Efficient ventilation systems
Controlled ventilation is highly recommended for hotels, for the following reasons:
- air quality: the amount of fresh air required depends on occupancy and use of each space (for example, bathroom air must be renewed at a high rate); fresh air intake must be adjusted accordingly,
- reducing heat losses: avoid excessive ventilation in cold weather, because it can lead to high heat losses (up to 15% of heat losses in winter),
- air conditioning in hot weather: extra ventilation can be useful in spring or autumn, or at night in summer, to ensure coolness and comfort in the hotel.
Several efficient ventilation solutions are available; the most reliable to date are demand-controlled mechanical ventilation systems (*). These systems can be installed only once air infiltration and draughts around windows and doors have been resolved. (*) Natural or hybrid (partly natural, partly mechanical) ventilation is also a possibility, but cannot be regulated as accurately as controlled systems.
What are the main types of mechanical ventilation systems?
• Exhaust air only, or inlet and exhaust air: in this case only exhaust air (or inlet + exhaust air) is mechanically controlled. The air flow may be constant (no possibility of regulation) or regulated by systems listed below:
- In rooms, for instance, exhaust air may be evacuated mechanically from bathrooms, and air taken in from vents in the exterior wall.
• Inlet/exhaust air systems: in this case two fans are used, one brings in fresh air, and the other vents indoor air to the outside. This system offers better control of ventilation, because air intake is controlled. This type of system can also be used to preheat incoming air in the winter if a heat recovery unit is installed on the exhaust air circuit. This improves indoor comfort and reduces heating needs.
- This system uses more electricity, due to the second fan, but the energy savings achieved with heat recovery generally compensate for the extra power consumption.
- This type of system can be used for extra ventilation in spring and autumn, and on summer nights (if it is designed for high air flow), which reduces air cooling needs.
- A thermodynamic machine (a small reversible heat pump) can be coupled to the ventilation system to improve air preheating and precooling.
- This system is suited to noisy environments (unlike natural ventilation or exhaust-air-only or inlet-air-only ventilation.
• Reminder: ventilation can be coupled with heating and air conditioning in "all air" systems (see solution no. XIX).
What solutions are available for regulating air flow according to actual needs?
• Humidity control: air inlet and exhaust vents can be fitted with humidity sensors (humidity is an indicator of room occupancy and air pollution); when room humidity is too high air intake is increased,
Programmed timers: can be used to switch ventilation on or off according to room occupancy.
• Presence detectors such as CO2 detectors or motion sensors: presence detectors.
Ventilate as much as necessary:
• Determine the amount of fresh air needed to satisfy your conditions. You can intentionally under-air rooms to determine the least airing time that is adequate.
• Adjust operating times to actual times of use.
Important! Rooms with large exterior wall surfaces that are insufficiently insulated are susceptible to mould. They must be aired regularly during the heating season, in particular if they are only partly heated. Insofar as possible, relative humidity should not exceed 40%. With sufficient airing the risk of mould on cold walls is greatly reduced.
Install automatic ventilation controls:
• Ventilation can be automated using sensors that detect CO2 or particle pollution in ambient air; they measure air quality and switch on ventilation only as needed.
• Timers can be installed to adapt ventilation to times of use (toilets, storage areas, etc.).
• Little-used spaces can be ventilated periodically.
• If the intake air fan is switched on, the heating must be in operation as well (excepting protection from freezing).
Inspect heat recovery:
In the case of heat recovery systems temperatures before and after heat recovery should be measured, and the level of efficiency calculated by a specialist; the by-pass conduit should be inspected for fouling.
Ensure proper kitchen ventilation:
The "extra ventilation" mode uses much more energy than normal ventilation operation. Extra ventilation should be used for a limited length of time, via a push-button system that reverts to normal operation after a period of 15 to
30 minutes. Timers can manage ventilation according to need, switching if off in the restaurant dining area at night, and in the kitchen in the afternoon, and can set fans to run at low speed for a given time: 15 min in the kitchen, 30 min at the bar.
Maintain your installation:
Cleaning and replacing filters is very important, as is keeping ventilation grills, ducts and heat exchangers clean (fire risk if too greasy).
Open windows to air rooms:
• If you do not have controlled mechanical ventilation, air for 3 minutes 3 times a day; air rooms fully when they are cleaned, and air the dining room after each meal.
• Install magnetic devices to turn off heating or cooling when windows are opened.
• In summer take advantage of cool morning air and air rooms before it gets too hot outside (free cooling).
A number of solutions are eligible for energy savings certificates. Among them:
• Self-adjusting single flow mechanical ventilation • Double flow mechanical ventilation with exchanger
• Proportionally regulated mechanical ventilation • Demand controlled mechanical ventilation with presence detectors
The list of all standard energy-saving operations that are eligible for certificates under the ECS scheme can be found on the French ministry website www.developpementdurable.gouv.fr/-Operations-standardisees-.html
General recommendations for mechanical ventilation
• Ventilation fans on air exhaust and inlet ducts offer greater comfort and better control of ventilation, but are more expensive. The choice between the two types of systems must be made according to the specific needs of the hotel, in terms of ventilation, noise levels, etc. It is also recommended that heating, cooling and ventilation needs be considered together, as these systems and choices are interdependent.
• Independent ventilation systems must be used for spaces that have very different activities and pollution sources.
General recommendations pertaining to ventilation
Type of space Air flow control
Rooms • presence detector highly recommended: either a stop-start presence detector, or CO2 detector
• humidity sensors can also be used
Large restaurants • humidity sensors can be used.
Kitchen • temperature and humidity controls are particularly useful
presence detectors can also be used
• Automatic ventilation regulation can be put into place by installing an independent regulation system in each room, or a central computerised system. • Automatic ventilation controls can also be integrated into a building energy management system, if there is one. In this case ventilation regulation by zones is recommended.
What are the steps for choosing and installing a new ventilation system?
* The choice of ventilation system depends on a number of factors, such as occupancy and activities in each area etc. Given the technical complexity of this technology, we recommend that you consult a manufacturer or qualified HVAC installer for advice on choosing the equipment that best meets the needs of your hotel.
• If you want to convert your exhaust air fan ventilation system to an exhaust and inlet air fan system, the exhaust duct system can be reused, but dropped ceilings must be installed for inlet air fans.
• When installing new fans be sure that electricity consumption is a low as possible for the new equipment.
• Depending on system configuration, it may be necessary to insulate air ducts and the heat exchanger, especially if they are located in an unheated area of the hotel.
Maintenance and upkeep
• Mechanical ventilation systems must be serviced and maintained to preserve equipment energy efficiency over time.
• When installing a new system be sure to allow easy access to the equipment for maintenance and upkeep.
• Programmed timer ≈ €50
• Installation of a heat recovery unit (partial modification) ≈ €6,500
Approximate payback time:
• exhaust air fan only ≈ 2 to 5 years
• inlet and exhaust air fans <≈ 12 years
It should be noted that costs and payback times are highly dependent on the local setting and the initial situation of the hotel.
The inn Le Chamois in Colmars-les-Alpes is the result of the rehabilitation in 2013 of an earlier hotel that closed in 2008.
Equipment implemented: When the ventilation system was designed, areas of the building were differentiated according to occupancy and activities, so as to provide ventilation as needed for each zone. A central double flow air treatment unit was installed for the kitchen, restaurant dining room and reception area (with double flow for the kitchen), while the guest rooms are ventilated by a type B hygro-regulated single flow system.
Results: From a regulatory standpoint, this solution reduced electricity consumption for ventilation by 79% compared to the previous installation. In addition subsidiary electricity meters were installed to monitor energy consumption, in particular for ventilation.
The Hotel de Francs in Soissons was built in 2010 and has received NF Bâtiments Tertiaires (tertiary premises) certification and the HQE environmental quality label.
Equipment implemented: As part of the energy saving strategy, a double flow ventilation system with heat recovery was installed (for halls and passageways). CO2 detectors were installed in meeting rooms to adjust ventilation according to need in these intermittently occupied spaces.
Energy renovation work was done at the Hotel de la Clape (Narbonne Plage), built in 1970, in order to obtain the low-energy building label BBC Renovation (Bâtiment Basse Consommation).
Equipment implemented: A double flow ventilation system with heat recovery (60% efficiency) was installed to reduce heating needs at the establishment. Heating is provided by a reversible air-air heat pump.
Les Aires Passagères is a B&B in Sernhac, housed in a rehabilitated farm building dating from the 16th century. The techniques used for this renovation qualified the building for Bâtiment Basse Consommation (BBC) certification.
Equipment implemented: Type B single flow hygro-regulated controlled mechanical ventilation was chosen to maintain indoor air quality.
A heat exchanger can eliminate up to 50% of heat losses due to ventilation.
If ventilation accounts for 15% of building heat losses, fitting the system with a heat exchanger can save 7% in heating costs.
A study by the Centre Technique des Industries Aérauliques et Thermiques (CETIAT, France) also shows that 50% of the energy used to heat meeting rooms that are occupied 10% of the time can be economised by adjusting ventilation air flow to room occupancy.
Reduced CO2 emissions
• For a hotel of 1,000 m² that uses 77.5 kWh/m² of natural gas heating annually, and applying emission factors for France, a 7% savings in energy consumption represents:
1.35 CO2 eq of avoided emissions each year
Emission factors for electricity in France: 84.3 g CO2 / kWh.
Emission factors for natural gas in France: 331 g CO2 / kWh (Source: ADEME).
For establishments in climate zone H3 (Mediterranean coast of France):
Solutions Annual energy savings
Proportional regulation 20 to 28 kWh/m²
Presence detector 14 to 20 kWh/m²
Self-adjusting single flow mechanical ventilation 7 to 12 kWh/m²
Double flow mechanical ventilation with exchanger 11 to 18 kWh/m²
The savings achieved on building surface area and initial circumstances.
Solutions Implementation Investment Benefits
Heat recovery ++ -- +
Ventilation at night in summer ++ + +
Network balance ++ - +
Ventilation system replacement - - ++
• Ease of implementation: Moderate to difficult (**/***).
• Best time for implementation: when the heating or air conditioning system is renovated.
• Relevant initial situation: The hotel has no mechanical ventilation system, or is equipped with ventilation without controls.