Ventilation

7/21/2019 Ventilation

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BUILDINGSERVICES-VI

Lecture -1

Contents:Need

Defne ventilation

Type:

Natural ventilation

Mechanical ventilation

Hybrid ventilation

•Air change

•Air change rate

•Air movement

•Orientation

• Temperature eects

•Minimum requirement



NEED

• To reduce Carbon-di-oxide content and control dust and

other impurities in the air.

• To suppress odours ,smoke ,concentration of bacteria, etc.

•To maintain desired relative humidity and favorableambiance to live-in.

• The ventilation of a building can have a significant affect on

energy consumption and a thorough assessment of natural as

against mechanical ventilation should be made as the decision

could significantly affect the energy efficiency of a building.



VENTILTI!N

Ventilation – Free passage of clean air in a structure.

• VENTILTI!N is the process of changing or replacing air in

any space to provide high indoor air "uality.

• The systematic removal of heated air, smo#e, and gases from

a structure and replacement $ith cooler, cleaner air.

• Ventilation includes both the e%change of air to the outside as

$ell as circulation of clean air $ithin the building.



&'( VENTILTI!N

Improving thermal comfort and inoor air !"ality through

provision o resh air is !no"n to be vitally important toindividuals# perception o a space$ their health and "ell%being$and productivity&

• Any ventilation system should be 'e(ible because it "ill need to

"or! under a "ide range o conditions)

I# To remo$e e%cess heat from people an e!"ipment#II#To remo$e moist"re& smells an poll"tants 'enerate (y

people$ pets and coo!ing$ "hich can be unpleasant or ha*ardousto health and+or buildings&

III#To remo$e 'aseo"s emissions from materials& f"rnishin's&

cleaning agents and$ in aected areas$ the products o radon&IV#To act as a carrier for heatin'& coolin' an)or h"miity

control&

V#To pro$ie o%y'en for (reathin'& altho"'h the saferequirement is a tiny proportion compared to the other needs&



VENTILTI!N T()E*

• N!"#$ V%N!&$!&'N

– +lo$ driven by $ind and temperature.

• F'#C%( &# – )%C*N&C$ V%N!&$!&'N

– E%haust ,*upply and plenum process.

• *+#&( V%N!&$!&'N

– ombinations of the above systems.



NTL VENTILTI!N NTL VENTILTI!N

/ Natural ventilation includes the

movement of outdoor air throughintentional openings such as doors

and $indo$s and through

unintentional openings in the

building shell such as crac#s $hich

result in infiltration and e%-

filtration.

/ This ventilation type is mostly usedin smaller buildings .

/ Normally it is driven by $ind

pressure and density variations.

/ The various types are,

0 single sided ventilation

1density driven2

0 stac# ventilation 1density

driven2

0 cross flo$ ventilation

1$ind driven2



&N$% &(%( V%N!&$!&'N

/N!"#$0

!C1 V%N!&$!&'N. /N!"#$0

C#' F$'2 V%N!&$!&'N

/N!"#$0

This air is replaced by cold outdoor air

that enters near the bottom of the building

or from the ground. This phenomenon is

called the building 3*tac# Effect4.



• Natural ventilation is the ventilation of a building $ith outside air $ithout

the use of a fan or any other mechanical system.

• It can be achieved $ith open-able $indo$s or tric#le vents $hen the spaces

to ventilate are small and the architecture permits.

Clerestory 0

are any high $indo$s

above eye level . Thepurpose is to bring

outside light, fresh air,

or both into the inner

space.



5

T()E* !+

NTL VENTILTI!N !)ENIN6*

&indo$s 1&indo$s sliding vertically, sliding hori7ontally, tilting,

s$inging2.

Doors, monitor openings and s#ylights.

oof Ventilators 1$eather proof air outlet2.

*tac#s connecting to registers 1A device attached to an air%

distributing duct or the purpose o controlling the

discharge o air into the space to be heated$ cooled$ orventilated&

*pecially designed inlet or outlet openings.



+!ED VENTILTI!N• 8echanical or forced ventilation is used

to control indoor air "uality.

• E%cess humidity, odours, and

contaminants can often be controlled via

dilution or replacement $ith outside air.

• 9itchens and bathrooms typically have

mechanical e%haust to control odours and

sometimes humidity.

• eiling fans and table fans circulate air

$ithin a room for the purpose of reducing

the perceived temperature because of

evaporation of perspiration on the s#in of

the occupants.



T()E*

• upply ystem

– *upplying fresh air by input fans in outside $alls.

• %xhaust ystem

– reating partial vacuum by e%haust fans and blo$ers.

• )lenum process

– *upply of fresh air by inlet ducts and e%haust of vitiated air

by outlet fans.



*))L( *(*TE8*

Components3

ir inlet section

+ilters

'eating and:or cooling e"uipment

+an

Ducts

egister:grills for distributing the air $ithin the $or# space



E;'*T *(*TE8*

4urpose3

n e%haust ventilation system removes the air and airborne

contaminants from the $or# place air

The e%haust system may e%haust the entire $or# area, or it may

be placed at the source to remove the contaminant at its source

itself

!ypes of exhaust systems3

6eneral e%haust system

Local e%haust system



6ENEL E;'*T *(*TE8*

sed for heat control in an area

by introducing large "uantities

of air in the area. The air may

be tempered and recycled.

sed for removal of

contaminants generated in an

area by mi%ing enough outdoor

air $ith the contaminant so that

the average concentration is

reduced to a safe level.



L!L E;'*T *(*TE8*1LE*2

The ob<ective of a local e%haust system is to remove the

contaminant as it is generated at the source itself.

dvantages3

8ore effective as compared to a general e%haust system.

The smaller e%haust flo$ rate results in lo$ heating costs

compared to the high flo$ rate re"uired for a general e%haust

system.

The smaller flo$ rates lead to lo$er costs for air cleaning

e"uipment.



&'T I* T'E DI++EENE =ET&EEN

E;'*T ND *))L( *(*TE8*>n E%haust ventilation system removes the air and air borne contaminants

from the $or# place, $hereas, the *upply system adds air to $or# room to

dilute contaminants in the $or# place so as to lo$er the contaminant

concentrations.

Plenum Process



Hybrid ventilation is a two mode system combining of natural ventilation and

mechanical ventilation.

Mechanical ventilation is used when natural driving forces cannot fulfill the

required ventilation level.



Hybrid -entilation%Advantages

• 'ybrid ventilation systems offer many advantages?

– elative lo$ running costs for energy conditioning the ventilation

air

– Energy savings compared to full mechanical ventilation systems

– Easily controlled by the inhabitants compared to natural ventilation

– elative lo$ maintenance

– educed use of mechanical e"uipment compared to mechanically

ventilated building



Hybrid -entilation%Disadvantages

• Disadvantages include?

– elative high initial costs

– Depending on climatic conditions, hybrid ventilation is not suitable

for many types of buildings $here mechanical ventilation might be

the only solution

– oom space for e"uipment might be needed 1space for ducting2

– =uilding design might impose restrictions to the use of hybrid

ventilation

– The urban aspects 1noise, outdoor pollution, $ind velocity,humidity2 might limit its use



SELECTING T*E VENTIL+TI,N STR+TEG



SELECTING T*E VENTIL+TI,N STR+TEG

B+SIC D,.ESTIC SC+LE .V*R SSTE.



B+SIC D,.ESTIC SC+LE .V*R SSTE.#

+DV+NT+GES +ND DIS+DV+NT+GES ,/ N+TUR+L +ND .EC*+N



+DV+NT+GES +ND DIS+DV+NT+GES ,/ N+TUR+L +ND .EC*+N



I 'N6E*

The volume o resh air .ma!e up air/ required or proper

ventilation is determined o the si*e and use o the space&



The air change rate refers to the number of times in a 1-hr eriod that thevolume of air in a sace is renewed.

Design Consideration:

The factors affecting air change rate are!

• The resence of air oc"ets or dead sace in the #ontrolled area.

• The relative ositioning of $uly and %eturn air grills.

• Tye of Machine and &quiments laced inside the area

I 'N6E TE



I 8!VE8ENT

'ir movement is affected by the following!

(ifferences in air ressure as air moves from areas of high ressure toareas of low ressure.

Circulation- heating and cooling equiment both

use blowers to distribute conditioned air throughout

buildings.

Ventilation fans for bathrooms) laundries

all vent conditioned air to the outside which must be relaced.

Combustion processes- aliances such

as boilers) furnaces) heating stoves and

water heaters ull air from the home

interior as they e*haust the roductsof combustion to the e*terior.

.



I 8!VE8ENT

(ifferences in temerature

Thermal buoyancy- describes the action ofair as it is heated. +ecause heated air is less

dense it rises) moving from a cool) high-

density area to ward a warm) low-density

area.

Stack effect- describes the action of warm

air rising through a building. 's warm airrises) it ulls cold ma"e-u air into the home

through the lower building enveloe and

ushes warm air out through the uer

building enveloe.

Convection currents- The movement ofcooler air moving in to relace rising warm

air will establish convection currents any

lace in the home in which temerature

differentials e*ist) with main areas of concern

being the living sace and attics.



E+RT* TUBES

One urther approach to the provision o resh air to a building$ and that can be used "itheither a mechanical or natural system$ is the earth tube& The temperature o the ground a e"metres belo" the surace is typically similar to the mean annual air temperature & This meansthat i the supply air is brought to the building via a long tube buried in the ground its "ill

ad0ust is temperature closer to the ground temperature& Thus in "inter cold air "ill be slightly"armed and in summer hot incoming air "ill be slightly cooled& Thus ree heat o cooling isprovided$ but is ar more popular in locations "here there is a much greater s"ing in annualtemperature&



TE8)ETE E++ET*

Temperature inside a structure is often different from the outside

ambient temperature.

8a%imum temperature differences occur $hen the indoor environment

is heated

In the $inter $hen indoor air temperatures are high relative to those

outdoors, the $armer and less dense air inside rises and flo$s out of

the building at its top.

During hot $eather $hen air conditioning produces lo$er

temperatures inside than outside, the reverse process occurs.

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Ventilation