Term
|
Definition
Simplest form of air handling. Under 5000-15,000 SF
Advantages:
Centralizes control of temp. humidity, filtration, ventilation. Air distribution. Low first cost.
Disadvantages:
Poor control where loads differ btw. rooms. Cannot supply heating and cooling simulaneously. |
|
|
Term
| Variable Air Volume System |
|
Definition
Volume of air is changed to meet varying zone loads. Temp is constant. Single zone AHU
advantages:
Low first cost, lower operation costs (relatively), High and low velocity
Disadvantages:
Cannot supply heating and cooling simultaneously, high velocity noise, poor control at low loads, supply volume variation over 20% can create drafts. |
|
|
Term
|
Definition
Varying loads are compensated by adding heat within a terminal in the space. Single duct with air supply and temp. set to meet the needs of the space with the highest cooling loads.
Advantages:
good multi-zone control
low first cost, good flexability
Disadvantages:
high operating and maintenance cost
high velocity noise |
|
|
Term
|
Definition
Supplies constant volume to all spaces. Supply temp varies to meet demand. There is one heating and cooling coil, but separate dampers for each zone. Cooling and heating dampers work in parallel. Temps at both docks need to be set to meet maximum loads.
Advantages:
Good zone control. Agerage operating cost lowered by cutting off heating or cooling depending on the season.
Disadvantages:
high first cost, bulky ductwork, inherently inefficient, but better in real operation
lacks flexibility if space changes require modifying the HVAC system. Installed only in special instances w/ less than 12 zones. |
|
|
Term
|
Definition
warm air duct and cold air duct supply air to mixing terminal, similar to multizone, but air is mixed at terminal box instead of by the AHU
Advantages:
Excellent control, optimum flexibility since heating and cooling ducts supplied throughout the building. High or low velocity.
Disadvantages:
High first cost, double duct work, cost of mixing boxes and controls. Inherently inefficient, high maintenance cost. |
|
|
Term
| By-pass provided at Zone or Room |
|
Definition
"Neutral" air supplied through space to compensate varying loads. Multi-zone sometimes uses bypass distribution.
Advantages:
Average cost, less than dual duct, greater than varying air volume. can reduce duct sizes and costs. Better control than VAV. Lower operating cost |
|
|
Term
| Direct Expansion (DX) System |
|
Definition
Also called direct refrigerant system. Located within or near the space. Heating is usually separate. Good for low temp. control spaces. Controls in smaller cheaper spaces are usually on/off/
Advantages:
decentralized mechanism
low first cost
low op. cost
disadvantages:
Noisy equip. in or near the space. DX unit evaporator must be within 60' of evaporator. |
|
|
Term
|
Definition
| used for first floor heating from basement, crawl space or slab on grade, but predominantly when the plan is similar in size to a small residence. The individual ducts are sized to supply air volumes needed at each space. |
|
|
Term
|
Definition
| Used for first floor heating for slab on grade construction in colder climates. The perimeter loop keeps the slab edge warm. Usually residential but could be used for light commercial. Ducts sizing is more comlicated than with the radial cuct layout. Designed for constant pressure along hte perimeter loop. |
|
|
Term
|
Definition
| The trunk duct has continuous section dimension for the length of the plenum, which can't exceed 24'. Can be used in residential or small compace commercialzones. The static pressure decreases further from the AHU. Branch ducts are sized for air volume required at spaces. Simpler to design and construct that reducing trunk duct system, but harder to balance the air velocities at the outlets. |
|
|
Term
|
Definition
| This is the common approach for commerical buildings, where the ducts are designed first based on individual space loads. Each section of trunk duct between branches is then sized for the air volume that will pass through that section. |
|
|
Term
| design cooling Temperature |
|
Definition
| A temperature close to the most extreme expected for a location. Used to determine the design cooling Load |
|
|
Term
|
Definition
| Determined by the Design cooling temp. maximum cooling load expected in a location. |
|
|
Term
|
Definition
| an additional charge for electric power psupplied by a utility company based on the peak electrical demand during a period. Design heating or cooling load- The total heat loss or gain from a house under the most severe winter conditions likely to occur. |
|
|
Term
|
Definition
| Heat that raises the body temperature. |
|
|
Term
|
Definition
| The temperature at which an air-water vapor mixture will become saturated and begin to yield drops of condensed water vapor (water) |
|
|
Term
|
Definition
| The time required for the cumulative net benefits derived from an investment to pay back the investment cost, taking into account inflation and the time value of money |
|
|
Term
|
Definition
| The ratio of net cooling capacity in BTU/h to the total rate of electric input in watts under designated operation conditions. |
|
|
Term
|
Definition
| The ratio of useful energy at the point of use to the thermal energy input for a designated time period, expressed in percent. |
|
|
Term
|
Definition
| The interest rate for which the total discounted benefits from an investment equal its total discounted costs. |
|
|
Term
| Coefficient of Performance |
|
Definition
| The ratio of the rate of net heat loss in BTU/h through a square foot of a wall or other building surface when the difference between the indoor and outdoor air temperature is 1F (U-1/R) |
|
|
Term
|
Definition
| A technique for converting cash flows that occur over time to equivalent amounts at a common point in time- usually the present. |
|
|
Term
|
Definition
| A rise in the general price level (for al goods and services) resulting from a decline in the purchasing power of a dollar. |
|
|
Term
|
Definition
| The weight of the actual water vapor in aa mixture per pount of dry air. |
|
|
Term
| heating System Performance Factor |
|
Definition
| The total heating output of a heat pump (in BTUs) during it's normal usage period for heating, divided by the total electric power input in watt-hours over the same period. |
|
|
Term
|
Definition
| A term used to express the energy involved in a change of state. |
|
|
Term
| Seasonal Energy Efficiency Ratio |
|
Definition
| The total cooling of a central air conditioner in BTUs during it's normal usage period for cooling, divided by the total electric input in watt-hours over the same period |
|
|
Term
|
Definition
| Past and future cash flows expressed in terms of current dollars by adjusting for inflation and any other factors that affect the time value of money. |
|
|
Term
|
Definition
| The net sum to be realized fromt he disposal of an asset at the time of it's replacement, resale, or at the end of the study period. |
|
|
Term
|
Definition
| The incremental changes in costs associated with alternative investments. |
|
|
Term
|
Definition
| The total of all relevant costs associated with an activity of project during the time it is analyzed. For buildings the Life-cycle costs include the costs of owning, operating and maintaining the building including energy costs. |
|
|
Term
|
Definition
| That portion of supply air which comes from outside plus any recirculated air that has been treated to maintain the desired quality of air within a designated space. |
|
|
Term
|
Definition
| Term used to express the energy involved in a change of state. |
|
|
Term
|
Definition
| A period of economic analysis over which time the costs and benefits of an investment are calculated. |
|
|
Term
|
Definition
| The total heat in the mixture measured about 0F and including the latent heat of the water vapor |
|
|
Term
| annual Fuel Utilization Efficiency |
|
Definition
| The efficiency rating required by the federal government for rating gas or oil fired furnaces and boilers, based on average usage conditions including on/off cycling. |
|
|
Term
|
Definition
| Vapor compressor, Absorption Chiller, Dessicant cooling, Evaporative Cooling. |
|
|
Term
|
Definition
Made from wood fibers, used as backing for surface for siding. Often asphalt impregnated to reduce the susceplibility to moisture degradation
-moisture absorption and degradation problems
-susceptible to mildew and rot |
|
|
Term
|
Definition
Closed cell foam boards cut to length and width. Used for exterior sheathing of fiberboard. As an interior wall insulation must be covered w/ 1-1/2" or 5/8" gyp. bd. because it is combustible and out-gases toxic chemicals when burnt.
-no moisture degradation
-no mildew or rot
-dimensionally stable
-slight UV degradation, but R-value is stable |
|
|
Term
|
Definition
heat and pressure treated to cause beads to adhere into molded shape, then cut to length and width
-Cheaper than Styrofoam
-more susceptible to vermin damage |
|
|
Term
|
Definition
Foamed into boards or directly into wall cavities. Pre-formed boards will have surface layers of low moisture permeability to reduce R-value degradation. Usually have aluminized foil surface for this purpose and add to rigidity. Often used in pre-fabricated metal building panels and inlulated doors.
-one of the highest R-values, but expensive
-Appreciable R-value degadation with exposure to air and UV light
-no mildew or rot
-not susceptible to vermin
-burns and gives off toxic gas |
|
|
Term
| Fiberglass blankets and batts |
|
Definition
Made from melted glass, usually backed with craft or aluminized paper on one face
-fire proof
-not suscetible to mold or rot but will hold moisture that may rot adjacent mat.
-susceptible to vermin
-when used in horizontal applications will mat down over time. |
|
|
Term
| Mineral Wool blankets and batts |
|
Definition
Made from melted rock instead of glass. Other than lower R-value, has many of the same attributes of spun fiberglass insulation.
more susceptible to vermin |
|
|
Term
|
Definition
| can be blown in or hand placed. Has the same properties and thermal characterstics as in blanket/batt form. Lower listed R-values take into accoutnt he less uniform density that will result from the loose fill application method |
|
|
Term
|
Definition
Loose granual volcanic material compound. Over a period of 60 years 80% of the words supply of vermiculite has come form W.R. Grace & Co. in Libby, MT.
-very cheap
-fire proof
-not susceptible to mildew, rot, or insect problems
-no moisture degradation
-seggling can reduce R-value significantly and can create cold spots at the top of vall cavities where settling has occurred.
-asbestos tainted vermiculite in existing building spaces is a health hazard |
|
|
Term
|
Definition
| Loose granule mineral based insulator like vermiculite, but expanded and therefore lighter. Has many of the same properties as vermiculite but a higher R-value. Used as an additive for light weight concrete where the insulation properties are of greater importance than concrete strength |
|
|
Term
|
Definition
made from recycled paper
-very cheap
-combustible and must be treated with fire retardant which presents quality control problems in the manufacturing process
-as with all fiber based products, susceptible to vermin
-Settling can be a problem |
|
|
Term
|
Definition
Most loose fill insulations can also be blown into place
-fiberglass, mineral wool, vermiculite, perlite, cellulose |
|
|
Term
|
Definition
blown insulation in wall cavities for new constrction and retrofit applications. outgases formadehyde which is a health hazard to building occupants. It's use has been discontinued, but the product is still in place where it had been used with no national program for removal.
-relatively cheap
-fireproof
-chemically stable, but outgases formaldehyde
-no moisture or insect problems
-tends to bond with the wall |
|
|
Term
|
Definition
| The precent of incitent visible radiation transmitted by the glazing |
|
|
Term
|
Definition
| percent of incident total solar radation transmitted by the glazing |
|
|
Term
| Near-infared tranmittance |
|
Definition
if solar radiation is assumed to be half light and half near-infared radiation
-approximated by doubling solar transmittance and subracting visible transmittance. |
|
|
Term
|
Definition
| solar radiation that arrives at a given glazing at a certain time and date can still be described by the diagrammatic spectral distribution curve described earlier, with reductions in the power of certain wavelengths and perhaps even slight increases in teh power of other wavelengths. |
|
|
Term
|
Definition
| The rate at which glass absobs solar radiation |
|
|
Term
|
Definition
| bending of light passing through a medium |
|
|
Term
|
Definition
| More radiation is reflected as angle of incidence is greater, measured w/ perpendicular angle = 0 |
|
|
Term
|
Definition
| Angle at which all incident light is relected (87) |
|
|
Term
|
Definition
| Glass admits most visible and near infared radiation, but not far-infared radiation creating the greenhouse effect. This is an example of this term. |
|
|
Term
|
Definition
| Dimensionless ratio defined as the solar gain through a given fenestration compared to what the solar gain would have been through an unshaded opening the same size and orientation glazed with a standard single pane of 1/8" double strength clear window glass. Developed to provide a simple reference to a known product. |
|
|
Term
|
Definition
| Sensible cooling load (Qrs)/Sensible heat gain(Qes) |
|
|
Term
|
Definition
| Uses sun angle/ time of day charts |
|
|
