Why is blower door and duct tightness testing important

Blower doors and duct blasters are basically just smart fans that know how much air is passing through them at any given pressure.  In the case of the duct leakage test, when you seal off all of the duct registers, you can then pressurize the entire system with the duct blaster.  (Don't worry, we're not going to "blast" your ductwork apart.  The pressure we test at is designed to mimic the natural pressures inside the ductwork when the unit is on.)  The duct blaster helps us maintain a constant pressure in the system.  As air leaks out of the system through the unknown holes, new air must be introduced to maintain that same pressure.  That's where the fancy gauges and hoses come into play.  They know exactly how much air is being introduced into the system to maintain that pressure, which is a direct indication of how much duct leakage there is. 

Similarly, when all windows, doors, and known sources of leaks in the home are closed, the blower door can then pressurize or depressurize the home and help us to know how much hidden leakage there is.

It's important to know how much duct leakage and building envelope leakage there is because they can be two of the biggest energy wasters in the home.  They can also have a significant impact on comfort and indoor air quality.  When air leaks uncontrollably through your home, it often comes from areas you don't want it to, like your attic or crawlspace.  This air has the potential to carry pollen, dust, mold spores, humidity, pests, insulation fibers and other contaminants into the home, which we don't want.


Most often noticed areas of air leakage in the home are around windows and doors.  While these areas are important, they are often not as important as the hidden leaks that are constantly robbing your home of its conditioned air.  Energy Star states that the average house has over a half a mile of hidden gaps and cracks.  Hidden air leaks in the home are often due to the nature of the construction process.  Electrical, Plumbing, and HVAC contractors drill through and cut everything in their way and often these holes don't get sealed.

Framing lumber is also extremely rough and doesn't naturally seal well to drywall, plywood, or the foundation. Many recessed lights leak significant amounts of air.  Large holes under bathtubs, you name it, there's a gap.  These gaps begin to work together to create a chimney effect that works on its own 24 hours a day.  In fact, if you added up all the holes in a typical house, it would equate to leaving a large window open all of the time!  I have seen more than my share of homes that would equate to a large garage door open all the time! 

Duct leakage is important obviously because it blows the air you've just paid to be conditioned directly outside.  This means the room the air was intended for gets uncomfortable, and the unit has to run longer.  While this is horrible enough alone, that's only the supply (pressurized) side of the system.  When the return side of the system leaks, this sucks in air wherever the leak happens to be.  Most of the houses in the Charleston area we work on every day have ductwork in the attic or the crawlspace.  Often times, this air gets a free pass by coming into the system after the air filter and then gets evenly distributed throughout the home (after it clogs your coil, of course).  How's that for indoor air quality?

By now it's pretty obvious why these leaks are important and must be dealt with if we want our homes to be more comfortable, healthy, and efficient.  They also begin to tell the story of the "house as a whole".  In the world of building science and energy efficiency, these leaks are still just small pieces to a much larger puzzle of the home's overall performance.

Blower door and duct blaster testing are just two of the many important tools we utilize in our comprehensive whole house assessments.  At High Performance Homes, we have the experience, training, and passion to help you get the most out of your home.  To learn more about our assessment process, click here.


Josh can be reached at (843) 509-7577

High Performance Home Shines Again!

Here we go again with the severe weather. This blog wasn't meant to be about severe weather and my home, but I can't resist talking about what we just went through.

Shortly after my first blog post, we had an ice/snow storm that hit the Charleston area and shut down all local bridges making travel impossible.  Other than traffic problems, the storm was pretty much a non issue.  Exactly two weeks after that storm, we got a much worse ice storm that brought most of South Carolina to its knees.  Not only was this ice storm a nightmare for travel, it was very hard on the trees and the power grid. Over 350,000 South Carolinians were without power at the peak of the outage, with over 100,000 still without power 5 days later.



My house lost power about 8 am Wednesday morning and with temperatures in the low 30's and the large amount of ice in the trees, I knew the damage was just getting started.  So midday Wednesday, I decided to get my generator up and running, since everyone in my family (spread out all over the Charleston area) was without power as well.

Now was the time for a true test on my home and how it would perform.  Once the generator was setup and running it was around 5 pm. The first indication things were going to go pretty well was that the interior temp of my home had only dropped to 66 over the course of almost 9 hours!  I got the fridge and some lights on first and then got a small space heater running in the living room.  Within an hour, the temperature in the house had actually climbed to 69!  (no, we didn't close off the living room and light a fire either)  The coolest part is the heat traveled throughout the home instead of instantly vanishing like it would have if I hadn't sealed and insulated it so well.  It warmed up so nicely inside that I shut the generator off and went to bed in full confidence that my family and I would stay comfortable overnight.  When I got up in the morning it was back to 66, so I repeated the process and quickly warmed the house back up.  Even I was surprised at how well the house did!

A drafty, poorly insulated home could never have been able to perform this well.  So even though we were on limited power with only one space heater, we were able to be comfortable throughout the home, rather than huddled in one room, like many I know had to do. 

This is why everyone needs a high performance home!

The power was finally restored to my home late Friday evening.  I know that I am very fortunate that I had a generator and a comfortable home when so many others suffered.  I know that as I write this Sunday night there are still many without power.  Luckily it has warmed up significantly and the ice is gone.

Record breaking cold and energy demand

We're a few days into 2014 and are now getting the coldest air we have seen in Charleston in decades.  That is great news for the electric companies, but not at all for us.  It turns out that it actually didn't work out so well for the power companies either. 

The record setting electric demand was so high that SCE&G had to phase in rolling blackouts throughout the state. The map below shows over 18,000 outages in the Charleston area alone with a total of over 51,000 throughout the state. 

I was downtown when the power went out and it was out for over two hours with lots of traffic lights out.  Some kids even went to school on a three hour delay, only to find the school didn't have any power when they got there!

One day prior to the big drop in temperatures, the utility companies asked us to unplug unnecessary appliances and conserve as much as possible.  While that may have helped some, the biggest draw of power was obviously for heat.  With the vast array of homes that I've seen that are so drafty and poorly insulated, I'm not surprised at all that the system got overloaded.  I know that even with the power on and the heat running constantly, some homes still were not comfortable!  We don't have to put up with homes like these where we are hostage to extreme weather.  This type of weather only amplifies the inefficiencies that go on every day in our homes that we ignore.  There are so many things that can be done to reduce our utility use, starting right at home.

A well sealed and insulated home keeps the temperature for much longer, reducing heating and cooling bills and increasing comfort significantly.  Weather like this allows a high performance home to really shine.  While the temperature in many homes dropped significantly in that 2-3 hour window, my home may have dropped 2 or 3 degrees.

My home has undergone the High Performance Homes treatment that millions of homes throughout the country need.  It has been very well insulated, the drafts have been virtually eliminated, and the heating and cooling system was properly designed and installed, among many other things.  If only we all had homes like this, I bet this blackout wouldn't have happened.