EBGE
4. Semester
4. Semester
Set of flashcards Details
| Flashcards | 28 |
|---|---|
| Language | Deutsch |
| Category | Career Studies |
| Level | Other |
| Created / Updated | 23.02.2016 / 23.02.2016 |
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What describes Building physics?
It describes the basics about energy flows in buildings.
List 5 influences on a building
Sun, Wind, Noise, Snow, Rain, Hunidity, Lightning, Earthquakes, Plants, Animals
Describe the ideal building design.
It would create the desired internal room conditions without additiona technical equipment or generating an enrgy demand.
List the two kinds of heat loss:
Heat loss by transmission
Ventilation heat loss
How works the first kind of heat loss?
Heat is transmitted through walls (and windows,doors,roofs) if there is a temperature gradient between the inside and the outside of a building. The magnitude of the heat transmitted is proportional to the thermal insulation (heat transfer coefficient U), to the area of the structure, and to the temperature difference.
Which is the most important part of a building to insulate?
The roof, the warm air rises beneath it and gets stucked there. If the warmth just gets lost there it never gets warmer at the bottom.
Why is there nearly no transmitted heat flux from the outside to the inside even if the outside temp exceeds the inside temp?
This is because most of the time the daly mean temp outside is lower than inside. During the day, the outer wall becomes heated up and during the night the direction of the heat flux changes and the heat stored is emitted to the exterior.
When effects the heated up wall the interior temp?
If its a lightweight wall or roof.
What are the conditions that assume standard calculations for heat loss?
The temperature is constant at 20°C.
Where leads poor thermal insulation to?
- Damage from condensation
- cool inner surface of walls
- higher energy costs
Explain the second kind of heat loss:
Ventilation heat loss: This type of heat loss is reliant on air flow and occurs
- through leakages in the structure
- exhaust air from mechanical ventilation systems and
- natural ventilation
From where in the structure occure the leakages from?
- leaky windows
- joints
- component transitions
- incorrectly closed openings to the outside
A difference in air pressure between inside and outside provides a constant loss of heat through the leakages in the structure.
Mechanical ventilation systems
In Switzerland heat recovery is obligatory. This is possible withe the mvs. Nevertheless, 10-30% of the heat from the exhaust air can not be recovered.
Why should houses be built as airtight as possible?
Since ventilation heat losses increase significantly when the outside temp falls.
What indicates dry indoor air in winter?
Severe leakages in the structure.
With which method can you calculate the air-tightness of a building?
Blower door method
+ user influences
the two (three) kinds of thermal gains:
- Internal heat gain
- Solar heat gain
- (Heat storage)
Where come the internal heat gains come from?
- Human body
- Electric lighting
- Devices
How much thermal power do people produce?
- Person at rest: 85 W
- office work: 130 W
- Hard work: 300 W
The two methods for determining heat dissipation from light:
- Specific installed power
- Counting the existing lighting devices
The two expressions for solar heat gains:
- Solar gain
- Passive solar energy use
Why is a solid contsruction importing by using solar energy for heating?
The sun may compensate for the major part of the heat losses or even overcompensate. If the solar gains temporarily exceed the heat demand, the room temperature increases. The temporary excess heat is then absorbed by the walls, floor, and ceiling. Their heat storage capacity determines the level of heat absorption. Since heat is stored, the amplitude of the room temperature decreases. The solar heat gains can be used after a certain time delay (in the evening and perhaps, if it is overcast even during the next day).
How much heat loss can be replaced by passive solar gains in normal residential buildings?
25 - 40%
What characterizes the solar radiation transmitted?
g-value
- G-value of old non-coated glazing and
- new, heat-insulating glass (Double
- and triple layer)? (compared to the u-value)
- 85-90%
- 60%
- 40-60%
Which factor characterizes the transmitted light?
t-value (tau)
Which solar heat gains count the g-value?
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What is the weak point of a window if you look at the insulation?
The frame
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