Diagnostic Tools-Blower Doors

This week, I’m going to start a new category of subject matter to discuss, the tools I own and use when conducting energy audits, assessments and performing home diagnostic testing.  We are going to start with my number one diagnostic tool, the blower door.

My Minneapolis Blower Door being controlled by a laptop computer and Tectite software.

I purchased my first blower door in 2009, The Energy Conservatory’s (TEC) Minneapolis Blower Door Model 3 with a DG-700 digital manometer.  This blower door has tested hundreds of homes and has been a very reliable workhorse.  Other than periodically sending the DG-700 for calibration, the unit has not had any problems.  Recently, TEC has sent me their newest digital manometer, the DG-1000.  I will be discussing the DG-1000 in more depth later.

Retrotec’s model 5100 and DM32 manometer.

I’ve also received Retrotec’s Model 5100 blower door and DM32 manometer.  I’ve now had the opportunity to run the Retrotec about a dozen times.  Much like the Minneapolis Blower Door, the Retrotec is super easy and intuitive to use, again I’ll get into more details later.

The basics of the tool.  Both the TEC and Retrotec have the same basic parts and pieces.  An adjustable metal frame that fits tightly in a door or window, a cloth panel that fits over the frame with a hole to accommodate the fan.  A powerful fan capable of moving several thousand cubic feet per minute of air, and the brains of the equipment the digital manometer.  One small difference between the two companies, Retrotec’s fan speed control is built into the fan itself whereas TEC has a separate fan speed control.

Retrotec’s 5100 blower door kit with the DM32.

Assembling the equipment.  Some testers choose to leave their frames assembled, it speeds up the testing process.  In my case, I use my truck for many construction duties and leaving them assembled would take up too much space, so I leave them broke down and in the soft cases they came in.  Assembly takes a couple minutes, simply snap the corners of the frame together.  Retrotec’s frame is numbered, 1 snaps into 1, 2 snaps into 2 and so on.  TEC’s frame also snaps together, you just have to make sure you have all the cams facing in the same direction.  Both manufacturers use cams to easily tighten the frame into the opening.  I typically assemble the four corners and size it to fit the door or opening where I will be conducting the test.  Once the frame is assembled, the cloth panel can be installed.  There are a couple methods to fit the panel over the frame, the first is to lay the panel on the ground and set the frame on top.  You can then fold the panel to engage the Velcro straps that secure the panel to the frame.  Often on job sites, there isn’t much room on the floor to spread the panel and frame out.  I usually place the panel over the opened entry door where I will be testing, and set the assembled frame in front of it.  You can then adjust the panel to fit the frame.  A tip I got from Emily Mottram.

TEC’s frame and cams.
Retrotec’s frame with numbering system.
Panel and frame on floor method.
Emily Mottram’s panel over door method.

If you’re working with the TEC equipment, you’ll have to remember to setup your outside reference hose before installing the frame and panel, when you forget, you end up doing the crawl of shame.  You either have to take the frame out of the door or crawl through the opening for the fan to setup the hose.  I’ve crawled through the fan opening enough times that I rarely forget anymore.  The Retrotec panel I own is the SmartCloth which has the reference tubing stitched into the cloth panel.  Definitely saves time during setup.  I have had a discussion with TEC about using their equipment with the SmartCloth panel, they recommend not crossing the two manufacturer’s blower door parts and pieces.  They have experienced some pressure differences when using TEC equipment and the Retrotec SmartCloth panel.  They recommend keeping the two manufacturers equipment separate.

Retrotec’s Smartcloth reference tube sewn into the panel.

After the frame and panel is set, there are additional cross bars that will need to be installed in the frame to further stabilize the frame in the door or window opening.  The cross bar also helps support the fan.

Frame crossbar supporting the fan.

Now that the frame and panel is installed, along with the reference tube, the fan can be installed into the panel.  If installed correctly, the cloth panel will fit tightly around the fan with no large gaps or air holes.

Up to this point, with the exception of the Retrotec SmartCloth, both manufacturer’s equipment has the same basic setup.  We are now ready to hook up the manometers to the fan and outside reference tube, which is different between the manufacturers.  We’ll start with the Retrotec.  They have an umbilical cord that contains the hoses and communication cabling all in one bundle.  Everything is color coded and easy to assemble.  One end of the connections plug into the DM32 with the other end into the fan and integrated fan speed control and to the outside reference.  TEC’s system is a little different, they use an onboard tubing assistant built into their manometer, the DG-1000.  One piece of tubing goes to the fan, the other to the outside reference.  If you are using the DG-1000, laptop, tablet or smart phone to control the fan, there is a fan speed control cable that need to go between the fan speed control and DG-1000.  If you are just using the fan speed control to operate the fan, this cable is not needed.

The DG-1000 with tubing assistant.


DM32 with color coded umbilical cord and communication cable.

Both models have other cabling options, for instance if you are using a laptop computer to run the blower door, you can have a communication cable between the manometer and computer.  Both can also connect using WiFi and the DG-1000 can also connect using Bluetooth.  Either manufacturer’s blower door can be operated wirelessly using a tablet or phone.  Very handy when searching for air leaks.  Both manometers have built-in rechargeable batteries, and if you forget to charge them before a test, both manometers can be used while charging.

The fans manufactured by the two companies have some differences.  First, the listed CFM capacity of the Retrotec is 6400 CFM with the TEC having 6300 CFM capacity.  Another difference is how the two control flow rates.  When the fan speed becomes too slow during testing, we decrease the size of the opening of the fan so the fan speed increases.  The specific sized opening for the Retrotec is called a “range” and with TEC, it’s “rings”.  The tighter the structure, the smaller the hole(s) needed to maintain fan pressures.  If we feel the home is very leaky, we will remove all the ranges or rings to open the fan completely.  We can also close the fan off to the outside, this is done to determine the baseline or pressure difference between the inside and outside.  We can adjust the openings for the fan of either manufacturer to account for how tight the home is.

Retrotec’s “range plugs”. There is a specific order to which range plugs are removed depending on the tightness of the structure.


TEC’s “rings”, I own rings A through D. The D ring can test a structure down to 30 CFM of air leakage, very tight.

My intent with this blog is to simply talk about the equipment, not how to conduct a test.  But I do want to briefly touch on testing options.  About half the testing I conduct are code compliant tests.  This type of test will require me to submit a report to the builder, owner, and often a building official.  With code compliant testing, I will use software on a laptop, tablet or my phone to conduct the automated test.  I just need to fill in some info and the software does all the work.  If I’m testing to get a quick leakage rate, such as in the middle of a high performance build, I may choose to just conduct a quick single point test, which I can do manually with the fan speed control, or with software controlled by a computer or phone.  I could also perform a test using the software that comes on the DG-1000 and DM32.  Both manometers are capable of conducting a test.  The last type of testing I might need to conduct is one that we look for air leaks.  This will require the fan to be set at the appropriate pressure and operate on “cruise control” for a period of time.  Again, I could simply use the fan speed control, or the manometer, or laptop, tablet or phone.  Both manufacturer’s have many options on how to operate the equipment.

So, we’ve taken a quick look at the equipment.  I know I’m going to get asked the question, which manufacturer do I recommend?  Flip a coin, you won’t go wrong with either.

Retrotec Blower Door Test Equipment | Duct Testing Equipment

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