How Many Cubic Metres of Firewood for an 80 to 120 m² House?

Preparing for winter and intending to heat with a wood-burning stove or range soon raises a practical question: how many stacked cubic metres of firewood should you buy to keep a detached house of around 80 to 120 m² reliably warm? The answer can vary considerably, depending on the property, appliance, wood species and location.

What really determines firewood consumption

Although finding the “right” amount of firewood sounds straightforward, in reality several variables are involved. Understanding them lets you estimate your needs fairly accurately and avoid costly buying mistakes.

• Floor area: A larger home has a greater volume of air to heat and higher heat losses.
• Insulation standard: A well-insulated property needs less heating, while a poorly insulated older house requires substantially more wood.
• Heating appliance and efficiency: A modern stove operates far more efficiently than an open fire.
• Local climate: In exposed, colder areas, the stove will need to run for longer and at a higher output than in milder locations.
• Wood species and quality: Hardwood provides more energy per log than softwood, while dry wood burns better than damp wood.
• How you use it: Using the stove as the main heating source consumes more wood than lighting it only in the evening “for a cosy atmosphere”.

For the same house, annual consumption can range from 4 to 12 stacked cubic metres, depending on insulation, climate and the type of stove.

How much wood does a stove actually need?

The key factor is the heating appliance’s efficiency: in other words, how much of the energy stored in the wood reaches the room instead of disappearing up the chimney.

Typical guide figures by appliance type

• Modern wood-burning stove (good efficiency, clean combustion): A typically insulated house of around 100 m² will usually need 4 to 6 stacked cubic metres each winter.
• Built-in fireplace / fireplace insert (with a closed glass door): For 100 m², expect closer to 6 to 8 stacked cubic metres.
• Open fireplace (very inefficient): The same area may require 12 to 15 stacked cubic metres, as a significant proportion of the heat escapes directly through the chimney.

For the common house size of 80 to 120 m², you can use the following broad range if wood is your primary heating fuel:

Floor area	Insulation standard	Heating appliance	Guide figure: stacked cubic metres per winter
80 m²	well insulated	modern stove	3–4
100 m²	average insulation	modern stove	4–6
100 m²	average insulation	built-in fireplace / insert	6–8
120 m²	average insulation	built-in fireplace / insert	7–9
80 m²	poorly insulated	open fireplace	10–12

These figures are intended as guidance only. Your requirements may be noticeably higher in areas with prolonged hard frosts, and considerably lower during mild winters.

Insulation: the most effective way to use less firewood

If you want to reduce wood consumption, look at the building envelope before focusing on the stove. Otherwise, some of the heat you have paid for will escape through the roof, windows and uninsulated walls.

• New windows and draught-proof doors reduce heat loss and cold draughts.
• Insulating the roof and top-floor ceiling often delivers the fastest results.
• Sealing common weak points, such as roller-shutter boxes, gaps and cellar ceilings, immediately saves heating energy.

A well-insulated 100 m² house can manage on 4–6 stacked cubic metres, whereas a poorly insulated older property of the same size can easily consume 8–12.

Even without undertaking major refurbishment work, noticeable improvements can be achieved with simple measures such as window sealing strips, curtains across external doors and closing shutters on cold nights.

Firewood is not all the same: choosing the right species

The wood species affects how much energy you obtain from each stacked cubic metre. Hardwood clearly outperforms softwood.

Recommended wood species for a stove

• Oak, beech, ash and hornbeam: These hardwoods have a high calorific value, produce long-lasting embers and are ideal for the base heating load in winter.
• Birch: It has a slightly lower calorific value, but burns very pleasantly with a calm flame.
• Spruce, fir and pine: These are softwoods that burn more quickly, making them well suited to lighting the fire or for milder periods of the year.

Residual moisture also has a major influence. Freshly felled wood can contain more than 40 per cent water and should not be put in the stove. A moisture content below 20 per cent is ideal.

Only dry wood heats efficiently: damp wood uses part of its energy to evaporate water and puts additional strain on the chimney.

Storing firewood correctly to keep it properly dry

To deliver its full heating output, firewood needs suitable storage for at least one to two years, depending on the species.

• Stack wood with good airflow rather than pressing it directly against a fully enclosed wall.
• Always place it on battens or pallets so that moisture cannot rise from the ground.
• Cover it from above, for example with a sheet that still allows air to circulate at the sides.
• Build stacks in a south- or west-facing position, where the wood will dry more quickly.

If space allows, many people keep a two-year supply. This provides enough reserve if winter proves colder than expected and gives the wood time to dry out completely.

Practical examples for homes with 80 to 120 m² of floor area

To put these figures into context, here are several typical scenarios for a winter in which heating is mainly provided by wood:

• Terraced house, 90 m², good insulation, modern stove: In an average winter, 4 to 5 stacked cubic metres of hardwood will often be sufficient.
• Detached house, 120 m², average insulation, fireplace insert: A realistic requirement is 7 to 9 stacked cubic metres, depending on how warm you want the rooms to be.
• Small house, 80 m², barely insulated, open fireplace: Allow for 10 to 12 stacked cubic metres if the fire is intended to heat the property rather than simply provide decoration.
• Well-refurbished older house, 150 m², high-output wood-burning stove: Despite the larger floor area, many households manage with 8 to 10 stacked cubic metres.

Stacked cubic metre, loose cubic metre and solid cubic metre: what suppliers mean

Different terms are used when purchasing wood, which can easily cause confusion. Knowing what they mean makes comparing prices easier.

• Stacked cubic metre (Raummeter, rm): 1 m³ of stacked wood including the air gaps between logs; the traditional measure for split logs.
• Loose cubic metre (Schüttraummeter, srm): Loosely tipped wood, for example delivered in a container. It contains more air and less wood than a stacked cubic metre.
• Solid cubic metre (Festmeter, fm): 1 m³ of pure timber without air gaps, a unit more commonly used in forestry.

As a rule of thumb, 1 stacked cubic metre is equivalent to approximately 0.7 solid cubic metres. When converting from loosely tipped to neatly stacked wood, it is best to ask the supplier specifically which definition they are using.

How to estimate your actual firewood requirement more accurately

If you are planning your first full heating season with wood, it is easy to buy too much or too little. A two-stage approach is useful: purchase a little generously in the first year, record your consumption, then buy more precisely in the second.

• Record how many stacked cubic metres are in storage at the start.
• Check how much remains once the heating season has ended.
• Keep track of temperatures and your personal heating habits (at home a lot? Preferred temperature of 22 rather than 20 degrees?).

Within one or two winters, this will give you a fairly accurate sense of how much wood your home actually “gets through”. Many households with a modern stove and standard insulation fall within 5 to 8 stacked cubic metres when heating 80 to 120 m² mainly with wood.

If you also run another heating system, such as gas, a heat pump or pellets, you can reduce your firewood requirement dramatically. In these mixed systems, one to three stacked cubic metres of wood are used more for comfort and covering peak demand than for the entire basic heat supply.