Blower Door

Is anyone out there doing Blower Door Testing? Or Duct Testing? Does HI license qualify us in Florida to complete this type of inspection. I am wanting to add this into my inspections and would like your feedback.

What’s that?

Blower Door Tester is designed specifically to measure residential duct leakage. It can then be used to locate duct leaks and to measure the results of duct sealing. You can use them for both HVAC duct installs and the whole house (Blower Door system)in your Energy Aduits. Florida 2010 building code will mandate duct testing before they pass the installation of it on new and re-installs.

I address some of this on my site. You actually need a duct blaster, not a blower door, to measure duct leakage. A blower door with a pan test will help you locate … but not measure … duct leakage. Two different tools.

Thanks James. I am looking at Retrotec Q32 Duc-Tester Blower System for testing ducts after installs. What do you recommend? The Blower door was for the energy aduit use only. I just started looking into these systems and looking for advise on them. I appreciate the info.

James would be okay for me to call you with some question?


How do you test for air leakage to the “exterior” which is the only duct leak that really matters with a duct fan only?

Testing for air leakage and measuring air leakage is two separate and distinctly different things. You can “test” for duck leaks with a blower door using one of several methods, but you can only “measure” duct leakage with a duct blaster. Which are you referring to?

I disagree with your opinion that “the only duct leak that really matters” is a leak to the “exterior”. Duct leakage within the pressure boundary can result in unbalanced room pressures resulting in “hot” or “cold” rooms as well as other issues.

If you leak air into the house from the air duct system or you pull air into the return air system from the interior of the house, what is the difference then air discharging out of a supply register or air being drawn into the return register?

The interior pressure boundary is an open system in 99% of all HVAC designs. You cannot get a pressure differential when the air is leaking inside the open system from a duct that is located within that open system.

Let’s be clear; I am talking about small leaks. I’m not talking about totally detached air duct. Obviously if you have a totally detached duct leaking into another part of the interior of the house, you may not get enough air flow to other parts of the house where it’s needed. This is not what I’m talking about.

We are talking about “efficiency losses” not comfort conditions. Let’s try to stay on the same subject matter.

Besides hot or cold rooms, what are the other issues you are talking about?

Measuring … that is to say “quantifying” or assigning a percentage to … air leakage from a duct system is done through the use of a duct blaster and not a blower door.

As for your lack of concern as to air leaking inside of a house … I do not share it with you. Nor do I discount or separate comfort issues from efficiency issues since they are usually one in the same since person in an uncomfortable room is more likely to compensate by calling for more heat or cold through the HVAC system than to take other steps. Both need to be equally considered.

BTW, your example of a completely detached duct is a good one. A blower door test would not reveal it, if it were contained within the pressure boundary, where a duct blaster would.

Yes, very good!
A duct fan measures air leakage in a qualitative manner from the duct system.

So you’re trying to tell me that comfort issues are the same as efficiency issues therefore do not require consideration?

An improperly balanced HVAC system that does not leak but makes you uncomfortable is the same as a detached air duct leak discharging directly to the outdoors but you’re still comfortable in the house is the same thing?

No. Quite the opposite.

You are the one that introduced a distinction between them.

I consider them to be one in the same when conducting diagnostic testing. Uncomfortable people will usually use the thermostat to address their discomfort and use more energy than they would, otherwise.

What are you trying to diagnose? Comfort issues or efficiency issues?
Do you not realize that you can be uncomfortable and not have an efficiency issue?
Isn’t it important to know one from the other?

Do you not realize that uncomfortable people will often increase their heat or cold air by calling for more energy by adjusting the thermostat, add an energy consuming space heater, etc?

Diagnosis: is the ability to differentiate where the leakage is occurring, when and why.
Wouldn’t you agree that Adjusting your thermostat is a miniscule loss in comparison to the efficiency loss blowing out of the building envelope?
Increasing your thermostat causes heat loss through conductance. Mechanical air loss is the greatest efficiency loss there is. Not worrying about air leakage to the exterior is hard to ignore, is it not?

LOL. Who suggested “not worrying about air leakage to the exterior”?

The question posed by the author of the thread regarded the measurement of leakage through ducts. Your argument that “exterior” duct leakage is “all that really matters” is incorrect, in my opinion. Duct leakage needs to be addressed whether it leaks to the exterior or interior.

It seems to me that you are implying that only a duct blaster can be used to quantitatively determine air duct leakage.

If you are testing air duct for leaks, are you assuming that 100% of the air duct leakage should be considered a loss (a direct loss, not a loss due to someone changing their thermostat)?

Are you or are you not saying that quantifying the air duct leakage is not a major concern in your diagnosis?

Would you not agree that air leakage to the exterior from the air duct system is twice the efficiency loss of other efficiency concerns?

The volume of air (CFM) leaving the building envelope (is discharging conditioned air that you paid to condition) which must be replaced by unconditioned air from the exterior which must then be reconditioned by the HVAC system before the unit will reach its thermostat setpoint and turn off.

I am not implying anything.

I am stating … explicitly and for the record … that duct leaks cannot be “quantified” with a blower door test. They can only be “quantified” with a duct blaster.

I am also stating, not implying, that duct leaks can be problematic whether they are leaking to the interior or exterior. I will add, as previously stated, that comfort issues are often inseparable from efficiency issues since they are often addressed through the increased use of energy.

That is what I am saying. Not “implying”.

Would you prioritize one air duct leak type over another (considering some more accessible than others)?

Do you know how to quantify air duct leakage that is leaking to the exterior versus that which is leaking to the interior?

Or do you just not want to bother with that?