An older fireplace has no damper at all in its throat. What is the practical consequence?

A damper is the closure between a conditioned house and an open vertical shaft to the outdoors. With no damper at all, that shaft is permanently open, and stack effect drives continuous air movement through it: warm indoor air rises out in winter, and outdoor air, moisture and odour enter in other conditions. The energy cost is real and often surprisingly large, comparable to leaving a window open all year, but the inspector's finding is broader than energy — the opening also admits birds, insects and rain, and it undermines the pressure balance of the house, which matters where other atmospheric appliances depend on draft. The remedy is straightforward, with a throat damper or a top-sealing damper at the crown, so the report describes the condition, its consequence, and the available correction.

Without a damper the flue is a permanently open path between the house and the outdoors, so conditioned air escapes continuously and outside air, moisture and debris enter. It behaves like an open window that cannot be shut.

Fireplace dampers close the flue when the fireplace is not in use, limiting air exchange between the house and the outdoors. Options include traditional throat dampers and top-sealing dampers mounted at the crown, which also keep out rain and animals.

A Chimney Without a Damper Is a Window Stuck Open — one you cannot close, in the ceiling, all year.

Check whether a damper that exists actually closes and seals. A rusted-open or warped damper produces the same consequence as no damper at all and is more commonly found.

• •Excusing the absence as a characteristic of older fireplaces
• •Framing the finding as a legal restriction on use
• •Overlooking a damper that is present but no longer seals