Research Trends and Results

Development of Estimation Method for Energy
Saving Technique of Residential Envelope Design
MIURA Hisashi (Ph.D.), Senior Researcher
AKAMINE Yoshihiko (Ph.D.), Researcher
Residential Environment Planning Division, Housing Department(Key words) House, Energy Saving, Envelope Design, Estimation Method, Building Energy Standard
1. Revised Building Energy Standard
The Building Energy Standard for residential houses
was revised in 2013, and the energy performance of abuilding changed to be represented by Design Primary
Energy Consumption. In the standard prior to the revision,
insulating performance and solar shading performance
were only evaluated as the envelope performance. By thisrevision, envelope performance changed to be able to beevaluated based on heating and cooling loads (Figure 1).
This change of the index gives a structure allowing
flexible evaluation of the rise of the solar radiation heatacquisition rate, such as improvements of windows, therise of heat storage performance such as utilization of
concrete blocks and earthen walls, cross-ventilation
performance in summer and the middle season, etc.
2. Revised Building Energy Standard
Since the standard prior to the revision mainly
evaluated insulating performance and solar shading
performance, the evaluation of insulating and solar
shading techniques can be said to be sufficient, such as
insulating reinforcement for heat bridges, utilization ofeaves and characteristics of solar shading of various typesof glass, i.e. low-e glass. However, the techniques toimprove solar radiation heat acquisition performance andthermal storage performance are still not evaluatedsufficiently in the revised standard. Therefore, NILIM
started a research project named Research on Evaluation
Method of Energy Saving Techniques corresponding toLocal Home Building Techniques, of which the research
period is from 2013 to 2015. In this project, theestimation methods for envelope energy saving
techniques which have not hitherto been evaluatedsufficiently will be developed. From the techniques
discussed in the project, the examples about the solar
control techniques are shown in Figure 2.
3. Development of Simple Evaluation Methods
The solar radiation heat acquisition rate ( value) as
the index for the performance of openings changes hour
to hour depending on the sun’s position. This  value canbe calculated theoretically taking into account the type of
the attached materials such as blinds, the direction of thewindow and its construction location and so on, but it is
not realistic that designers calculate this index because

this calculation is too complex. Therefore, we aredeveloping simplified evaluation methods for  values
and other indices.
4. Utilization of Research Results in the Standard
This report introduced the research implemented by
NILIM relating to the development of evaluation
methods for envelope performance of residential houses.
The research results will be utilized in the documents
and online programs1,2 as the calculation methods for thedesigned primary energy consumption.

Figure 1 Structure of Evaluation for Envelope
Performance in Revised Building Energy Standard

Figure 2 Example of Energy Saving Techniques(Evaluation Methods Developed in NILIM Project)[References]
1) Technical Note of NILIM No.701 Relevant Materials for
Certification Standards of Low-Carbon Buildings(Promulgated in Dec. 2012) – Manual of Program forPrimary Energy Consumption in Houses –2) Technical Information of Building Energy Standards andCertification Standards of Low-Carbon Buildings (BuildingResearch Institute (Cooperated by NILIM))
http://www.kenken.go.jp/becc/house.html
3) Ministry of Land, Infrastructure, Transport and Tourism,
Information about Revised Building Energy SavingStandards
http://www.mlit.go.jp/jutakukentiku/build/jutakukentiku_ho
use_tk4_000005.html