📊 Firewood Heat Values – How to Choose the Most Efficient Fuel?
values of your firewood and the type of your heating appliance saves you money and helps
you avoid overheating your firebox.
🌲 Wood Species Heat Value Comparison Table (at 20% Moisture)
| Wood species | Energy content (kWh/kg) | Loose value (kWh/loose m³) | Stacked value (kWh/stacked m³) |
|---|---|---|---|
| 🌳 Birch | 4.15 | 1010 | 1700 |
| 💨 Aspen | 4.00 | 790 | 1330 |
| 🌲 Pine | 4.15 | 810 | 1360 |
| 🎄 Spruce | 4.10 | 790 | 1320 |
| 🍂 Alder | 4.05 | 740 | 1230 |
💡 Note: Per kilogram, the energy content of all wood species is nearly the same.
The difference lies in density – birch is denser and gives noticeably more
heat per cubic meter than alder.
🛠️ Heating Appliance Efficiency Determines Real Heat Output
Not all of the wood's energy content automatically becomes room heat.
The technical design of the heating appliance plays the decisive role:
- 🔥 Modern fireplace stove / masonry heater: Efficiency 80–85%. Stores heat in its
walls and releases it evenly over 24–48 hours. - 🍳 Classic stove or oven: Efficiency 50–70%. Needs regular firing, heats up fast but
also cools down fast. - 💨 Open fireplace (without glass doors): Efficiency < 30%. Most of the heat escapes
straight up the chimney; it mainly serves as an ambiance feature.
📐 Golden Rule: How Much Wood Can You Put in the Stove at Once?
To avoid overheating and damaging your firebox, use the mass-based heating formula:
1 kg of dry firewood per 100 kg of fireplace weight.
- 🧮 Example: Your masonry heater weighs 1500 kg.
- 📝 Calculation: 1500 / 100 = 15 kg of firewood per heating cycle.
- 💡 Split this amount into two loads (e.g. 9 kg for the initial lighting and 6 kg added
afterwards) to maintain an optimal burning temperature without damaging the firebox.
🪵 Practical Fireplace Heating Guidelines
To ensure efficient, clean combustion, follow a consistent heating routine:
- 🌡️ Pre-warming: Use only dry firewood. Bring logs indoors from outside or the shed
1–2 days before heating to reduce surface moisture. - 💨 Ensuring airflow: Fully open the flue damper and air regulators before lighting.
Remove the ash. - 📐 Correct stacking: Stack the firewood in the firebox with air gaps. At least 1/3
of the firebox must stay free at the top. - 🔝 Lighting: Place birch bark or an eco firelighter on top of the stack and always light
from the top. This ensures immediate, smoke-free combustion. - 🪵 Adding wood: Don't add logs one at a time. Add a new batch only once the previous
logs have nearly burned down and formed a stable bed of embers. - 🔒 Closing the damper: Close the flue damper only after the embers have fully
darkened and there is no more flame.
📦 Order High Heat Value Firewood From Tammaru Farm
We deliver precisely dried, clean, quality firewood. Choose birch for maximum heat
or alder for a steady fireplace fire.