Title:
Calculations of U-Values of Hollow
Concrete Masonry
Author(s):
Rudolph C. Valore
Publication:
Concrete International
Volume:
2
Issue:
2
Appears on pages(s):
40-63
Keywords:
aggregates; cellular concretes; cement
pastes; concrete blocks; concretes; density
(mass/volume); heat transfer; heavyweight ag-gregates;
insulation; joints (junctions); lightweight ag-gregates;
lightweight concretes;
DOI:
Date:
2/1/1980
Abstract:
U-values, obtained by six laboratories during the last 50 years in tests of 38 hollow concrete masonry walls and 38 walls with cores insulated, have been compared by linear regression with values calculated by two methods. Method 1 assumes parallel heat flow through contiguous sections having different resistances; Method 2 assumes a series-parallel ar-rangement. Thermal conductivity of air-dry concrete, calculated from density, was used in calculations of U-values. Values calculated by Method 2 provided good overall correlation with test values for walls with cores empty and filled, and is recommended as a standard for specification purposes. Calculated U-values for six additional walls of multicore units were in good agreement with test values. Method 2 is believed to be applicable not only to concrete masonry but also to hollow structural clay masonry and hollow concrete elements. Procedures presented for calculating thermal conductivity and correcting conductivity for moisture apply to all types of concrete.