Steady state R-values give just a snapshot in time of thermal performance under laboratory conditions.
Oak Ridge National Lab researchers have found a way to measure thermal performance of mass walls over time. The term is called Dynamic Benefits for Massive Systems (DBMS).
DBMS describes thermal performance across four seasons and diurnal temperature swings.
DBMS assigns an R-value to a mass wall by asking the question: “What wall R-value should a house with wood frame walls have to obtain the same space heating and cooling loads as a similar house containing massive walls?”
While "effective R-value" is thrown around rather casually in different contexts in the building industry, DBMS actually refers to a performance- based "effective" R-value that can at least act as a basis for understanding how a system will perform over time, as opposed to how it will perform in the lab.
As energy models become both more accurate and easier to create, the industry is moving toward a whole building approach based on performance metrics.
This makes sense, as there is no better
measure than a utility bill.
Take a look at NRG's Independent Lab Results below:
Thermodynamic product assessment of NRG 12" concrete block performed by Energy Management, Inc., of Louisville, KY.
"The NRG Brand 12" EPS foam insulated and thermally broken concrete block has undergone extensive computer simulation on its thermal performance with software subroutines that contain the ability to model thermal mass for the Louisville, KY, area.
The assessment indicates an Average Annual Effective R-Value R-22"
That is in climate zone 4.
While the energy model describes an "effective R-value", let's look at it a different way. Compare NRG's performance difference with an energy model of an NRG building with that of the same building with conventionally insulated (interior insulation) R-54 walls.
Based on utility bills, in climate
zones 5 and 6, actual NRG buildings have been shown to thermally outperform energy models of buildings with R-54 walls.
Energy Usage Comparison: NRG Buildings
Reeds Supermarket, Genesee, PA $.33/sq.ft/year Private Residence, Madisonville, KY $.28/sq.ft/year Transit Ready-Mix, Clarence, NY $.26/sq.ft/year Paristown Condominiums, Louisville, KY $.31/sq.ft/year Ridgewood Bible Church, Lockport, NY $.25/sq.ft/year.
Kentucky School District Buildings Using Brick/Block:
Jefferson County, KY $.80/sq.ft/year Oldham County, KY $.84/sq.ft/year Fayette County, KY $1.04/sq.ft/year Franklin County, KY $.96/sq.ft/year