Course: Climate Responsive Design (3672) Semester: Spring, 2020

ASSIGNMENT - 1

Q.5 With reference to the context of Pakistan, Which Active and Passive techniques
could be used to achieve sustainable ventilation in domestic building? Explore in the
context of your city.
1. Active Building
It is a structure which has evolved from the passive-model, not only focusing on energy
efficiency but also a degree of energy self-sufficiency. How we generate enough electricity to
meet a rapidly growing demand is a conundrum which is starting to influence how we design
buildings. This presents its own unique challenges as we look to simultaneously divest
ourselves of fossil fuels and shift towards green renewables.
Active Buildings provide a potential answer, one which will support societal shifts to electric
vehicles (EV) and away from gas powered heating, easing pressure on the grid and saving
consumers, landlords and business owners significant amounts on energy bills.

Figure 1: Active Building Model

Active Building Models mainly uses plant and equipment to modify climate. These buildings
are called “conditioned buildings” and guarantee a level of thermal comfort through the
active systems. The use of plant and equipment can lead to often over-sizing and redundancy
in the deployment of this equipment to accommodate the environmental loads.

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 Figure 2: Active Building Model

Localized problems of thermal comfort occur with poorly balanced plant and localized heat
gain from environmental loads.

2. Passive Building
Passive building comprises a set of design principles used to attain a quantifiable and
rigorous level of energy efficiency within a specific quantifiable comfort level. "Optimize
your gains and losses" based on climate summarizes the approach. To that end, a passive
building is designed and built in accordance with these five building-science principles: 
 Employs continuous insulation throughout its entire envelope without any thermal
bridging.
 The building envelope is extremely airtight, preventing infiltration of outside air and
loss of conditioned air.
 Employs high-performance windows (double or triple-paned windows depending on
climate and building type) and doors - solar gain is managed to exploit the sun's
energy for heating purposes in the heating season and to minimize overheating during
the cooling season.
 Uses some form of balanced heat- and moisture-recovery ventilation.
 Uses a minimal space conditioning system. 
Passive building principles can be applied to all building typologies – from single-family
homes to multifamily apartment buildings, offices, and skyscrapers. 

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 Figure 3: Passive Building Model

Passive design strategy carefully models and balances a comprehensive set of factors

including heat emissions from appliances and occupants to keep the building at comfortable
and consistent indoor temperatures throughout the heating and cooling seasons. As a result,
passive buildings offer tremendous long-term benefits in addition to energy efficiency: 
 Superinsulation and airtight construction provide unmatched comfort even in
extreme weather conditions.
 Continuous mechanical ventilation of fresh filtered air provides superb indoor air
quality. 
 A comprehensive systems approach to modelling, design, and construction
produces extremely resilient buildings. 
 Passive building principles offer the best path to Net Zero and Net
Positive buildings by minimizing the load that renewables are required to provide. 
Such buildings are called ‘free running” as its internal temperature follows that of the
climate. The best that can be achieved with this building is that the thermal performance will
be kept at the external shade temperature. In the days when the comfort level is exceeded,
behavior modification can be used to minimize thermal discomfort.

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 Figure 4: Passive Building - Solar Design

Potential of Passive Cooling Strategies in Pakistan: A Case Study of Peshawar Region

ABSTRACT:
Passive cooling strategies have important energy, financial, environmental, operational and
qualitative advantages over air-conditioning. For the successful application of different
passive cooling strategies into buildings, it is necessary to have knowledge of the basic
concepts of passive cooling and different factors (climate, building type, occupancy patterns
and activities in the building) on which the choice of passive cooling depends. There is a lot
of potential for passively cooled buildings in the climate of Pakistan. As an example, in this
article passive cooling strategies have been discussed for Peshawar; the Northern city of
Pakistan. Climatic data has been gathered from different meteorological information sources.
This publication will be helpful while developing an energy efficient building design. We
have tried to show with the help of a bio- climatic chart that in the climate of Pakistan the
passive cooling strategies could be an attractive alternative to the active cooling strategies.
Mechanical cooling in buildings can be eradicated or at least the cost and size of the cooling
equipment can be decreased using passive cooling methods into modern buildings.

Introduction:
The energy, consumed in a building, can be reduced by adopting simple methods using
suitable building design and energy efficient strategies, such as, passive cooling strategies.
Passive cooling eliminates the use of mechanical equipment and provides cooling using
passive processes. To improve the efficiency of the building envelope, passive cooling
strategy reduces heat gains from the external sources and helps heat loss to the natural
sources of cooling, such as, cool air, earth coupling and evaporation. Passive cooling is based
on the principle of preventing heat from getting into a building during a hot day and bringing
in external cool air into the building when the external temperature falls.

There are various parameters that affect the thermal behaviour of buildings, such as the
climatological ones, which are environmental variables, and which are not subject to human
control. The other type of parameters is the design variables, which are under control at the
design stage. Inadequate attention to the aspect of a building’s thermal behaviour at the initial
stages of its design can lead to an unwelcoming internal environment. During summer,
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buildings located in hotter regions often face overheating conditions due to exposure to
intense amount of solar radiation and high temperature. When these overheating conditions
inside the buildings surpass the threshold of thermal comfort; cooling them become
extremely significant.

Energy consumption of buildings both in the developed countries as well as in the developing
countries for cooling the building has increased tremendously over the past few decades
(Perez-Lombard et al., 2008). The reason for this is the extensive use of mechanical air
conditioning for cooling the buildings. One reason for heavy reliance on mechanical cooling
is due to affordable cost and easy availability of electricity as well as cooling equipment.

Now, the world realises that eventually there would be running out of fossil fuel; the main
source of energy in buildings at present thereby creating problems in fulfilling the energy
demands. Extensive use of fossil fuel is also causing an irreparable damage to the
environment. One of the solutions to address the above issues is to build energy efficient
buildings using passive heating and cooling strategies. Passive cooling techniques not only
offer energy and environmental benefits, but they are also very economical.

Materials and Methods of Passive Cooling:

Passive cooling can utilize several heat sinks and a variety of climatic influences to create
thermal comfort in warm regions, unlike the passive heating, which is driven by sun only.
Traditionally, passive cooling has been in use in indigenous buildings (Santamouris and
Asimakopoulos, 1996).
The first step towards achieving thermal comfort conditions is to take preventive measures
against the radiation from the sun, by shading & reflective barriers and by heat transfer the
envelope (by insulation and infiltration and infiltration sealing).
The main techniques of natural cooling according to the mode of heat transfer and fluid flow
can be classified as follows:
 Cooling with natural ventilation
 Radioactive cooling
 Cooling by evaporation
 Earth cooling

Passive Cooling Strategies:

The bioclimatic chart tells us that conditions are comfortable in the shade and in still air; if
the plotted point lies within the comfort zone. If the points lie outside the comfort zone, we
need to take corrective measures to get the conditions into the comfort area. A brief
description of different passive strategies shown on the chart for bringing conditions into
comfort zone is elaborated in the subsequent paragraphs.
Natural ventilation is the movement of fresh air into a space without mechanical assistance.
Deliberate openings in buildings, such as, doors, windows, etc., can be used to control natural
ventilation. In natural ventilation the movement of outdoor air across the building is caused
by pressure difference. Buoyancy effect or the wind can be used to create pressure difference,
which is created by humidity difference or difference in temperature. Ventilation based on the
buoyancy effect utilises stacks, which are tall spaces inside the buildings. The cooler outside
air moves into the building from openings near the ground, whereas the hot air leaves the
building through openings close to the top of the stack. In ventilation, in order to allow to
airflow through buildings, we need to keep the building open during the day.

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Ventilation in buildings is needed not only to provide cooling in summer but also provides
fresh air for occupants to dilute and exhaust pollutants. A good ventilation design not only
caters the residents’ comfort by making the spaces inside the building ‘airy’ (not draughty)
and ‘fresh’ (not stuffy) but also ensures good air quality that has low levels of pollutants. We
need to have optimum ventilation, because excessive and unnecessary ventilation during the
heating season incurs an energy penalty while too small ventilation can adversely affect the
health and comfort of the residents.
Ground cooling, evaporating cooling, radiative cooling and convective cooling utilises the
heat dissipation techniques for cooling the buildings. Dissipation of the additional heat
mainly relies on two conditions: presence of a suitable environmental heat sink; and creation
of a suitable thermal coupling between the sink and the building, besides adequate
temperature difference required for the heat transfer.
For the above referred techniques, the following heat sinks are used:
 Sky is used as the heat sink in radioactive cooling
 Air & water are utilized as the heat sink in evaporative and convective cooling
 Soil and ground are used as the heat sink in ground cooling

Advantages of Passive Cooling

Passive cooling decreases the need for conditioned cooling by minimising or eliminating the
periods in which cooling is required.
The energy requirement for heating and cooling of buildings is around 6.7% of the total
world energy consumption (Agrawal, 1988). Out of this, we may save around 2.35% of the
world energy output, just by making appropriate environmental design. The cooling energy
requirements are normally two to three times higher than the heating energy requirements on
an annual basis in hot climates. Utilisation of the basic principles of heat transfer coupled
with the local climate and exploitation of the physical properties of the construction materials
could make possible the control of the comfort conditions in the interior of buildings.
Passive cooling helps in protecting the environment because air conditioning is associated
with various environmental problems, such as, ozone depletion etc.
People working in air-conditioned buildings have been reported to suffer from sick building
syndrome and show increased illness symptoms, such as, tiredness, headache, congested or
runny nose, dehydrated or sore eyes sore throat and sometimes dry skin and asthma.
Results and Discussions Climate:
The climate has clear effects on human thermal environment. A strong understanding of the
environmental features that affects a building site is extremely important for designing an
energy conscious building. While designing an energy efficient building, we must incorporate
the useful factors that the environment and the climate have to offer and guard against those
that are unfavourable to comfort.
The average daily temperature of Peshawar greatly varies in winter and summer, for example
in January the average temperature is around 4°C whereas it rises up to 42°C in June. The
majority of the rainfall happens in the months of July to August and March to April while it is
quite low in other months of the year. Rainfall in other months of the year is very low. The
humidity level is not very high, and hailstorms are common in the spring.
Conclusion:
The climate of Pakistan has a lot of potential for passive cooling. There is a need for creating
more awareness amongst the people for adopting passive cooling strategies. Bioclimatic chart
can be used for preliminary investigation of the weather appropriateness of weather
conditions for a building design strategy. Adopting passive cooling strategies for Pakistan
would not only help to reduce the building cooling loads by a significant amount but also
help to build a green Pakistan.
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Although the climate of Pakistan has a lot of potential for passive cooling but there is a need
to remove this misconception from the minds of the people that passive cooling strategies
cannot be adopted in modern building. More awareness programmes need to be created
amongst the people for adopting passive cooling strategies in building design.

Reference:
1. https://www.activebuildingcentre.com/expert-blog/what-are-active-buildings/
2. https://www.phius.org/what-is-passive-building/passive-house-principles#:~:text=A
%20comprehensive%20systems%20approach%20to,renewables%20are%20required
%20to%20provide.
3. http://std.com.pk/fulltext/?doi=std.2014.159.164
4. Class Lectures

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