02_03.3_Steel

(calm electronic music)

- [Instructor] So here's
my question, what's wrong

with an aluminum nail
through a copper flashing

on a roof detail?

Go ahead and hit pause.

We talked about this a little bit

in the wood discussion, I want to expand

on it a bit in the metal context.

If we have two different metals touching

and if it's either in a humid environment

or a roof, some place where
it's gonna be exposed to water,

then there can be what's
called galvanic action.

Galvanic action, or galvanic corrosion.

Now, any time an old battery,
you see an old battery

that has that kind of weird
oozing, that's the same process.

And really any time you see rust,

what you're looking at
is galvanic corrosion.

And so what happens is when we have metals

that have different galvanic number,

and so the numbers range
from anode to cathode,

so aluminum is the most
anode in this list,

and copper is on the cathode side.

You see there are two
different stainless steels

here and here, that's because
there are different flavors

of stainless steel depending
on what the alloy makeup

is of the chromium and
the nickel and so forth.

So it depends with stainless steel,

there are different
places it can be on this.

But anyhow, you see it
goes aluminum, zinc, steel,

iron, stainless steel
that's active, tin, lead,

copper, and stainless
steel that's passive.

If the surface, like an
aluminum roof, or copper roof,

if the surface is closer to
the anode side of this list

and the fastener is
closer to the cathode side

you're probably gonna be okay.

If the surface and cathode
are close together in number

you may be okay.

So, if they're close
together on this list,

but if they're far apart on the list

and the surface is on the cathode side,

and the fastener is on the anode side

of the surface on this list,
that's where you have trouble.

Especially in the presence of water.

Especially in the presence of water.

So if we have mild steel
bolts that are in contact

with stainless steel
that could be a problem.

Other common difficult adjacencies,

if we have copper and
galvanized steel fasteners,

if it's a humid condition and a roof

that could be a problem.

If we have brass and
galvanized steel fasteners

under humid conditions or a
roof, that could be a problem.

If we have aluminum and
galvanized steel fasteners

under humid conditions,
that could be a problem.

If we have stainless
steel, as I mentioned,

and galvanized steel fasteners
under humid conditions,

or a roof that could be a problem.

If copper and zinc are
anywhere near each other

that could be a problem.

If steel and zinc are
anywhere near each other

that could be a problem.

If mortar and zinc, even, are in contact

with each other that could be a problem.

And even certain woods,
those with really low PHs,

like white cedar and Douglas fir,

if they're mixed with zinc
that could be a problem.

And so, to separate the
two, we need an insulator,

we need something that's
gonna kind of separate them.

Now when I was a kid I remember hearing

about them finding some problem
with the Statue of Liberty,

and they actually closed
it down for a while.

They closed the Statue of
Liberty down for a while

to tourists, and I remember
when they reopened,

not long after they reopened we went there

and they had fixed it,
and they tried to explain

what they fixed, but as a
10-year-old or however old I was,

I don't really remember understanding it.

But let me tell it to you,

so what happened was
Gustave Eiffel, the same guy

who built Eiffel Tower, he
was, around the same time,

the engineer of the Statue of Liberty,

and the Statue of Liberty
has a wrought iron structure,

and it's affixed to a copper skin.

So we have copper with
iron, the same trouble

we keep hearing about, especially
if it's exposed to water,

and obviously the Statue of Liberty

is in a pretty humid climate,
in a very maritime area.

It's surrounded on water by every side.

So, Eiffel anticipated this actually,

where there was an iron structure attached

to the copper skin, he
put a piece of insulation

between the two, to help
prevent galvanic corrosion.

But, after like 100 years,

during routine inspection of the statue,

they found that the
insolation had worn away,

and there were many places
where the iron structure

was now in contact with the copper skin,

and galvanic corrosion
had started to set in.

So, what they did is they
closed the Statue of Liberty,

and they replaced all of the connections

that had had insulation,
they replaced the insulation

with a plastic instead,
and reopened the statue.

Eiffel's kind of an interesting character

because he was trained as an architect,

and he was trained as an engineer,

he went ahead and built Eiffel Tower,

and he did the Statue of
Liberty, he became wildly famous.

The French, of course, tried
to build a Panama Canal

before we did, and Eiffel was the engineer

in charge of that effort,
or part of that effort,

and when that effort
failed catastrophically

and there were allegations
and confirmation

of corruption, he was put on trial.

I don't think he was ever
accused of direct corruption,

but he was accused of
helping to solicit money

for the endeavor, when he supposedly knew

that it wasn't gonna work out.

And he was sentenced to two years in jail,

he won an appeal but he
was done with architecture

and engineering at that point,

and he set his sights
instead to experiments

in meteorology, and aerodynamics.

And actually, Eiffel became a pioneer

in aerodynamics in the same
way he was in steel structure.

Now, there are times when we actually want

this kind of corrosion to happen.

It's called cathodic protection,

and they're pretty rare, but I figured

I'll pass them on to you anyway.

If we have like a steel water tank,

we'll sometimes put pieces
of zinc on the bottom

of the steel water tank, we'll
attach them to the bottom,

and the zinc is used as
kind of a sacrificial anode

and when it corrodes it produces a layer

of protection on the
bottom of the steel tank,

that the steel itself can enjoy.

Next question, what metal has
the lower embodied energy,

aluminum, or steel?

Go ahead and hit pause.

This is always difficult,
this kind of discussion

about embodied energy, and again,

in your practice I would hope that you

would focus primarily on the operations

of buildings when you're
looking at energy,

rather than the construction of them.

But, it's still worth
knowing and understanding

which materials have more embodied energy.

This is kind of difficult,
because there's lots of reasons

not to worry about this stuff, frankly,

and to worry instead about the operations.

One is because the
operations are a bigger part

of the environmental
footprint of a building,

so it's better to have an
efficient heating system

than a lower embodied
energy building material.

But the second problem
is that each industry

has kind of commissioned its own study

of the embodied energy
of a building material,

and each one,
coincidentally, seems to find

that their material does
well and others don't,

because it depends on how much

you count for transportation, it depends

if you're looking at a material
on a per-square-foot basis,

a per-cubic-foot basis,
or a per-kilogram basis.

So it depends if it's by surface area,

by volume, or by weight.

But I went ahead and
Googled embodied energy

of building materials,
and this is the first one

that came up.

It came up from the
Government of Australia,

and it shows that steel has
much more embodied energy

than stainless steel or aluminum.

This, of course, is not
really true, typically,

but it's the first hit
on the Google search.

And then, when I looked
a little bit closer

you see a list that's
above it, the same website.

And you look at the list, and
then now you see something

that's kind of different.

You see aluminum has quite
a bit more embodied energy

than steel, and that's
probably more accurate.

Now, in reality it also depends

on how much of a particular
material is recycled.

So, something like 90%
of steel is recycled,

something like 15% of
aluminum is recycled.

So, that makes a big difference.

And of course it makes a big difference

where it's shipped from.

So if you're looking at stone
that's quarried locally,

it's gonna have a
different embodied energy

than stone that's quarried
in Italy and shipped over.

As a general rule, materials that have

more embodied energy are
materials that are more finished.

So, engineered lumber
has more embodied energy

than dimension lumber.

Stainless steel has more embodied energy

than steel and mild steel, and so forth.

Generally, materials that are heavier

have more embodied energy than
materials that are lighter.

Generally, materials that
have a lot of petroleum

in their makeup, things like styrofoams

for rigid insulation,
have more embodied energy

than things like cellulose
or glass fiber mineral wool.

Generally, materials
that use a lot of glues,

like particle board, have
a higher embodied energy

than those who don't.

Generally, materials
like cement, that require

large amounts of heat in
their manufacturing process

have higher embodied energy
than materials that don't.

Generally, materials, like
aluminum, that require

just an insane amount of mining,

they have to go through
an insane amount of soil

to get the aluminum out of the earth,

those have more embodied energy.

So, if you ever kind of are wondering,

that's generally the kind of arc,

that's generally the arc.

But then I went to the second one

on the Google search, and it told me

a totally different list, and
a totally different order,

and you start to see the difference.

It depends whether it's on a per-kilogram,

or per-cubic-foot basis.

Now about 90% of steel is recycled,

and in the US about 30%
of aluminum is recycled.

Now the recycled aluminum uses only 5%

of the energy, because
you don't have to mine it,

that new aluminum uses.

So recycled aluminum is a huge saver

in the energy to produce the material.

I went on to the third
Google Image return,

and it told me something
totally different again,

so until I see a source that I trust,

you know I look at it a bit askance.

I take it with a grain of salt,

when we're talking about
embodied energy in materials.

Which is more likely to
become a thermal bridge,

a metal stud or a wood stud?

Go ahead and hit pause.

As you might imagine, a metal stud

is more likely to become a thermal bridge.

So if we look at the R-value,

if we look at the thermal resistance,

of three different walls
here, and on the Y-axis

is the R-value for the whole wall,

and we see a SIP here,

a SIP here has no studs
bridging it, right?

So it's a Structural Insulated Panel,

it's typically a piece of OSB
glued to a rigid insulation

glued to another piece of OSB.

So, there's no thermal
bridging to speak of,

or there's not meaningful thermal
bridging across structure,

and we see that the whole wall assembly

out-performs the other two.

If we have a wood stud,
with glass fiber in between,

we see that it's kind of in between,

it doesn't lose as much as a steel stud,

which we're about to look at,

but it loses more heat than a SIP.

And then, if we look at a steel stud,

we see that we have
less performance still,

that we have an effective
R-value that is much lower

than the center of cavity
R-value between studs.

And just for reference, I put the R-value

of the insulation itself,
if, you know in theory,

without any thermal bridging,
both for the rigid insulation

used in the SIP,

and for the fibrous insulation
used in the wood stud,

and metal stud configurations.

Let's talk about items and steel

to study the night before the exam.

You're gonna want to
study and just look over

anything that might be
difficult to remember,

and just put it into
your short-term memory.

So for instance, when
I ask: which open-web

steel joist type spans the longest?

And I gave you the choice
between LH, DLH, and K,

you'll want to remember
that K is the shortest span,

LH is longer, and DLH is deeper still.

Likewise, if we're talking about corrosion

from galvanic action, you'll want to look

at that list of metals, and
either put it to your memory,

or just get familiar with it enough that

you might see it the next day.

And you'll want to understand, of course,

something like the depth and
the weight per-linear foot

of a beam based on the
nomenclature that we use for beams.

Now, let's talk a little bit
about how you should study

for the exam in general.

In my opinion, your goal should
not be to pass this exam,

your goal should be to get licensed,

and by that I mean your
goal isn't to give yourself

the greatest possible chance
of passing one single exam,

but your goal is to get licensed

in the shortest amount of time.

So, if this is the learning curve

for studying for an exam,
where this is the likelihood

of passing the exam on the Y-axis,

and this is the amount of time
you spend studying for it,

the learning curve looks
something like this.

What we wanna do is we wanna study

just to about this point, and
then we wanna take the exam.

Because rather than spend
a whole bunch more time

just to get a tiny more
yield in our likelihood

of passing the exam, we want
to study just a certain amount

and then take the time we would've studied

to get a little bit better on this exam

and get to that same
level of another exam.

So we'd rather take two exams,
each with an 82% likelihood

of passing, than in the same
amount of time take one exam

and have an 88% likelihood of passing.

You're not gonna get to 100.

Now, one of the most common
things people will tell me

is they'll say, yeah,
but the test is so picky,

so we have to study these picky things

because the test is picky.

And to that I ask you this, here are two

Powerball lottery tickets
for the $1.6 billion jackpot.

On the one on the left, it has numbers

one, two, three, four, five,

and a Powerball of six.

The one on the right
was selected randomly,

it has numbers two, four, 30,

39, 62, and a Powerball of 21.

So go ahead and hit pause,

and answer the following question:

is the one on the left more likely to win,

the one on the right more likely to win,

or are they equally likely to win?

Go ahead and hit pause.

Of course, they are equally likely to win.

And you'll say but
Michael, I've never seen

a lottery winner that had one, two, three,

four, five, six, that's preposterous.

And I would respond, well I've never seen

a lottery winner that has two, four, 30,

39, 62, and 21, have you?

And so, just going for
something, just studying

picky stuff because there may
be picky stuff on the exam

is not a good strategy,
unless you happen to know

that that particular
picky content is likely

to be on the exam, it's not
a good use of your time,

because you're unlikely to
select the right numbers,

you're unlikely to study the
exact correct picky stuff.

If you spend 100 hours studying
all kinds of picky stuff,

you may or may not get
one more question right,

but if you spend 100 hours
studying the concepts

and the important stuff,

not only are you more likely
to get more questions right,

but the questions you
don't know you'll have

a better foundation for
making a good, educated guess.

And it has the side
benefit that it'll make you

a better architect.

It'll be less about architecture trivia,

and more about the
concepts and the theories

you need to understand
to become an architect.

So our goal then, going
back to our learning curve,

our goal is to study as much as we can,

until a lot more studying
really doesn't improve

our chances that much, and
then go ahead and take the exam

with some confidence.

Good luck, and I will see you
on concrete, which is next.

(calming eletronic music)