MIT Architecture
M. Andersen
Introduction to Building Technology
Course 4.401
Spring 2006
March 22, 2006
QUIZ #1
Thermal and Lighting aspects of a building – 1h30’
Questions
2.5 pts 10 pts
a. How would you advise an architect from the equatorial region to design openings and solar
protections for his building?
3.5 pts b. Apart from rainwater leaking, what other process can potentially result in the presence of
liquid water inside a building’s envelope? What factors contribute to worsening this
problem?
2 pts c. Two friends decide to build a small house in the desert. One suggests using lightweight
materials in order to increase the heat exchange as much as possible, the other
recommends using heavyweight construction materials instead. Who do you think is right
and why?
2 pts
d. From a visual perception point of view, how can you interpret the V(λ) curve ?
Problems
1 pt 1.5 pts 30 pts
1. You leave a big wet towel in your bathroom, supposed to be a perfectly sealed enclosure.
Just before the towel was added, the relative humidity of the air inside the bathroom was
70%, and the temperature 25°C. Point out this initial situation (with number 1) on the
psychrometric chart provided on the last page.
If you wait long enough, what will be the new values of air temperature and relative humidity
(point 2)? Describe what has happened and show the evolution of the situation on the
psychrometric chart by drawing the path leading from point 1 to point 2.
1.5 pts You then remove the towel, being able to keep the air conditions exactly as they are, and
decide to cool the air down to 16°C. Describe what happens and show the evolution of the
situation on the psychrometric chart by drawing the path leading from point 2 to point 3.
2 pts What is the relative humidity at point 3? What is the absolute humidity? If condensation
has occurred, what is the mass of liquid water that was formed?
3 pts Then you remove any liquid water that might have formed, still being able to keep the air
conditions exactly as they are, and decide to decrease the relative humidity to 50%.
Propose two ways to do this, and show how the situation evolves in both cases on the
psychrometric chart (draw the paths leading from point 3 to points 4a and 4b).
1 pt What is the final air temperature in both cases ?
1/3 Name : ________________________________
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2. The architectural space of the church of the Convent of La Tourette designed by Le
Corbusier is characterized by narrow lateral and zenithal openings, actively taking part in
the dynamic and richness of the luminous ambiances inside the church, chapels and
oratories. These openings are of small area and of strong luminosity compared to the
opaque parts of the envelope. On a sunny morning, you come in to make a diagnostic about
visual comfort and about the thermal properties of the building, equipped with a luminancemeter, a luxmeter and a thermometer.
You first enter the main church and are fascinated by the interaction of the strong light
with the bare concrete. Out of curiosity, you point your luminance-meter directly at the
opening on the right side of the back wall (see picture on the right) then at the wall itself
close to the opening. You get 3200 Cd/m2 and 400 Cd/m2 respectively.
2 pts
Is this contrast acceptable for visual comfort recommendations?
3 pts
If the wall was painted in white (ρ = 0.8) rather than being bare concrete (ρ = 0.3), what
would the contrast become?
3 pts
You go out and measure the illuminance on the outside of this same wall and get
100,000 lux. Knowing that natural light has an efficacy of about 110 lm/W and that the
wall’s surface is of about 80 m2, how many Watts does the wall receive?
2/3 0.70
0.75
0.80
0.85
0.90
0.95
1.00
Axonometric view of the Church
Inside of the Church
When you were outside, you looked at your thermometer which indicated 18°F. Then you
continue your visit and enter a small, pitched-roof oratory (picture below), illuminated by a
narrow zenithal opening and still made out of bare, dense cast concrete. Your
thermometer now indicates 68°F.
3.5 pts What is the heat flow rate through the back wall of the oratory if its thickness is 30 cm
and its surface 16 m2? (use the data sheets provided in your textbook)
5.5 pts Standing inside silently, you hear a faint whistling and interpret it correctly as due to a draft
caused by a shattered piece of glass in the zenithal opening (pointed out by a circle on the
drawing). What is pressure difference between inside and outside at the opening’s height
(the entrance being open to the corridor, the pressures are equal at ground level)? In what
direction does the air flow through this unintentional crack of area 0.05 m2?
3 pts If the air speed is of about 7 km/h, what is the ventilation heat flow rate due this crack? Is
this a significant flow?
7.5 m
128 m3
Oratory
3/3