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

Value

Units

Ductwork R Value

4.7

ft2??F?h/BTU

Ductwork Leakage Rate

0.15

Percent

Estimated Supply Ductwork Surface Area

1,440

Square Feet

New Unit Rating

15

SEER

Return Duct Surface Area

240

Square Feet

UA for Supply Duct

306

Btu/h-F

UA for Return Duct

51

Btu/h-F

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.

Thanks,
Brian Wiggins
(803)-521-4991