ASTM C1155-95(2021)
(Practice)Standard Practice for Determining Thermal Resistance of Building Envelope Components from the In-Situ Data
Standard Practice for Determining Thermal Resistance of Building Envelope Components from the In-Situ Data
SIGNIFICANCE AND USE
5.1 Significance of Thermal Resistance Measurements—Knowledge of the thermal resistance of new buildings is important to determine whether the quality of construction satisfies criteria set by the designer, by the owner, or by a regulatory agency. Differences in quality of materials or workmanship may cause building components not to achieve design performance.
5.1.1 For Existing Buildings—Knowledge of thermal resistance is important to the owners of older buildings to determine whether the buildings should receive insulation or other energy-conserving improvements. Inadequate knowledge of the thermal properties of materials or heat flow paths within the construction or degradation of materials may cause inaccurate assumptions in calculations that use published data.
5.2 Advantage of In-Situ Data—This practice provides information about thermal performance that is based on measured data. This may determine the quality of new construction for acceptance by the owner or occupant or it may provide justification for an energy conservation investment that could not be made based on calculations using published design data.
5.3 Heat Flow Paths—This practice assumes that net heat flow is perpendicular to the surface of the building envelope component within a given subsection. Knowledge of surface temperature in the area subject to measurement is required for placing sensors appropriately. Appropriate use of infrared thermography is often used to obtain such information. Thermography reveals nonuniform surface temperatures caused by structural members, convection currents, air leakage, and moisture in insulation. Practices C1060 and C1153 detail the appropriate use of infrared thermography. Note that thermography as a basis for extrapolating the results obtained at a measurement site to other similar parts of the same building is beyond the scope of this practice.
5.4 User Knowledge Required—This practice requires that the user have knowledge that the data empl...
SCOPE
1.1 This practice covers how to obtain and use data from in-situ measurement of temperatures and heat fluxes on building envelopes to compute thermal resistance. Thermal resistance is defined in Terminology C168 in terms of steady-state conditions only. This practice provides an estimate of that value for the range of temperatures encountered during the measurement of temperatures and heat flux.
1.2 This practice presents two specific techniques, the summation technique and the sum of least squares technique, and permits the use of other techniques that have been properly validated. This practice provides a means for estimating the mean temperature of the building component for estimating the dependence of measured R-value on temperature for the summation technique. The sum of least squares technique produces a calculation of thermal resistance which is a function of mean temperature.
1.3 Each thermal resistance calculation applies to a subsection of the building envelope component that was instrumented. Each calculation applies to temperature conditions similar to those of the measurement. The calculation of thermal resistance from in-situ data represents in-service conditions. However, field measurements of temperature and heat flux may not achieve the accuracy obtainable in laboratory apparatuses.
1.4 This practice permits calculation of thermal resistance on portions of a building envelope that have been properly instrumented with temperature and heat flux sensing instruments. The size of sensors and construction of the building component determine how many sensors shall be used and where they should be placed. Because of the variety of possible construction types, sensor placement and subsequent data analysis require the demonstrated good judgement of the user.
1.5 Each calculation pertains only to a defined subsection of the building envelope. Combining results from different subsections to characterize...
General Information
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: C1155 − 95 (Reapproved 2021)
Standard Practice for
Determining Thermal Resistance of Building Envelope
1
Components from the In-Situ Data
This standard is issued under the fixed designation C1155; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope sectionstocharacterizeoverallthermalresistanceisbeyondthe
scope of this practice.
1.1 This practice covers how to obtain and use data from
in-situ measurement of temperatures and heat fluxes on build- 1.6 This practice sets criteria for the data-collection tech-
ing envelopes to compute thermal resistance. Thermal resis- niques necessary for the calculation of thermal properties (see
tance is defined in Terminology C168 in terms of steady-state Note 1). Any valid technique may provide the data for this
conditions only. This practice provides an estimate of that practice, but the results of this practice shall not be considered
value for the range of temperatures encountered during the to be from an ASTM standard, unless the instrumentation
measurement of temperatures and heat flux. technique itself is an ASTM standard.
1.2 This practice presents two specific techniques, the
NOTE 1—Currently only Practice C1046 can provide the data for this
practice. It also offers guidance on how to place sensors in a manner
summation technique and the sum of least squares technique,
representative of more than just the instrumented portions of the building
andpermitstheuseofothertechniquesthathavebeenproperly
components.
validated. This practice provides a means for estimating the
1.7 This practice pertains to light-through medium-weight
meantemperatureofthebuildingcomponentforestimatingthe
construction as defined by example in 5.8. The calculations
dependence of measured R-value on temperature for the
apply to the range of indoor and outdoor temperatures ob-
summation technique. The sum of least squares technique
served.
producesacalculationofthermalresistancewhichisafunction
of mean temperature.
1.8 The values stated in SI units are to be regarded as
standard. No other units of measurement are included in this
1.3 Each thermal resistance calculation applies to a subsec-
standard.
tion of the building envelope component that was instru-
mented. Each calculation applies to temperature conditions
1.9 This standard does not purport to address all of the
similartothoseofthemeasurement.Thecalculationofthermal
safety concerns, if any, associated with its use. It is the
resistance from in-situ data represents in-service conditions.
responsibility of the user of this standard to establish appro-
However,fieldmeasurementsoftemperatureandheatfluxmay
priate safety, health, and environmental practices and deter-
not achieve the accuracy obtainable in laboratory apparatuses.
mine the applicability of regulatory limitations prior to use.
1.10 This international standard was developed in accor-
1.4 This practice permits calculation of thermal resistance
dance with internationally recognized principles on standard-
on portions of a building envelope that have been properly
ization established in the Decision on Principles for the
instrumented with temperature and heat flux sensing instru-
Development of International Standards, Guides and Recom-
ments. The size of sensors and construction of the building
mendations issued by the World Trade Organization Technical
component determine how many sensors shall be used and
Barriers to Trade (TBT) Committee.
wheretheyshouldbeplaced.Becauseofthevarietyofpossible
construction types, sensor placement and subsequent data
2. Referenced Documents
analysis require the demonstrated good judgement of the user.
2
2.1 ASTM Standards:
1.5 Eachcalculationpertainsonlytoadefinedsubsectionof
C168Terminology Relating to Thermal Insulation
the building envelope. Combining results from different sub-
C1046Practice for In-Situ Measurement of Heat Flux and
Temperature on Building Envelope Components
1
This practice is under the jurisdiction of ASTM Committee C16 on Thermal
Insulation and is the direct responsibility of Subcommittee C16.30 on Thermal
2
Measurement. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Oct. 1, 2021. Published October 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1990. Last previous edition approved in 2013 as C1155–95 (2013). Standards volume information, refer to the sta
...
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