AIR207PART2
HTM is used for
-Doors -Windows -Wall systems
Why are heat load calculations necessary
-It improves operating efficiency of the selected HVACR equipment. -It helps to assure human comfort conditions -Heat load calculations are required by local ordinance.
The amount of heat transferred by conduction through a window or door depends on:
-Presence of a storm window -Materials of construction -Size of the unit -Quality of installation
Rs J Zr T S D
-System Concept -Load Calculation -Zoning System -Air Distribution -Equipment Selection -Duct Size Calculation
Assumptions made in using the Manual J for heat gain calculations include: Click all that apply.
-The standard inside design temperature will be 75F at either 50% or 55% RH. -Room by room solar heat gains and transmission loads are computed for average values - - not on the peak for each room. -Transmission through walls will be based on the Equivalent Temperature Difference. -Glass in walls is <25% of the floor area.
What is the "U" value for a wall with a total "R" value (including inside and outside film resistances) of 20 Ft2- ̊F-hr/BTU?
.05
The standard given Ashrae CFM0.35 = ? This is a two digit decimal. (.50)
.35
What is the Ashrae infiltration threshold for minimum ACH rate? This is a two digit decimal: (.58)
.35
On the table on page 86 of the pdf. (MJ8 Table 5A) what is the infiltration CFM for one fireplace in a tight structure?
0
###Use the table on page 86 of the OA pdf. This is MJ8 Table 5A. What is the ACH for a semi-loose 2500 SF home in the cooling calculation?
0.25
A window with 100% solar gain would be good in Alaska. The correct SHGC for this window is a ______________. (Numerical answer)
1
The CFM occ = 20 x (Number of bedrooms +________)
1
According to the SCAHACC-Understanding-MJ8-Luis-Escobar pdf. his slide depicting heat gain is between 80 to ___ degrees F.
100
CFM infl = 200 ∆T = 60 What is the Btuh loss?
13200
From the ACCA Manual J book, in Table 1, what is the Daily Range for the Canadian city of Halifax, Nova Scotia.
16 M
1: Calculate the CFM occ with a ventilation rate of 7.5 CFM per person and a 4 bedroom home. 2: Calculate the CFM.35 for a home having 1600 SF and 10' high ceilings AG (Above Grade). 3: Calculate the CFMcomb with two atmospheric burners having the combined capacity of 80,000 Btuh. Which is higher: 1, 2, or 3?
2
In the example on page 100 of the pdf. in figure 10-10, MJ8 Table 3-E calcultes the Midsummer Shade Line Multiplier (SLM) as __________ what value?
2.60
Calculate the CFMinfl : (p. 87) ACH = .10, structure footprint is 40 LF by 40 LF with 10' high ceilings. Round up to a 2 digit number.
27
A window with a SHGC of .35 lets what percent of the available solar radiation through it? (Two digit answer: 66)
35
CFM infl = 200, ∆gr = 30. What is the latent heat gain in BTUH.
4080
Use the HL notes to solve for BTUH. What is the BTUH loss for a 8' x 20' wall that has a R value of 19? The IDT is 73ºF and the ODT is 19ºF. Q = U x A x ∆T U = 1/R
455
Typical Exhaust system CFM is listed in Table 9. What does a bathroom require? Choose the best answer.
50 CFM
Use HL Class notes posted on BB to calculate a total R value. Q = 1/R x A x ΔT Rt = 1/3.12 + 1/.96 + .5/.25 = .32 + 1.04 + 2.0 = 3.36 hr-degree F- ft2 / BTU Area = 100 SF TD = 20 What is Q?
595
What is the 2.5% Summer DB for National Airport as listed in the ACCA manual J book (under the District of Columbia)?
91
The ____________ is the most common approach to residential infiltration. (Answer with Three Letters Only)
ACH
CFM infl x 1.1 x T∆ = __________
BTUH
It is necessary to calculate the "load ( in ____________ ) that outside air will" add to the calculation.
BTUH
A thermal ____________ is a material, which is a poor conductor of heat, placed between the glass panes.
Break
Our class example on the plans provided does not have AED. Which condo on page 105 of the pdf. also does not have AED? one letter answer (J)
C
The Blower Door test produces an infiltration ____________value.
CFM
Common window types are Single Hung, Double hung, Mullioned and _____________. Bay, garden, and Jalouise windows are also mentioned in the chapter on fenestration.
Casement
Low-emittance coatings are microscopically thin, virtually invisible, metal or metallic oxide layers _______ on window or skylight glazing.
Deposited
AED stands for Adequate ________________ Diversity.
EXPOSURE
.................is the uncontrolled flow of air exiting the conditioned space through openings in the thermal envelope.
Exfiltration
A 2.5% design DB - could be exceeded up to 2.5% of the time in any given for the Heating season. This is the Heating design DB.
F
Duct losses are usually insignificant, less than 5 %.
F
In Box 9 of the Manual J, the construction numbers for the walls and the associated HTMs are subtracted from the window areas.
F
Infiltration is an issue with doors and windows. The average window at a 25 MPH wind speed will leak .25 CFM. High quality window at the same speed will not leak.
F
Line 3 of the Manual J identifies the ceiling heights.
F
Line 4 of the Manual J identifies the gross exposed wall area. wall.
F
Loads can be estimated for every eventuality. If there's a big party at a house in the middle of the summer, with maybe 50 people in attendance, the normally adequate air conditioning system should be adequate.
F
NFRC ratings concentrate on the center of the glass pane to adjust for the worst case scenario. True or False?
F
Net wall area for exposed walls subtracts windows and doors from the basement walls.
F
Solar energy is a key factor in the winter heat loss calculation.
F
We use one value to calculated heat loss through a basement wall that is partially below grade.
F
We use winter TD's for the heat load calculations rather than summer because the temperature range is more extreme.
F
Fenestration is any opening in the structural envelope that allows the _____________ flow of light, air, and/or people.
Free
CFM infl x ∆gr x .68 = Btuh __________ gain.
Latent
The reason we calculate the SLM is so that the unshaded glass area is calculated with full radiant energy gains and the shaded portion of the glass is treated as if it faced __________?
NORTH
Why does oversized equipment operate inefficiently
Oversizing equipment causes shot-cycling, and in the case of air conditioning, results in insufficient moisture removal.
###The ___________ mechanism of heat transfer in multilayer glazing is thermal radiation from the sun.
Principal
A major concern of summer time energy gains is _____________ heat from the sun.
Radiant
_____________ heat can be mitigated by shading and direction.
Radiant
From page 100 of the pdf. the Midsummer Shade Line Multiplier is abreviated with what 3 letters? Example: (HTM)
SLM
SHGC stands for _____________Heat Gain Coefficient.
SOLAR
Glass is treated differently in the cooling calculation because of direction, _____________ (internal and external) and solar heat gain.
Shading
Fenestration can be the largest _____________ contributor to a cooling load calculation.
Single
Which item has the highest solar gain - Jalouise window or a Skylight? (Choose the underlined word)
Skylight
###During the _____________we are only concerned with the Btuh transmission through the glass, and not radiation.
Summer
When do we need to calculate the Btuh latent heat gains for OA? Winter or summer?
Summer
Another term used to describe the overall heat transfer rate of a wall is the Overall Heat Transfer Coefficient "U".
T
Conductivity is a property of the material and is designated by the letter "K." It is also described on a per inch thickness basis. Finally, it is described on a per degree Fahrenheit basis from one side of the material to the other. The units for this characteristic are: BTU-inch/hr-degree F-ft2
T
Conductivity or Thermal Conductivity is the measurement of a homogeneous material's ability to transfer heat. (How rapidly does heat transfer through the material?)
T
Every material will resist heat transfer to some degree.
T
For Heat Loss Due to Infiltration: Use 1.1 x CFM x (IDT - ODT)
T
For the below grade SF calculation for Manual J heat loss a 10' long basement wall that is 8' below grade and 8' high will be calculated as 10' x 6'.
T
In order to calculate the winter infiltration HTM, the area of all external doors and windows must be determined.
T
Line 1 Manual J identifies the Name of the areas.
T
Line 14 from the Manual J calculates duct heat loss for each room.
T
Line 2 of the Manual J identifies the running feet of wall.
T
Outside design conditions are found in a variety of documents including those found in ASHRAE and ACCA manuals. The design conditions chosen, however, must be approved by the local authorities.
T
Solariums do not use HTM's. True or False?
T
The amount of heat transferred though a material is directly proportional to the difference in temperature from one side of the material to the other.
T
The amount of heat transferred through a material will be inversely proportional to the thickness of the material.
T
The general formula for the sum of the resistances (which is known as the Overall Resistance) is: Ro = 1/fi + 1/C1 + X/K1 + 1/C2 + ... + 1/fo
T
The gross area of walls includes windows and doors
T
Thermal Resistance is the inverse of conductance and is a measure of the resistance to heat transmission. Thermal resistance is designated as "R" and since it is the inverse of "C", R=1/C or R = X/K
T
These walls are usually found in Table 2 at number 15. This page reference may be off in the latest Manual J. - Walls that are < 2 ft below grade are treated as if they are above grade. - Walls that are > 2 ft but < 5 ft are to use 15 A-D. - If > 5 ft, use 15 E-H. - You will need to use an average depth where terrain is uneven (Look at 15a for an example.)
T
Using the heat transfer coefficient, we can calculate to total heat transfer through any given wall using the formula: Q = U x A x Delta T
T
Wall losses below grade need to be considered in the winter heat loss calculation.
T
Low-emittance coatings reduce the ______ factor. (Single Letter answer: P)
U
Three acceptable methods for determining the OA infiltration are ACH, ____________ Leakage Area method, and the Blower Door Test method
component
"Ventilation is the ____________ (engineered) movement of" OA into, and out of, a structure.
controlled
One of the required components of an accurate heat load calculation is "to determine how much OA (in CFM) is _____________ your residential structure". (for infiltration)
entering
According to the SCAHACC-Understanding-MJ8-Luis-Escobar pdf., the designer's objective is to design a mechanical system that can add or remove heat energy at a rate that will allow the home's indoor __________ to achieve the design conditions. This will keep occupants comfortable and safe.
environment
The Component Leakage Area method requires you to ____________ every component in the system.
evaluate
Air in the structure leaves the building via
exfiltration
Positive pressure creates................
exfiltration
Infiltration is caused by a collection of pressure drivers such as wind, the stack effect, vents, chimneys, ____________ fans, and duct leakage.
exhaust
Negative pressure creates - Choose one of: infiltration or exfiltration.
infiltration
OA creates a _____________ on the thermostat. (System)
load
The ____________ and sealing quality of an operating duct system can cause changes in building pressurization.
location
Blocking the transfer of radiant heat through a window lowers the total heat flow through the glass and does what to the U-value? Choose one: Lowers or Raises
lowers
###Ideal structure pressure is
neutral or near neutral
###If you supply more air than you are returning you have created a ____________ pressure in the structure.
positive pressure
If the duct system is sealed on either the supply side or the return side, and not on the other end, you will unintentionally create unwanted negative or positive ____________.
pressure
###Peak radiation depends on glass direction, time of day, month of the year and _________.
the latitude
The flow of air may exit through cracks and penetrations in the ____________ envelope. Relief openings, exhaust systems, ERV's, chimneys, and vents also drive the energy movement in a structure.
thermal
Infiltration is the ____________ OA leakage into a conditioned space.
uncontrolled
Outside air enters a structure by means of infiltration and or/
ventilation