Chimney Services in Ewing, NJ

What the numbers suggest for chimneys in Ewing

Census estimates show 74% of Ewing's occupied homes heating with utility gas, 15% with electricity and 7% with fuel oil. Burning gas makes water vapor. DuraVent's technical guide on relining notes that gas-fired appliances produce a significant volume of moisture, and that efficient modern units leave little heat in the chimney to keep that moisture in vapor form.

Of Ewing's 14,908 housing units, 31% were built from 1940 to 1959, 29% from 1960 to 1979 and 12% before 1940. Masonry chimneys from those years were sized for the appliances of their day, which sent hotter exhaust up the flue than many current furnaces and water heaters. Our guide to chimney condensation explains the mechanism.

Detached houses make up 60% of units and buildings with five or more units 26%, and 16% of all housing was built in 2000 or later. These are township-wide estimates and tell you nothing certain about one chimney.

What condensation damage can look like

Condensation forms inside the flue, out of sight, so the evidence tends to surface somewhere else. The DuraVent guide lists signs such as wet spots, discolored plaster, peeling wallpaper, blistering paint and mildew on walls near the chimney; white efflorescence and spalling on the brick; and sand or small pieces of masonry collecting at the bottom of the flue.

In an article for ASTM Standardization News, reproduced on Rumford.com, Jim Buckley describes the chain of events: flue gases that enter the chimney just above their dew point cool below it, condense into water and acids, eat out mortar joints and soak the surrounding masonry, which repeated freezing then breaks down. The worst case he describes is a small, cool vent emptying into a much larger tile flue.

Several of those signs have other possible causes. A ceiling stain can come from failed flashing, and white staining can come from rain soaking the brick from outside. The guides on white staining and stains near the chimney cover those possibilities.

Confirming the cause and correcting it

Telling condensation apart from rain entry means looking at both ends of the chimney and the flue between them:

• At the base. The cleanout and the bottom of the flue, where debris from failing tile and mortar collects. Clearing it is part of furnace and boiler flue cleaning.
• Inside the flue. A camera scan, when the flue allows, shows eroded joints and flaking tile and where they are worst.
• At the top. Crown, cap and flashing, so that a rain leak is not mistaken for condensation, or the other way around. When the source is still unclear, controlled water testing on the outside helps rule rain in or out.

The usual correction is a flue matched to the appliance it serves. DuraVent describes a properly sized, insulated stainless steel liner as a way to keep flue gases warmer, reduce condensation and restore draft, and the appliance's installation instructions set the size. See chimney liners.

Local questions

Sources

1. U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates (tables B25034, B25040, B25024), via Census Reporter
2. DuraVent: Relining Chimneys for Gas Appliances (Ventinox technical guide L1039, PDF)
3. Jim Buckley: Gas Flues and Masonry Chimneys (ASTM Standardization News, 1995), via Rumford.com