Firewood

When to buy

Spring and summer are the best times to buy firewood. Why buy so early? For wood to burn well and cleanly it needs time to dry. You can buy “unseasoned” wood and store it (in an area where air can circulate) ready for use when the cold weather arrives. If you leave it until later you may have to buy dry firewood – and pay more.

How much to buy

To keep a woodburner going most evenings and weekends through winter you’ll need at least 10 cubic metres of wood. It’s best to buy in larger quantities – many suppliers will provide free delivery to a local address but only for orders of at least 2 cubic metres.

Tip: Get a dated receipt with the supplier’s name and address, the type of wood, quantity delivered and price.

Type of wood

Softwoods like pine dry in around 6 to 12 months but burn rapidly. This means regularly adding wood to keep a cosy blaze going. “Old man pine” is from trees aged 30 years or more. It’s denser than ordinary pine and contains more resin, so it burns for longer and puts out more heat.

Medium-density woods like macrocarpa burn a bit slower and contain more energy. If you have an open fire, avoid macrocarpa as it’s prone to sparking.

Hardwoods such as gum and manuka make a better fire as they have greater heat content and burn slowly. But freshly felled hardwoods can take up to 18 months to dry.

Many suppliers also offer a blend of softwood and hardwood called “hot mix”. The idea is to use softwood (usually pine) to get the fire started, then to add slow-burning hardwood once the room is warm. There is no standard ratio to hot mix so you should ask your supplier about proportions to make sure you’re getting a good deal. In general, the more hardwood in the mixture, the better.

Dryness

Only burn dry, well-seasoned wood. Green wood cools the fire, creating smoke that adds to air pollution.

Not sure if your wood is ready to burn? Firewood should have less than 25% moisture. You can test it by throwing a small piece onto hot glowing coals. If it catches fire on the top and sides within 1 minute, it’s dry enough to burn well.

If you’re buying wood to burn straight away, ask if it’s dry. Green, wet firewood will not be “fit for the purpose” under the Consumer Guarantees Act – it won’t burn properly and will clog up the flue.

You can buy inexpensive moisture meters which let you check the moisture content of firewood you are about to buy or burn.

Woodburner vs. open fire

Modern woodburners are cleaner-burning and more efficient than open fires. An average woodburner is about 70% efficient, which means it transfers around 70% of the heat to the surroundings. With an open fire you’ll be lucky to get 20%.

If a woodburner is permitted in your area, it’s a pleasant way to reduce your electricity bill. Some models can be fitted with a wetback, to preheat water for the hot water cylinder, giving further savings.

Burning efficiently

Woodburners are almost twice as expensive to run as heat pumps, but you can reduce costs by making sure you’re burning dry firewood of the right size (less than 110mm in diameter) and burning cleanly by managing the amount of wood burning rather than turning down the air supply.

Firewood storage

Stack the firewood under cover or against a sheltering wall, and leave enough gaps for drying air to pass through.

Comparing firewood prices from different suppliers can be a problem. While it’s not illegal to sell landscaping products or firewood by description, how much is in a sackful of this, a trailer-load of that, the back of a ute of the other?

Known volume

We recommend buying bulk materials by a known volume – that is by the cubic metre for firewood, mulch, top soil and other materials.

A cord (equivalent to 3.6 cubic metres) is not a legal measure, although some suppliers we contacted for our survey still use it.

Firewood is sold as a “thrown measure” unless specifically stated otherwise. This means that the quantity of wood is measured as if it was thrown into a container, and not as if it was stacked. Stacking it will reduce the volume by about 1/3 (3 cubic metres of thrown wood is roughly equivalent to 2 cubic metres stacked).

Volume certification

Known volume is more exact, but accuracy is not guaranteed. How do you know that the scoop of firewood dumped on your trailer is the volume you are charged for?

It is illegal for a supplier to say a scoop equals a specified volume unless the scoop’s volume has been certified. Trading Standards will approve and certify that a firewood trader’s vehicle holds a stated cubic metre volume. We recommend you buy firewood from such a trader.

There is also a certified 1 cubic metre measure. It was jointly developed by Trading Standards and a Christchurch landscaping and garden supply business. The container is also certified to accurately measure smaller volumes of 1/3 and 2/3 of a cubic metre.

If you believe you have been sold short, complain. If you get nowhere, contact Trading Standards. They have offices in Auckland, Wellington and Christchurch. It has powers of prosecution.

If you’re calling to check firewood prices, there are some questions you should ask:

• Does the supplier have a certificate of approval for their measure? Traders that sell firewood by the cubic metre must use a measure – a truck, trailer or bin – that has been certified by the Measurement and Product Safety Service.
• Does the quote include GST?
• What are the delivery costs?
• What is the condition of the wood? If you’re buying it to burn straight away, green or unseasoned firewood will not be “fit for purpose” under the Consumer Guarantees Act.