House Entrance Exam

Here's a new term home buyers should learn.  It's called a HERS rating and I just spent the morning witnessing all the exams required to provide an East English Village home with one.  HERS stands for Home Energy Rating System.  A score of 100 means that the home's energy performance is equal to that of a home built to minimum energy code standards.  A score of 85, which is required for any home meeting Energy-Star standards, means the home will perform 15% better.  In other words, the lower the score, the better energy performance.

Minneapolis Blower Door
Source

The data collected in the series of tests performed today will be input into modeling software, which will generate the home's HERS rating.  The following tests were performed today:

The Blower Door Test

To perform this test, the home is de-pressurized by sealing all openings except one, typically the front door.  A fan is placed within this opening.  When the fan is turned on, it pulls air out of the house.  The fan pressure is raised to 50 Pascals (Pa) and using the gauges attached to the fan, the amount of air being pulled into the house through cracks and openings is measured.  The rate of leakage is measured as the number of air changes in an hour, or ACH.  Current energy code requires all new homes to have a maximum of seven (7) ACH.  For a typical home, like mine which was built in the 1960s, this number is typically around 14 ACH.  Today's renovated home performs well with 8 ACH.

Duct Leakage Test
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The Duct Blaster Tests

Part 1 - Pressurized Duct Test

Next we move to duct performance.  To perform this test, covers are placed over all supply registers sealing the entire duct system.  The furnace cover is removed and a fan pushes air into the ductwork.  Hoses attached to the fan and to nearest supply register measure pressure.  The difference between the two pressures is converted to a leakage rate.  The higher the pressure, the more accurate the measurement. Typically, the pressure must be raised to at least 25 Pa to get the most accurate measurement.

Today's test indicates a leakage rate of 2350 cfm, but at only at a pressure of 3 Pa. The fan is unable to raise the pressure above 3 Pa.  In other words, the system is very leaky. 2350 cfm of air is being lost through leaks within the home's ductwork system.  Unfortunately, these results are more the norm than atypical.

Infrared camera KT-384
made by Sonel
Source 

Part 2 - Pressurized Ducts & House Test

Next, the ducts are pressurized at the same time the blower door fan pressurizes the house.  This requires reversing the fan direction so that air is blown into the house. The pressure within both is equalized and a gauge at the blower door fan measures the difference between the two fan rates.  The difference is converted to the rate of air leaking from ducts outside the thermal envelop.  In other words, this test measures the rate of air being leaked from ducts within unheated spaces like attics and crawl spaces.

Today's test indicates 186 cfm of air is being leaked through ducts that are located out side the thermal envelop.

Thermogram of two buildings.
Darker colors indicate
 cooler temperatures.
Source

Part 3 - Direct Measurement of Supply Register Pressure

The final test again pressurizes the supply duct system and pressurizes the entire house using the blower door fan.  In this test, however,  the difference in pressure between the blower door fan and the pressure taken at various supply registers throughout the house is compared.  For a good duct system, the differences will never be more than 2 Pa.

Today's home performs well.  The pressure difference at two 1st floor supply registers is measured at no more than 0.8 Pa.

Foam used to seal air infiltration
points at the rim board

Identifying Leakage Points

During the performance of the blower door test, a thermal imaging infrared camera is used to locate areas of air leakage. Pointing the device at surfaces within the home, the camera measures surface temperature differences.  On a cold winter day, where outside temperatures are hovering around 20 degrees and indoor temperatures are around 68 degrees, the camera reveals temperatures below 68 degrees in varying gradations of dark colors.  The darker the color, the colder the surface.  The colder the surface, the more likely the location is a source of cold air leakage.

Poorly sealed fireplace doors were a
 major source of air infiltration

Today's test reveals the fireplace doors, doors to an attached sun room and the headers over basement glass block windows as the greatest source of leakage.

Conclusion

With the ultimate goal of improving home energy efficiency, improving homeowner comfort and reducing homeowner utility bills,  more and more homes are going to be tested for air and duct leakage. Homeowners will expect architects to use tests as described above to push contractors to raise their own standards.  And let's be clear, the savings that can be achieved by a homeowner are significant.  And the same way buyers use MPG (miles per gallon) to gauge the fuel efficiency of cars, HERS ratings will begin to educate home buyers on home energy performance.

American Radiator & Standard Sanitary Corp.

I discovered this original cast iron boiler in the basement of an historic Detroit home.  Curious about how it operated, I did a little research.

Boiler systems operate simply:

1. A fuel like natural gas or oil is mixed with air and ignited inside the boiler.  (This boiler probably was fueled by coal and later converted to natural gas).

2. The water circulating through the boiler's heat exchanger is heated by the flame and combustion gases.

3. The heated water is circulated to radiators which heat the house.

Photo Credit



In order to maximize efficiency, the correct air and fuel mixture must be found.  In other words, finding the correct ratio between the amount of air and fuel added to the boiler will maximize the amount of heat transferred to the water. Three gases are generated during combustion: Carbon Dioxide (CO2), Carbon Monoxide (CO) and Oxygen (O2). Too much air generates unburned oxygen, which will carry heat up the chimney. Too little air means incomplete combustion which generates poisonous CO gas and soot (which will clog the heat exchanger). The correct ratio will transfer all the combustion heat to the water and generate only CO2.

Modern boilers are rated by their annual fuel utilization efficiency (AFUE).  In Michigan, code requires all boilers to have a minimum AFUE of 90%.  The above boiler's efficiency was probably between 56% and 70%.

Imprinted on the door of the boiler are the words "American Radiator and Standard Sanitary Company ".  Per the brief history recounted below, this dates the boiler to at least 1967 when the company renamed itself "American Standard", but my guess is that it is probably much older.

 Planning your home for health and comfort with American Standard heating equipment and plumbing fixtures. (1950)
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Brief History of American Radiator and Standard Sanitary (ARSS)

The history of ARSS begins in 1886 when Clarence Mott Woolley and his partner formed the Michigan Radiator & Iron Company of Detroit.  They would become makers of cast iron (rather than the more expensive steel) radiators.  The business immediately took off, introducing the world to radiant heat.  In 1891 the company merged with two other leading manufacturers of cast iron radiators, the Detroit Radiator Company and the Pierce Steam Heating Company of Buffalo, New York.  Woolley was only 28.

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The Ideal fitter : American Radiators & Ideal boilers (1910)
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The company would weather the economic depression of the 1890s by expanding into European markets.  By the 1920s, 40% of its revenue was generated overseas.  After World War I, Woolley hired architects John Howells and Raymond Hood to design and oversee the construction of his new world headquarters which still towers over Manhattan.

American Radiator Building - NYC 2012
Jean-Christophe Benoist

By 1929, Woolley planned a merger of the four largest building products corporation in the US: --H.W. Johns-Manville, Otis Elevator, Standard Sanitary, and American Radiator.  He was only able to complete a merger with Standard Sanitary, the nation's leading supplier of plumbing products.  Hence the name American Radiator and Standard Sanitary was born.

During the Great Depression, the company's sales were challenged by new forced-air heating technology.  The company met additional challenges as World War II cut into its European profits and new "direct-to-you" stores sold products directly to the consumer.  But the storms were weathered aided by a building boom that began after World War II.

Planning your home for health and comfort with
American-Standard heating equipment and plumbing fixtures. (1950) (pgs. 26-27)
Source

But the company's survival also meant diversification into new markets such as industrial controls, plastics, heat-transfer equipment, and nuclear reactor construction.   To reflect this, the company changed its name in 1967 to "American Standard".

By the 1970s, the company was now moving away from its original heating business concentrating more on its railroad, truck brake, and mining equipment operations.

 First step to better plumbing and heating for your home. (1947)
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Finally during the 1980s, the company returned to its plumbing and air conditioning roots by selling off most of its unrelated businesses.  In 1983, it completed a merger with the Trane Company the largest commercial air conditioning products company in the United States.

In 2007, American Standard announced plans to break up its three divisions – plumbing, air conditioning and automotive products – keeping only The Trane Company. American Standard’s plumbing products – and its name – were sold to Bain Capital Partners, LLC, and the original American Standard changed its name to Trane. Later that year, Ingersoll-Rand Company Limited acquired Trane for $10.1 billion.

Quite amazing roots for a small Detroit radiator company that began in 1880s.

 

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Source: History of American Standard at Funding Universe