use a Flashlight to Test for Visible Air Leakage

This is the visual alternative to a blower door test. Between you and a family member, position yourselves on either side of the building envelope component you suspect to be leaking. Have one person point the flashlight at the area in question while the other inspects for visible light. You have a leak if light shines through. 

Employ the “Candle Test”

To inspect places that you think may have small air leaks like baseboards, electrical outlets, and crown molding, walk around your house with a lit candle. Put the candle up to the area of the potential leak. If the flame begins to move, it indicates a leak.

A woman using a candle to test a window for air leaks
Courtesy of DIY Network

Turn the air conditioning off if you are doing this test when it is hot outside, or if it is a cold day, turn off your central heating system.

Depressurize Your House to Pinpoint Leak Areas All Over the Home

On a cold and windy day, close all windows and exterior-leading doors and shut off the furnace. Next, turn on all fans in your kitchen and bathrooms.

Proceed to sweep your house while holding a lit stick of incense. Run the incense past the edges of windows, doors, and vents, and other areas where air leaks are suspected. A leak is present if the smoke is blown in or sucked out of the house.

While all of these techniques are quick-fix, cost-free solutions, the bottom line is that a blower door test is the best course of action if you want to fully optimize your home for energy efficiency, longevity, and your family’s health.  

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