Equest Duct Losses Question

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Hello everyone,

I have a question. I want to look at a scenario of energy consumption and costs for ductwork thermal and leakage losses outside the thermal envelope as compared to the ductwork being inside the thermal envelope. Below is the key information. I saw under the detailed data edit mode, the option to imput duct losses information under the air side tab. My understanding is that you can estimate a leakage rate based on the percentage of air lost in the duct system. Also, the thermal losses can be estimated either by the UA of the ductwork or the temperature difference between the supply temp and air distribution supply temp to the space. I opted to choose the UA option. Below is the information that I input.

Description of Value



Ductwork R Value



Ductwork Leakage Rate



Estimated Supply Ductwork Surface Area


Square Feet

New Unit Rating



Return Duct Surface Area


Square Feet

UA for Supply Duct



UA for Return Duct



Duct Zone

Roof Zone

There are a couple of things that I have noticed.

1) When I select a residential system (split system), the duct leakage option is grayed out under duct losses. Why is that?

2) When I change the information for the duct losses as shown, to 0 for the UA of the supply and return duct, and 0 for the leakage rate, I get the same values for the LS-D and LS-E reports for the MBTUs for the roof zone.
I am new to equest and any help you can give me will be greatly appreciated.

Brian Wiggins

Bigwiggz83's picture
Joined: 2017-05-29
Reputation: 0

Hi Brian,
Congrats on giving eQUEST a try! It runs quickly and has an extensive help library which helps make it easy to learn.

1. I'm not sure about duct losses in the residential systems. It might depend on which system type (RESVVT or RESYS) or DOE2.2/2.3 version you are using. My guess is that duct leakage options would be grayed out if the system type does not support some aspect of duct losses. The RESYS system is old and does not allow outside air for example.
2. The LS and other loads reports are based on the LOADS simulation which uses the building geometry and SPACE inputs. LOADS does not include ventilation requirements and does not depend on the specific system design. (I believe the loads reports will stay the same when you change system types and other system inputs.) You need to look at SYSTEM reports (SS-A, SS-F, SS-G etc.) for impacts of duct losses. This may have changed when running in DOE-2.3 mode but I'm not sure.
William Bishop, PE, BEMP, BEAP, CEM, LEED AP
Senior Energy Engineer

[Pathfinder-EA-logo-2]T: (585) 698-1956 F: (585) 325-6005
bbishop at pathfinder-ea.com www.pathfinder-ea.com
134 South Fitzhugh Street
Rochester, NY 14608 [cid:image005.png at 01D48723.9E03C7C0] Ask me why Carbon Fee & Dividend may be right for you.

Bill Bishop's picture
Joined: 2012-02-25
Reputation: 7

I believe the split-system residential assumes a ductless system. Condenser outside and fan coil unit wall/ceiling or floor mounted inside.

Christopher R Jones, P.Eng.
T+ 1 416-644-0252

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Jones, Christopher2's picture
Joined: 2017-10-12
Reputation: 0