New study was released in December 2013:The building industry is continually moving toward higher
insulation levels and continuous insulation. Many building codes and
standards recognize that thermally massive buildings need less
insulation because they can store and gradually release heat compared
to lightweight metal or wood-framed buildings. This relative reduction
in required minimum insulation values for a massive building compared
to a lightweight building varies by climate, but in general, ASHRAE
Standard 90.1 allows about a 30% reduction in insulation levels.
California's energy code allows up to an 86% reduction in insulation
levels for "mass heavy" walls in certain climate zones.
However,
most state building codes and energy standards do not currently reflect
whether the thermal mass is located on the interior or exterior side
of the insulation in the wall system. Also, the building type, geometry,
window-to-wall ratio, and internal loads are not considered with
respect to thermal mass in the prescriptive tables of ASHRAE 90.1 and
various state energy codes. Our paper discusses the results of a series
of whole-building energy simulations that we completed using the
EnergyPlus computer program to study the effect of thermal mass
relative to these parameters.
Our results show that the increased
U-factors in the prescriptive tables in ASHRAE 90.1 and various state
energy codes are justified in terms of accounting for the benefit of
thermal mass. However, in all cases, having insulation on the exterior
side of the thermal mass outperforms cases where the thermal mass is on
the exterior side of the insulation.We show the most important
parameters to maximize the benefit of thermal mass with regards to
energy efficiency and demonstrate how the prescriptive tables in ASHRAE
90.1 and most state energy codes do not currently account for these
benefits or parameters.
Presented at Thermal Performance of Exterior Envelopes of Whole Buildings XII, December 2013
Citation: Thermal Performance of Exterior Envelopes of Whole Buildings XII
Anyone out there with this study? It's probably worth the $15 to download but I am curious as to what it has to say about ICF.