WINDOWS (Grille) AND VENTILATION IN 10 Question and Answer

1 – Ventilation of dwellings what is it for?

Humans (and their pets) breathe oxygen in the air. Release carbon dioxide (CO2) and water in the form of vapor (mist). If people are in an insufficiently ventilate house. The result is a sharp increase in the ambient humidity rate as well as an increase. In the CO2 rate which gradually makes the air unbeatable and the rooms grille unhealthy.

In addition, humans are used to piling up in their homes all kinds of products that release pollutants called Volatile Organic Compounds (VOCs). VOCs have mainly emitted solvents in paints, varnishes, floor coverings, nail polish, cleaning products, glues, and adhesives.  Amounts of chemicals in daily use. Note that contrary to popular belief, PVC. Windows are guaranteed to be free from VOCs and are classified as A + (lowest level) according to the law relating to air quality (Decree of April 19, 2011 Annex I).

The permanent renewal of indoor air eliminates all these pollutants, excess humidity. Bad odors in order to breathe healthy air and prevent the proliferation of dust mites and molds. Which favors hot and humid environments. A good number of respiratory diseases (Asthma) and headaches are often due to unsanitary housing. Because poorly ventilated and often without the knowledge of their occupants. Air renewal is therefore quite simply vital!

Note: The outside air is drier than the inside air even if your hygrometer placed outside Indicates the opposite. Because it measures the relative hygrometry and not the absolute hygrometry. Cold outside air can have a relative humidity close to 100% (Condensation on the outside windows). But once entered the room and warmed up. Its relative humidity can drop to 40%. Because the hot air absorbs more water in the form of steam than cold air.

2 – Can changing my windows (Grille) have an influence on the ventilation of my home?

Windows that were manufactured until the 1970s and even beyond, had a high air permeability. Because they allowed thin streams of air to pass around the perimeter of the openings. This had the only advantage of allowing the renewal of the indoor air in a fairly natural way. However, this ventilation principle today poses many problems, in particular:

  • No control of the amount of incoming air
  • Permanent discomfort when approaching windows, feeling of cold drafts
  • Exterior noises that are easily propagated in rooms (Noise nuisance)
  • Significant heating expenses to compensate for unnecessary losses

To avoid all these drawbacks. Current windows are designed with flexible joints between sashes and frames to ensure. Good air tightness, index A * 4 for example, which indicates an excellent air classification measured on a bench. AEV test (Air, Water, and Wind).


As a result, the installation of new watertight windows risks seriously disrupting the “natural” ventilation provided by old “leaky” windows.

3 – If my new windows are airtight. How do I get in the air that is essential for renewing the stale air?

It will be necessary to drill ventilation holes in the upper cross-piece of the windows (or in the front of the integrated shutter box if applicable). To attach a ventilation grid to them. Thus we will continue to bring in the quantity of air necessary for renewal. But without having the aforementioned drawbacks in paragraph 2 because:

The air intake grille will be fitted with a deflector allowing. The incoming cold air to be directed first towards the ceiling so that it mixes with the ambient air (Coanda effect). To heat and thus minimize the inconvenience it could produce for occupants.

  • The air inlet grille is calibrated and self-adjusting in order to be able to regulate. The incoming airflow to around the nominal value which will be 15, 20, 30 or 45 m³ / h depending on the volume of the room. Thus we perfectly control the quantity of incoming air.
  • The air intake grille will also be fitted with a sound absorber according to the degree of sound insulation required from external noise pollution in order to comply with the regulations in force.
  • The air inlet will be fitted with an anti-insect grid (flies, mosquitoes, etc.).
  • Finally, the grilles can optionally be hygrometric, so open automatically when the humidity level increases in the air (presence of occupants) and close automatically. When the home is unoccupied to achieve substantial energy savings, however, provided that they are coupled to a so-called “Hygro B” CMV.

4 – Will the installation of ventilation grilles at the top of my new windows be sufficient to ensure optimal air renewal in my home?

Yes, unless your home is not equipped. With efficient Controlled Mechanical Ventilation (CMV) operating permanently. Because the “natural” ventilation that occurred with your old leaky windows may now be insufficient. In fact, to ensure “natural” ventilation, it is necessary to generate air circulation. The principle of natural convection causes hot air to rise and escape from the top. It thus sucks in the cold outside air from the bottom. But as the air inlet grilles are located at the top. The draft natural does not occur and the quantity of incoming air may prove to be insufficient. To ensure air renewal compatible with the degree of indoor pollution.

The most effective solution, widely proven and mandatory in new construction since the decree of March 24, 1982 (more than 30 years ago!). Is to install a Controlled Mechanical Ventilation (CMV) at the same time as the installation of your new windows. The VMC will create a depression in the service rooms through exhaust vents forcing fresh air to enter. The living rooms through the air inlets located above the windows.

If your home is already equipped with a VMC, you will simply have to make sure. It works perfectly and possibly carries out a complete overhaul if you have forgotten the date of the last maintenance.

5 – Should there be ventilation grilles on all windows? (Grille)

An air inlet grille must be provided in all the living rooms (bedrooms, living room. Office, living room) and especially not in the service rooms (WC, bathroom, kitchen, laundry room). Because in these rooms, in principle, there should be a stale air extractor connected to the VMC.

If an air inlet is placed on the window of a utility room. The air coming from the outside will be sucked directly in through. The exhaust port. This will nullify the efficiency of the VMC which will not succeed in renewing the air of the other rooms.

6 – Why should we provide a clearance of at least 15 mm under the interior doors?

In order to ensure permanent and sufficient air circulation between all rooms. Interior doors, when closed, must allow free air circulation. Hence the need to provide a free passage of at least 15 mm under each door. Beware of thick carpets, floating parquet floors laid on an existing floor, tiles placed on the old coating, etc.

7 – What is the point of replacing a window with little cold insulation. A very insulating window if you have to put an unheated air inlet above it, isn’t that contradictory?

No, because we must distinguish 3 types of losses at the level of the glass walls.

1 –   Losses due to heat transfer through the glass wall. Thanks to current high-performance double glazing (low emissivity treated) these losses. Due to the cold wall effect will be a divide. A factor of 5 or 6. multi-chamber profiles (PVC windows) or thermal break bars (Aluminum windows) will reduce these losses.

2 –  Losses due to an excess of outside air infiltrating between the sash and the frame, this is the case. For example, of entry doors without threshold or windows without joints between sash and frame.

3 –  Losses due to fresh air inlets at the top of the windows. Essential for the renewal of indoor air (evacuation of CO2, pollutants, humidity, odors, etc.).

The new windows will make it possible to considerably reduce the losses of cases n ° 1 and n ° 2 which can represent up to 40% of the energy losses of a dwelling or even more in particular in collective housing.

On the other hand, the replacement of the windows will have no influence on the losses due to the only renewal of the air in case 3.

The reduction in losses due to the renewal of the air can only be envisaged by heating the incoming air from the heat recovered. In the exhausted stale air (double-flow VMC) or other air heating devices. He entering air from renewable energy such as a Canadian well or a waterspout wall for example.

8 – Aren’t the air intake grilles likely to degrade. The sound performance of my windows? (Grille)

Not on the condition that the sound reduction level of the air inlet grille is suitable. And in relation to the sound performance of the facade required according to the external environment. It is estimated that the normalized sound attenuation of the air. Inlet grille measured in the laboratory called the Dn, e, w + Ctr must be at least 6 to 7 dB (Decibel) above the sound performance required from the facade.

For example, for a standard window fitted with 4/16/4 glazing, required for a facade classification of 30 dB. The air inlet grille will have a standardized attenuation Dn, e, w + Ctr of 36 dB minimum. For a window fitted with 10/16/4 sound-proof glazing, facade classification required of 35 dB, the grille will have a Dn, e, w + Ctr of 41 dB.

Note that if there are 2 grids in the same room. The performance of each grid will have to be increased by 3 dB.

Acoustic sleeve – Manufacturer: Nicoll

Beyond a required attenuation of 35 dB facade vis-à-vis road traffic noise. It is forbidden to provide air inlets at the top of the joinery as there are no suitable grids. With sufficient performance. The air inlets must therefore be made in the wall (Core drilling). The incoming air must pass through an acoustic box incorporated in the thickness of the lining partition (or the wall) equipped. With anti-absorbent foams. -noise. (See Nicoll acoustic sleeve opposite).

9 – Does the ventilation of my home have an influence on my energy consumption?

Yes. In particular on the efficiency of radiators (hot water or electric) because they only work by convection. The air circulating in contact with the hot parts of the radiator spreads heat throughout the room. Poor air circulation in the rooms lowers the efficiency of the radiators and induces overconsumption. To maintain the same temperature in the room. Controlled ventilation. Therefore allows good air circulation and a uniform temperature in the rooms. While reducing the consumption of heating devices.

The electrical energy consumption of a high-performance VMC motor operating 24 hours a day is less than 40 € per year (maximum consumption of 25 Wh / m3 extracted).

10 – Is double-flow CMV (Controlled Mechanical Ventilation) compulsory for new construction. In accordance with RT 2012 standards (Thermal Regulation 2012)?

Not even if it is very desirable to reduce energy expenditure due to heat losses from the exhausted stale air.

In addition to the incomparable comfort it provides. Double-flow ventilation eliminates the need for unheated air inlets at the top of the windows. Which is excellent especially in the presence of noise. Highly polluted or sensitive external environment. increased to allergens (Pollens, dust …).

However, its price is significantly higher than the single flow CMV. Which must add to the necessary regular maintenance of the filters (approximately every 6 months).

The most important thing in order to be compliant with RT2012 will be to hunt for parasitic air intakes. That risk disrupting the renewal. Circulation of the air has the effect of inducing overconsumption of heating (Infiltrometry test mandatory before receipt). Click Here For More

Read Next