External air-enabled fireplace insert

Sealed, external combustion air (room-sealed) fireplace insert

The modern fireplace inserts manufactured by us are sealed, external combustion air designs capable of providing 99% of the air required for combustion from an outdoor air source. They cannot be classified as room-sealed because they do not comply with the German DIN-18897-1/2005 standard. This standard specifies the criteria for room-sealed qualification: when testing the tightness of heating appliances, it determines tightness after 6000 openings/closings of the firebox door and 1000 of the ash door, measured at a pressure difference of 8 Pa. They must maintain this pressure difference for 48 hours.

An external air fireplace insert refers to an appliance that delivers combustion air into the firebox through a duct intended for fresh air supply, but the firebox itself is not necessarily pressure-independent—meaning it is not required to receive combustion air exclusively from the air duct.

A room-sealed appliance functions independently of the room’s air pressure. In other words, 100% of the incoming air is drawn from outside, and the combustion chamber itself (as well as the connecting flue pipe components) are independent of the prevailing pressure in the room, making them pressure-tight.

In accordance with standard requirements, we need to replenish the volume of air consumed; however, we are not obligated to use an external air or room-sealed fireplace.

Our experience with the certification of room-sealed fireplace inserts

Based on our experience and knowledge to date, in recent years the majority of space heating appliances—especially fireplace fireboxes—require external combustion air. Builders often speculatively, without technical documentation and at great expense, construct ducts for external combustion air intake, erect modern chimneys, and purchase costlier fireplace inserts designed for external air. Yet after installation, they face the reality that these appliances cannot be certified as room-sealed during technical acceptance. Then comes the surprise: additional wall-penetrating air inlets and other equipment meeting safety regulations become necessary to operate the system legally.

The main problem is that these appliances (the components of the complete combustion circuit) do not satisfy the strict criteria of the aforementioned DIN 18897-1/2005 standard. In such cases, the high-cost investment assumed to be safe appears to have been in vain. However, if there existed a third category alongside room-sealed and open-combustion appliances—one supplied with external combustion air but operating with only minimal air demand from the internal space—retrospective installations and investments, along with their associated costs, would become unnecessary. In Austria, this is inventively referred to as room-air independent appliances.

Unfortunately, many domestic fireplace distributors and foreign manufacturers loosely label their fireboxes as room-sealed, even though they do not meet the criteria mentioned above. In addition to the manufacturer’s rating, it is worth requesting the internationally accredited certification issued by TÜV to ensure you purchase an appliance that meets your expectations.

When buying a fireplace insert, you can face a major dilemma if you do not inform yourself properly beforehand. Nowadays, the advantages of the internet make this easier and faster, but if we are not thorough, we can easily consider information valuable and constructive when it may not come from a reliable source.

One such issue regarding fireplace inserts is combustion air supply. The increasingly strict requirements set by regulations in this area require careful attention during the design and construction of your fireplace.

Our modern room-sealed (external air) corner fireplace inserts feature front and side glass panels fitted flush against each other. Along the line of jointing, the system is not 100% airtight. Due to the continuous draft effect of the chimney, the negative pressure formed in the firebox prevents flue gas backflow.

Fireplace construction is the job of a qualified professional, as is the design and construction of the chimney. Circulating warm air, creating the convection casing, and selecting the correct materials all require attention and expertise. Without proper installation, not only can the performance of fireplaces be impaired, but warranty conditions may also be voided.

Request a quote online, or if you have any questions, reach out to us via one of our contact options.