What to know
It starts with an assessment, not a quote
A price given before anyone has looked at your ductwork is a price list rather than a quote. How much of the system is reachable, what condition the connections are in, and whether anything is damaged rather than leaky all change the job substantially.
If somebody is willing to quote sealing over the phone, that is worth noticing.
What the work involves
Accessible joints, seams, collars and register boots are prepared and sealed, usually with a flexible mastic-type material that stays workable as the ductwork expands and contracts. Where a run is reachable only from inside, that changes the method and should be explained to you.
Expect people in the attic or crawl space, equipment in the house, and floors covered. Registers come off and go back.
The questions worth asking
- What portion of the system does this figure cover, in writing?
- What happens if you find a run that is damaged rather than leaking?
- Will the ducts be cleaned first, and how is that decided?
- Will I be shown my own ductwork before and after?
- Who is doing the work — you, or a subcontractor?
Order of work matters
It depends on the method, and the distinction is worth knowing before somebody sells you both. Sealing joints, seams, collars and boots from the outside does not close the system off — it stays just as cleanable through the registers and service openings afterwards, so cleaning is a separate decision on its own merits, not a prerequisite. Where the order genuinely matters is a method that coats or lines the inside of the duct, because that goes over whatever is already there and the surface has to be prepared for it. So ask which method is being proposed. If you are told the ducts must be cleaned before ordinary joint sealing, ask why, and expect a specific answer about your system rather than a general one.
When to say no
If nobody has looked. If the scope will not go in writing. If the answer to what happens when they find damage is vague. And if the conversation contains urgency that appeared there rather than in your house.
Where to start
Which of these applies to your system depends on how it was built and what shape it is in now, and that is not something a page can settle.
Our inspection is free. We will show you what we find, and if the answer is that your ductwork is sound and simply needs cleaning, that is what we will tell you.