Fireplace ventilation grilles are an important and mandatory element of a fireplace heating system. Ventilation grilles draw in cold air and return warm air to the room. It is therefore essential to know how to install fireplace grilles correctly, how to calculate the size of the ventilation grilles and how to fit them in accordance with the requirements.
Here are 5 basic rules for installing fireplace ventilation grilles that will help you choose and fit grilles for a wood-burning fireplace correctly.
What are the rules for installing fireplace ventilation grilles?
1. The airflow entering the room should be directed towards the centre of the room.
2. The internal opening of a ventilation grille above the fireplace insert must face downwards, and that of a grille below the insert must face upwards. This ensures correct convection.
3. To fit a grille into the box, openings of the required size have to be cut. Bear in mind that the overall dimensions of the grille and the dimensions of the mounting opening differ. If a grille measures, for example, 17 × 17 cm, the real dimensions of the opening through which the air passes are 15.2 × 15.2 cm, and the free cross-sectional area is 231.04 cm² — not 289 cm².
4. To protect the ceiling from overheating, install a ventilation grille for cooling the decompression chamber about 40 cm below the ceiling. That is the zone with the highest temperatures.
5. Install grilles as far as possible from doors, and seal all gaps around the grille with an appropriate heat-resistant sealant to fix it in place.
How do you calculate the area of the ventilation grilles?
The number and size of grilles are not chosen by eye but calculated from the nominal output of the fireplace insert. The rule is:
- inlet grilles (through which cold air from the room enters the heat chamber) — at 50 cm² per 1 kW of the insert's nominal output. They are installed in the lower part of the heat chamber, below the insert;
- outlet grilles (through which heated air passes from the heat chamber into the heated room) — at 70 cm² per 1 kW of the insert's nominal output.
Important: this calculation refers specifically to the free (open) area of the grille — the area through which air actually passes — and not to its overall size. As rule 3 above shows, the difference between the overall size and the free cross-section is substantial, and if it is not taken into account there will be too few grilles and the insert will run in an overheating regime.
How many grilles are needed for a given output?
To save you the arithmetic, here are the ready figures for the most common insert outputs. The values are the total free area, which can be made up either by one large grille or by several smaller ones.
| Insert output (kW) | Inlet area (cm²) | Outlet area (cm²) |
|---|---|---|
| 8 | 400 | 560 |
| 10 | 500 | 700 |
| 12 | 600 | 840 |
| 15 | 750 | 1050 |
| 18 | 900 | 1260 |
| 20 | 1000 | 1400 |
Which SAVEN grilles are available?
The SAVEN catalogue has four lines of fireplace ventilation grilles. They differ in shape and installation method, so a solution can be found for practically any fireplace surround:
- CLASSIC — classic ventilation grilles, the familiar look for most fireplace surrounds;
- LOFT — straight grilles in the modern loft style, the widest choice of sizes;
- LOFT ANGLE — corner loft grilles, designed for corner fireplaces;
- HIDE — concealed grilles, almost invisible in the surround.
All the lines are gathered in the fireplace grilles section. For current sizes, colours, availability and prices please check with a manager or a representative in your region.
Grilles are always selected for a specific appliance, so it is worth starting with the insert — straight steel inserts, corner inserts or inserts with a guillotine door. How the box around them should be built is described in the article how to properly build a convection fireplace box.
SAVEN — European quality for safe warmth at home
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