CEN/TR 14788:2006

SLOVENSKI STANDARD
01-junij-2006
Nadomešča:
SIST EN 13465:2004
Prezračevanje stavb - Projektiranje in dimenzioniranje stanovanjskih
prezračevalnih sistemov
Ventilation for buildings - Design and dimensioning of residential ventilation systems
Lüftung von Gebäuden - Ausführung und Bemessung der Lüftungssysteme von
Wohnungen
Ventilation des bâtiments - Conception et dimensionnement des systemes de ventilation
résidentiels
Ta slovenski standard je istoveten z: CEN/TR 14788:2006
ICS:
91.140.30 Prezračevalni in klimatski Ventilation and air-
sistemi conditioning systems
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL REPORT
CEN/TR 14788
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
March 2006
ICS 91.140.30
English Version
Ventilation for buildings - Design and dimensioning of residential
ventilation systems
Ventilation des bâtiments - Conception et Lüftung von Gebäuden - Ausführung und Bemessung der
dimensionnement des systèmes de ventilation résidentiels Lüftungssysteme von Wohnungen
This Technical Report was approved by CEN on 30 January 2006. It has been drawn up by the Technical Committee CEN/TC 156.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 14788:2006: E
worldwide for CEN national Members.

Contents
Page
Foreword.3
1 Scope .4
2 References.4
3 Terms and definitions .5
4 Symbols and units.6
5 Need for ventilation in dwellings (residences) .6
6 Design assumptions for residential ventilation.9
7 Performance requirements for ventilation systems.10
8 Design rules for residential ventilation systems.22
9 Specification and documentation .27
Annex A (informative) Residential pollutant production rates .28
Annex B (informative) The relationship between humidity and temperature and use of the
psychrometric chart .31
Annex C (informative) Method of calculating water vapour absorption effect .33
Annex D (informative) Residential ventilation systems and their interaction with the dwelling.35
Annex E (informative) Calculation methods for ventilation requirements .40
Annex F (informative) Examples of assumptions and resulting calculated values for ventilation air
flow rates .43
Annex G (informative) Noise .52
Annex H (informative) Nomograph for calculating air flow rate to reduce the risk of surface
condensation occurring on the inner wall surface for various wall U-values and ambient air
conditions.59
Bibliography .61

Foreword
This Technical Report (CEN/TR 14788:2006) has been prepared by Technical Committee CEN/TC 156 “Ventilation
of buildings”, the secretariat of which is held by BSI.

1 Scope
This Technical Report specifies recommendations for the performance and design of ventilation systems which
serve single family, multi family and apartment type dwellings during both summer and winter. It is of particular
interest to architects, designers, builders and those involved with implementing national, regional and local
regulations and standards.
Four basic ventilation strategies are covered; natural ventilation, fan assisted supply air ventilation, fan assisted
exhaust air ventilation and fan assisted balanced air ventilation. Combinations of these systems are not excluded
and a ventilation system may serve only one dwelling (individual system) or more than one dwelling (central
system). The ventilation aspects of combined systems (ventilation with heating and/or cooling) are covered.
The ventilation of garages, common spaces, roof voids, sub-floor voids, wall cavities and other spaces in the
structure, under, over or around the living space are not covered.
Ventilation systems covered by this Technical Report may affect the entry and dilution of radon and other gases
from the ground but these effects are not covered in this Technical Report. Ventilation systems designed to reduce
the entry of radon and other gases from the ground are not covered by this Technical Report.
2 References
The following referenced documents are indispensable for the application of this Technical Report. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced document
(including any amendments) applies.
EN 779, Particulate air filters for general ventilation — Determination of the filtration performance
EN 1507, Ventilation for buildings — Sheet metal air ducts with rectangular section — Requirements for strength
and leakage
ENV 12097, Ventilation for buildings — Ductwork — Requirements for ductwork components to facilitate
maintenance of ductwork systems
EN 12236, Ventilation for buildings — Ductwork hangers and supports — Requirements for strength
EN 12237, Ventilation for buildings — Ductwork — Strength and leakage of circular sheet metal ducts
EN 12792:2003, Ventilation for buildings — Symbols, terminology and graphical symbols
EN 13141-1, Ventilation for buildings — Performance testing of components/products for residential ventilation —
Part 1: Externally and internally mounted air transfer devices
EN 13465, Ventilation for buildings — Calculation methods for the determination of air flow rates in dwellings
EN 14134, Ventilation for buildings — Performance testing and installation checks of residential ventilation systems
EN 13779, Ventilation for non-residential buildings — Performance requirements for ventilation and room
conditioning systems
EN 20140-10, Acoustics — Measurement of sound insulation in building and building elements — Part 10:
Laboratory measurement of airborne sound insulation of small building elements (ISO 140-10:1991)
EN ISO 140-3, Acoustics — Measurement of sound insulation in buildings and of building elements — Part 3:
Laboratory measurement of airborne sound insulation of building elements (ISO 140-3:1995)
EN ISO 10211-1, Thermal bridges in building construction — Heat flow and surface temperatures — Part 1:
General calculation method (ISO 10211-1:1995)
ISO 9972, Thermal insulation — Determination of building airtightness — Fan pressurization method
3 Terms and definitions
For the purposes of this Technical Report, the terms and definitions given in EN 12792:2003 and the following
apply.
3.1
activity room
room used for activities such as cooking, washing and bathing which is characterised by relatively high pollutant
emission (which may be intermittent), e.g. a kitchen, bathroom, laundry/utility room, WC
3.2
background pollutants
group of indoor pollutants mainly represented by water vapour and carbon dioxide from respiration, but also
including a large number of other pollutants emitted by materials, furnishings and products used in the dwelling.
Their source rates are relatively low but continuous and diffuse
3.3
common space
corridor, stairway or atrium used for access to a dwelling or dwellings
3.4
cross ventilation (in a natural ventilation system)
natural ventilation in which air flow mainly results from wind pressure effects on the building facades and in which
stack effect in the building is of less importance
3.5
fan assisted balanced ventilation
ventilation which employs powered air movement components in both the supply and exhaust air sides in order to
achieve a design flow rate/pressure ratio
[EN 12792:2003, 149]
3.6
fan assisted exhaust air ventilation
ventilation which employs powered air movement components in the exhaust air side only
[EN 12792:2003, 150]
3.7
fan assisted supply air ventilation
ventilation which employs powered air movement components in the supply air side only
[EN 12792:2003, 154]
3.8
low pollution room
room used for dwelling purposes which is characterised by relatively low pollution emission, e.g. a bedroom, living
room, dining room, study, but not a space used only for storage
3.9
outdoor air
controlled air entering the system or opening from outdoors before any air treatment (coded green)
[EN 12792:2003, 280]
3.10
natural ventilation system
ventilation system which relies on pressure differences without the aid of powered air movement components
3.11
specific pollutants
group of indoor pollutants mainly represented by water vapour, carbon dioxide and odours, whose production is
related to specific human activities in the dwelling (such as cooking, washing, bathing). Their source rates are
relatively high but of short duration, and in specific locations in the dwelling
3.12
stack effect
movement of air or gas in a vertical enclosure (e.g. duct, chimney, building) induced by density difference between
the air or gas in the enclosure and the ambient atmosphere
3.13
standard air
. -3
atmospheric air having density 1,2 kg m at 20 °C, 101 325 Pa (1 013,25 mbar) and 65 % relative humidity
[EN 12792:2003, 340]
3.14
ventilation
designed supply and removal of air to and from a treated space
[EN 12792:2003, 388]
3.15
ventilation flow rate
volume flow rate at which ventilation air is supplied and removed
[EN 12792:392]
NOTE Normally uses standard air condition.
3.16
ventilation installation
combination of the ventilation or air conditioning installation and the building itself
3.17
ventilation system
combination of all components required to provide ventilation
NOTE The definitions 3.16 and 3.17 are the reverse of those given in EN 12792 and reflect the terms in more common
usage in the industry.
4 Symbols and units
For the purpose of this Technical Report, the symbols and units given in EN 12792:2003 apply.
5 Need for ventilation in dwellings (residences)
5.1 General
A supply of outdoor air in buildings is normally regarded as being required for one or more of the following
purposes:
a) dilution and/or removal of background pollutants such as substances emitted by furnishings and building
materials and cleaning materials used in the building, odours, metabolic CO and water vapour;
b) dilution and/or removal of specific pollutants from identifiable local sources such as toilet odours, cooking
odours, water vapour from cooking or bathing, environmental tobacco smoke, combustion products from fuel
burning appliances;
c) provision for occupants for respiration;
d) control of internal humidity;
e) provision of air for fuel burning appliances.
These purposes are all with regard to the health of the occupants and the building. Ventilation is primarily
concerned with the first four purposes (a) to d)) but it is linked to the last one (e)). In providing ventilation it is
important to also consider other aspects of performance including thermal comfort, durability, fire safety, noise and
energy use.
5.2 Composition of outside air
The proportions of the three main elements of outside air, oxygen (20,9 %), nitrogen (79,0 %) and carbon dioxide
(0,034 %) do not vary significantly in outside air. Carbon dioxide may be found at higher concentrations in built-up
areas and may be high enough to affect ventilation provision.
The main variable constituent of outside air is water vapour. Across Europe the typical specific moisture ranges
from 1,0 g up to 16 g moisture per kg dry air during yearly weather conditions (see Annex B for further information).
However, in some situations the concentrations of other outdoor pollutants (mainly pollutants from motor vehicles in
city areas) may reach unacceptable levels. The designer may wish to consider filtration of outdoor air by adding
filters to the ventilation system. At present it is generally only practicable to provide filters for particulate matter.
5.3 Dilution and removal of indoor pollutants
A wide range of airborne pollutants is generated by sources within dwellings, including gases, vapours, tobacco
smoke, biologically inert particulates (e.g. dusts and fibres) and viable particulates (e.g. fungal spores, viruses and
bacteria). Such pollutants may have the potential to harm the health or comfort of occupants or may lead to
damage to the dwelling fabric.
Indoor pollutants may be divided into three groups: specific pollutants which can be substantially removed by local
ventilation close to identifiable local sources; background pollutants which have diffuse sources or for other
reasons cannot be dealt with by local ventilation; and combustion products from fuel burning appliances
(combustion products are discussed in 5.6 and 7.3).
Production rates of pollutants are best known (or predicable) where the source is combustion or where the pollutant
results from the presence or activities of occupants. Production rates are less well defined where the source is
related to the fabric or furnishings of the dwelling.
At present there is no consistent approach to setting acceptable indoor concentrations for many of the diverse
source pollutants in dwellings, however, in the general case they are believed to be adequately removed by
ventilation for those few pollutants whose source rates and acceptable levels are known. The known pollutants are
discussed in the following subclauses.
5.4 Human respiration
The body requires oxygen for the production of energy at a rate proportional to metabolic rate. However, the main
limiting factor is not the supply of oxygen but the build-up of water vapour and carbon dioxide in expired air, whose
production rates from human respiration are given in Annex A.
5.5 Control of indoor humidity
The relative humidity of air is equal to the ratio of the partial vapour pressure in the air to the partial pressure of
water vapour in saturated air at the same temperature. Low relative humidities (below approximately 30 %) can
give rise to respiratory discomfort and nuisance from electrostatic effects. High relative humidities (above
approximately 70 %) incur the risk of condensation and mould growth on surfaces that have temperatures close to
or below the dew point temperature of the air. In very cold climates it may be desirable to reduce ventilation rates,
and tolerate consequent higher CO levels, in order to avoid relative humidity being uncomfortably low (below
approximately 30 %). The concentrations of pollutants (including CO ) in the dwelling may then rise to
unacceptable levels in which case increased ventilation air flow rates can become necessary.
The contribution made by ventilation is to lower the moisture content of the internal air by dilution with outside air
which normally has a lower absolute moisture content (as described above, relative humidity of the outside air is
reduced when it is heated to indoor temperatures). In cold climates (e.g. central and northern Europe) the problem
tends to be low indoor humidity. In temperate climates (e.g. European maritime areas) the problem tends to be high
indoor humidity.
For any required indoor humidity level the air flow rate required depends upon the moisture content of the outside
air, the rate of moisture input (from such sources as respiration, cooking, bathing, clothes drying and flue-less
combustion of certain fuels), the indoor air temperature, the temperature of surfaces in the room(s) and the water
vapour absorption characteristics of surfaces and furnishings in the room(s). The latter is discussed in Annex B and
Annex C.
Typical moisture generation rates for some common household activities are given in Annex A. It should be noted
that these are only a guide because they are strongly dependent upon the habits of the dwelling occupants.
Depending on the type of ground floor construction water vapour can also enter dwellings in significant quantities
from the ground. The designer should take it into account when appropriate (see Annex A and national or local
building regulations).
5.6 Provision of air for non sealed fuel burning appliances (open flued appliances)
An air supply to a non sealed fuel burning appliance is required for one or more of the following purposes:
a) to supply air for correct combustion and flue operation;
b) to limit the concentration of combustion products within the spaces to an acceptable level (normally taken to be
a maximum of 0,5 % carbon dioxide and relative humidity low enough to avoid condensation leading to mould
growth);
c) to prevent overheating of the appliance and its surroundings.
Carbon monoxide (CO) may also be produced by fuel burning appliances but should be dealt with by correct
adjustment of burners and by providing adequate air supply to limit CO concentration and avoid its conversion
to CO.
NOTE Room-sealed and balanced-flue type appliances do not require air for a) or b) but may require ventilation air for c).
It is strongly recommended that flue-less space heating appliances are not used in dwellings because of their high
CO and water vapour output rates and their high air supply requirement. Flue-less cooking appliances are
acceptable because of their relatively low fuel use and intermittent use. In some countries national regulations may
forbid the use of flue-less space heating appliances.
Air supply to prevent overheating of the appliance is considered to be a heating issue, not a ventilation issue, and
should not be discussed further.
When designing a ventilation system there are two distinct problems to consider with respect to fuel burning
appliances: (i) avoiding spillage from open flued appliances and, (ii) dilution of pollutants from flue-less appliances.
For correctly designed and installed appliances with flues or chimneys all the combustion products should be
discharged directly to outside. For this to happen it is important that the ventilation system does not cause spillage
of combustion products by significantly depressurizing the room. Ventilation systems can be designed to remove
ventilation extract air and combustion products by the same duct system and fan. In such systems it is essential
that safety controls are included to ensure that a failure of the exhaust fan does not result in spillage of combustion
products into any dwelling.
Ventilation to limit the concentration of combustion products in the indoor environment should only be applicable to
flue-less combustion appliances. These appliances may be categorized as (a) continuous (such as kerosene or
gas space heaters) or (b) intermittent (such as gas water heaters and cookers).
The criteria most usually applied in assessing the required ventilation rate for flue-less appliances is the need to
maintain the concentration of carbon dioxide below the widely accepted occupational (8 h) exposure limit of 0,5%
and indoor relative humidity low enough to avoid condensation leading to mould growth. For continuously operating
appliances an equilibrium condition is appropriate but for gas appliances which operate intermittently for limited
periods of time a lower air supply rate is permissible. CO and water vapour production rates for fuels commonly
used in flue-less appliances are given in Annex A.
NOTE In some countries other criteria may dominate that for CO , such as particularly low limiting concentrations of
formaldehyde or oxides of nitrogen.
6 Design assumptions for residential ventilation
A ventilation system is designed to provide outdoor air for human and building needs under certain defined
conditions. The design performance of a ventilation system can only be achieved within the limits of these
conditions. It is essential that the designer specifies these conditions as well as the design performance of the
ventilation system.
External environmental and climatic conditions may influence the application of different ventilation principles.
EXAMPLE 1 A slight under-pressure in relation to outdoors especially in severe climates can help to avoid damage to
structures caused by moisture.
EXAMPLE 2 In areas where under-pressure can cause the potential risk of an increase in the concentration of radon, the
under-pressure indoors should be designed to be a minimum.
EXAMPLE 3 Alternatively, the building can be designed for slight overpressure if the building structures, indoor air humidity
and climate conditions are suitable. Special attention should be given to the risk of condensation and moisture damage.
The designer should consider making assumptions about the following:
 outdoor meteorological conditions (e.g. wind speed, air temperature, humidity) which might be expressed as
extreme values, average values, value exceeded for a percentage of the time, and may be on a monthly or
yearly basis;
 pollutant levels in the outdoor air;
 outdoor noise level;
 shielding of the building;
 air-tightness of the building;
 thermal characteristics of the building;
 noise characteristics of the building (walls, windows etc.);
 maximum acceptable pollutant levels in the indoor air;
 thermal comfort;
 acoustic comfort;
 number of occupants the rooms and/or dwelling are designed for;
 indoor pollutant production rates;
 noise from the ventilation system;
 proper installation of the ventilation system/components (e.g. duct leakage);
 proper use of the ventilation system/components (e.g. running times);
 proper cleaning and maintenance of the ventilation system/components.
These resulting design conditions should be listed in the specification for the system and the operating manual for
the ventilation system (see Clause 9). Guidance on the proper use and maintenance of the ventilation system is a
particularly important part of this manual.
7 Performance requirements for ventilation systems
7.1 Ventilation air volume flow rate
7.1.1 General
The ventilation system should be designed to provide ventilation according to the performance requirements and
design rules given in Clauses 7 and 8. Informative Annex D may also be a useful source of general information and
guidance on residential ventilation and air-tightness.
For all residential ventilation systems it is necessary to specify ventilation air volume flow rates such that assumed
or predicted concentrations of certain known indoor pollutants are not exceeded. The ventilation air volume flow
rate is specified in many different ways in the regulations and standards of different countries and it has not been
possible to draw up a simple table with classes which cover all, or even most, of the widely varying requirements
and options currently used in European countries. Therefore, this Technical Report does not contain mandatory
requirements or classes for residential ventilation air flow rates. The required ventilation air flow rates should be
obtained from national and local regulations and/or standards prevailing in the country concerned.
However, this Technical Report does describe a method of establishing the required ventilation air volume flow rate
by calculation using pollutant production rates and indoor and outdoor air conditions specified by the user. The
equations for use in the calculation method are given in Annex E. Examples of the ventilation air flow rates
resulting from such calculations are given in Annex F on the basis of a range of assumptions about pollutants and
other parameters.
7.1.2 Pollutant groups
The most common pollutants occurring in dwellings may be grouped into three different groups which can lead to
different, but complementary, ventilation strategies.
a) Group of background pollutants. Two types:
 first type includes a large number of pollutants emitted by materials, furnishings and products used in the
dwelling. They are generally not perceivable by the occupants and their sources are at a relatively low but
continuous rate;
 second type includes metabolic products from the occupants mainly represented by water vapour and
carbon dioxide from respiration, and odours;
b) Group of specific pollutants, mainly represented by water vapour, carbon dioxide and odours. Their production
is related to specific human activities in the dwelling such as cooking, washing, bathing etc., whose duration is
relatively short, which result in relatively high pollutant production, and which occur in specific locations in the
dwelling;
c) Group of combustion products from fuel burning appliances for space and water heating, the most dangerous
of which is carbon monoxide. These should be dealt with by proper design of the appliance and a chimney or
flue system which carries the pollutants directly to outside the dwelling, if possible.
NOTE it is strongly recommended that flue-less space or water heaters are not used in dwellings because of their high
rates of pollutant production.
For residential ventilation purposes it is common to use water vapour as an indicator of ventilation need in activity
rooms. In low pollution rooms both water vapour and CO are used as indicators of other metabolic pollutants.
7.1.3 Ventilation strategies
One of the following two ventilation strategies are normally used. First, a continuous and nominally constant
ventilation air flow rate may be provided to deal with both specific and background pollutants together.
Alternatively, a continuous (relatively low) background ventilation air flow rate may be provided to deal with the
background pollutants together with a higher intermittently operated extract air flow rate provided in the activity
rooms to deal with most of the specific pollutants. The intermittent operation may be controlled manually by the
occupant or automatically by suitable sensors. A typical pattern of intermittent operation over a period of one day,
compared with an equivalent extract system operating continuously at a constant rate, is illustrated in Figure 1.
Key
1 total air ventilation air volume flow rate (L/s)
2 time of day (hours)
3 continuous extract ventilation at constant rate
4 intermittent extract and natural background ventilation
Figure 1 — Example of two ventilation strategies
7.1.4 The ventilation air volume flow rate requirement
In all cases the basic intention is to achieve a reasonable level of indoor air quality without wasting energy, i.e.
i) CO concentration to be kept below a reasonable level;
ii) humidity is kept between reasonable levels to avoid an atmosphere which is too dry and to avoid
mould growth or condensation;
iii) to remove odours within a reasonable time;
iv) to keep concentrations of other unspecified pollutants below a reasonable level.
Considering the diversity of sources and pollutants in indoor air, and the range of susceptibility in the population,
compliance with this Technical Report will not necessarily ensure acceptable indoor air quality for everyone. There
may be a conflict between the above criteria; e.g. the ventilation rate to keep below a particular CO level may lead
to a level of humidity which is too low to be acceptable. Compromises may then have to be made allowing some
pollutant concentrations to rise above intended limits for a limited period.
When determining ventilation air flow rates the total design extract air flow rate and the total design supply air flow
rate obtained for the whole dwelling are usually different. The ventilation system should generally be designed to
extract air at the greater of those two air flow rates to avoid overpressure and the risk of interstitial condensation in
the structure. The ventilation system should be designed to supply air at least to the design total supply air flow
rate. The difference between the design total supply and extract air flow rates may be provided by air leakage
through the dwelling structure and/or by additional air supply components in the ventilation system. As buildings
are getting tighter and tighter, relying only on building leakage could lead to too low ventilation rates.
If air leakage alone is used for the additional air supply then there may be problems with spillage from open-flued
combustion appliances in airtight dwellings (see 7.1.9).
Where products intended for high flow intermittent operations, e.g. range hoods, drying machines, consideration
should be given to the replacement air requirements.
7.1.5 The calculation method
The starting point for the calculation method is to define the most important, or key, pollutants in each type of room
in the dwelling. It is assumed that if the key pollutant is adequately controlled then other pollutants in that room are
also adequately controlled. In some rooms it may not be clear which is the key pollutant until some calculations
have been made. Key pollutants for various room types are as follows:
Low pollution rooms: CO (metabolic) or water vapour;
 kitchen: water vapour, odours, CO (from combustion of fuels);
 bathroom: water vapour;
 WC: odours;
 laundry/utility room: water vapour.
Other pollutants can be released during specific activities, such as vapours from paints and adhesives used as part
of a hobby. If known these may be included in the calculation method.
Pollutant emission rates should be calculated for each room separately based on either known emission rates
(where available) or the data given in Annex A. This may require assumptions about the number of occupants in
the dwelling, the type and rating of combustion appliances, and occupant habits (clothes washing, cooking, bathing
etc.).
7.1.6 Minimum and maximum ventilation air flow rate
Minimum ventilation airflow rate is intended to ensure that a minimum level of air quality is maintained by removing
pollutants which are continuously emitted from materials and activities in the dwelling, removing residual pollutants
(particularly water vapour) after occupation ceases, and to reduce the risk of a build-up of condensation in
ventilation ducts. There may be different minimum air flow rates for when the dwelling is occupied and when it is
unoccupied. The minimum ventilation rates (if any) should be as specified in national and local building regulations
and standards.
If the ventilation system has automatic demand control of air flow rate, and is kept operating when the dwelling is
unoccupied, it should be possible to design the ventilation system with a minimum air flow-rate lower than the
specified minimum ventilation air flow rate. There may be a maximum ventilation air flow rate specified for energy
efficiency reasons. The maximum ventilation air flow rate (if any) should be as specified in national and local
regulations and standards.
7.1.7 Effect of weather on ventilation air flow rates
Natural ventilation is driven by variable forces (wind and stack effect) and therefore the ventilation air volume flow
rate is not constant. Fan assisted ventilation systems may also be affected by wind, although the effect should be
less than with natural ventilation. The ventilation air volume flow rates specified in this Technical Report are
therefore nominal values for appropriate weather conditions.
For natural ventilation systems air flow rates should be calculated on the basis of assumptions about outdoor
temperature, internal temperature, wind speed and direction in addition to data on the physical and aerodynamic
characteristics of the dwelling and ventilation system. These design values should be according to local climatic
conditions during the heating season. It is possible to use local weather statistics to calculate a natural ventilation
air volume flow rate which is likely to be exceeded for a chosen percentage of the time using the calculation
methods given in EN 13465.
There may be specified a low air flow rate to be exceeded for a large proportion of the time to maintain adequate
indoor air quality and a high air flow rate to be exceeded for only a small proportion of the time to limit energy
consumption.
7.1.8 Tobacco smoke
It is unusual to make special provision for removal of tobacco smoke in dwellings. However, in rooms where
smoking is likely to occur such provision may be made, if required, for example by increasing fan air flow rate, by
openable windows or by another device (e.g. an electrostatic filter). Ventilation air flow rates may need to be
increased by a factor of 2 to 10 to deal with tobacco smoke.
7.1.9 Combustion appliances
Air supply requirements for open flued combustion appliances are contained in other standards and in national and
local regulations. However, such air flows contribute to the removal of pollutants from dwellings and so, for the
purposes of this Technical Report, combustion air supplies may be included in the ventilation air flow rates for
ventilation of the dwelling.
The air flow rate through the appliance is a function of the design of the appliance, the principle on which it
operates and for some types (mainly oil and gas appliances) frequency of burning cycles. This is outside the scope
of this Technical Report but a simple method of estimating the contribution made to ventilation air flow rate by
combustion appliances may be found in EN 13465. Attention is drawn to the requirements of 7.3 Interaction with
combustion appliances in this Technical Report.
Flue-less space heating appliances require very high ventilation air flow rates for removal of their combustion
products. Combustion products given off by flue-less appliances for each kW of rated input are equivalent to the
CO production from about 8 people, and water vapour production of about 3 people. It is strongly recommended
that flue-less space heating appliances are not used in dwellings, but if the ventilation system is designed to deal
with them then Equations E.1 and E.2 should be used to calculate the necessary ventilation air flow rates.
7.2 Direction of air flow between rooms
It is a design aim that the direction of air flow inside the dwelling is from low pollution rooms to activity rooms (see
Figures 2, 3, 4 and 5). Therefore, air should be supplied and extracted in such a way as to restrict, so far as is
practical, the movement of air from rooms containing the main sources of pollutants and excess water vapour
(activity rooms) to other rooms (low pollution rooms). Low pollution rooms therefore usually have an outside air
supply whilst activity rooms usually have an air extract device. The design condition should be with windows and all
doors closed in which case the designer may have to consider making provision for air transfer between rooms to
ensure that design air flow rates are achieved in practice.

2 b - Example
2 a - Example
2 c - Example
2 d - Example
Key
shaded part extract area
non shaded part supply area
hashed part transit area
Figure 2 — Examples of natural ventilation

3 b - Example
3 a - Example
3 c - Example
3 d - Example
Key
shaded part extract area
non shaded part supply area
hashed part transit area
Figure 3 — Examples of fan assisted supply ventilation

4 b - Example
4 a - Example
4 c - Example
4 d - Example
Key
shaded part extract area
non shaded part supply area
hashed part transit area
Figure 4 — Example of fan assisted extract air ventilation

5 b - Example
5 a - Example
5 c - Example
5 d - Example
Key
shaded part extract area
non shaded part supply area
hashed part transit area
Figure 5 — Example of fan assisted balanced air ventilation
7.3 Interaction with combustion appliances
The ventilation system should not adversely affect the safe operation of open-flued combustion appliances
(ventilation systems do not normally interact with room sealed appliances). Air extract devices which are not
located in the same room as the combustion appliance should be considered because they may also interact with
combustion appliances. Particular requirements may be specified in national and local building regulations and
standards.
Combustion appliances installed without a specific air supply may be supplied with air through the ventilation
system. The compatibility of the ventilation system air extract and supply flow rates with the appliance's air supply
rate should then be checked. Combined extracting of air and flue gases is permitted provided this does not lead to
improper operation of the combustion appliance.
7.4 Cleaning and maintenance
The ventilation system should be so arranged, designed and installed as to facilitate easy cleaning, maintenance
and repair of those components which reduces the performance of the system if they are neglected. Those
components which are intended to be replaced during maintenance should also be easily accessible. The basic
requirements for ductwork components to facilitate maintenance are given in ENV 12097.
If a component has to be removed for cleaning and/or maintenance its construction should allow remounting and
the service instructions should include sufficient guidance for the checking of its function.
Provisions for filter pressure drop measurements or exchange should be provided when applicable as well as clear
indications of the limits of range of use of the filter.
NOTE National and local regulations for routine maintenance work may require checking of air flow rates and in such
cases permanent air flow measuring points should be installed in the system at convenient places. These measurements are
covered in detail in EN 14134.
7.5 Pollutants distributed by the ventilation system
Pollutants should not be allowed to spread between dwellings or between a dwelling and another part of a building
through the air ducts of the ventilation system.
Filtration of outdoor air may give a measure of protection to both the occupants of the dwelling and to components
of the ventilation system. EN 13779 contains categories of both indoor and outdoor air with recommended filter
classes according to EN 779 which may be used for residential purposes.
Filtration of indoor air does not generally protect the occupants but it is desirable to protect, and perhaps extend the
life of, components of the ventilation system. Fans and heat exchangers in particular may require less frequent
maintenance and cleaning if suitable particulate filters are used upstream of them.
7.6 Strength and durability
A ventilation system should be installed using supports of adequate strength, e.g. as specified in EN 12236.
All components should be made of durable materials which are resistant to the environment in which they are
installed over an economically reasonable working life.
7.7 Fire precautions
Ventilation systems and installations should be executed in a manner which ensures that they do not promote the
spread of smoke or fire between compartments or into fire escape routes (such as protected stairways and
corridors).
Ventilation system components should be made of materials, and mounted in a manner, which ensures that the
intended fire resistance is maintained.
NOTE National and local regulations for fire safety may impose other requirements on ventilation system design.
7.8 Noise
7.8.1 Introduction
The ventilation system should be designed in such a way that the acoustic requirements (sound insulation)
between dwellings, or between a dwelling and outside are fulfilled. In particular, noise transmission between
dwellings via the duct system of a central ventilation system (such as in an apartment type building) is carefully
considered.
The ventilation system should not generate excessive noise. Any noise produced should be steady and should not
contain any distinguishable tonal or impulsive characteristics. Relatively high noise levels are likely to be tolerated
in activity rooms from intermittently operated fans and continuous systems on boost, although even here noise may
not be acceptable if it affects activities such as listening to a radio or having a telephone conversation. Noise is
least likely to be tolerated in certain rooms and at certain times, particularly bedrooms at night and other low
pollution rooms during quiet periods of the day. In addition, a fan assisted ventilation system does not generate
unacceptable noise outside the building.
Controlling noise aspects, in particular reducing noise levels, is one of the most important factors that c
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