The Complete Guide to Firewood: How Moisture, Wood Type, and Seasoning Determine Whether Your Fireplace Is Clean or Polluting

Most people assume the environmental impact of a wood fireplace comes down to the appliance. It doesn’t. The single biggest variable is the fuel — specifically, how dry it is. A certified, high-efficiency fireplace flue kit burning wet wood will pollute more than a basic unit burning properly seasoned timber.

This matters because the difference isn’t marginal. Wood at 20% moisture content burns hot and clean; wood at 40% moisture wastes roughly half its energy boiling off water instead of producing heat, while generating far more smoke, creosote, and fine particle pollution in the process.

If you heat with wood, understanding firewood is the highest-leverage thing you can do — for your heating costs, your flue’s health, and your local air quality. Here’s the complete breakdown.

Why Moisture Content Is Everything

When you burn wood, the fire has to evaporate all the water in the timber before the wood itself can combust efficiently. That evaporation consumes energy — energy that should be heating your home.

The Numbers

• Freshly cut (“green”) wood: 45–65% moisture content
• Partially seasoned: 25–35% moisture content
• Properly seasoned (target): 15–20% moisture content
• Kiln-dried: 10–15% moisture content

At 20% moisture, wood releases the large majority of its energy as usable heat. At 50% moisture, a significant portion of the fire’s energy is wasted evaporating water — which is why wet wood hisses, produces excessive smoke, and struggles to sustain a hot flame.

What Wet Wood Actually Costs You

Burning unseasoned wood causes a cascade of problems:

• Wasted heat — you burn more wood for less warmth, increasing fuel costs
• Excessive smoke — incomplete combustion releases PM2.5 fine particles, the pollutant most associated with respiratory harm
• Creosote buildup — unburnt volatiles condense in the flue as flammable tar, the leading cause of chimney fires
• Glass fouling — the door glass blackens quickly, a visible sign of a dirty burn
• More frequent flue cleaning — creosote accumulation means more maintenance and cost

The takeaway is simple: dry wood is cleaner, cheaper, safer, and more efficient. Everything else is secondary.

Choosing the Right Wood: Hardwood vs Softwood

Not all firewood is equal. The key distinction is density, which determines how long and how hot the wood burns.

Hardwoods (Preferred for Sustained Heat)

Hardwoods are denser, so they burn longer and produce more heat per log. They take longer to season but deliver superior overnight and sustained burns.

Common Australian hardwoods for firewood include:

• Red Gum — very high density, long burn, excellent heat output
• Ironbark — extremely dense, one of the longest-burning options
• Box (Grey/Yellow) — high heat, good coaling
• Jarrah (WA) — dense, long-burning, popular in the west

Softwoods (Faster, Cooler Burns)

Softwoods ignite easily and burn fast, making them useful for kindling and getting a fire established — but they burn out quickly and produce less sustained heat. Pine, for example, is fine for starting a fire but poor for maintaining one, and its higher resin content can contribute to creosote if burned unseasoned.

The Practical Approach

Use softwood kindling to establish a hot fire quickly, then transition to seasoned hardwood for sustained, efficient heat. This combination gives you a fast, clean start and a long, hot burn.

How to Season Firewood Properly

Seasoning is simply the process of drying wood to the target moisture content. It’s not complicated, but it takes time and the right conditions.

Timeframes

• Softwoods: 6–12 months to season adequately
• Most hardwoods: 12–24 months (denser woods take longer)
• Very dense hardwoods (Ironbark, Red Gum): up to 2 years for optimal dryness

The most common mistake is buying “seasoned” wood that was only cut a few months prior. Genuinely seasoned dense hardwood needs a year or more.

The Five Rules of Proper Seasoning

1. Split it first. Split wood dries far faster than whole logs because more surface area is exposed. Split to a range of sizes for flexibility.
2. Keep it off the ground. Ground contact wicks moisture back into the wood. Stack on pallets, timber rails, or a raised rack.
3. Cover the top, leave the sides open. Rain protection matters, but so does airflow. Cover only the top of the stack — wrapping the whole thing traps moisture and prevents drying.
4. Maximise airflow and sun. Stack in a sunny, breezy spot with gaps between rows. Air circulation is what carries moisture away.
5. Stack loosely, not tightly. Air needs to move through the pile. A loosely stacked, single-depth row dries much faster than a dense block.

Verify With a Moisture Meter

A firewood moisture meter costs very little and removes all guesswork. Split a log, press the probes into the freshly exposed inner face (not the weathered outer surface), and check the reading. Under 20% means it’s ready to burn. This one cheap tool is the difference between guessing and knowing.

Storage: Keeping Seasoned Wood Dry

Once wood is seasoned, poor storage can undo your work by letting it reabsorb moisture.

• Store under cover with good airflow — a woodshed, lean-to, or covered rack
• Keep it off the ground on a raised base
• Bring only a few days’ supply indoors at a time (indoor warmth gives a final moisture reduction)
• Rotate stock using first-in, first-out so older, drier wood is burned first
• Don’t seal wood in plastic or an unventilated space — trapped humidity causes mould and reabsorption

What Never to Burn

Some materials should never go in a wood electric fireplace, regardless of convenience. Burning these releases toxic compounds and damages your flue:

• Treated, painted, or stained timber — releases toxic chemicals including arsenic and formaldehyde
• Plywood, MDF, particleboard — contain adhesives and resins that release harmful fumes
• Driftwood — salt content produces corrosive, toxic compounds when burned
• Household rubbish, plastics, or packaging — release dioxins and other pollutants
• Green or wet wood — the pollution and creosote problem covered above
• Glossy or coloured paper — inks and coatings release toxins

Stick to clean, seasoned, untreated firewood. Nothing else.

How Firewood Connects to the Bigger Environmental Picture

Getting your firewood right is the foundation — but it’s one part of a larger equation that also includes the appliance itself, the flue system, and how you operate the fire. A certified, correctly installed fireplace running on properly seasoned wood, operated with hot, clean burns, is a genuinely different proposition environmentally than an old open fire burning damp timber.

If you’re weighing up whether a wood fireplace is the right and responsible choice for your home — including how modern sealed units compare to open fires and electric alternatives, what the Australian emissions standards actually require, and how installation affects performance — CountDeals has a thorough, balanced breakdown worth reading: their guide to whether inbuilt wood fireplaces are environmentally friendly covers the full picture, from combustion standards to real-world operation.