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From PSV to relative humidity, here are some definitions in order to help you better understand terms and notions used in the world of ventilation.

Bioclimatic

Qualifies architecture that wisely use all surrounding environment resources, for a better comfort and energy savings.

Boiler

Device which, on one side transforms a solid, liquid or gaseous fuel or electricity into thermal power, and on the other side transfers this energy to a heat transfer fluid (air, water or vapour) that will convey it to radiators.

Calorie (cal)

Old unit of measurement of thermal power. Today, the official unit in the International System is joule (J). 1J=0,239cal. In actual fact, one uses watt-hour (Wh) 1Wh=3600J=860cal.

Calorific contribution

Sum of all heat sources contributing to warm up a building: occupants, lighting, machines, office equipment, sun, fresh air.

Condensation

Condensation is the process whereby water vapour is returned to its original liquid state, every time the air humidity rate reaches a given value, depending on temperature. It is particularly visible on cold walls in humid and hot rooms, and may cause damages if it happens inside walls. It is very often linked with bad insulation and/or lack of ventilation.

Condenser

Heat exchanger that drains calories. Inside it, the refrigerating gaseous fluid condenses by transferring its heat to outside air or to a water circuit (change from gaseous to liquid state).

Condensing boiler

A boiler that condenses combustion gases, which increases its efficiency by 15 to 20 % compared with a standard boiler.

Contracting authority

It is the customer, whether a person or a company. The works are done on his behalf.

Convector

Boiler body made of one or several heating finned tubes, fitted horizontally in a volume in which air is moving from bottom to top between fins, either by natural stack effect or by convection, or with the help of a fan.

Decibel (dB)

Unit that measures and compares noise intensity, sounds and their attenuation.

Fabric

All elements that form the body of a building and ensure its stability and its solidity, as well as all elements that make it closed, covered and tight, as opposed to finishing jobs, which deal with its equipment, its ventilation, its insulation, its decoration, etc.

Finishing jobs

All works in a building that are not taking part in the construction of the fabric, and are therefore not contributing to its stability and solidity (ventilation, lighting, etc).

Geothermy

Strictly speaking, it is the use of heat contained in the deep layers of Earth's crust. In its broadest sense, the use of heat stored in shallow ground. The origin of heat is then mainly the sun.

Greenhouse gas

Any gas in the atmosphere that absorbs part of the heat emitted by Earth. This phenomenon ensures an average temperature compatible with life on the planet. Human activities heavily increase the amount of greenhouse gases, which causes climatic changes.

Heat loss

Heat flow, measured in kW, that comes out of the envelope of a building or a dwelling through walls as well as from air change and burnt gases elimination. Heat input from heating, internal inputs and free input (sun) must be able to compensate for this heat loss and maintain the required indoor temperature, called comfort temperature. Ventilation and insulation are the main elements that limit the heat loss.

Heat Recovery Mechanical Ventilation

A heat exchanger warms the incoming clean air with the heat coming from the extracted air, just before supplying the dry rooms with it. However, at the design stage, sufficient and adequate room must be allowed for ducts.

Humidity sensitive

Something that controls according to the ambient humidity level.

Humidity Sensitive Mechanical Ventilation

Humidity sensitive inlets and extract grilles control the airflow according to the relative humidity rate in each room. This "intelligent" system limits heat losses by adapting the airflow to the need in each case. A greater airflow during a shower, a lower airflow when the room is empty allow energy savings and air quality improvement.

Lambda (heat sciences)

This Greek letter is the symbol for thermal conductivity. It is the quantity of heat that passes through one m2 of material over one metre thickness when the difference in temperature between the two faces is 1 degree C. This coefficient "L" is stated in watts per metre per degree Celsius (W/m.degree C).

Low temperature boiler

A boiler that works at a lower temperature than a standard boiler, which permits savings from 12 to 15 %.

Mechanical Extract Ventilation (MEV )

See "Mechanical Ventilation".

Mechanical Ventilation

System including one or two electric fans that move air, in order to extract it or to supply it inside. In a humidity sensitive mechanical ventilation system, the inlets and extract grilles automatically control the airflow, in order to ensure sufficient air change while limiting heat losses.

Natural Ventilation

See "Passive Stack Ventilation".

Passive Stack Ventilation (PSV)

Ventilation without the help of any fan. Wind or temperature difference between inside and outside create an airflow (stack effect), thanks to extract grilles and vertical ducts.

Project manager

Person or company (architect, design department, engineer, etc.) in charge of designing and studying the building, and then of conducting works and coordinating the different building professions, in accordance with the scope of the mission he has been entrusted with by his customer, the contracting authority.

Relative humidity

Ratio, in percentage, between the mass of water in the air and the mass that the same volume of air would contain, in the same conditions, if it was saturated with water.

Sealed-combustion boiler

The air inlet and the fumes exhaust are independent from the room where the boiler is installed, because combustion air comes from outside. A fan provides the necessary draught.

Storage heating

Heating or hot water production principle consisting in slowly transmitting heat to a fluid or to a mass with high thermal inertia, in order to return it as needed.

Thermal bridge

Isolated or linear area in the envelope of a building which offers less thermal resistance (end of concrete slab, junction of walls, etc). Thermal bridges may tremendously reduce insulation's efficiency.

Vapour control layer

Sheet or membrane water-vapour proof. When installing thermal insulation, vapour control layer must be put on the inside of the heated room, in order to avoid condensation inside the wall.

Ventilation

Supply of clean air from outside in order to change the air inside the dwelling and extract polluted air.

VOC (Volatile Organic Compounds)

VOC include a variety of carbon-based chemicals. They are emitted as gases in the air, and are emitted by a wide array of products numbering in the thousands. Examples include: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, etc.).

Wall soundproofing

Difference between the sound level outside and inside a dwelling. The actual soundproofing differs from the performance mentioned by the manufacturer because it depends on many other parameters than the insulation products (types of building components, construction method, architecture).

Water heater

Independent domestic hot water production device. It may be linked to a storage tank equipped with a thermostat set up for 60 degree C and with an insulation that reduces heat loss.

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