Manual J Study
Porous
having minute spaces or holes through which liquid or air may pass.
Internal Heat Gain
heat generated by internal sources. For example, Lighting, Motors, Appliances, People, and Cooling System Gains
Convection
heat transfer occurring through gas and liquid by movement of currents
The Federal Trade Commission (FTC) regulations deals with...
home installation labels, fact sheets, ads, and other promotional materials.
Radiant heat goes....
in an infinite number of directions
Air conditioners can not....
independently control heat and humidity.
If a night setback thermostat is anticipated...
it will be necessary to install sufficient heating capacity beyond the calculated load to warm the building back up to the daytime setting in a reasonable length of time.
All of the calculations are based on....
one fixed set of conditions.
Foam Spray is used in...
open or closed cavities as well as around ducts or pipes that pass through the building envelope
Building exposed walls
refers to walls which are exposed to the direct force of the wind (Perimeter)
Cooling load calculations include
sensible heat and latent heat loads
The lower the U value.....
the lower the heat transfer rates
The leakier a building is....
the more airflow is necessary to induce a specific indoor/outdoor pressure difference
The temperature in an unheated space between the outside and the inside spaces will always be between....
the outside air temperature and the inside air temperature.
Everytime outside temperature or wind speed changes....
the rate of heat loss also changes.
Air tightness
the resistance of the building envelope to air flow
The greater the resistance of a material, the slower heat passes through it when.....
the temperature difference is maintained across it.
The R-value for moist soil is about 10, and...
the temperature of the soil averages about 45°F in the wintertime
If the outside temperature is changed by the original ΔT....
then the rate of heat transfer doubles
Without temperature difference....
there is no heat transfer
Garden windows
they look like miniature greenhouses with a fixed window in front, single-hung windows on the sides and a glass roof. Used over a kitchen sink.
One way to find out if a wall is insulated is to....
use an exterior wall electrical outlet
Building Envelope includes
walls, windows, doors, and floor
Moisture control within a cavity is very important because...
wet insulation has little insulating value.
If the estimated heat loss is too low, the building....
will be uncomfortable during cold winter
Thermal Bridging
"Short circuits" around the insulation
Using a blue print marked 1/4"= 1 Foot, you measure an exterior wall with a ruler. The measurement is 8 3/4 inches. What is the actual dimension of the wall?
(8 x 4) + 3 = 35 feet
The target rate of air change per hour is....
0.35
Typical ACH values range from....
0.5 for new construction 1.0 air changes per hour for leaky, older buildings.
On a 3/16 scale a piece measures 1 3/8. What us the actual measurement
1 3/8 / 3/16 = 7' 4"
Blower door test procedure
1. A large fan or blower is mounted in a door or window to induce a large and roughly uniform pressure difference across the building shell. 2. The airflow required to maintain this pressure is then measured.
A ton of cooling is....
12,000 BTUs/hr
The minimum outside air supply per person for any type of space is....
15 CFM. The minimum rate will maintain indoor carbon dioxide concentrations below 0.1%
An office worker is estimated to give off
300-500 BTUs
Air changes
400 cfm/ton
Setback thermostat
A device, containing a clock mechanism, which can automatically change the inside temperature maintained by the HVAC system according to a preset schedule.
U-Value
A measure of rate of heat transmission through a material
Delta T
A shorthand term for the difference between two temperatures. ΔT
Three numbers needed to calculate basement loss are...
Above-grade wall, Below-grade wall, and basement floor.
Design air temperature
Air temperature which an HVAC system or apparatus is designed to maintain (inside design) or to operate against (Outside design)
Windows
An assembled unit consisting of a frame/sash component holding one or more pieces of glazing functioning to admit light and/or air into an enclosure and designed for vertical installation in a external wall of a residential building.
Building Assembly
Any part of the building enclosure that has boundary conditions at the interior and the exterior of the building
Infiltration loss
Energy required to warm outdoor air leaking in through cracks and crevices around doors and windows, or through open doors and windows, and through porous building materials
Zones
Ensures that thermal energy is supplied at a rate that matches the rate of thermal loss.
Gross walls
Exposed walls (perimeter) x ceiling height
3 basic types of insulation
Fiber, Foam, and Reflective
3 basic types of Batts insulation
Fiberglass, Cotton, and Rock Wool
Net walls
Gross walls minus windows and doors
What is heat loss?
Heat loss is a combination of infiltration losses and transmission losses
Sensible heat
Heat that can be felt. Heat load calculations involve only "sensible heat".
Conduction
Heat transfer occurring through solid materials and stationary liquids
Transmission loss
Heat transferred through confining walls, glass, ceiling, floor or other surfaces.
Does heat rise or does hot air rise?
Hot air rises
Natural draft (or stack effect)
Hot air rises through the building and escapes through cracks in the top ceiling.
Stratification
Hot air rises, Finds cracks to exfiltrate, Colder air replaces the hot air by infiltration.
Thermal conductivity
How well a material transfers heat. Higher conductivity, the faster the rate.
Measure of heat loss
If the area of a wall is doubles, the rate of heat transfer doubles
U-Value change
If the u-value is doubled , the rate if heat transfer is cut in half
Fenestration
In an external wall of a building, any area which allows light to pass. Commonly used to refer any opening, usually glazed, in a building envelope. (Windows, doors, skylights)
Hot and cold spots are caused by
Inconsistency in Construction, Inconsistency of Materials, Thermal Bridges and Thermal Breaks, Quality of Workmanship and Settling of Materials
U-Value is the _________ of R-Value
Inverse
Thermal Bridge
Low thermal resistance path connecting two surfaces.
Solar Heat Gain (SHG)
Measures how well a product blocks heat from the sun.
Types of convection
Natural/Free and Mechanical/Forced
Natural draft causes....
Negative pressure at lower levels and Positive pressure at upper levels
Thermal Break
Non-conducting frame around a door or window acting to retard heat flow
Higher R-Value
Numbers indicating greater insulating value
Building Envelope
Outer elements of a building.
Low-density urethane spray foams can achieve up to _____ per inch
R-11
Steady state conditions are used for...
R-Values/U-Values building materials, and design loads for equipment sizing.
Reflective insulation
Reduces radiant heat flow
R-Value
Resistance to thermal transfer or conductive heat flow.
What causes heat loss?
Temperature difference
Factors affecting heat loss include...
Temperature difference, Reducing inside temperature, Moving to a warmer climate, Area of building envelope, Smaller house, Thermal resistance, Adding insulation to the walls and ceiling, Energy conservation measures and Better window frames.
Emissivity (Low-E)
The ability of a product to absorb certain types of energy and radiate that energy through itself and out of the room.
Solar gain
The increase in temperature in a space, object, or structure resulting from solar radiation
Air Changes per Hour (ACH)
The total volume of air in a building that is turned over in one hour
Infiltration
The unintentional and uncontrolled flow of air through cracks and creaks in the building envelope.
Thermal convection
Transfer of heat by the movement of fluid
Measure of heat loss
U value x Area x ΔT= BTU/hr
The gabled roof _______________________ because the construction details of the sloped section will be different that the flat portion of the ceiling
adds several feet to the ceiling area and possible adjustments to the ceiling U-factor
Reflective insulation must be next to a(n)....
air gap other wise heat will conduct to the next solid layer.
Radiation can not
bend around corners, but can be reflected.
Ventilation is a way to control ___________ by exchanging moisture laden air with less moist air (internal/external exchange)
condensation
The basement is considered a ____________ if a minimum of 50°F is maintained over the heating season.
conditioned space
Methods of heat transfer
conduction, convection, radiation
Grossly over estimated heating loads lead to systems that....
cost more to install and operate at reduced efficiency
R-Value increases
directly proportionately with the thickness, L, of the material. R-values for different materials in a structural cross-section can be added directly
Radiation
electromagnetic energy
Casement windows
feature one hinged sash that uses a crank to swing out left or right
Rough Opening
framed opening in a wall into which a window or door is to be installed.
The summary....
gives the designer the opportunity to see if any calculated values are out of line.
Obscure glass
glass with a textured surface. It provides low visibility, but allows in natural light.
Things that affect total R-Value are
Effects of compressing insulation, imperfect installation, electrical conduit, studs, etc. THERMAL BREAK, THERMAL BRIDGE, QUALITY OF WORKMANSHIP, and SETTLING OF MATERIALS
Building Thermal Envelope
Elements of a building with enclosed spaces, and which control or regulate heat and mass transfer between interior spaces of insulated floors, walls, windows, and ceiling.
Relevance of mass
Depending on the mass of a structure, the absorption and transmission rate will be affected.
Set point
Desired temperature. Sometimes mandated by law
How do you convert R-Value to U-value?
Divide R-Value by 1
How do you convert U-Value to R-Value?
Divide U-Value by 1
How do you convert inches into a fraction?
Divide the inches by 12
