. So I am going to take off from where architect
Anupama left off and this is really shows way how a typical design project unfolds in
our firm where initially the architecture team looks at the site a in addition with
the environmental context comes up with the forms the spatial layout. And once that is
frozen then the green building advisory team joins the project and also comes and works
along with them to work on the finer aspects of the energy efficiency and the other environmental
aspects of the project. So, in this particular case study today we
are going to specially focus on the building envelope design and the design was specifically
done to ensure energy efficiency . Given that the facility was going to be primarily naturally
ventilated we wanted to make sure that the building would be naturally cool and comfortable
for the occupants without the use of extensive conditioning.
So, in this regard we used as many as 6 different strategies you can think of them as passive
strategies, you can think of them as building envelope strategies, but these were concious
design choices that we made to make sure that the building stays cool and comfortable which
is very important for assuring the productivity and the well being of the occupants .
So, if you look out the strategies number one was; obviously, the building shape and
orientation on this site the second one which again architect Anupama already talked about
is the central courtyard. It is a feature that is essential to keeping the spaces well
ventilated airy and this is something that we have drawn upon from the historical design
context of Tamil Nadu where central courtyard are key features of old buildings . The
third strategy was the spatial layout of each space each regularly occupied space was done
in a way to maximize cross ventilation. So, we wanted to make sure that because it
is a naturally ventilated building there will be breeze moving throughout the day and keep
the interiors airy. The fourth strategy was wherever fenestration happens, we wanted to
make sure that it was adequately shaded. This again in a tropical zone in a warm and humid
zone is very important that the direct sun ray does not fall on fenestration also
does not fall on the walls because that is where most of the heat gain is going to happen
. The fifth strategy that we used was making
sure that the building envelope is insulated. This includes the walls; obviously, the fenestration
and also the roof to make sure that internal heat gain is minimized. The sixth strategy
was all the regularly occupied spaces should have access to glare free natural light. Often
times it is seen especially in contemporary buildings where there is a lot of glass used.
Yes there is a lot of light coming in, but often it comes with. So, much glare, but again
forces the use of internal shearing. So, these were the 6 strategies that we employed
in this project to make sure that the spaces inside are cool comfortable and give a productive
environment for the students and the faculty .
So, first strategy again Anupama has already talked about it, but I just walk you through
in the context of energy efficient design. So, again the circular form made sure that
there is no direct heat gain on any facade and specifically the way the forms are cut
out. The smallest segment faces the west which is where in that particular area is a lot
of heat gain. So, we ensure that the west facade is the smallest also curved. So, this
helps minimize the heat gain from there. The breezewaves as anupama talked about brings
a lot of airiness into the central courtyard and from there it moves into the various rooms.
And again a the sloped roof which is very traditionally used in in a hot tropical place
like India is that through the day the suns direct exposure does not keep falling on the
flat surface. So, this is again a key strategy in making sure that the heat gain into the
building was kept at minimum. The second design strategy that we used was
again something that Anupama has referred to, but this was the central courtyard. So,
the open central courtyard from a usage point of view was a key aspect of bringing in socialization
interaction amongst the occupants, but from an energy efficient point of view there were
two aspects that we looked into here. So, one is that the courtyard itself is open
on the top and this forms a stack effect. So, as the air inside the space gets hot and
heated up it rises and then finds a way out. This in turn keeps forming a circulation.
So, the breeze comes in from the openings and goes up. So, this whole thing keeps the
central courtyard airy and comfortable the second part was the conscious decisions to
keep the openings into the courtyard along the prevailing wind direction. So, the wind
comes in from the south exists through the north and in that process spreads into the
courtyard and funds breeze into the regularly occupied spaces. So, this was a second strategy
that we used. Here is a an image of the central courtyard.
So, that gives an idea of how the space looks and feels So, I as Anupama mentioned there
is the statue of a Buddha right in the middle that brings a visual focus into the centre.
There are 3 levels the ground the first and the second and a the courtyard a on the top.
While the central part of the courtyard itself is a has a glass cover to avoid rain there
are openings on the sides. So, the hot air can go up and then exit from
this side. You can see from this behind the Buddha statue is the opening towards the east
and that is again a direction from which natural light comes in and then as the sun moves up
it comes in through the top and then moves on to the west and that is where the built
form on the west. Shields the harsh sunlight during the afternoon part of the day.
The strategy number three that we used was ensuring that the spatial layout of all the
regularly occupied spaces. lent itself for good cross ventilation. So, as a we you know
the building is circular and it has a central courtyard and all the regularly occupied spaces
are arranged around it. So, if you look at anything for example, the training hall number
one it has openings towards the exterior as well as towards the courtyard. And then when
you open out the fenestration, the breeze naturally comes in and flows from the outside
into the courtyard or vice versa depending on the time of day and the breeze direction.
So, this arrangement of spaces makes sure that cross ventilation is happening there
is also natural light coming into those spaces. So, keeps the interior generally comfortable
at adding to that the stack effect of the courtyard makes sure that hot air whatever
forms goes up and exits out and because of this kind of an arrangement space conditioning
was kept to a minimum and any how generally used only during peak summer days.
Strategy number 4 is adequate shading of fenestration. So, what we saw here was a there was a need
to have lot of openings to bring the natural light also ventilation, but given that how
could we make sure that the internal spaces do not get heated up . This is something that
is very well known to people who have cars . When you have a option to park you rather
park it under a shade, then keep it open similarly whatever fenestration we create should be
well shaded in a tropical place. So, here what we did was we decided to overhang
the roof and the slabs at various levels to make sure the adequate fenestration covering
is achieved. This again then turned into a functional usage which added to the charm
and the usability of the building. So, for example, wherever the slabs were extended
out those becames balconies step out spaces. So, between classes or during seminars the
occupants have a space to come out enjoy nature, then go back in a it also definitely adds
to the aesthetics of the building But the main and important point is that the
shading makes sure that direct solar radiation is not impacting the fenestration or the
walls for that matter. Then this in turn makes sure that its only secondary heat a through
conductivity and not through radiation that gets into the spaces . This also ensures that
there is no direct sunlight and light going into the spaces which again reduces the
glare in that space makes it much more comfortable gives adequate light, but keeps it at a comfortable
lux level . What we did was the slab overhangs where about 6 feet and this led to a reduction
in the SHGC which is a solar heat gain coefficient by forty percent.
So, this allowed us to also make sure that we can select a a glass that has a the right
amount of solar control, but has adequate a visual light transmission also . So, this
was the fourth strategy that we employed .
Moving on to the fifth strategy and this is a formed a core part of the envelope design
was to make sure that the building envelope was a well insulated. A in this a regard we
had a reference to the IGBCs green new building rating system. So, given that the
building was meant to be naturally ventilated. We wanted to make sure that the envelope
heat conductivity of aspects the well in line with this rating system . So, some of the
a design benchmarks we considered were number one the window to wall ratio was not to exceed
forty percent. When you do that you a have a little more leeway in some of the other
factors where it is a required to bring in enough light ; directly this leads into the
solar heat gain coefficient of the fenestration. So, as per the standard we should not exceed
1042 what this means is that if solar radiation is falling on a piece of fenestration 42 percent
of the heat the infrared part of the radiation can come in to the space, the rest is kept
out . While 42 was the minimum level as per the standard the ideal level was 0.32 .
So, what we wanted to do was make sure whatever glass product we choose that along with the
shading that we create makes the a solar heat gain coefficient not go more than 0.32 . The
next factor we considered was again another aspect of the glazing which is the U-value
or the thermal conductance for somebody who is may not be familiar with this term
a U-value is the extent of heat that can go from one side of a surface of a piece of object
to the other side a in 1 square meter of area when the thermal gradient from one side to
the other is 1 degree Celsius. So, this gives a way to quantify how thermally conductive
a certain object is. So, in this case the as per the standard the
maximum heat gain that you should allow through glass was 5.7 watts per meter square
Kelvin. So, what this means is that in every square meter of glass if there was one degree
centigrade difference from the inside to outside not more than 5.7 watts of heat should go
through. This also leads to the fact that going back to the window wall ratio. So, more
extent of fenestration you give that is the kind of heat that can flow through the glass
. The fourth aspect we look at was the thermal
conductivity of the exterior wall system. So, while we make sure that the windows
do not exceed 40 percent of the built form the facade. We now need to look at the
thermal conductivity of the wall itself. So, here again as per the standard , we should
not exceed more than 2.5 watts per meter square kelvin and ideally not exceed 1.8 watt per
watts per meter square Kelvin . And the last aspect we looked at was the U-value or
the thermal conductivity of the roof which again in a warm and humid region should
not exceed 1.2 watt per meter square kelvin and in ideal case should not exceed 0.5 watt
per meter square kelvin. So, to just explain why there are two benchmarks
we are looking at. As per the IGBC green new building standard which draws upon the ECBC
or the Energy Conservation Building Code of India. These this strategy is typically
called a prescriptive method where a the rating system or the standard gives certain benchmarks
and U as a designer will try to keep a your a buildings benchmarks below this
as per the case b. So, here there is a minimum which is looked
at as a mandatory requirement and an ideal which is looked as an enhanced requirement.
So, ideally we should be achieving the enhanced requirement, but at the least we should be
conforming to the minimum benchmark. The some other things that we need to look at is sometimes
when you are trying to achieve the ideal benchmark. There is a cost associated with it and specifically
in this project where cost consideration was a key a factor that we had to consider making
sure that we meet and adhere to sum of these benchmarks without greatly shooting up the
cost was a key consideration . So, if you look at the exterior wall assembly,
what we again considered was number 1 as I mentioned earlier the thermal conductivity.
So, in the ideal case we should not be exceeding 1.8 watts per meter square kelvin, but at
the minimum we should not exceed 2.5 watts per meter square Kelvin. The second aspect
that helped us choose a proper wall material was the aesthetics which being rooted in
the cultural context of the space call for expose masonry a and this was not the only
reason. The other reason was to consciously and have a sensitive material use policy where
we said we will not use material unnecessarily. So, again avoiding plastering of these walls
make sure that a polluting a material like cement it is minimized.
. So, these were two of the aesthetics and cost related factors that went into the selection
of a wall material. Here we looked at 3 options a given these two factors, one was conventional
clay bricks; the kind of bricks a kiln fire bricks that are normally available a. And
generally the U-value of a wall 90 inch or 3 230mm wall a plaster on both sides or
plaster on one side would be around a 2.5 watts per meter square Kelvin.
We also looked at hollow a clay blocks or hollow terracotta blocks a. These are typically
larger blocks which have several voids across the cross section its U-value if
you look at plastering on one side comes to about 1 watt per meter square Kelvin. And
the last a option, we looked at was fly ash bricks where a typical 9 inch fly ash brick
wall a would lead to a resulting U-value of about 1.3 watts per meter square kelvin.
So, we looked at these 3 and we ; obviously, wanted to go for the lowest U-value product.
So, we looked at hollow clay blocks, it had the best U-value. It had the aesthetics that
would suit the building and it also allowed us to leave it unplastered which also worked
well with the material used strategy. So, the wall material that we used here was
hollow terracotta clay blocks and this typically has a thickness of 8 inches or
200 mm . The next factor we considered was the roof
assembly of the building. So, again the first aspect that we looked into was the U-value
or the thermal conductance of the assembly itself. And here as per the standard we should
not exceed 0.5 watts per meter square kelvin and in the worst case not exceed 1.2 watts
per meter square Kelvin . Again this is in the context of the region which is warm and
humid. So, given the the climatic context the standard
says ideally you should not allow more than 0.5 watt in every square meter of the roof.
The kind of options we considered were Mangalore tiles which a worked well would work well
with the aesthetics of the building a. We could also look at an RCC roof or something
like a metal sandwich roof with insulation in the middle . In this particular case,
we went with the metal sandwich roof. So, this is a cross section which has two
metal layers with a layer of grass wool in between. The reason for this was number one
it yielded the best U-value of 0.5 watt per meter square kelvin RCC could have been
used with some over deck or under deck insulation, but the form of the building and the that
tricky shape makes it a little harder to use RCC in this form. And again that was one
of the reasons why Mangalore tiles was also not as suitable And the final reason is
that Mangalore tiles though aesthetically beautiful and do have some amount of thermal
insulation. They do not come close to this kind of a value that we were looking for
from the IGBC new green building standard point of view .
So, by now so, we selected the wall material we selected the roof material. So, we move
on and a we are looking at the fenestration now. . So, again some of the factors we looked
at just to reiterate was that the solar heat gain coefficient should not exceed 0.42 and
ideally it should not exceed 0.32 so; that means, that if a sun's rays were to fall directly
on that fenestration not more than 32 percent of the heat gain or the solar infrared part
should transmit through the fenestration . The next part is the U-value of the fenestration
and again according to the standard it should not exceed 5.7 watts per meter square kelvin
and ideally 3.3. Now the way you look at solar heat gain versus the U-value or the
thermal conductance is this is that the first part the solar heat gain happens when there
is direct incidents of solar radiation on that fenestration.
So; obviously, this is a key consideration during the day and again given the used case
of this building which was primarily educational through the day. Now this was the key factor
that we wanted to achieve the second part which is the thermal conductance that comes
into play due to thermal difference or difference in temperature between one side
versus the other side. So, in this case the difference in the outdoor temperature or the
ambient temperature through the indoor temperature .
Now given that a this building was going to be naturally ventilated this required fenestration
to be kept open for a a large part and also given that we were not going to air condition
most of the building the thermal conductance a aspect becomes a little less important than
the solar heat gain. So, what we decided to do here was we selected
a product which gave a good SHGC value in this case the product had a value of 0.5
and then in combination with the 6 feet overhangs that we had provided. The effective solar
heat gain coefficient comes down to 0.3. So, we were able to come under the ideal SHGC
value a and a we were also able to come under the U-value a given that the products yoU-value
was 5 watts per meter square Kelvin. We could not achieve the ideal value of 3.3
because that would require double glazing and given that this was a naturally ventilated
building where the fenestration be kept open most of the times and also the given cost
which was a very important factor where a double glazed system would increase the window
sections and then the cost we decided to keep adhere to the mandatory requirement
and not the ideal requirement . The last part of this is that the visual
light transmission of the product was 50 percent which was a good balance in letting
natural light come in versus avoiding glare. So, this led to the selection of the glass
for the fenestration So, to summarize what we did in terms of
the building envelope was the window to wall ratio was kept at 40 percent a. This was again
in line with the IGBCs new a green green new building standard the exterior wall assembly
was made out of hollow terracotta clay blocks a with plaster on the interior surface and
expose on the outside with overall U-value of about 1 watts per meter square Kelvin.
Roof assembly consisted of a double metal skin with glass wool insulation in between
achieving an overall U-value of 0.5 watts per meter square kelvin and lastly the fenestration
consisted of well shaded French doors and windows with a glass that had a SHGC value
of 0.5 and a U-value of 5 watt per meter square kelvin with an effective SHGC value coming
down to 0.3 The sixth envelope design strategy was
access to natural light. So, given that a we are minimizing the heat and we are going
to keep the windows open , we wanted to make sure that a all the spaces are well a have
abundant natural light, but not to a point where it becomes a glare and then you are
forced to use shades or other kinds of objects like blinds.
So, as I said before all a regularly occupied spaces have a direct connect to the exterior
and also to the interior courtyard. And along with that well shaded fenestration with heat
control glass that makes sure that there is light without too much of glare and heat
as I said earlier the glass VLT or Visual Light Transmission value was 50 percent. What
this means is that if again the solar radiation falls on light 50 percent of the light would
stay out whereas, 50 percent of light would come in.
But this should be looked at in the context of the kind of light or lux level, you need
to do your tasks a for building of this sort as per the a green new building standard
a minimum level of 110 lux was a what was minimal acceptable. And given the spatial
layout the kind of a glass used, this was easily achieved a in 100 percent of the regularly
occupied spaces. What this led is again minimal use of artificial lighting during the day
and that is when the building is mostly occupied and used is again goes back into reducing
the energy consumption of the building. . So, just to summarize what happened. So,
in terms of the design of energy efficient building, we looked at two things we looked
at all the passive measures which means the measures that go into the building itself.
So, again just to summarize, the strategy number 1 was the building shape and orientation;
so, this the round shape with minimal exposure to the west breeze waves to the south which
is the prevailing wind direction that was the first strategy.
Number 2 was a central courtyard which allows for a stack effect helps ventilation and cross
ventilation . Number 3 was as part of the cross ventilation making sure that all the
regularly occupied spaces have openings at least two orientations. So, in this particular
case every space had an opening into the courtyard as well as an opening into the exterior environment.
This makes sure that there is a movement of breeze from one side of the building to the
other; making all the interior spaces well ventilated strategy four was a adequate shade
shading of the fenestration which was achieved by the slab overhangs and the roof overhang
which again led to some very usable balcony and walkway spaces. Fifth strategy which we
talked about in detail was the thermal insulation. So, the walls the roof and the glazing they
were all selected to minimize heat gain from outside into the spaces. The fifth strategy
was access to glare free natural light. So, these were the passive or the building
related measures that went into the building to keep its energy footprint low. The other
side of it was some of the active systems which means the lighting the fans or the air
conditioning. So, some of those choices were led lights
a BE 5 star rated ceiling fans and wherever minimal spaces which required air conditioning
which is the auditorium and a couple of training rooms. A VRV air conditioning system was
used which has a high coefficient of performance and has a low energy footprint .