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[′är ‚val·yü]
An index of the ability of a substance or material to retard the flow of heat; higher numerical values correspond to higher insulating ability.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


A unit of thermal resistance. A material’s R-value is a measure of the effectiveness of the material in stopping the flow of heat through it. The higher a material’s Rvalue, the greater its insulating properties and the slower the heat flow through it. Examples of higher R-values for residential buildings: R-50 ceilings, R-21 walls, and R-30 floors.
Illustrated Dictionary of Architecture Copyright © 2012, 2002, 1998 by The McGraw-Hill Companies, Inc. All rights reserved


A measure of the thermal resistance of a material or component.
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.


(1) (Metal Oxide Semiconductor) See MOSFET.

(2) (Mean Opinion Score) The quality of a digitized voice line. It is a subjective measurement that is derived entirely by people listening to the calls and scoring the results from 1 to 5. Toll quality audio is generally considered to have a MOS rating of 4 and above. See toll quality audio.

The MOS is an average of the numbers for a particular codec. Because MOS testing requires carefully prepared and controlled test conditions, the best way to get a MOS test done is to have it outsourced. See codec.

An Objective Model
The E-Model is another rating system that provides an objective measurement of quality based on packet loss, jitter and delay. The E-Model reports results as R-values. Following is an approximate relationship between MOS and E-Model quality ratings.

Subjective Interpretation         MOS  R

 Perfect                           5.0 100

 Excellent - almost all satisfied  4.5  90

 Very good - most are satisfied    4.0  80

 Good - some are dissatisfied      3.6  70

 Fair - many are dissatisfied      3.1  60

 Poor - most are dissatisfied      2.6  50

 Bad - not recommended             1.0   0
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in periodicals archive ?
Caption: Kingspan underscores Kooltherm K20's potential to attain higher thermal performance in thinner profiles than conventional insulation boards: R-value up to R17 in 2-in.
Pearson corelation after treatment in this group showed conversion of significant negative correlation prior to intervention (p-value 0.003 and r-value -0.955) to non significant positive correlation (p-value 0.513 and r-value 0.337).
Conversely, through the criteria based only on [pH.sub.45min], on [pH.sub.45min] and R-value (HONIKEL & FISHER, 1977) and only on [L.sup.*] (MAGANHINI et al., 2007), most of the samples (53 to 68%) were classified as RFN, whereas a large part of them (32 to 38%) was classified as PSE.
R-value rates reflect a product's ability to restrict heat flow which, in turn, reduces energy costs: the higher the R-value, the better the product's insulating ability.
The performance of the constructed models was evaluated on the basis of R-value and MSE analyses.
The thermal conductivity of the panel with 5-mm layers was 0.0532 W [m.sup.-1] [K.sup.-1], which corresponds with a US R-value of 6.8 (2.7/in.
Density, k-factor, R-value and percent closed-cell content were measured.
* Polyiso (polyisocyanurate) or polyurethane foam installed under the roof system, instead of in the attic floor, helps seal the building against leaks and helps increase the R-value of the roofing system.
Both are available in rolls and batts with an R-value of between three and four per inch of thickness.
Table 1 shows that with a calculated r-value of 0.400, there is significant relationship between multiple taxation and tax evasion in Lagos State.
Griffiths and Zuluaga (2004) used a two-dimensional, steady-state FEM to calculate the effective R-value of ducts buried under three levels of loose-fill insulation, as shown in Figure 1.