WHAT TYPE OF HEATING IS RECOMMENDED FOR ASTHMATICS AND ALLERGY SUFFERERS?

Although using a renewable energy source, wood heating contributes significantly to air pollution episodes and to the ambient level of fine particles suspended in the outdoor air. According to a 2015 study (source AIRPARIF) in the Paris region, domestic wood heating contributes to 28% of primary PM10 and 42% of PM2.5 (< 2,5 microns). Open fireplaces and closed fireplaces built before 2002 account for 75% of the particles emitted.

Wood combustion emits pollutants that vary according to the efficiency (output) of the appliance and the moisture content of the wood. Generally these are carbon monoxide (CO), water, nitrogen oxide (NOx), NMVOCs, soot, tars, coal, volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), H², SO², etc.

According to the health protection agencies (regional health observatory – ORS), wood heating with fuel loading directly into the room to be heated (not to be confused with a wood boiler in your basement) is a major source of pollution in residential housing.

If the particles resulting from the (imperfect) combustion of wood are inhaled (open fire, smoke that escapes when starting or (re)loading the wood, leaks linked to a lack of airtightness, pollutants following the elimination of ashes, wood combustion of neighbours by the outside air that comes inside, etc.), the health risks are real. When they penetrate the respiratory system they will promote asthma, coughing, respiratory allergies. Never burn damp wood, which will give off a lot of water vapour, and therefore moisture and mould. Globally (without distinction by pollutant) the deleterious effects are (according to the regional observatory of health of Ile de France): irritation, inflammation, oxidative stress, carcinogenic, neurotoxic, mutagenic, impacts on the cardiovascular system.

For people who do not suffer from respiratory problems, limiting indoor air pollution remains an essential factor in limiting headaches and concentration difficulties, irritations (eyes, nose and throat), and the other toxic effects mentioned above.

In all cases, it is recommended that a carbon monoxide (CO) detector be installed in addition to the smoke detector. Even if it does not detect the various toxic compounds, it will at least indicate the presence of a leak.

A distinction should be made between the different types of electric heating to avoid confusion. As detailed in the following paragraphs, heating methods that diffuse warm air by stirring the air and that dry out the air in the room should be avoided.

Forced-air heaters, where the air passes through a series of fins to heat up, work on a principle comparable to convectors. Supplementary heaters are not designed for continuous heating and can emit significant pollutants..

Principle of radiant heating

Radiant heating allows heat to be transferred without contact, just as the sun does not heat the air of our planet directly. Two examples to understand the principle of radiation :

• In winter on a ski slope in beautiful sunshine with an outside temperature of -2°C, you can feel a gentle sensation of comfort. The sun transfers heat to you by infrared radiation. Yet the air in the room remains at -2°C! As soon as a cloud comes between you and the sun, you feel an immediate chill.
• In the middle of winter, you make a fire outside (brazier), the outside temperature is -2°C, yet the fire warms you up and you feel good by the fire. The fire has not heated the air (which would be impossible), it has simply transferred its energy by radiation!

This is the principle of radiant heating, which can be found in wood-burning stoves, underfloor or ceiling heating, old-fashioned centrally heated radiators or today’s infrared heaters.

Impacts of the heat transfer method on health

What are the health impacts of the heat transfer method? They can be important. In fact, the two most widespread heating methods are contrasted here: convection heating and radiation heating. Most conventional heating technologies (electric convection heaters, low-radiant inertia heaters, air-to-air heat pumps that blow hot air, etc.) work by convection (heating the air). Apart from the energy inefficiency of this method of transferring heat to the ambient air, convection is not ideal for people with respiratory problems.

Understanding radiant heating in 2 minutes

Which heaters work by radiation?

• Infrared or radiant panels. Note that only panels emitting at least 50% radiation (and therefore 50% convection) should be considered. The lack of legislation in this area means that caution should be exercised when faced with claims that should be checked with the manufacturers. The range of radiation must be at least 3 metres in all directions from the location of the heater.
• Low-temperature underfloor heating systems (electric or hot water coils) which radiate upwards and heat the entire thermal mass that makes up the floor. Preferably choose a reversible system to generate cooling during the summer.
• Heated ceilings (usually electric) that radiate heat downwards.
• Some boilers (gas, wood, oil) connected to peripheral hot water heaters and if they are (already) installed in a ventilated room separated from the rest of the house. Non-renewable character (fossil fuels) and air pollution to be taken into account….
• All electric or solar boilers connected to hot water radiators (e.g. cast iron hydronic radiators) or hot water underfloor heating.
• Heating with a wood pellet stove that radiates directly into the room. Unlike conventional wood-burning stoves, it is not necessary to open the appliance to reload the logs during combustion. Also, the ambient air is less likely to be contaminated by fine carbonaceous particles. However, care must be taken to avoid any leakage. Attention should also be paid to the disposal of ashes, which leads to long-lasting air pollution during handling (high concentrations of copper and manganese according to a study by Italian researchers conducted in 2018 and presented in the journal Chemosphere  «Influence of advanced wood-fired appliances for residential heating on indoor air quality«.

Heating systems that rely on forced air (via fans) will dry out the room air.

Chimneys with or without inserts should be swept once or twice a year to ensure that the draught is good enough to remove the smoke.

For electric radiant heaters, there is no special maintenance.

For radiant heating by combustion boilers (wood, gas, oil) or pellets, maintenance (recommended twice a year) must be carried out by a professional on the boiler, its gas exhausts and the heat emitters (radiators). These gases, even in small doses, are toxic for the occupants.