In layman’s terms, what is a duct test?
A duct test is simply hooking up a specialized fan & checking to see how “leaky” your duct’s are.
How does one perform a duct test / what should I expect to see?
Using a calibrated fan & connector as shown above, we hook the fan up to your system, and we temporarily seal off all of remaining duct registers and grills on that system. Once this is done, we then turn on the fan (red & yellow box with the gauge) to pressurize the duct system. The fan slowly ramps up until we reach 25 pascals (PA) of pressure (assuming your system is not too leaky). Using the attached gauge, we can then read how many Cubic Feet of Air is required to maintain your system at that pressure. The less leaks, the lower amount of air is required.
Will this test hurt my ducts?
Not in the least, the 25 PA of pressure applied is equivalent to the pressure applied by your HVAC system when it is running.
Will this test void any warranties?
Not any manufacturer’s warranties
Why should I get my ducts tested?
If you have had a new system installed, a duct leakage test will show you that your contractor (or as a contractor a way of showing your customer) that the ducts were installed properly. It is also useful to determine where leaks are and what is required to seal them up properly.
Why are properly sealed ducts important?
- Tired of trying to cool or heat the outdoors, while you are left sweating or freezing inside your house? In many cases, that is exactly what is happening as that conditioned air that is supposed to be delivered inside the house is leaking outside. (for example, if you are losing 200 CFM of air conditioning, that is half a ton of air condition power lost)
- Most HVAC systems are designed to cool or raise the incoming air temperature by at least 20°. If you have leaks on the “return side,” some of that incoming “return air” could be 140° or zero based on the location of the leaks.
- Indoor Air Quality
- Always dusting – no matter what, one will never escape from dusting as we bring it in with us, or when we open up a door or window. With that said, if you have leaky ducts, &/or a leaky house, you will be pulling in that more dust & pollen
- What is that smell, I think something crawled in there & died…?
- Well, first off – if they were sealed up properly, one wouldn’t have to worry about that issue as nothing would be getting in
- Generally – it is not that something died in there, but the fact that the smell is being pulled into the house because of said air leakage (yes even with the system off)
- Besides those two main issues, you can also pull moisture, pollen, pests, and fumes into the home
- Money, Money, Money…
- By testing and improving the efficiency of the system, you’re equipment should last longer as it doesn’t have to work as hard
- While some companies love throwing numbers out there (10 to 40% savings) the fact is, that no one knows how much you can or will save without knowing how often the system is used & just how leaky it is
- As a reminder, a test or audit will not save you a cent unless you properly implement the recommendations given
Wasn’t this done already?
Probably not unless you have an ENERGY STAR, Earth Craft, MN GreenStar, LEED or other “green” certification that requires it. While there are numerous states & cities that are ahead of the curve, your house probably has not been tested unless it has had a new unit installed after the *regulation was enacted in those areas. *FYI: in some areas – it may only apply to new construction, not replacements
Why don’t the HVAC companies normally test them?
That is a good question, and generally, it comes down to five items.
- In many states & locals, they are not required to, even though it has been in the codebooks for a while.
- Many “green building” programs & inspectors require an independent third party to verify the work was done properly
- It takes money & time – just to address the upfront cost; the lowest price one can expect to pay for an entry-line Blower Door & Duct Tester is around $4,500. This does not include any training, supplies required, or the ongoing maintenance charges.
- They are not trained or certified on how to do it which also takes time & money.
- Then we get down to two that are closely related – No one else does, so why should I, followed up with famous “I have no idea what you are talking about”
How leaky is too leaky?
In a perfect world – no leakage is optimal, but that is basically, impossible to reach. The 2009 codes (minimum standards for many) require a maximum of 12% total leakage (8 outside) while the 2006 codes actually listed 10% (5). Other programs like ENERGY STAR® require a maximum of 6% (4), while other states & locations have set their own limits ranging from 6 to 10%. For those on the 2012 & 2015 codes, they are looking at a maximum of 4% which is very doable but requires one to pay attention & keep the runs as short as possible. (2009-2015 Duct Leakage Chart)
Where did this percentage come from & how does one arrive at it?
The IRC, RESNET, ENERGY STAR & others all come to this percentage using the same simple formula; the CFM of leakage divided by conditioned floor area served equals the leakage percentage. To find out what the allowable leakage is, you simply multiply the conditioned floor area by the percentage to get the maximum allowed leakage, or you can simply refer to this chart we created covering the various duct testing requirements.