Top-Sealing Damper Installation in Greater Burlington, Vermont
A traditional throat damper is metal resting on metal, and it never sealed well even when it was new. In a Vermont winter that means heated air leaving up the chimney continuously whenever there is no fire, and in summer it means humid outside air coming down the flue carrying the smell of old creosote into the room. A top-sealing damper addresses both. It mounts at the top of the flue with a rubber gasket and is operated by a stainless cable running down to the firebox, so when it is closed the flue is sealed, not approximately covered. It also functions as a cap, keeping rain and animals out. The cases where it is the wrong answer are worth knowing: a flue serving a gas appliance that must remain permanently open, and a fireplace whose real problem is a throat damper that will not open.
What a top-sealing dampers visit can cover
- Assessment of the existing throat damper and whether repair is viable
- Confirmation that the flue is not serving an appliance that needs it open
- Correctly sized top-sealing damper with a gasket seal
- Stainless operating cable run down to a firebox mount
- Installation on a sound crown, with crown condition assessed first
- The unit also functioning as a cap with an animal screen
- Demonstration of operation, and where the cable control sits
- A plain statement of what it does and does not fix
Reasons people book top-sealing dampers
- A throat damper that no longer seals, or never did
- A fireplace smell in warm humid weather when nothing is lit
- Cold air pouring down the chimney into the room in winter
- Heated air noticeably escaping up the flue when there is no fire
- A rusted or seized throat damper that cannot be repaired
- A missing chimney cap as well as a failing damper
- An open fireplace used occasionally in a house you heat expensively
- A flue you want sealed without giving up the fireplace entirely
What happens in top-sealing dampers, in order
- Tell us what the fireplace is used for, whether anything else vents into that flue, and what the current damper does.
- We confirm no appliance requires the flue to stay open, and assess the crown the unit will mount on.
- The damper is sized and fitted, with the cable run down to a control at the firebox.
- Operation is demonstrated. You are shown what it seals and what it does not.
What changes the quote for top-sealing dampers?
Prices come from the independent company that visits your property, because the work is quoted and carried out by that company. These are the variables that move the number, so you can read a quote correctly and compare two of them.
How chimney quotes are built, and what makes two comparable →If top-sealing dampers turns out not to be what you need, the full list of chimney and stove services sets out what separates each one, and the chimney problem pages work back to it from the symptom you can see.
- Flue size, which the damper is made to fit
- Number of flues in the stack if more than one is being sealed
- Roof access, height and pitch
- Crown condition, since the unit mounts on it
- Whether the existing throat damper is being removed or left in place
- Cable run length and the firebox mounting detail
- Whether a cap is being replaced by the same unit
- Whether crown repair has to happen first
Throat damper against top-sealing damper
Both close a flue. Only one of them seals it, and the difference shows up on a Vermont heating bill.
| Throat damper | Top-sealing damper | |
|---|---|---|
| Where it sits | In the fireplace throat | At the top of the flue |
| How it seals | Metal resting on metal | Rubber gasket |
| Sealing quality | Leaks even when new | A genuine seal |
| Heated air lost when closed | Continuous | Effectively none |
| Keeps rain out | No | Yes: it also acts as a cap |
| Keeps animals out | No | Yes, with the screen |
| Stops summer chimney smell | No | Yes |
| Operated from | The firebox | The firebox, by cable |
| Not suitable for | — | A flue that must stay open, e.g. a vented gas log set |
When top-sealing dampers is ordinarily booked
Year round, roof access permitting
What can be done in which season in Vermont →Common questions about questions about top-sealing dampers
What exactly are you installing?+
A damper mounted at the top of the flue with a rubber gasket, operated by a stainless cable running down to the firebox. Closed, it seals the flue instead of approximately covering it the way a throat damper does.
How much better does it seal?+
Substantially. A throat damper is metal on metal and leaks even when new and clean. A gasketed top damper is a seal. Over a Vermont winter the difference in conditioned air lost up an unused flue is real, not marginal.
Does it replace the chimney cap?+
It does the cap's job as well: it covers the flue opening and carries an animal screen. Part of why it makes sense on a chimney that needs a cap anyway, because you are buying one component instead of two.
Will it fix my summer fireplace smell?+
It addresses the airflow half of that problem, which is commonly most of it. The other half is the deposit producing the smell, so sweeping plus a top-sealing damper is the combination that broadly settles it for good.
Can I fit one to any fireplace?+
Almost any open fireplace with a sound crown to mount on. Where it is not appropriate is a flue serving an appliance that requires it to stay open: a vented gas log set being the clearest example.
What happens if I light a fire with it closed?+
The same as with any closed damper: smoke in the room. The cable control sits at the firebox precisely so it is obvious and to hand, and opening it becomes part of lighting a fire in the same way a throat damper was.
Does the old throat damper come out?+
Not necessarily. It can often be left in place, either operable or fixed open, and the top unit becomes the working damper. Where the throat damper is seized shut it does have to be dealt with, since you cannot vent a fire past it.
How long do they last?+
The metalwork is long-lived; the gasket is the wear item and it eventually hardens or compresses. A replaceable part instead of a reason to replace the unit, and it is checked at annual service along with everything else.
Is it worth it if I rarely use the fireplace?+
Frequently it is exactly then that it pays, because an unused fireplace with a leaking throat damper is losing conditioned air all year for no benefit at all. A rarely used fireplace is the strongest case for sealing it correctly.
Can it be operated from the roof?+
No, and it should not need to be. The cable runs down inside the flue to a mount in the firebox, so it is operated from the room like any damper. Nobody should be going on a roof to open a fireplace.
What if my crown is cracked?+
The crown gets dealt with first, because the damper mounts on it and because a cracked crown is letting water into the masonry regardless. Fitting a unit onto a failing crown means taking it off again later.
Does it help with downdraft?+
It stops downdraft entirely when closed, which is what solves the summer smell. It does not change how the fireplace draws when it is open. That is a draft diagnosis question about the flue, the chamber and house pressure.