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Frequently asked questions about heating

We receive lots of questions about saving heating and energy every day. We have summarised the answers to the most frequently asked questions for you in our FAQs.

Disposal of packaging

The packaging material (wooden crates, cardboard boxes, inserts, plastic films and bags, etc.) must be properly disposed of in accordance with local statutory provisions and ordinances.


Disposal of components or boiler

  • Dispose of properly, i.e. separate according to material groups of the parts to be disposed of.
  • Under no circumstances throw electrical or electronic waste in the garbage, instead hand it in at the public collection points provided for this purpose.
  • Always dispose of in an environmentally friendly manner that corresponds to the state of the art in environmental protection, recycling and disposal technology.

The “start-up” of a boiler involves more than just “switching it on”. The service technician will explain the heating system to you in detail. This way, if problems do arise you can remedy minor faults yourself. The new heating system is subjected to a function check, exhaust gas values are checked and settings are readjusted if necessary. The control values determined are entered in a setting log located directly on the unit

All the natural raw materials we consume for eating, living, travelling, etc. need space on our planet to grow back. Likewise, nature needs resources to break down our waste (e.g. forests to bind the CO2). The ecological footprint makes this land requirement clear.

The red-white-red footprint calculator was launched on the initiative of the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management to give people the opportunity to determine their personal footprint. It was implemented with scientific support (Institute of Social Ecology) and the assistance of environmental experts from the Footprint Platform.

The footprint not only vividly conveys the ecological limits of our planet, it also shows what measures everyone can personally take against the destruction of our planet.

You can calculate your individual ecological footprint here:

Sustainability is understood as the natural regenerative capacity of forests. In a sustainable timber industry, only as much wood is removed as will grow back again. In Austria's forests, about 26 million solid cubic metres of wood are harvested per year. This compares with about 30 million solid metres of renewable wood every year.

Water vapour and oxygen are released when wood is heated above 150°C. As the temperature rises further, the lignin and cellulose contained in the wood also gasify, producing a combustible gas mixture. If air is supplied, this "wood gas" ignites at a temperature of approximately 230 – 280°C. So the wood itself does not burn, but the escaping wood gases do. What remains are the solid residues of ash and charcoal.

Different volume units are used for wood. A distinction is made between cubic metres, solid cubic metres and loose cubic metres. The cubic metre is a stack of logs, the outer edges of which are 1 m x 1 m x 1 m. The spaces in between are included in the calculation. The loose cubic metre, on the other hand, is wood that has been loosely poured into a container measuring 1 m x 1 m x 1 m. Here, too, the spaces in between are included in the calculation. There are no gaps in the solid cubic metre. This consists of 1 m³ of solid wood without gaps.

Freshly cut wood usually has a high wood moisture content. Softwood has a wood moisture content of about 55 –70% (water content 35 – 41%), hardwoods about 70 – 100% (water content 41 –50%). For combustion of the wood, the wood moisture should preferably be below 20% (water content < 16%). For this, the wood must be stored dry for at least one year before it can be burned.

Logs should be clean and as dry as possible before they are burned. Under no circumstances should treated wood (impregnated or painted), chipboard, plastics or other waste be burnt. This is prohibited by law and can also lead to the loss of the manufacturer's warranty.

Modern wood gasification boilers work very efficiently and comply with all legal flue gas and dust values. The prerequisite for this is wood of good quality so that the heating system can be operated in an environmentally friendly manner, with low emissions. For example, if wood that is too moist is burned, more than one fifth of the energy is lost in the energy required to dry the wood in the boiler. The efficiency deteriorates enormously and the burden on the environment from poorly burnt wood increases.

For low-emission and efficient heating with wood, the quality of the fuel is crucial. The wood must be clean and must not have any mould or rot. The wood moisture content must never exceed 25%. The drier the wood, the more efficient and environmentally friendly your heating. The wood should be dried for at least two to three years to achieve an optimal degree of dryness.

The stored carbon in the wood, which was originally taken from the CO2 in the atmosphere, combines again with the oxygen contained in the air when wood is burnt. In the process, the originally stored CO2 is released again in the same quantity that was once taken out of the air. This means that burning wood is absolutely CO2-neutral!

The heating value varies depending on the how coarse or fine the wood chips are, their water content and whether they are made from hardwood or softwood. This means that for different qualities of chips, different amounts of wood chips are required to provide the required level of heat. You can read about the amount of wood chips you will need for your system in the folder “Fuel Info – Wood Chips”.

  • Use natural, chemically untreated wood
  • Ensure low and homogeneous water content (no pockets of moisture)
  • The proportion of needles, leaves, fine twigs, bark should be low
  • Uniform particle size plays a role
  • The wood chips should have smoothly cut edges and not be frayed
  • They should not contain any dirt or foreign bodies
  • Store logs in an airy, sunny place for at least one summer (for wood chips W25-30)
  • Wood chips with a water content > 35% are not suitable for storage (decomposition, formation of mould, self-heating/risk of fire)
  • During summer months with high precipitation, it is advisable to cover the wood that is to be chipped

The quality of the wood chips is an important factor in achieving optimum operation of the heating system. Because of the many producers and different types of wood, wood chip is a raw material which comes in many different forms. PuroWIN is approved for wood chips of classes P16S and P31S and also A1 and A2 If you use these grades, we can guarantee compliance with the specified emission limits without any additional measures such as filter technology or prior cleaning. For ideal system operation, wood chips with a water content of 20–30 percent should be used.

Wood chips (average) Split logs Pellets Heating oil Natural gas
2500 kg (air dry) 2500 kg (air dry) 2000 kg 860 kg 840 kg
12500 l 5000 l 3500 l 1000 l 1000000 l
12.5 m³ (srm) 7.5 m³ (rm) 3.5 l 1 m³ 1000 m³

If you use wood chips for your heating system, you can use the following comparisons as a guide. One solid cubic metre (fm) of wood yields 1.4 cubic metres (rm) and 2.5 loose cubic metres (srm) of wood chips.

Wood chips are defined as mechanically shredded wood that is processed into pieces of wood a few centimetres in size. The small pieces of wood are burned in fully automatically controlled incinerators and guarantee the same convenience as their fossil-fuel competitors.

Pellets must be transported and stored absolutely dry. They swell up greatly if stored in moist conditions. Therefore, the pellets must be protected against moisture during transport, storage and through to combustion. Learn more about pellet storage here.

The quality guidelines for transport and storage logistics are defined in ENplus and ÖNORM M7136.

Pellets are sold by fuel merchants in the following form:

  • for manual filling of the fuel hopper in 10, 15 and 30 kg bags and also Big Bag with approx. 1 tonne on Euro pallet 
  • For automated room and building clearing in loose form by means of bulk road trailer, quantity as required (offered and delivered in kg)

Trees absorb CO2 from the air as they grow. When wood is burned, precisely that amount of CO2 is released back into the air, so it is no higher than it would have been had the tree rotted naturally in the forest. Heating with wood pellets is therefore CO2 neutral and makes an important contribution to climate protection.

Diameter: 6 ± 1 mm

Length: 3.15 to 40 mm

Bulk density: > 650 kg/m³

Heat value: > 4.6 kWh/kg

Ash content: < 0.7%

Fines material portion: < 1%

Some visual characteristics of good pellet quality are a shiny, smooth surface, uniform piece size and little dust. Quickly and easily test the quality yourself by throwing wood pellets into a glass of water. Good quality pellets sink immediately.

The quality of the pellets is an important factor in achieving optimum operation of the heating system. When buying pellets, make sure that they meet the quality standards of EN ISO 17225-2 A1. For maximum reliability, source pellets from manufacturers with EN-Plus certification (or DIN-Plus, ÖNORM M7135 or UZ38), as they are required to perform ongoing internal quality control. Make your pellet supplier aware of these quality requirements before ordering and seek confirmation upon delivery.

If you use wood pellets for your heating system, you can use the following comparisons as a guide. In terms of calorific value, two kilograms of wood pellets are comparable to one litre of heating oil. For 650 kg of wood pellets you need one cubic metre of space. Thus three cubic metres of wood pellets for your wood pellet heating system correspond to about 1,000 litres of heating oil. Wood pellets, the liquid wood that combines economical space requirements with environmentally friendly operation.

Pellets are small standardised cylindrical rolls comprising 100% natural wood residues such as wood shavings and sawdust. The dried wood residues are ground and compressed into wood pellets under high pressure using special presses. No binding agents or additives are required, and neither are they permitted. Manufacturing wood pellets from dried wood shavings takes about 1% of the energy contained in the fuel, or about 5% if moist sawdust is used. The "liquid wood" therefore has the best energy efficiency of all fuels.

Research which pellet boiler is best suited to you. You can find lots of information online. You can contact most manufacturers by phone. Go to trade fairs to receive guidance in person or visit showrooms to take a look at possible boilers before making a decision.

Contact a trusted local installer. They will be able to offer expert advice and will recommend a suitable heating solution to meet your requirements.

Make sure that you clarify certain things before deciding on a heating system, for example:

  • Ask your chimney sweep whether your flue needs to be renovated.
  • Do you have enough space for a year’s worth of pellets? In most cases, the oil tank or tank space will be large enough to easily convert it into a pellet store. With the free Windhager app for planning a storage space, you will have an answer at the touch of a button.
  • Decide which kind of pellet storage and feed system is best for you (brick-built storage room, fabric tank, sheet metal tank or buried tank).
  • Can you carry on using elements of your existing heating system (pumps, radiators, etc.) or are they outdated? It is almost always worth modernising everything at the same time.
  • What subsidies are available? Conversions to environmentally friendly pellet heating systems are often subsidised. Find out whether you are supported by the Austrian federal government, the province or your municipality and apply for funding even before implementation.
  • Who will do the electrical work? The electrics of the new heating system must be connected up properly. Some installers work closely with specialist electrical companies to this end or will have trained electricians already within their organisation.

The following items and costs need to be included in the quote:

  • New boiler with controller
  • New hydraulic components such as pumps and distributors (if necessary)
  • Disposal of the old oil-fired boiler and oil tank (if necessary)
  • Renovating the flue (if necessary)
  • Pellet storage room (removal system and storage system)
  • Installation work
  • Insulation of the heating pipes
  • Electrical connection of the new boiler
  • Start-up of the heating system by the customer service team

When you are happy with all the elements of the quote, commission a trusted installer to convert your heating system.

Before you start any modernisation work, many local authorities require you to submit a building application. If this is the case, take this opportunity to also submit your subsidy application. Your trusted installer will usually be able to help you with this.

It is recommended to have your flue inspected by a chimney sweep before starting any conversion work. They will be able to advise you whether or not the flue needs to be renovated. You will usually need a new flue for modern boilers as they are much more efficient than older ones and so have much lower flue gas temperatures as well. This is quite a simple process, which involves pulling stainless steel pipes into the flue.

Discuss the schedule for the modernisation with your installer and go through the individual steps together. The boiler replacement will usually take a few days. 

Note that the delivery time for the small compacted wood granules is usually two to three weeks. 

Have your heating system commissioned by a trained expert or the customer service team of your chosen boiler manufacturer. Take this opportunity to check with the technician whether the heating system is working as required and have them explain exactly how to operate the system.

Questions about our pellet boilers?
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Further information about heating

We have collected a lot of interesting information for you on the subject of heating.

To the knowledge overview