Publications in Scientific Journals:
P.P. Housez, U. Pont, A. Mahdavi:
"A comparison of projected and actual energy performance of buildings after thermal retrofit measures";
Journal of BUILDING PHYSICS,
This article addresses the discrepancies between projected and actual energy performance
of thermally retrofitted buildings. Toward this end, we use detailed data and
observations pertaining to seven residential buildings in Austria that were thermally retrofitted
recently. These include five multifamily residences in Vorarlberg, the upper level
of a duplex house in Lower-Austria, and a residential complex for the elderly in Styria.
During the heating season 2009-2010 (1st October-30th April), indoor temperature
and relative humidity levels were measured and logged in these buildings. For each
building, the actual energy use during this period was derived based on bills for gas and
electrical power. Additionally, we obtained and examined existing energy calculations
(energy certificates) for these buildings. In six cases out of seven, we found a large discrepancy
between projected and actual space heating demand. To explore possible reasons
for this discrepancy, we generated for each of the buildings an energy certificate
and performed detailed thermal simulations. Thereby, we took the main input parameters
for energy calculations into consideration (air change rate, indoor air temperature,
outside air temperature, and internal gains). If we use standard (default) values as
suggested by Austrian standards for these parameters, the above-mentioned discrepancy
cannot be explained. Measurements in the buildings, as well as interviews with
the building´s inhabitants implied that standard-based input data assumptions were not
reliable. A subsequent multi-factor study suggested that specifically the assumptions
Department of Building Physics and Building Ecology, Vienna University of Technology, Vienna, Austria
A Mahdavi, Department of Building Physics and Building Ecology, Vienna University of Technology, Karlsplatz
13, 1040 Vienna, Austria.
regarding air change rates might be responsible for the large deviations of the calculated
values from the actual heating demand.
none see english version
energy performance of buildings; thermal retrofit; Passivhaus Standard; Monitoring
"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
Created from the Publication Database of the Vienna University of Technology.