Energy Performance of Residential Buildings

A Practical Guide for Energy Rating and Efficiency

Mat Santamouris

• Publisher: Routledge
• Year: 2010
• Print ISBN: 9781138968806
• eBook ISBN: 9781136534805
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Energy Rating is a crucial consideration in modern building design, affirmed by the new EC Directive on the energy performance of buildings. Energy represents a high percentage of the running costs of a building, and has a significant impact on the comfort of the occupants. This book represents detailed information on energy rating of residential buildings, covering:

* Theoretical and experimental energy rating techniques: reviewing the state of the art and offering guidance on the in situ identification of the UA and gA values of buildings.
* New experimental protocols to evaluate energy performance: detailing a flexible new approach based on actual energy consumption. Data are collected using the Billed Energy Protocol (BEP) and Monitored Energy Protocol (MEP)
* Energy Normalization techniques: describing established methods plus a new Climate Severity Index, which offers significant benefits to the user.

Also included in this book are audit forms and a CD-ROM for applying the new rating methodology. The software, prepared in Excel, is easy to use, can be widely applied using both deterministic and experimental methods, and can be adapted to national peculiarities and energy policy criteria.

Energy Performance of Residential Buildings offers full and clear treatment of the key issues and will be an invaluable source of information for energy experts, building engineers, architects, physicists, project managers and local authorities.

The book stems from the EC-funded SAVE project entitled EUROCLASS. Participating institutes included:

* University of Athens, Greece
* Belgium Building Research Institute, Belgium
* University of Seville, Spain
* Royal Institute of Technology, Sweden

Chapter 1

Review of selected theoretical and experimental techniques for energy characterization of buildings

P. Wouters and X. Loncour

Division of Building Physics and Indoor Climate, Belgian Building Research Institute, Brussels

Introduction

The aim of this chapter is to present selected theoretical and experimental energy rating methodologies developed for dwellings. It is not the intention of the authors to present all existing methodologies, but to inform the readers about the main types of proposed theoretical methodologies and to present representative methods of each type.

This chapter consists of two parts:

• The first part presents the result of the bibliographic study on the state of the art of the theoretical and experimental techniques used to determine the energy consumption of residential buildings.
• The second part deals with the in situ identification of the transmission heat loss coefficient + (UA value) and the gA values (characterizing the solar gains) of buildings.

Part 1. State of the Art – Measurement Techniques

Calculation Methods and Experimental Techniques

Several remarks need to be made before going into more detail:

• Much information can be found here about the calculation methods used to determine the energy consumption of the buildings.
• Some of these calculation methods are firmly based on experimental data. It should be noted that very often the articles focus more on the description of the calculation method than on the way of realizing the experimental monitoring.
• In general, few papers focus on the experimental techniques used to collect the data on site.
• Some of the experimental techniques described in the literature are quite old (some of them were developed more than 20 years ago). These experimental techniques do not take into account the latest developments in measuring techniques (for instance, the use of the Internet) and are therefore less interesting within the context of this project.

We mention in this chapter the different calculation methods. We give the references of the papers concerned and, when they are available, we describe the techniques used to collect the relevant information on site.

The different calculation methods that are considered in this document can be regrouped into five categories:

1. the university projects and the Energy Barometer
2. the Save HELP method
3. short-term energy monitoring and primary and secondary term renormalization
4. neural networks
5. other related methods.

The University Projects and the Energy Barometer

The University Projects

The two ‘university projects’ have been developed in Sweden. References [1] and [2] describe these two projects. Since these references are in Swedish, we give more detail here about the methodology applied in the scope of these two projects than for other methods described in this document.

In 1974, the Swedish government introduced financial support in the form of loans and subsidies for energy-saving measures within the existing building stock. The aim was to stimulate efficient energy use and to reduce energy for heating. The goal was to decrease the gross heating consumption for residential areas by 39–48 TWh over a 10-year period (1978–1988) with a total investment of SEK 31–48 billion (1977 value). The retrofitting measures were voluntary.

In order to evaluate the plan during its initial stages, a programme was set up during the first three years (1977–1980) to determine whether or not it was worth continuing the plan. The evaluation was also intended to assess the characteristics of the building stock and to estimate energy savings. The aim was to estimate, on the basis of collected data on energy bills and building technical descriptions, the actual mean energy savings resulting from several retrofitting methods. Reference [1] describes this project, which is called the ‘university project’ (UP1), and the method applied.

The Task

The task was to calculate the energy savings resulting from different retrofitting means on the basis of collected energy-bill data and of an inspection of building technology and the systems installed. In total, 1,144 buildings and apartments were audited, of which 944 were single-family houses and 200 were multi-family buildings. Broadly, the following steps were taken:

• Energy bills were collected before and after the retrofitting was carried out.
• Bill values were normalized according to temperature variations over the years.
• The energy saved was measured in corresponding litres of oil, during a reference year.

It was found that 841 buildings had a complete set of bills and 303 had an incomplete set. More details are given below, especially on the underlying assumptions made.

The static energy signature was determined for each building, and from this data could be statistically applied to the Swedish building stock as a whole.

The Indoor Temperature

The indoor temperature was assumed to be 21^°C, with the exception of the period during and shortly after the oil crisis. The motivation for this was that information on indoor temperature that was supplied by the inhabitants was considered to be inaccurate.

The Outdoor Temperature

The Swedish Meteorological and Hydrological Institute (SMHI) supplied outdoor temperatures on the basis of data from climate stations across the country. Surveyors had to judge which climate station best described the temperature at a particular site. This eliminated local variations of temperatures.

The Efficiency of the Heating System

The efficiency of heating systems varied from building to building, but within this work was assumed to be the same for various categories of houses. The values decided upon are listed in Table 1.1.

Table 1.1 The efficiency of heating systems during winter and summer. Values are given for the various types of single- and multi-family dwellings

Energy saving calculations were made as if all buildings were heated with oil and a conversion factor was used for each fuel used as a heat source, based on the energy content of the fuel (Table 1.2).

Table 1.2 Fuel conversion factors

Fuel (unit)	Conversion factor
Oil (m3)	1.000
Gas (m3)	0.471
Electricity (kWh)	0.101
District heating (kWh)	0.101

Energy for Appliances and Hot Water

The use of energy for electrical appliances and hot water was assumed to be as shown in Table 1.3 for each household.

Table 1.3 Values assumed for energy consumption by appliances and hot water

Energy (kWh)	Single-family house	Multi-family house
Electrical appliances	4,600	2,800
Hot water	4,000	3,500

Degree-hours

Among the climatic factors, such as temperature, solar irradiation, wind, snow, long-wave irradiation and moisture, that influence the heat balance of a building, the outdoor temperature was considered to be the most important factor. Because of the seasonal variations in outdoor temperature, the periods taken into consideration before and after retrofitting were chosen so as to be complete years, if possible. The number of degree-hours was computed from

where T is the number of hours during the heating season, θ_i is the mean indoor temperature and θ_e is the mean outdoor temperature based on mean monthly values. Linear interpolation was used to calculate the mean outdoor temperature.

For the calculations, the heating season was limited to months with sufficiently low outdoor temperature by starting in October and ending in April.

In order to compute the number of degree hours for a reference year, the collected outdoor temperatures for the years 1972–1979 were used.

U Values

U values were ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright
• Contents
• Preface: Introduction on the Energy Rating of Buildings
• Chapter 1. Review of selected theoretical and experimental techniques for energy characterization of buildings
• Chapter 2. Experimental methods for the energy characterization of buildings
• Chapter 3. Energy normalization techniques
• Chapter 4. The Euroclass method – description of the software
• Chapter 5. Examples and case studies
• Appendix 1: Audit form
• Appendix 2: Energy transmittance by glazing and shading factors
• Appendix 3: Estimated average fuel combustion efficiency of common heating appliances
• Index