Author: William Bahnfleth
Date: December 1997
This report
is the product of one of four projects on basements recently conducted by the
Pennsylvania Housing Research Center (PHRC). The four reports together represent a comprehensive effort to address
basement-related issues with reference to Pennsylvania in particular, and the
north-east in general.
Financial
support has been provided by:
· The Pennsylvania Department of Community and Economic Development (DCED),
· The Pennsylvania Builders Association (PBA),
· The individuals, associations, and corporations that are
members of the PHRC,
· The Hankin Endowment, and
· The Pennsylvania State University.
Economic
Assessment of Basement Insulation for Pennsylvaniawill
be of interest not only to builders and developers but also to the regulatory
community. The cost and the contribution of the basement to
space-conditioning energy is often relatively small. Quantifying the energy-related performance of the below-grade
area presents problems such as the following:
· A reasonably accurate analytical procedure is required.
· It is difficult to model the actual ground conditions.
· Use of the basement space and the degree of finish are highly variable.
This study
seeks to address each of these concerns and arrive at insulation strategies that
are both economic and practical.
The study
was conducted by Dr. William Bahnfleth, Ms. Cindy Cogil, and Dr. Grenville Yuill. Valuable assistance was given by the following individuals and
corporations and associations:
Mr.
Eric Werling of ICF Kaiser
Mr.
Mike Ngugen of the Pennsylvania Public Utility Commission
Mr.
John Boyer of the Pennsylvania Department of Community and Economic Development
Mr.
Chris Fennell of the National Association of Home Builders
Mr.
Mike Schieuer of Lite-Form
Mr.
Carl Martin of Superior Walls of America, Ltd.
Thanks are
due to each of these individuals for their time, interest, and patience. The assistance of Michelle McMullen and Angela Burnett in producing the
final version of the report is also appreciated.
The PHRC is
responsible for producing this report. We
welcome questions or other feedback.
E. F. P.
Burnett
Director
This study was undertaken to
investigate the effectiveness of foundation insulation for both conditioned and
unconditioned basements. A foundation heat-loss model of a representative
basement was developed specifically for this purpose. Foundation assemblies considered include conventional
cast-in-place concrete, cast-in-place concrete with insulating forms, and
precast insulated concrete panels.
Parametric studies compared the
effects of insulation location and R-values from zero to R-20 for basement
exterior walls and from zero to R-30 for basement ceilings for three locations
representing the range of Pennsylvania climates and two common residential
heating and cooling plants.
It was found that some level of
insulation can be economically justified for most conditioned basements in
Pennsylvania. The optimal amount of
insulation, however, is sensitive to the type of heating system, cost of heating
energy, climate, and the economic life over which the added cost of insulation
is recovered. Interior insulation
was most cost-effective from the perspective of installed cost, and the largest
R-values were justified for homes with electric heating.
Insulation requirements found in other
sources were reviewed and compared with results of this study. Previously published guidelines for energy-conscious, cost-effective
basement insulation vary widely in published codes, standards, and design
guides. In general, these sources
recommend lower levels of insulation than the findings of the present
investigation.