Rectangular Metal Duct - Expected Service Life

[GuillaumeSavoie]

I'm having a hard time finding any definitive information regarding the expected service life of typical sheet metal ductwork. I'm looking at a 52 year old commercial building with original ductwork. It's all internal and serving an office environment with heating and cooling. Any clues?

Thanks in advance.

 

[IRstuff]

I don't get it. Why wouldn't the service life of ductwork not be comparable to or longer than the expected life of the building? There's no wear and tear, and if designed and operated correctly, there's no corrosion or fatigue.

TTFN

FAQ731-376

 

[MintJulep]

53 years.

 

[GuillaumeSavoie]

I'm writing up a mechanical systems condition evaluation and will be reporting on expected service life of all mechanical equipment. Seeing as how ductwork is included in what I consider to be mechanical systems, I want to let the owner know whether or not he'll have to budget to replace the ductwork in the near future.

 

[EnergyProfessional]

the duct itself lives forever if it doesn't corrode. but the owner should consider:
- it likely is leaky hence wasting energy and damaging the building (condensation etc.), not insulated --> does not provide comfort needed
- too small for proper ventilation, too much fan energy, too noisy
- likely has dirt/mold inside since 50 yeas ago they didn't have good filters.
- not routed for the zoning you wanted

Long story short, when you retrofit HVAC (i.e. install VAV boxes) you probably will replace it and the owner should budget for that.

 

[IRstuff]

"I'm writing up a mechanical systems condition evaluation"

Presumably, you're actually evaluating the condition of the ductwork, then. Does it look like it needs replacing? Ever?

TTFN

FAQ731-376

 

[KiwiMace]

Pressure test it as well, required in CA, required for sensible engineers. (Required at the point of recommissioning I might add - a tad late for the consultant). The duct might be fine, but all the sealant could be long gone.

 

[QualityTime]

I would agree....the ductwork will last "forever". In the old days the joints were never sealed and there was a lot of leakage. You may want to look at sealing the joints and replacing all of the canvas joints

 

[GuillaumeSavoie]

Thanks for the advice everyone. I will be making recommendations for the owner to have the system pressure tested and possibly tested for mold/bacteria.

 

[mauricestoker]

QualityTime,

Much of the old duct work is sealed very well. That is when you need to have asbestos sampling done on the sealant, mastic and lagging.

 

[sprinkler1000]

Most of the times, the sheet is in good shape, but the insulation is not, depending on the material used.
I have seen buildings with 50 years and the ducts are still in use.