Building Energy Measurement and Performance Analysis

Indicators of Energy Efficiency in Cold Climate Buildings




[forward] Click here to access more documents about the "Indicators of Energy Efficiency" project. Password is required for further access.


Proposed Workplan

October 1995

Alan Meier

Lawrence Berkeley National Laboratory

University of California

Background

This project was originally proposed as the "Northern Homes" compilation. It proposed to compile energy data on houses in very cold climates and compare performance. As a result of the Experts meeting, the project orientation was greatly revised to meet energy performance issues affecting homes in both very cold climates and milder climates.

Historically, the concept of "low energy" homes has been equated with "low-space heating". Progress in residential energy efficiency is typically measured with respect to energy consumed for space heat. This was perhaps appropriate for the time because space heating was such a large fraction of total energy use for most homes in the developed countries.

Since the oil embargo, energy used for space heating in some countries has dropped as much as 40%. At the same time, the energy used by appliances has increased significantly and that used for water heating has not appreciably changed. Even in cold-climate homes, space heating is now often the third largest end use of energy after water heating and "other" electric appliances. This trend has been hidden partly by the mixing of site and primary energy consumption. The obsolescence of the present energy efficiency indicators, such as space heating per degree-day, has direct policy applications. For example, several countries are designing home energy rating systems based on these indicators of energy efficiency, even though it ignores over half of total energy use. The objective of this project is to test new indicators of residential energy efficiency. The project will focus on regions where space heating is significantly larger than cooling, that is, Europe, Scandinavia, North America, and Japan.

The quality of the indoor environment needs also to be included in efficiency indices. Homes with mechanical ventilation to control air quality or radon should not necessarily be penalized for the energy consumed to create a healthier indoor environment (as is now the case).

Finally, the distinctions in the definitions of key terms have risen in importance. Both domestic and international comparisons are now highly suspect due to inconsistencies in definitions or calculation procedures. This is partly due to the increasingly diverse roles of electricity.

Objectives

The objective of this project is to test new indicators of energy efficiency that will more accurately reflect a building's overall energy efficiency and permit better comparisons among buildings. The testing will be conducted on field data from houses located throughout the world. The results will be useful for those countries developing energy rating systems or evaluating the overall performance of energy conservation programs. At the same time, this study will help these groups determine what information to collect.

New research has also established techniques for quantifying the contribution of occupant behavior to variations in energy use. This research can also establish rough precisions, or confidence levels, for the indicators. In other words, it will be possible to estimate the extent to which the indicator reflects technical aspects of the building rather than occupant behavior.

Activities

The general approach will involve collecting building detailed characteristics and energy use data for a wide range of homes in cold climates. The Experts decided that climates colder than 3000 degree-days (base 18°C) shall be considered "cold-climate". This definition includes Scandinavia, most of Europe and North America, and parts of Japan.

Numerous well-documented studies have been identified as suitable for use in this project, including the Orebro project near Stockholm, the Canadian R2000 database, the US ELCAP database, and smaller, detailed studies throughout Europe and Japan.

These data will permit us to evaluate numerous energy efficiency indicators in a wide range of situations and different fuel mixes. In addition, the Experts decided that both efficient and conventional homes should be included to test the robustness of the indicators. We will rank a group of buildings with each indicator. A hypothetical example is shown below. Each letter ("House A") represents a specific home. Each column is a ranking by that indicator, in descending value.

Indicator-->

Ranking \/

MJ/degree-day
MJ/m2
GJ/occupant
Simulated E-use (GJ/year)
1
A
C
E
A
2
B
A
A
B
3
C
B
F
E
4
D
F
B
F
5
E
E
C
-
6
F
D
-
-
commentary
commentary
commentary
commentary


Specific information needed to calculate the indicator will be absent for some homes. In such cases, they will not be ranked, as happened for two homes in the right-hand column. There, the local sources did not collect sufficient information from homes 'C' and 'D' to calculate a simulated energy use.

This table (and others like it) shows how the rankings change with different indicators. We can then assess if the ranking accurately captures the building's performance because of the detailed information available from the case studies. (This assessment is represented by the "commentary" below each ranking scheme.)

These assessments would be performed for groups of homes from several countries (tentatively, Sweden, Canada, USA, and Japan). In addition, single-country comparisons will be made where sufficient data are available. (However, this must be negotiated separately with the Expert in that country.) These comparisons will allow us to assess the strengths and limitations of each indicator. We expect to make recommendations regarding:

Each country will exploit the results differently but, in general, the expected users include government and utility evaluations of residential energy consumption, developers of home energy rating systems, energy auditors, and building scientists testing and evaluating whole-house energy performance.

Some countries may decide to eventually revise their data collection procedures while others will simply understand the weaknesses of their current energy consumption data. This report is also expected to influence those countries developing energy rating systems (such as Japan, the United States, and parts of Germany). To date, these rating systems have focused almost entirely on space heating aspects energy use. This report will provide guidance on techniques to expand the rating beyond space heating.

The following is a list of some indicators that will be constructed and compared. Note that some of them demonstrate the impact of differing definitions of terms.


Energy use per occupant or per bedroom has often been considered as an indicator of use, but it has never been satisfactorily explored. These have certain attractions because they are more absolute than, say, normalizations to floor area. In addition, we will explore the impact on indicators of energy efficiency when normalized for:


The characteristics for one group of buildings will be entered into the HOT2000 building simulation tool. Each home will be simulated, using default operating assumptions. The energy rankings will be compared to other building indicators, such as measured total primary energy use. This task will demonstrate the accuracy of a ranking based purely on simulated energy use and default values.

Many case studies of building energy performance have reported energy consumption in terms of two or more of the indicators listed here. Energy use per unit of floor area versus volume or site energy versus primary energy are examples of indicators typically reported. However, these reports typically focused on just a few buildings, often similar in construction or climate, so the impact of the different indicators is obscured. This project will evaluate a much wider range of conditions and specifically address the implications of changes in rankings.

Many (but by no means all) of the case studies that we shall collect have enough information to calculate these indicators. However, the inability to calculate certain indicators will be useful, too. We expect to devote considerable effort to exploring the distortions caused by inconsistent distinctions between site and primary energy.

Participants

The original formulation of this project--"Northern Homes"--involved Finland, Norway, Sweden, Canada, Japan, and the United States. The re-structured project greatly enlarges the area of relevance. Participation from other countries will be solicited.



[info] For further information about Indicators of Energy Efficiency, please contact Alan Meier, at +1 (510) 486-4740

[Projects] Back to Building Energy Measurement and Performance Analysis projects
[back] Return to the Building Energy Measurement and Performance Analysis home page
This web page last modified by Brian Pon on April 3, 2000
Questions? Send e-mail to Alan Meier.