Power point Flashcards
What are some cons of installing larger equipment?
- Cost more
- Requires large air distr.
- short cycling
Oversized air conditioning equipment will cool faster which decreases the ______________ effect
dehumidification
Undersized heating/cooling systems will not be able to ____________ set-point
maintain
True or False?
It is more beneficial to have your Heat/AC run all day vs periodically in extreme conditions. Why?
True. It will never catch up if extreme set-points are desired in extreme conditions
What is required in order to qualify for many government rebates?
Heat gain/loss calculation
Heat flows from hot to cold until?
temperatures are equalized
In warmer months, heat leaks ____ the structure
in
In colder months, heat leaks ____ the structure
out
Rule of thumb load estimate is the first type of load estimate that occurs up front in the design process
it includes
sqft
btuh
cfm
gpm
Temperature differential is the difference between the _______ and ______ of the building
inside and outside
As the TD increases the _________ _____ increases and rise versa
transfer rate
Name three environment effects on a building envelope
- solar gains (transfer gain tg.)
- humidity grains
- wind (infiltration gain ig)
True or False?
Daily range is the TD from morning to night
True
What is the typical design indoor temperature in heating season?
70F
Typical indoor design temperature in cooling season?
75F
Name 4 heat loads for heating
- heat escaping through cracks
- poor insulation
- heat transferring to colder areas
- exposure to wind forcing cold air in
Name 4 heat loads for cooling
- sun through windows
- cracks and openings
- sun exposure on outside of building
- heat from appliances
What is the R value used for?
rate the thermal resistance of insulation materials
The higher the R value, the _______ it is for heat to pass through the material
harder
If the wall is made up of different materials, how is the R value calculated?
The R value of each material used is added for a total R
Heat ________ is the heat conducted through walls, ceilings, and floors when. temperature difference is present
leakage
The amount of heat that will pass through 1ftsq of material 1’’ thick in 1 hour when the temperature difference is 1F is known as ?
Thermal conductivity (K value)
High __ values indicate high rate of heat transfer
K
Amount of heat that will pass through 1ftsq of material that is NOT 1’’ thick in 1 hour when the temperature difference is 1F is known as?
C-value
What is the difference between C and K values?
K value is based on material that IS 1’’ thick.
C value is based on material that is NOT 1’’ thick
How to determine thermal conductance?
Find on chart and divide K value of each material by its thickness
What is Thermal Resistance (R value)
Resistance to heat transfer
Higher R value indicates ________ heat transfer
slower
What are some examples of composite building materials?
wood, drywall, siding
Formula for calculating homogenous materials R value?
R = 1/C (using c factor)
Formula for calculating composite building materials R value?
RT = R1 + R2 + R3
What is Thermal transmittance? (U value)
Similar to C-value but includes adjustment for boundary air films
Thermal Transmittance (U value)
Formula U = 1/Rof +R1 + R2 + R3 + Rif
What does Rof and Rif mean?
Thermal resistance of outside air film and inside air film
The U-value describes the thermal _________ of a material
conductivity
The higher the U value, the _______ it is for heat to pass through a material
easier
Use construction materials with high __ values and low __ values
high r values low u values
R and U values are _______ of each other
inverse
U= 1/R
Summertime indoor design temperature and humidity?
75F (24C) @50% relative humidity
The rate of heat transfer through a wall is this formula:
Describe each variable
Q=U-value x TD x Area
Q = heat in btuh
U-value = U-value of the wall
TD = TD across the wall
Area = Area of the wall
Do partition walls require a separate heat loss calculation?
yes
_________ and ________ are calculated separately in wall heat loss calculations
windows and doors
What is the net wall area?
combined area of windows and doors
How to calculate total wall area?
perimeter x ceiling height
Where to find heat transfer factor (U)
from tables
How to calculate Transmission gain and loss through a wall?
Q= U value x TD x area
Heat loss through __________ walls account for a large percentage of total heat loss of a structure
exposed walls
It is important to know what lumber was framed with and the __ value of the insulation
R value
Describe heat lag
time it takes for heat to travel through a substance heated on one side
Normal buildings have _ to _ hours of heat lag
3 to 4 hours
Well insulated buildings or thick walls have what benefits?
Transfer heat into room during the night
Provide warmth after temperature drops
Calculate the heat transfer rate using k-values
R = 1/K x thickness
Calculate the heat transfer rate using C -values
Rt= 1/c1 + 1/c2 + 1/c3
U is the inverse of R so the formula is?
1/Rt
Difference between gross and net wall area?
gross is before doors or windows net is after
How to calculate heat loss through windows and doors?
Same method as walls
How to calculate heat loss through roofs?
Same method as walls but calculating with geometry
What is a partition wall?
Separates conditioned interior space from an unconditioned interior space
TD through partition walls?
Indoor design temperature and temperature of unconditioned space
The rate of heat loss ______ as the floor gets deeper?
decreases
Heat loss through floors located above unconditioned spaces is calculated the same as?
partition walls
Heat loss through slab floors is calculated using the ________ ft of the exposed slab edge not the area of the floor
running feet
Heat loss through cracks, openings, and deficiencies in structure calculated by;
Q-infiltration = 1.08 x cfm x TD
1.08 = constant
com = cubic feet of air entering
TD = design temp diff
Duct losses to unconditioned spaces such as attics, ceiling spaces, etc is when?
heat is lost passing through an unconditioned space
What is one of the major sources for heat gain?
windows
When calculating heat gain (cooling mode) take into account; (4)
- envelope contact w outside
- occupancy
- heat/moisture generating elements
- orientation of house
Heat gain through exposed exterior walls/Doors is calculated by;
Qwall= U value x TDcool x Area
Qdoor = U value x TD cool x Area
Qwall = heat attributed to wall
U value = u value of door
TDcool= two part chart needed
Area = area of the wall
Triple glazed glass has a ____ R value and ____ U value
high r low u
Name 4 types of windows
- Casement
- Double Hung
- FIxed
- Sliding
Infiltration is best described as;
air pressure inside is lower than outside due to air leaking in
Exfiltration is best described as;
air pressure inside is higher than outside due to air leaking out
What environmental element causes infiltration and exfiltration?
wind
Common rule of thumb for building pressure is
supply exceeds return + exhaust by 10%
Negative pressure is calculated by adding return air cfm and
direct exhaust air cfm
Balanced pressure means air in =
supply air cfm
Are internal loads calculated when sizing heat capacity?
NO
Greatest need for heat is during _________ hours
unoccupied hours
Warm-up ______ ________ reserve capacity is recommended if set-point setback is used during unoccupied times
safety factor
Heat is transferred from the body by; (4)
- Conduction
- Convection
- Radiation
- Evaporation
Calculate fluorescent lighting heat gain to space and to return air plenum
space = watts x 4.1btuh/watt x 0.60
ra= watts x 4.1btuh/watt x 0.40
In a low pressure system, how much static is there and how much cfm is lost?
under 2’’ static and 5% cfm lost
In a mid pressure system, how much static is there and how much com is lost?
2-6’’ static and 2% to 5% cfm is lost
In a high pressure system, how much static is there and how much com is lost?
over 6’’ static and 1% cfm lost
