The right chimney enhances the safety and performance of your high efficiency fireplace
Air cooled chimneys were designed for open wood burning fireplaces. Since open fireplaces produce very little heat, air cooled chimneys are not required to undergo severe chimney fire testing. These chimneys have no insulation; they stay cool by circulating cold air past the inner flue. As a result, the flue is colder than with an insulated chimney resulting in reduced draft and a greater chance of creosote formation. They are used on most entry level “builder box” fireplaces so they are usually constructed of the cheapest materials UL Standards allow.
Insulated chimneys were designed for wood stoves. Stoves can produce high flue gas temperatures and large amounts of creosote which can cause chimney fires. Stove chimneys are certified to much tougher safety standards which require the chimney system to withstand repeated 2100°F chimney fires. They utilize high temperature insulation and superior stainless steel making them much more expensive to build. They warm up quickly and are less likely to accumulate creosote.
High efficiency fireplaces are wood stoves with cabinets around them to keep the outside of the cabinet cool and circulate the stove’s heat into the room. They warm up faster, draw better and form less creosote when they are installed with an insulated chimney..
Insulated chimneys are far superior in cold climates. Air cooled chimneys circulate air past the flue continuously so in cold weather the chimney is very cold, which can cause condensation to form when the fireplace isn’t burning. This condensation can trickle down the system gathering on top of the fireplace. Air cooled chimneys were never designed for extreme temperatures. But don’t take our word for it. Here is what one of our competitors, a manufacturer of both systems, warns about air cooled chimneys:
“In areas where winter temperatures are normally below freezing, the air cooled chimney may produce condensation. This condensation may corrode the top of the fireplace and is not covered under warranty. For optimum performance of your fireplace, (we) recommend the use of a (packed chimney)...”