this slide is about ventilation in building

1. BUILDING
SERVICES..
VENTILATION IN
BUILDING….
CHITRA RANA 3RD
SEM….

2. Ventilation in Buildings
Ventilation is the process by which fresh air moved around the
building. Good ventilation is essential for the comfort and safety of
building occupants, and in many cases subject to a legal minimum
requirement.
Types of ventilation
Natural ventilation
Natural ventilation is the use of wind and temperature differences to create
airflows in and through buildings.
There are two basic types of natural ventilation effects: buoyancy and wind.
Buoyancy ventilation is more commonly referred to as temperature-induced or
stack ventilation. Wind ventilation supplies air from a positive pressure through
openings on the windward side of a building and exhausts air to a negative pressure on
the leeward side. Airflow rate depends on the wind speed and direction as well as the
size of openings. In summer, the indoor-outdoor temperature difference is not high
enough to drive buoyancy ventilation, and wind is used to supply as much fresh air as
possible. In winter, however, the indoor is much warmer than outdoors, providing an
opportunity for buoyancy ventilation.

3. Task ventilation
Traditional ventilation systems supply a mixture of outside and re-circulated
air in high velocity jets so that the indoor air in rooms is often well mixed. This
can be an inefficient method of delivering outside air to an occupant. Task-
ambient conditioning (TAC) systems are a ventilation technology with the
potential for r, desk, or partitions and enable occupants to adjust the supply
flow rate, direction, or tempeimproved ventilation to the occupant. TAC
systems may supply air from the
foliature so that thermal conditions can
be tailored to meet the individual's
requirements.
Task or personalized ventilation is a
method for providing occupants with
control of a local supply of air so that
they can adjust their individual thermal
environment. Controlled variables
could be the supply-air temperature,
velocity, direction, the ratio of room air
to outside in the supply air, and the
radiant temperature. These systems
may provide all or part of the
conditioned air to the occupied space.
Task or personalized ventilation
systems also have the potential to improve ventilation at the occupant's
breathing zone because they can provide supply air preferentially toward the
breathing zone. Supply air from these systems usually contains a high
percentage of outside air, which generally does not contain a high
concentration of indoor-generated pollutants. The air supply outlets of current
task or personalized ventilation systems are located at the floor, mounted on
the desk, or incorporated within the workstation partitions.
Mechanical ventilation
This system supplies the required air flow at a constant rate. Ventilation is
supplied by forcing air through the ducting with the use of a fan. The use of

4. the fan however uses a lot of energy and consequently greater CO2emissions.
Hybrid ventilation
Hybrid ventilation is the mix of natural and mechanical ventilation. In this project there is only
one aspect of mechanical ventilation, which contributes to the hybrid one: the fan which
enhances the natural stack effect if the conditions are poor.
Ventilation in Buildings

5. Air Changes
The replacement of a quantity of air in a space within a given period of time, typically
expressed air changes per hour. If a building has one air change per hour, this is equivalent
to all of the air in the building being replaced in a one-hour period. Under current regulations
(Part F) an air change rate of 8 liters per second must be achieved for new build offices.
Chilled Beams
A chilled beam is a building cooling device that circulates air using the principles of natural
heat convection. The major advantage of a chilled beam over more common forced air
systems is that it circulates building air without the noise and expense of ductwork and air
handlers. Typically mounted overhead near or within a ceiling, the beam is a type of

6. radiator, chilled by an external source such as Recalculated water. It cools the space below
it by acting as a heat sink for the naturally rising warm air of the space. Once cooled, the air
naturally drops back to the floor where the cycle begins again.
Condenser
A condenser is a heat exchanger in which the refrigerant, compressed to a hot gas, is
condensed to liquid by rejecting heat to achieve a cooled space. The condenser in an air
conditioning unit is very similar to that used in a common refrigerator.
Constant Air Volume (CAV)
Constant Air Volume (CAV) is a type of heating, ventilating, and air-conditioning (HVAC)
system. In a simple CAV system, the supply air flow rate is constant, but the supply air
temperature is varied to meet the thermal loads of a space. Most CAV systems are small,
and serve a single thermal zone. However, variations such as CAV with reheat, CAV
Multimode, and CAV primary-secondary systems can serve multiple zones and larger
buildings.
Convection Heating
In convection heating, air is heated when it comes into contact with hot surfaces in the
heater. People feel warmer because of the higher air temperature. Some convection
heaters use a fan to draw the cool air in.
Fan Coil System
A Fan coil system is an air conditioning system used in buildings. A fan unit is placed at
each place which needs to be heated or cooled. A central plant delivers hot or cold water to
fan units. The fan draws air from the room, blows it over the water coil and returns it to the
room. Dehumidified air from a central plant or fresh air from outside may also be used by a
fan coil system.
Internal Environment

7. In the context of mechanical building services the internal environment refers to the strategy
employed to heat, cool and distribute air around a building. The Internal environment can be
heated and/or cooled, whilst air distribution could be through natural or mechanical
methods, or a mixture of the both for a mixed-made strategy. If comfort cooling is provided
throughout the internal environment would be fully air conditioned.
Mixed Mode
A mixed mode system combines the best aspects of both natural ventilation and mechanical
ventilation/air conditioning. The simplest example of a mixed mode system is the opening of
windows to enable natural ventilation with air conditioning available when windows can not
be opened.
Natural Ventilation
Ventilation systems are considered natural if the air is supplied and removed from the
indoor space by non mechanical means. The use of natural ventilation reduces the need for
mechanical energy consuming plant and is therefore more efficient. The requirement for
natural ventilation to be utilized effectively in a building calls for early implementation in the
design of a building.
Radiant Heating
Radiant heating heats a building through radiant heat. The heat energy is emitted from a
warm element (floor, wall, overhead panel) and warms people and other objects in rooms
rather than directly heating the air. The internal air temperature for radiant heated buildings
may be lower than for a conventionally heated building to achieve the same level of body
comfort (when adjusted so the perceived temperature is actually the same).
Terminal Unit
A terminal unit is the final device in an air conditioning system located in the space being
heated or cooled. The terminal unit can be utilized to determine the flow and direction of air
whilst re-heating/re-cooling to achieve the desired local temperature.
Variable Air Volume (VAV)

8. Variable air volume (VAV) is a technique for controlling the capacity of a heating, ventilating,
and/or air-conditioning (HVAC) system. The simplest VAV system incorporates one supply
duct that, when in cooling mode, distributes approximately 55 degree F supply air. Because
the supply air temperature, in this simplest of VAV systems, is constant, the air flow rate
must vary to meet the rising and falling heat gains or losses within the thermal zone served.
Variable Speed Drive (VSD)
An electronic device designed to be used with a motor to provide a variable flow output,
thus reducing the energy required to turn the motor.
Natural ventilation: Breathe life into your building
Refresh your building with a natural ventilation system.
As buildings become more contemporary in their design, sustainable strategies,
such as natural ventilation, are becoming increasingly important to a structure's core
principles.
Not only does such an approach allow for a building to use 60 per cent less energy,
it also drastically improves the air quality for the occupants within.
How does it work?
Natural ventilation takes advantage of both wind and buoyancy in order to drive
fresh air through a building. This removes the need for the use of intensive fans -
which can often be expensive in terms of energy use and installation.
Using the 'stack effect' this ventilation method makes use of the fact that warm air
rises above cold air. Naturally ventilated buildings can utilize this so that an atrium
allows warm air from an occupied space to rise and escape through vents situated
at the top of the building
Gap ventilation
 Wind and airflow caused by temperature differences fluctuate too much in
Central Europe. In a house which is not leaky enough for sufficient air

9. exchange during periods with small wind forces, intolerable draughts are
still caused during periods with strong winds
 New constructions in many countries such as Germany are so airtight that
air exchange through leaks in the envelope is insufficient for good indoor
air quality. This also applies for modernized buildings with new windows.
 Apart from that, condensation damage can occur due to the warm air
escaping through cracks.
Windandweather fluctuate- so
does the air exchangein “free”
ventilation.Ifthis issufficent on wind-freedays,the heat losses
duringstrong windswill be intolerablyhigh.Gapventilationis
therefore no longer accepted by occupantsin colderclimates.

10. Purge ventilation through windows

11. Accordingly, the air quality is usually poor and there is an increased risk of
high air humidity. Because we cannot perceive the indoor air quality ourselves
and it is not possible for us to estimate the amount of fresh air actually
supplied through open windows, it is difficult, even for an expert, to achieve
“just the right” amount of air exchange.
 If ventilation is insufficient, the air quality will be poor and there will be a
risk of condensation occurring.
 If too much ventilation takes place, the air will become too dry and energy
consumption will become excessively high.
⇒ One of the reasons for home ventilation is to reduce the air humidity in the
home slightly, because a high level of moisture in the air often causes building
damage. However, the air should not be too dry either. You can find more
information on the page about Ventilation and Humidity ("Air volumes" page).
The right level of air humidity is not the only requirement for an adequate
exchange of air. Pollution of indoor air, due for example to the radioactive inert
gas Radon, must be reduced to safe levels by adding fresh air. 1)
Why opening the windows twice a day isn't enough
It's quite simple:
 If the window is opened wide for long enough, the stale indoor air will be
replaced by fresh outdoor air.
 When the air replacement is complete, the windows don’t need to be kept
open any longer (replacing of fresh air with fresh air?).
 Window ventilation provides this kind of just one complete air exchange
each time it takes place.
 If this is done twice a day, this means two air replacements in 24 hours or
an average air change of 2 / 24 h-1
which is less than 0.1 h-1
.
There is no doubt that 0.1 air exchanges per hour is insufficient for good
health and comfort

12. The simplest solution: exhaust system
The function of comfort ventilation is to supply fresh air in “just the right”
quantities to the living space. The simplest solution is an exhaust fan
system that extracts the stale and humid air from the kitchen, bathroom and
toilet. At the same time, fresh air (cold air in winter) is drawn in through
outdoor air inlets into the living areas.
These simple systems are now standard in France; exhaust systems have
been used in Sweden for more than 50 years and since 1980 it has become
obligatory to have home ventilation. In Germany this could be an effective
solution for new constructions built to Even standard and for refurbishment of
existing buildings (which have now become more airtight), but unfortunately
this has not been made compulsory.
For the Passive House, however, this simple system can't be considered
because the incoming air is cold, the ventilation losses will therefore be too
high . For one thing, a correspondingly high output heat supply near the inlet
will then be necessary and for another, the annual heating demand will be at
least double that of a Passive House. Less ventilation doesn't come into
question because energy conservation should not mean less hygienic
conditions or worse indoor air quality.

13. Controlled ventilation
Systematic examination of homes has shown that proper distribution of fresh
air in all rooms and safe dehumidification of kitchens and bathrooms is
possible through controlled ventilation.
 In this way the fresh air is directly supplied to the living room, office and
bedrooms. These rooms are equipped with at least one supply air inlet.
 As in exhaust air systems, the kitchen, bathroom and toilet as well as other
areas with high humidity and odours are ventilated directly through the
extract air outlets.
 There is a directed flow throughout the house: the fresh air first enters the
main living rooms (see illustration), from here it flows through the
transferred air zones (usually corridors) into the humid areas. The humid
areas have relatively high air changes so that e.g. towels can dry more
quickly.

14. Ventilationonlyfunctionsproperlyifused air iscontinuously
beingremoved from the kitchen, bathroom,toiletand other
rooms withhighpollutionandhumidity.Inreturn, fresh,
unusedexternal air is suppliedtothe livingroom,bedrooms
and functional rooms.

15. CONTINUOUS NATURAL VENTILATION
One of the most important requirements
for comfort in a hot and humid climate is continuous and free air
circulation and moisture evaporation through breezes. Our design
philosophy provides for large openings towards the windward and
the lee ward sides, within apartments, and cross ventilation is taken

16. care of through the air spaces in sky courts. The sky gardens in the
apartments act as wind scoops, creating air currents, drawing air
into the house.
NATURAL MATERIALS
In keeping with our design objectives of creating spaceswhich are
energy efficient and thermally comfortable,
we use a combination of late rite blocks, hollow terracotta blocks
and wire cut bricks for the external walls.
This forms an envelope with air cavities, the terracotta blocks on the
outside and the late rite blocks on the inside, keeping the interiors
cool, thus bringing down the use of air-conditioning. Besides serving
as a passive cooling system, the external wall is also very low on
maintenance bringing down the long term maintenance costs of the
building.

17. SKY GARDENS
The design of the sky gardens
minimizes the heat and moisture on the lower floors, by virtue of
protecting the walls below. The landscaped garden, acts as a buffer
from the dust, heat and the lashing rain. They are staggered on
alternate floors to form a chequer board like spacing,
which enhancesthe air movement between floors.
The double height spacing between the gardens, gives each one
a private uninterrupted bit of sky. The verandah, between interior
and exterior, is a comfortable space from which one can enjoy the
rain, only feeling the mild spray, or the cool breeze and shade from
the sun.