How Much Wood Do You Need to Heat 80–120 m² From November to March?

Heating your home with wood can often cut costs - but only if you plan a full winter’s supply properly.

More and more households are returning to wood as a heating fuel. The reasons are easy to understand: comparatively low running costs, a pleasant indoor feel, and a bit more independence from oil and gas. The key question, however, remains the same: how much wood should you set aside for a home of roughly 80–120 m² so that, from November through March, you do not suddenly find yourself short of heat?

How much wood does a house really need?

There is no single, simple figure, because consumption is driven by several variables. If you calculate purely by floor area, you can be wide of the mark. The biggest factors are usually:

• Floor area: 80 m² naturally needs far less wood than 120 m² - but the difference is often underestimated.
• Insulation: a well-insulated home retains warmth; a poorly insulated one effectively “burns the wood out of the window”.
• Heating appliance: a modern wood burner, a fireplace with an insert, or an open fireplace - the change in consumption between these can be huge.
• Region and winter severity: a mild Rhine Plain winter versus a windy upland location - the number of heating days can vary a lot.
• Wood species and quality: hardwood gives more energy per stacked cubic metre than softwood, and damp wood delivers far less than properly dry logs.

As a broad rule of thumb: for a well-insulated detached house of around 100 m², many households use 4 to 8 stacked cubic metres of wood per heating season.

With weak insulation or outdated equipment, that can quickly rise to 10 to 15 stacked cubic metres - and the cost rises with it.

Stacked cubic metre, loose cubic metre, ster: what do these terms mean?

Once you start ordering logs, you will immediately come across different units. In Germany, three terms are especially common:

• Stacked cubic metre (rm): logs stacked (including the air gaps) to a volume of 1 × 1 metre with a length of 1 metre.
• Loose cubic metre (srm): logs tipped loosely into a 1 m³ container - because of the voids, this contains less wood than a neatly stacked cubic metre.
• Solid cubic metre (fm): the pure wood volume with no air spaces, used more in forestry than household supply.

Most private customers order by stacked cubic metre or loose cubic metre. One loose cubic metre is roughly 0.7 stacked cubic metres, depending on log length and how uniformly the load is sorted. When comparing prices, it is essential to check which unit the supplier is quoting.

Consumption by heating technology: wood burner, insert or open fireplace?

How efficiently your appliance converts the energy in wood into usable room heat largely determines your overall consumption. The differences can be stark.

Modern wood burner for 80–120 m²

A modern wood burner with good combustion technology can achieve efficiencies of 75% and above. For a typical, reasonably well-insulated home, a realistic seasonal range is:

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

If the stove sits centrally in the living area and internal doors can be left open, heat often spreads across much of the home - and the lower end of the range is frequently enough.

Fireplace insert or closed fireplace

Inserts usually sit slightly below the best modern stoves, but they perform far better than an open fire. For a 100 m² home with average insulation and a fireplace insert, you can expect around 6–9 stacked cubic metres. At 80 m² with good insulation, 4–6 is often sufficient; at 120 m² in an older building, demand tends to move towards 8–10 stacked cubic metres.

Open fireplace - the wood guzzler

An open fireplace may look cosy, but from an energy perspective it is disastrous. Most of the heat disappears straight up the chimney. For 100 m² of living space with moderate insulation, 12–15 stacked cubic metres of wood is not unusual - and with poor insulation it can be even more. For 80–120 m², an open fireplace is rarely sensible as the main heating source.

Anyone who truly wants to heat with wood should consider a modern stove or a fireplace insert - it saves wood, money and effort.

Insulation: the hidden lever for using less wood

Even the best heating appliance cannot do much if the building cannot hold on to warmth. Insulation acts like an invisible wood reserve: the better it is, the less you need to top up the fire. The biggest consumption drivers include:

• uninsulated loft spaces
• old, single-glazed or draughty windows
• uninsulated basement/cellar ceilings
• gaps around doors and roller shutter boxes

Even modest improvements can cut demand noticeably - sealing strips on windows, insulating the cellar ceiling, or adding insulation to the roof afterwards. If your home has been refurbished or is a newer build, winter wood use can be significantly lower - often around half the requirement of an older property with no insulation.

Which wood species are worth using for heating

Not all logs contain the same usable energy. Hardwoods are denser, burn more slowly and release more heat. The most sought-after options include:

• Beech: very high calorific value, steady flame, ideal for longer burns.
• Oak: also high in energy and long-burning, but it needs a well-adjusted stove because it produces a lot of embers.
• Ash and hornbeam: similarly strong performers, sometimes slightly more expensive but efficient.

Softwoods such as spruce or pine catch easily and are useful for lighting the fire, but they burn through faster. If you rely mainly on softwood, you will need more stacked cubic metres to achieve the same heat output as with hardwood.

Dry hardwood with less than 20% residual moisture offers the best mix of heat output, clean combustion and low consumption.

Proper storage: how to keep your logs genuinely dry

Wood left in the rain or stored directly on the ground loses a large share of its potential. For an efficient winter supply, a few straightforward rules help:

• Stack logs so air can flow through - avoid packing them too tightly.
• Store off the ground on pallets or battens.
• Protect from rain above, while keeping the sides as open as possible so wind can pass through.
• Allow at least one to two years for drying, depending on species and how the logs are split.

A moisture meter costs only a few pounds, yet it helps prevent half-dry wood ending up in your stove. Heating continuously with damp logs means you need much more material, you create a lot of smoke, and you increase the risk of deposits building up in the chimney.

Practical examples for 80, 100 and 120 square metres

To make the range more tangible, here are a few common scenarios with realistic bands:

Floor area & condition	Heating technology	Estimated requirement per winter
80 m², well-insulated flat	modern wood burner	3–5 stacked cubic metres
100 m², detached house, average insulation	fireplace insert	6–9 stacked cubic metres
120 m², older house, poor insulation	open fireplace	10–15 stacked cubic metres
120 m², well-insulated home	high-output wood burner	5–7 stacked cubic metres

These examples underline the point: the same floor area can consume twice as much wood - or only half as much - depending on insulation and appliance choice.

Planning ahead of winter: how to calculate your supply

If you are new to heating with wood, you will almost always misjudge the first winter slightly. A rough approach can reduce the risk:

1. Note your floor area (for example, 100 m²).
2. Assess the insulation standard: good, average, poor.
3. Classify the appliance: modern stove, insert, open fireplace.
4. Choose a mid-point within the ranges above.
5. Add a safety margin of 20% to 30%.

If you discover after the first winter that some logs are left over, you have a buffer for the next season - and leftover, well-seasoned wood generally improves with time rather than deteriorating.

Health, comfort, costs: what else households should consider

Wood heating creates a homely atmosphere, but it also brings responsibility. A stove that is too small is often run at its limit, while an oversized appliance is frequently kept smouldering. Both are bad for the unit, the chimney and local air quality. Specialist installers can calculate the right heat output for your floor area and insulation level, and a chimney sweep can also advise on safe operation of the installation.

Those who use wood effectively tend to combine several elements: improved insulation, modern technology, careful storage and an honest view of their own heating habits. That way the living room stays warm, wood use remains manageable, and winter feels far less daunting.