Calculating The Correct Fireplace Size

The most effective and consistent method of comparing the heating capability of a selected fireplace is by looking at the nominal power in Kw of each fireplace. Every heating company uses a slightly different method of calculating the required heating for a specific area. At Sleeperwarehouse we have carefully selected 33 Watts/m³ as the working value of a room’s heating requirement, based on the fact that although South African winters are not nearly as cold as European winters, our homes are usually very poorly insulated and thus still get cold during winter.  If you wanted to select an appropriate size fireplace for your lounge with an open-plan kitchen and dining room, you would need to calculate the area of each of these rooms in m² and add them together. Then you would multiply that number by your ceiling’s height to obtain the total heated volume in m³. That would give you an indication of the power you require from your chosen fireplace to heat your room effectively.

For example:

Kitchen Area: 24m²

Dining Area: 13m²

Lounge Area: 42m²

Total area to be heated: 24 + 13+ 42 = 79m²

Total Volume to be heated: 79m² x 2.6m (height of ceiling) = 205.4m³

Total kW required: 205.4m³ x 33w/m³ = 6778.2 W (approximately 6 Kw)

Therefore, for this particular areas you would need at least an 6-10 kW fireplace. It is always advisable to purchase and install a larger Kw fireplace rather than smaller one, as you can always build a smaller fire in a large fireplace, but not visa-versa.