Insert pellet stove in existing fireplace: how does it work?

Why convert your open fireplace?

An open fireplace provides ambience, not heating. Most of the heat literally escapes through the chimney. An open fireplace has an efficiency of barely 10 to 15%. This means 85 to 90% of the energy in your wood logs escapes outside via the flue. Worse still: an open fireplace pulls warm room air up the chimney, causing your home to net cool down instead of warm up.

An insert pellet stove turns this around completely. With an efficiency of over 85%, most of the heat stays inside your home. The stove feeds automatically, ignites itself, and regulates the temperature via a thermostat. You keep the cosy atmosphere of a real fire, but gain effective home heating.

Is your open fireplace suitable for an insert stove?

Not every open fireplace is suitable right away. Here are the three key criteria:

1. Dimensions of the fireplace opening

Most insert pellet stoves require an opening of at least 55-60 cm wide and 50-55 cm high. Compact models may require slightly less. Measure the inside dimensions of your fireplace opening, not the external mantelpiece.

2. Chimney condition

The existing chimney must be structurally sound: no severe cracks, major damp penetration, or risk of collapse. The chimney interior does not need to be perfect, as it will be lined with a stainless steel pipe, but the structure must be stable.

3. Flue height

The flue, from stove to roof outlet, must be at least 4 metres long for adequate draught. This can be an issue in bungalows or properties with low chimneys.

Step-by-step conversion process

• Step 1: measurement: DK Works measures the fireplace opening, checks the chimney, and assesses possibilities
• Step 2: choosing the model: based on dimensions, required output, and your aesthetic preference
• Step 3: lining the chimney: a flexible stainless steel flue pipe of 80 or 100 mm is pulled through the existing chimney shaft
• Step 4: installing the insert: the stove is positioned inside the niche with proper ventilation gaps
• Step 5: finishing: fireproof insulation surrounding it, optionally adding a new surround or trim frame
• Step 6: commissioning and demo: tuning, initial burn, and instructions on operation and daily maintenance

Important considerations for conversion

• Ventilation around the insert: openings above and below the stove are required for air circulation. Without air flow, the stove will overheat
• Fireproof lining: rear and side walls of the niche must be protected if made from combustible materials
• Electrical connection: a grounded power socket must be accessible behind or next to the stove
• External air intake: strongly advised or mandatory in airtight homes
• Removing existing damper: the fireplace damper valve must be removed or fixed permanently open

What does conversion cost?

Converting an open fireplace to an insert pellet stove costs between €3,100 and €6,500 on average, including stove, chimney lining, and installation. Excluding the stove itself: €1,100 to €2,000 for complete installation.

For a detailed price breakdown, read our article on insert pellet stove prices.

Fireplace conversions across Limburg and Flemish Brabant

DK Works has extensive experience converting open fireplaces into pellet stoves across Limburg, Flemish Brabant, and the Kempen region. From traditional fireplaces to modern gas fire conversions, we offer reliable solutions.

Want to convert your fireplace? Call +32 484 90 69 58, we will visit for a free suitability check.