Determination of the thermal resistance of walls (masonry) in dry and moist state and of a conversion procedure to get the appropriate design value

• Forschungsstelle: EU FRP
• Projektnummer: 97.0331
• Projekttitel Englisch: Determination of the thermal resistance of walls (masonry) in dry and moist state and of a conversion procedure to get the appropriate design value

Schlüsselwörter (Englisch)

Masonry; thermal conductance; moisture; water vapour transmission

Alternative Projektnummern (Englisch)

EU project number: SMT4-CT98-2211

Forschungsprogramme (Englisch)

EU-programme: 4. Frame Research Programme - 2.2 Measurements and testing

Kurzbeschreibung (Englisch)

See abstract

Weitere Hinweise und Angaben (Englisch)

Full name of research-institution/enterprise:
Eidg. Materialprüfungs- und Forschungsanstalt EMPA
Abteilung Bauphysik

Partner und Internationale Organisationen (Englisch)

Coordinator: NPL Centre for Quantum Metrology (UK)

Abstract (Englisch)

This project involved twelve institutes from six European Countries intercomparing measurements of thermal conductance, thermal conductivity, water vapour transmission and hygroscopic sorption of masonry materials. The project had six objectives that were:
· To validate the measurement procedures specified in EN 1934, the hot box, heat-flow-meter (HFM) method standard. This was achieved by comparison with thermal conductance measurements carried out using classical Guarded Hot Box (GHB) and Calibrated Hot Box (CHB) apparatus.
· To determine the measurement uncertainty, repeatability and reproducibility of the thermal conductance measurements of masonry walls made using both the GHB & CHB and HFM/GHB apparatus.
· To determine the thermal conductivity, hygroscopic sorption and water vapour resistance factor properties of the material used in the three chosen blocks types, Aerated Autoclaved Concrete (AAC), Hollow Brick blocks, Hollow Concrete blocks, and two different density mortars. The properties were determined dry and at two different moisture contents.
· To measure the thermal conductance of a range of 'ideal wall' systems using acrylic sheets instead of mortar to enable Finite Element Analysis models to be verified.
· To measure the thermal resistance of walls made from the three different masonry materials, with the two mortar types, conditioned to different moisture contents.
· To derive a conversion procedure from the measured data produced above, to enable the thermal properties of real walls to be determined from knowledge of the thermal properties of their components in the dry state.

The agreement between the Institutes results for measurements on materials with thermal conductivity values less than than 0.2 W/m.K was very good but poorer for materials with higher thermal conductivities. There was also a wide range of values of water vapour transmittance factor and hygroscopic sorption. The agreement of the hot box measurements were encouraging and the measurement procedures specified in EN 19434 were found to be acceptable. The repeatability of the hot box and the hot box HFM measurements were found to be very good. In parallel with the measurement intercomparisons, a mathematical model of complex moist masonry structures was produced to facilitate the determination of design thermal properties from the properties measured in the dry state. This model was validated against hot-box measurements and numerical calculations.

Datenbankreferenzen (Englisch)

Swiss Database: Euro-DB of the
State Secretariat for Education and Research
Hallwylstrasse 4
CH-3003 Berne, Switzerland
Tel. [phone]
Swiss Project-Number: 97.0331