PDX_14_Hvac Building Design Flashcards
(39 cards)
The amount of heat lost at design outdoor and indoor conditions which must be made up by the HVAC system to maintain occupant comfort
Peak heat loss
The maximum output potential of a heating/cooling system in one hour and is used to size HVAC equipment
Full load hours
Used for calculating heat game through building envelope, and takes into account air temperature differences, effective son, thermal mass storage affect the material, color finishes etc.
Design equivalent temperature difference
DETD
Used for calculating he came through glazing, takes into account glazing type, interior shading, and outdoor temperature
Design cooling load factor
DCLF
And equivalent temperature difference used for calculating the instantaneous external cooling load across a wall or roof
Cooling load temperature difference
CLTD
The speed with which he passes through a material
Conductivity
Equipment that permits the use of outdoor air instead of refrigeration units for building cool link when conditions are right
Economizer
Evaluates both temperature and humidity, mixes appropriate outdoor/indoor air to achieve comfortable conditions without cooling
Enthalpy economizer
Gravity heating systems used by the Romans to keep public baths and private houses
Hypocausts
I’m out of cooling required to convert a time of water to ice in a 24 hour period, equivalent to 12,000 BTUH
Ton
1 Watt = ___ BTU per hour
3.41 BTU per hour
1 kWh = ___ BTU per hour
3,400 BTU per hour
1 ton of AC = ___ BTU per hour
12,000 BTU per hour
Or 3.5 to kilowatt ours
Units for ventilation:
CFM per person
Units for heating:
BTU per hour
Units for cooling:
BTU per hour
And tons
U-value is
The conductance of the assembly
The change in temperature, ΔT =
Difference between outside and inside air temperature
R-value is better the larger or smaller?
Larger
How to find the U-value:
Find the R-value of each component and add them together, then calculating 1 / total R-value
When HVAC systems exhaust more hair than they take in,
It can result in negative pressurization inside the building.
Ideally the air pressure in a building should be:
Equal to or slightly positive to the air pressure outside the building.
Negative pressure can cause cold draft and noxious odors coming in through cracks in openings.
When warm air rises and goes out the top, pulling in cooler air at lower levels through cracks in openings this is an example of:
Stack effect
Building success depends on:
How comfortable people are inside, and how affordable it is for them to be that way.