How Much Firewood Does an 80–120 m² House Need for Winter?

Heating a home with firewood can often save money – but only if you plan the quantity needed for the entire winter heating season properly.

Many households are turning back to wood as a heating fuel. The reasons are clear: comparatively low costs, a pleasant indoor atmosphere and a degree of independence from oil and gas. However, one key question remains: how much firewood should you allow for a home measuring between 80 and 120 m², so that you are not left in the cold between November and March?

How much firewood does a house really need?

There is no single short answer, as consumption depends on several factors. Calculating solely by floor area can quickly lead to the wrong result. The most important considerations are:

• Living area: An 80 m² home requires considerably less wood than a 120 m² property – obvious perhaps, but frequently underestimated.
• Insulation: A well-insulated home retains heat, whereas a poorly insulated one effectively sends the firewood’s warmth straight out through the windows.
• Heating appliance: A modern wood-burning stove, an inset fire or an open fireplace can differ enormously in their fuel consumption.
• Location and winter severity: A mild lowland area or an exposed, windy hillside – the number of heating days can vary greatly.
• Wood type and quality: Hardwood supplies more energy per stacked cubic metre than softwood, while damp wood provides far less than dry wood.

“As a broad guide, many households in a well-insulated detached house of around 100 m² use 4 to 8 stacked cubic metres of firewood per heating season.”

With poor insulation or outdated equipment, this figure can easily rise to 10 to 15 stacked cubic metres, increasing the cost accordingly.

Stacked cubic metres, loose cubic metres and solid cubic metres: what do the terms mean?

Anyone ordering firewood soon encounters several different units. Three terms are particularly relevant:

• Stacked cubic metre (rm): Wood stacked, including air gaps, within dimensions of 1 × 1 metre and a length of 1 metre.
• Loose cubic metre (srm): Wood tipped loosely into a one-cubic-metre container; it contains less wood than a stacked cubic metre.
• Solid cubic metre (fm): The pure volume of timber without air gaps, a term used more commonly in forestry.

Many private buyers order stacked cubic metres or loose cubic metres. One loose cubic metre is equivalent to approximately 0.7 stacked cubic metres, depending on log length and sorting. When comparing offers, it is therefore essential to check exactly which unit is being quoted.

Firewood consumption by heating system: stove, inset fire or open fireplace?

The efficiency of the heating system determines how much of the energy stored in the wood actually reaches the room. The differences are substantial.

Modern wood-burning stove for 80–120 m²

A modern wood-burning stove with effective combustion technology achieves efficiencies of 75 per cent or more. For an averagely well-insulated home, the following is a realistic range:

• 80 m², well insulated: around 3 to 5 stacked cubic metres per season
• 100 m², well insulated: around 4 to 6 stacked cubic metres
• 120 m², well insulated: around 5 to 7 stacked cubic metres

If the stove is positioned centrally within the living area and doors can remain open, the heat can often spread through large parts of the home. In that case, the lower end of the range is often sufficient.

Inset fire or closed fireplace

Inset fires perform slightly less efficiently than modern stoves, but are significantly better than an open fireplace. For a 100 m² house with average insulation and an inset fire, you can expect to need around 6 to 9 stacked cubic metres. A well-insulated 80 m² home will often manage with 4 to 6, while a 120 m² property of older construction is more likely to require 8 to 10 stacked cubic metres.

Open fireplace – the firewood guzzler

An open fireplace may look romantic, but in energy terms it is a disaster. Most of the heat disappears directly up the chimney. For 100 m² of living space with moderate insulation, 12 to 15 stacked cubic metres of firewood is not unusual, and poorly insulated homes may need even more. As a main heating source for 80 to 120 m², an open fireplace would scarcely make sense.

“Anyone genuinely intending to heat with wood should consider a modern stove or an inset fire – it saves firewood, money and work.”

Insulation: the hidden way to use less firewood

Even the best heating system achieves little if the house cannot retain warmth. Insulation acts like an invisible firewood store: the better it is, the less often you need to refuel the stove. The following have a particularly strong impact on consumption:

• uninsulated lofts
• old, single-glazed or draughty windows
• uninsulated basement ceilings
• gaps around doors and roller-shutter boxes

Even modest improvements can noticeably reduce demand, such as draught-proofing strips around windows, insulating the basement ceiling or adding roof insulation later. Anyone who has renovated their home or lives in a newer building can get through winter using substantially less firewood – compared with an uninsulated older property, the requirement is often halved.

Which wood types are worthwhile for heating?

Not every log delivers the same amount of energy. Hardwoods are denser, burn more slowly and release more heat. Particularly popular choices include:

• Beech: very high calorific value, an even flame and ideal for continuous use.
• Oak: also has a high calorific value and burns for a long time, but requires a well-adjusted stove because it produces plenty of embers.
• Ash and hornbeam: similarly powerful, often somewhat more expensive but efficient.

Softwood such as spruce or pine catches fire quickly and is well suited to lighting the fire, but burns away faster. Those relying mainly on softwood need more stacked cubic metres to meet the same heating demand than they would with hardwood.

“Dry hardwood with less than 20 per cent residual moisture offers the best combination of heating performance, clean combustion and low consumption.”

Proper storage: keeping firewood genuinely dry

Wood left in the rain or placed directly on the ground loses a large proportion of its potential. A few simple rules apply to an efficient winter supply:

• Stack wood loosely enough for air to circulate.
• Store it off the ground on pallets or timber battens.
• Protect it from rain above, but leave the sides as open as possible so that wind can pass through.
• Allow the wood to dry for at least one to two years, depending on the species and split size.

A moisture meter costs only a few pounds, yet prevents partially dried wood from ending up in the stove. Anyone who regularly burns damp wood needs considerably more material, creates a great deal of smoke and risks deposits building up in the chimney.

Practical examples for 80, 100 and 120 m²

To make the range easier to understand, here are several typical scenarios with realistic estimates:

Living area and condition	Heating system	Estimated requirement per winter
80 m², well-insulated flat	modern wood-burning stove	3–5 stacked cubic metres
100 m², detached house, average insulation	inset fire	6–9 stacked cubic metres
120 m², older property, poor insulation	open fireplace	10–15 stacked cubic metres
120 m², well-insulated house	high-output wood-burning stove	5–7 stacked cubic metres

These examples show that the same floor area can consume twice as much firewood, or half as much, depending on the technology and insulation.

Planning before winter: how to calculate your firewood supply

Anyone new to heating with wood will almost always misjudge their needs slightly in the first winter. A rough calculation can reduce the risk:

1. Establish the living area, for example 100 m².
2. Assess the insulation standard: good, average or poor.
3. Categorise the heating appliance: modern stove, inset fire or open fireplace.
4. Choose a mid-range figure from the ranges given above.
5. Include a safety margin of 20 to 30 per cent.

If, after the first winter, some of the wood remains unused, you will have a buffer for the following year – leftover seasoned wood generally improves rather than deteriorates over time.

Health, comfort and costs: other points households should consider

Wood-fired heating creates a homely atmosphere, but it also comes with responsibility. An undersized stove is constantly operated at its limit, while an oversized model often runs at a smouldering level. Both can harm the appliance, the chimney and air quality. Specialist installers can calculate the appropriate output for the floor area and level of insulation, while chimney sweeps can also advise on fireplace safety.

Those who use firewood wisely generally combine several measures: better insulation, modern technology, careful storage and a realistic understanding of their own heating habits. This keeps the living room warm and firewood consumption manageable – while making the next winter far less daunting.