1. technology and computing
2. software

C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
Decision Support Software for
Sustainable Building Refurbishment
C.A. Balaras, Ph.D.
Member ASHRAE
E. Dascalaki, Ph.D.
S. Kontoyiannidis, M.Sc.
AUTHOR NOTE:
C.A. Balaras is a mechanical engineer, E. Dascalaki is a building physicist, S. Kontoyiannidis
is a building physicist, in the Institute for Environmental Research and Sustainable Development
at NOA, Athens, Hellas.
KEY WORDS:
Software, Buildings, Audits, Energy Conservation, Refurbishment
ABSTRACT
This paper provides an overview of a new generation decision support software that have been
developed in the framework of European projects over the past few years, for the assessment of different
scenarios during renovations or refurbishment of apartment, office and hotel buildings. The software
include a structured methodology for performing a diagnosis of the existing building condition, modules for
load calculations, the assessment of energy conservation potential resulting from different scenarios
including the use of renewable energy sources (RES) and a first cost estimate, so that the user can set up
the right priorities during the first stages of a building renovation or refurbishment project. In addition, the
paper provides a brief overview of the results from pilot cases studies from the application of some
common RES systems and energy conservation techniques.
INTRODUCTION
Energy consumption in European buildings represents about 40% of the annual European Union (EU)
final energy use and about a third of greenhouse gas emissions of which about two-thirds is in residential
and one-third in commercial buildings (EC 2000). Residential use represents 70% of total energy
consumption in the buildings sector, reaching 252 Mtoe in 1998, with a ratio of electricity to heat of about
25%. RES is predominantly used in residential buildings and amounts for only 2.75%, a value that could be
increased dramatically with appropriate incentives. The energy use in commercial and public buildings is
108 Mtoe, with a ratio of electricity to heat of about 68%. The breakdown of energy consumption by end use
in the EU residential buildings is 57% for space heating, 25% for water heating, 11% for lighting and
appliances and 7% for cooking, and in the EU commercial buildings is 52% for space heating, 9% for water
heating, 14% for lighting, 5% for cooking, 4% for cooling, and 16% for other uses (EC 2000). In the United
States of America (USA), buildings consume about 36.6% of the total primary energy consumption for 2000
(Source: US Department of Energy). The total energy consumption in residential buildings is about 500
Mtoe and 415 Mtoe in commercial buildings. The environmental impact from buildings is estimated at 30%
of the total greenhouse gas emissions (Source: US Green Building Council). The breakdown of energy
consumption by end use in the US buildings for residential buildings is 49.3% for space heating, 17.6% for
water heating, 5.1% for cooling, 25% for lighting and appliances and 3% for cooking. For commercial
1
C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
buildings, 23.3% is for space heating, 10.8% is for water heating, 15.4% is for lighting, 3% is for cooking, 5.8%
is for cooling and 41.7% is for other uses.
The building sector uses about one third of all the raw materials and energy produced in Europe and
over half of the electricity. As a result of improved legislation (i.e. building codes and insulation standards),
the use of new building materials and more efficient equipment, much progress has been achieved in
energy efficient and environmentally friendly new buildings over the past decade. On the other hand,
higher living and working standards, along with the introduction of new equipment and appliances,
including air conditioning, may counterbalance these savings and actually increase the average energy
consumption in buildings and create considerable problems at peak load. Thus, the effort for energy
conservation, while maintaining an optimum indoor environment, is a continuous struggle in order to
minimize the dependency on conventional fuel sources, secure the energy balance and reduce the
environmental impact from fossil fuels.
Buildings are a major pollution source. They account for about half of sulphur dioxide emissions, a
quarter of nitrous oxide emissions and about 10% of particulate emissions. They also contribute to about
35% of carbon dioxide emissions that is closely related to climate change. At the same time, construction
wastes have a major impact on landfills. In the EU, construction and demolition (C&D) waste accounts for
10% to 33% of the total waste streams (EEA 2002); demolition waste comprises 40 – 50% of the total
C&D waste, renovation waste 30 – 50% and construction waste 10 – 20%. Waste amounts per capita vary
considerably in the EU member states as a result of economic and cultural differences that exist between
them. Recycling rates (i.e. crushing of bricks and concrete for use as filling in new building materials or
simply as filling under new constructions to replace the use of gravel) differ considerably, from as high as
80 % in Denmark, Germany and the Netherlands, to 10% in Luxembourg. In the United States, more than
136 million tons of building-related C&D debris are generated annually, of which 43% is from residential
sources (EPA 1998). Building demolitions account for 48% of the waste stream, renovations account for
44%, and 8% is generated at construction sites.
Building practices in the past have not properly addressed the current concerns about the optimum use
of energy in buildings or the minimization of the environmental effects. In addition, ageing installations
and facilities result in an even grimmer scenario. Existing buildings are often energy costly to operate, with
serious indoor environmental quality problems. However, existing buildings constitute a huge investment
in natural and human resources, and the building stock is an enormous pool of private and public
investment. According to studies carried out by the European Cooperation in the field of Scientific and
Technical Research (COST), the estimated value of our European Urban Heritage amounts to about 40
trillion Euro for the housing stock alone.
Refurbishment (i.e. upgrading to better condition) of the existing and ageing building stock offers an
opportunity to take cost-effective measures and transform them to resource-efficient and environmentallysound buildings, with an increased social and financial value. Similar opportunities may exist even during
building renovations (i.e. repairs and restorations to good condition). Protecting the architectural heritage is
a primary benefit, but it may also be financially attractive. In many cases, building refurbishment costs
much less (even for high investment retrofit operations) than demolition and reconstruction (about half to
one-third of the cost). In light of sustainability principles and policies it makes more sense than ever to
renovate or refurbish old buildings. Some have even suggested that we should stop constructing additional
new buildings, limiting ourselves to improve the existing stock, its functional quality and durability
(Kohler, 1999). In any event, the immediate goal must be to ensure that at least new buildings are
constructed in a sustainable way.
Energy conservation measures, including passive, active and hybrid systems, can take advantage of
commercially available and cost effective building practices, systems and techniques to improve the overall
building’s energy and environmental performance. Savings can amount to 20%, while existing technologies
have the potential to reduce consumption in households and offices by up to 60% (EC 2000).
Given the low turn-over rate of buildings (lifetime of 50 to more than 100 years) and the high number
of existing buildings, it is clear that the largest potential for improving energy performance in the short and
medium term is in the existing stock of buildings. This can also have a significant impact on the efforts to
reduce greenhouse gas emissions in accordance to the Kyoto protocol and the ratified commitments by
most EU member states (which call for an 8% reduction compared with 1990 values, by 2012). Building
refurbishment should also be viewed as an opportunity to exploit RES technologies with an emphasis on
passive and active solar energy solutions, daylighting, natural cooling, cogeneration of heat and power,
connection to district heating/cooling, which are becoming a part of national strategic policies.
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C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
The new EU Directive on the energy performance of buildings (EU 2002) mandates that by end 2005
all EU member states bring into force national laws, regulations and administrative provisions for setting
minimum requirements on the energy performance of new and existing buildings that are subject to major
renovations, and for energy certification of buildings. Additional requirements include regular inspection of
building systems and installations, an assessment of the existing facilities and to provide advice on possible
improvements and on alternative solutions.
Building materials also have an energy content and an environmental impact throughout their lifecycle (i.e. primary materials, manufacturing, transportation, installation and disposal). Although the choice
to use the specific materials for the initial construction of the building cannot be altered, the critical
decision is to assess the proper materials that can be used to perform certain retrofit actions and to assess
their cumulative impact on energy over the life-cycle of a building. The decision making process should
also account for the entire aspects of occupancy and maintenance, examine alternatives for renovation or
refurbishment against demolition and possible recycling and disposal.
A new generation of European methodologies and software tools are under development that enable
architects and engineers to make an accurate first assessment of a building’s existing structural condition,
energy performance, indoor environmental quality, and some other criteria depending on the use of the
building, with an estimate of the total cost. The tools support the users during the building audits, that can
be performed in a short amount of time and ensure that all necessary data is collected. These decision aid
tools provide a global view of a building’s renovation and refurbishment processes and enable a user to
take well targeted decisions and to assess different scenarios.
The backbone of these methodologies was developed for apartment buildings. Following on a similar
concept, another methodology was developed for office buildings and currently another one is under
development for hotels. Another project has enhanced the work on apartment buildings by addressing
additional criteria in the decision making process, like housing market needs, tenant expectations,
upgrading potential associated to the building’s aesthetics, historical or cultural value and the
environmental impact of building renovation and refurbishment measures in relation to its energy
consumption and natural resources. All the methods are supported by multimedia computer programs that
assist the user in auditing a building and collecting all necessary data. This data is then used to evaluate
different scenarios for upgrading the building structure and improve its energy performance, with an
accurate cost estimate.
In this paper, the main features of the methodologies and software are discussed. In each case, the
results from pilot case studies are presented with an emphasis on the application of some common RES
systems, energy conservation techniques and the assessment of buildings’ environmental impact.
RESIDENTIAL BUILDINGS
The existing building stock in Europe is estimated at 150 million dwellings (UNECE 2000), whereas
only around 2 million are built every year. About 70% of the residential building stock is over 30 years old
and about 35% are more than 50 years old. This is an important observation given that most national
building regulations that mandate thermal insulation of building envelopes were introduced after the 1970’s
following the energy crisis. In relation to the ageing technical installations, it is estimated that about 10
million residential boilers are older than 20 years old, thus have a significantly lower thermal performance
than today’s existing units.
Annual energy consumption in residential buildings averages 150-230 kWh/m2 (Balaras et al 2000). In
eastern and central Europe the energy consumption for heating purposes is in the order of 250-400 kWh/m2,
often averaging about 2-3 times higher than that of similar buildings in western Europe. In northern
European countries, well insulated buildings have an annual consumption of 120-150 kWh/m2, while the
so-called low energy buildings may even drop down to 60-80 kWh/m2.
Overview of the Tool
The methodology was developed to assist architects, engineers and other professionals during the
refurbishment or retrofitting (upgrading) actions of apartment buildings (Jaggs and Palmer 2000). The
method and calculation tools are incorporated in a multimedia software (Flourentzos, Droutsa, Wittsen
2000).
The building is decomposed into discreet elements such as load bearing structure, windows, façade
finish, roof, heat and cool production system, electrical installations etc. For each building element, it is
3
C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
possible to have different types. The diagnosis is performed during a building audit. The auditor specifies
the specific elements/types for the building and determines the stage of deterioration, for example, excellent
condition to very poor condition. The categorization is done by selecting a deterioration code “a” - “d” that
best fits the observed state of each element/type; “a” - good condition, “b” - need for minor repairs, “c” need for major repairs, “d” - need for replacement. For making this selection, the auditor is assisted by a
description that corresponds to the four possible deterioration stages and several characteristic photos
(Figure 1). A total of about 500 photos and sketches support the user to select the appropriate deterioration
code. The software also contains, for each building element, a description of usual deterioration and
corresponding refurbishment work including costs, potential upgrading work as well as related national
standards and guidelines.
Actual building energy consumption data collected from the energy bills give a first assessment of the
buildings current state energy performance. The building’s energy consumption is compared to national
standard and best practice values to illustrate the saving potential. Energy calculation modules are then
used to estimate the building's energy balance and assess the energy conservation potential for space
heating and cooling, domestic hot water production and artificial lighting. A user-friendly interface
expedites energy data input. Building related data collected for the diagnosis and refurbishment cost
calculations are reused. A database with catalogued typical building constructions of walls, floors, roofs
and windows helps a non-expert user to easily enter the appropriate thermal data for the building
components.
Figure 1. Examples from the software interface, for the diagnosis of building elements/types during the
building audit, to determine the deterioration state of the load bearing structures (left) and the heat production
(right).
The software also includes the necessary climatic data for different European locations. A simplified
heating energy balance calculation based on EN-832 (Wittchen and Aggerholm 2000), is used to estimate the
breakdown of the building’s heat losses and guides the user to retrofit measures with a higher energy saving
potential (Figure 2). The cooling load calculations are based on the ASHRAE’s Total Equivalent Temperature
Differential values and a system of Time Averaging, TETD/TA method (Parsons 1989). Energy conservation
measures that can be assessed include actions like building envelope and thermal insulation, heating production
system efficiency, infiltration losses, solar control, ceiling fans, solar collectors, and energy efficient lighting
(Balaras et al 2000). For the selected action(s) the results include the resulting energy conservation, typical
costs as well as the typical pay back period.
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C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
Figure 2. Heating energy balance. The results are given for the existing condition or follow-up retrofit actions.
A similar interface is also used for the cooling energy balance.
The software also contains a questionnaire that may be distributed to the occupants to collect data
associated with IEQ (Bluyssen 2000). The data is then entered in to the software that automatically
performs a statistical analysis of the questionnaire data and relates complaints with refurbishment work and
energy retrofit measures. It then alerts the user during the audit for problems associated with specific
elements/types.
A residential building audit to collect the necessary data can be performed within half-a-day. The
software then supports the user with the data analysis and report preparation. The tool summarizes the
results from the building diagnosis on the deterioration for all the building’s elements and the
refurbishment cost. The user can select a set of actions and create different scenarios to directly assess the
effect on the total cost. National versions are available in French, German, Danish, English, Hellenic,
Italian and Polish. The main difference in the national versions apart from the language is the description of
the refurbishment works and related costs, and the relevant national data for energy benchmarking, fuel
prices, climatic files, and construction typologies.
A follow-up project (A decision-making tool for long-term efficient investment strategies in housing
maintenance and refurbishment) is developing a tool that can assist a user in elaborating long-term financial
investment strategies in apartment buildings’ maintenance and refurbishment. It is addressed to owners of a
large stock of buildings who need to decide which buildings and components have priority for investment
and also when this is an optimal investment.
The necessary input data is collected using a standardized building audit procedure. The tool will then
assist the user in the decision making process by taking into account a number of different criteria, in
addition to the buildings state of deterioration. These criteria include the local and urban neighborhood
quality, the environmental impact of buildings and building products, the necessary resources for the
building life cycle, the upgrading and maintenance potential, the cultural perceptions, the rental market
nature and evolution. This innovative approach will allow the user to account for a number of quantitative
and qualitative parameters (i.e. social, physical, cultural and economic) that can be aggregated in order to
emphasize the concept of investment over simple financial criteria that are commonly used.
The method and software will promote cost effective and affordable investments into existing
buildings, while addressing the environmental challenge and optimum use of natural resources. The
detailed evaluation of the degradation process will extend the building life span, optimize the use of natural
resources (including water, materials, energy and land) and minimize the production of pollutants
(including waste, noise and dust), for the benefit of both - owners and tenants. The tool will also assist the
user in predicting the optimal time to replace building elements, the use of primary raw materials as well as
the “best practice” life-cycle cost of construction process. Social and cultural problems of the inhabitants
will also be addressed, because it is necessary to ensure that tenants feel comfortable in their
apartment/building/district, enjoy higher quality living and social standards, in order to ensure a steady
return of the invested funds.
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C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
Case Studies & Potential Energy Conservation
About 350 European residential buildings have been audited, in order to collect the necessary input
data for the work that was performed. The database, along with a presentation of all the audited buildings,
is available on a multimedia CDROM (Balaras et al 2003). A total of 34 critical factors were investigated in
relation to their impact on the deterioration of the various building elements. Accordingly, building age and
ownership status were the most significant ones.
The breakdown of the deterioration codes of building Elements for the two most important factors is
presented in Figure 3. For new buildings (up to 15 years) as well as for very old buildings (more than 76
years) the deterioration of all building elements depends on the age and is independent of the ownership
status. Various building elements seem to be well maintained for new buildings with different ownership
status. For old buildings (exceeding 76 years) the element deterioration does not vary significantly for
different ownership status.
100%
100%
80%
80%
d
c
b
a
60%
40%
d
60%
c
b
40%
a
20%
20%
0%
0%
Other
0-15 years 16-30 years 31-45 years 46-60 years 61-75 years >76 years
Large real
estate Co.
Many owners
One owner
Small real
estate Co.
Public
Figure 3. Breakdown of element deterioration codes of European buildings according to the building age
(left) and ownership status (right).
According to the data from the 350 building audits, the actual heating energy consumption averages
174 kWh/m2 of heated area. Even in the same country, there are large variations as illustrated in Figure 4.
Preliminary data analysis of the environmental impact from heating energy consumption in European
residential buildings revealed that the main airborne emissions per building are as high as 663.3 tons for
CO2, 3.8 tons for SO2, 1.1 tons for NOx, 0.6 tons for CO, 0.02 tons for CH4 and 0.02 tons for NMVOC.
From solid waste indicators, unspecified bulk wastes are as high as 155 tons, and slag & fly ash are as high
as 17 tons.
800
kWh/m
2
600
400
200
0
1
6
11
16
21
26
31
36
41
46
51
Buildings
Denmark
France
Hellas
Poland
Switzerland
Figure 4. Actual heating energy consumption in audited European residential buildings.
6
C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
The potential for energy conservation in residential buildings is high, depending primarily on location
(weather conditions), building construction, installations for heating, cooling, production of domestic hot
water and lighting, and hours of operation. Data from representative European member states, reveals that
the penetration levels of basic energy conservation measures in the existing building stock of residential
buildings varies significantly (Balaras, Dascalaki 2003). For example, in Hellenic buildings with typical
southern European construction, only 5% of buildings have exterior wall insulation, 2% have double
glazing, 30% have roof insulation and 4.2% have insulation of heat distribution pipes. In northern Europe,
the penetration of building insulation, district heating and high efficiency boilers is relatively much higher
than southern Europe, but the use of RES (i.e. like the use of solar collectors for sanitary hot water
production) is very limited. Local air conditioning is becoming very popular in southern Europe, as a result
of increased standards of living and the drop of the units’ cost. As a result of this trend, there are wide
spread problems with peak power electrical demand during summer, setting new record highs every year.
Representative results on the potential energy savings for heating and cooling in Hellenic residential
buildings are illustrated in Figure 5 (Balaras et al 2000). Each measure was evaluated independently from
each other. Additional results reveal that for heating, the use of temperature control can save 10-30%, new
energy efficient boilers about 18%, and distribution pipe insulation 2-5%. For domestic hot water
production, the use of solar collectors can result to 60-74% savings, depending on the climatic conditions.
For lighting, the use of energy-efficient lamps to replace incandescent lamps ranges between 70-85%, and
63-67% to replace fluorescent lamps.
COOLING
HEATING
Reduced
infiltration
7% - 20%
Light ext.
surface color
3% - 13%
Floor insulation
8% - 10%
Ceiling fans
9% - 19%
3% - 10%
Double glazing
5% - 19%
Double glazing
8% - 16%
Roof insulation
Ext. wall
insulation
Roof insulation
External wall
insulation
3% - 14%
Shading
3% - 43%
29% - 42%
2% - 12%
Figure 5. Potential energy savings from representative measures in heating (left) and cooling (right), for
Hellenic residential buildings.
OFFICE BUILDINGS
The total stock of office buildings in Europe is estimated at 1200 million square meters of conditioned
floor space (Caccavelli and Gugerli 2002). About 70% of this stock is less than 25 years old, which implies
that they are relatively new buildings. However, the office building retrofitting market has been growing
strong since the life span of office buildings is much shorter than residential buildings, occupants needs and
expectations have increased demanding working spaces with improved amenities for comfort,
infrastructures and services.
Office buildings have a high annual energy consumption, particularly of electricity. European office
buildings average 89 to 203 kWh per square meter of conditioned floor space (Balaras et al 2002).
Depending on location, use, hours of operation, building form and envelope construction and the type of
installed services, energy consumption can vary considerably. In addition, electrical energy consumption
and consequently the environmental impact from office buildings continues to increase at a fast rate
because of increased use of office and information technology equipment, and air-conditioning.
Overview of the Tool
The methodology and software was a follow-up work for office buildings (Caccavelli and Gugerli
2002). The philosophy is the same as the one for apartment buildings, but with additional features to handle
7
C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
the more complex installations of office buildings and the addition of one more decision-criteria based on
functional obsolescence of building services.
The new features include additional elements/types for the electromechanical installations encountered
in office buildings, like central heating, air-conditioning and ventilation, fire protection, low current
networks etc. The current state of the building envelope and its electromechanical installations is diagnosed
in a similar manner. Additional calculation modules are also included to perform energy saving estimates
for controls in air handling units, energy recovery systems, ice and chilled water storage, daylighting, low
energy office equipment, zoning of elevators and service quality, and sanitary water savings (Balaras et al
2002).
The additional obsolescence criteria include compliance with user needs, flexibility, divisibility and
maintainability (Allehaux and Tessier 2002). For each criterion, there are three possible codes. The user
assesses the obsolescence codes for each object and each criterion and the tool proposes a standard
description text to assist the user. The user can also set priorities for the urgency of actions on each
element/type, for example, “obsolete, high priority for action”, “obsolete, but not high priority for action”,
“no necessary action”.
The collection of the necessary data for a building audit of an office building can be completed in one
to two days, depending on the size of the building and the complexity of its installations. The tool then
supports the data analysis and report preparation, in a similar way as with the one for apartment buildings.
Currently, the tool for office buildings is a research prototype and is available for only one country
(Switzerland), since the databases were filled-in with Swiss data (Flourentzou et al 2002). However, its
open structure allows for an easy adaptation to other countries (language, pictures and cost databases), a
process that is currently underway in a similar manner as its was done with the adaptation of the tool for
apartment buildings.
Case Studies & Potential Energy Conservation
Representative results on the potential energy savings for heating and cooling in Hellenic office
buildings are illustrated in Figure 6 (Balaras et al 2002). Each measure was evaluated independently from
each other.
COOLING
HEATING
Reduced
infiltration
12% - 20%
Heat recovery
12%
Ext. wall
insulation
5% - 55%
Light roof
color
6% - 7%
Heat recovery
3%
Ext. wall
insulation
9% - 33%
Ceiling fans
13% - 28%
Roof insulation
5% - 51%
Double glazing
6% - 61%
Double glazing
Shading
2% - 11%
Roof insulation
2% - 11%
1% - 5%
Figure 6. Potential energy savings from representative measures in heating (left) and cooling (right), for
Hellenic office buildings.
Energy savings can vary significantly depending on the building construction and installations.
Additional results reveal that for cooling, the use of cool storage (taking into account different operating
strategies) can range between 20-59% in south European buildings and 70-100% in north European
buildings, depending on cooling loads. For lighting, the use of energy-efficient lamps to replace
incandescent lamps can reach 62%. The use of daylighting in office spaces along the perimeter of the
building, the percentage of annual hours not needing artificial lighting can range between 24-67% for office
spaces with a south orientation, 42-48% with a north orientation, 20-61% with a west orientation and 1438% with an east orientation. Electrical energy consumption by office equipment can also be reduced by
replacing old equipment with energy efficient ones resulting to 52-62% savings. Automatic controls and
zoning of elevators can improve service and save upto 35%.
8
C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
HOTEL BUILDINGS
Most of the existing European hotels were built during the 1970 – 1980s. Low quality buildings, at
least for today’s standards, energy consuming installations, low performance equipment, as well as
unsustainable exploitation of the natural resources are some of the very common features of these
constructions. Most of the hotels, 15 – 25 years after their construction need complete or partial
refurbishment in order to keep up with the market demands. New hotel construction spending has
plummeted from an average growth rate of 8% per year in the 1970s and 1980s to an average to 1% per
year. On the other hand, the hotel refurbishment / conversion market is booming. The development of this
market is mostly driven by the integration of European hotels into large hotel chains.
According to Eurostat, the estimated number of hospitality establishments in Europe is estimated at
200000, with a capacity of 9.3 million beds. About half of the European hotel building stock are located in
the Mediterranean countries which are the leading tourist destination attracting 30% of the world tourism,
namely 220 million tourists per year, a figure expected to rise 50% in the next 20 years.
Energy consumption in hotels is also among the highest in the tertiary building sector, particularly of
electricity. In European hotels, the average total energy consumption ranges from 250 kWh/m2 for small
hotels to 450 kWh/m2 for large hotels. Average electrical energy consumption represents 48% of the total.
Hotels are also located in areas with high seasonal energy loads and frequently high energy cost and
low supply (i.e. islands). In addition, possible energy conservation techniques for rational use of energy
(RUE) and exploitation of renewable energy sources (RES) have a unique demonstration potential and a
high exposure to millions of people that visit hotels at one time or another. The hotel sector is uniquely
placed to provide the impetus for change in business behavior within tourism, because of its multiplier
effect - on guests, staff and suppliers as well as the central role that hotels play within local communities.
Overview of the Tool
The methodology and software is a follow-up work for hotel buildings. The goal is to prepare a
multimedia software for carrying out a hotel audit, supported by the necessary tools for making a first
assessment of where and how to integrate the most cost-effective energy efficient renovation practices. The
previous methodologies were adapted to include new elements/types encountered in hotels. The new
software will include all the relevant calculation modules from the previous tools, with additional ones that
are of importance for hotels, for example, central solar systems for sanitary hot water and swimming pools,
solar cooling, sea-water cooling, water desalination, and to assess different scenarios based on energy
savings and cost. The audit scheme will also identify potential problems and risks with the indoor
environment, which is of major importance in hotels. Recommendations will be integrated in the tool to
assist the user on how to improve indoor air quality (i.e. sources of indoor pollutants, control legionellosis
and microbiological water quality in hot and cold water services, heating and cooling systems), to identify
and to assess measures to save natural resources (i.e. water, waste management).
The collection of the necessary data for a building audit of a hotel can be completed in two to three
days, depending on the size of the building and the complexity of its installations. The software will then
support the data analysis and report preparation. The work will be completed at the end of 2003 and include
suitable data bases from European Mediterranean countries that participate in this project. Again, its open
structure allows for an easy adaptation to other countries, if necessary.
Parallel actions within this project are preparing dissemination material for hotel managers and hotel
guests to increase awareness on the benefits of using RES and RUE techniques in the hotel sector,
organizing dissemination campaigns to local authorities, hotels and hotel associations.
Case Studies & Potential Energy Conservation
Pilot case studies have been performed in four European Mediterranean countries in order to evaluate
the audit procedure and to ensure compliance with the specific characteristics encountered at national level.
A more comprehensive field test will also be performed in order to demonstrate the complete decision
making process (diagnosis, design and assessment of refurbishment strategies, decision).
Energy consumption in hotels varies significantly, depending on the characteristics of the building and
its installations. From a previous energy audit campaign in about 160 hotels at a representative southern
European country (Figure 7) it is evident that there is a great potential for considerable energy savings,
especially in hotels with a high annual energy consumption (Santamouris et al 1996). Potential energy
savings can reach 15-20% for heating, 5-30% for cooling, 40-70% for hot water and 7-60% for lighting.
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C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
The difference in terms of energy consumption between an environmentally friendly hotel that has
implemented measures to preserve natural resources and a hotel built during the 1970s and 1980s and not
yet refurbished, can be 30% to 40% all other factors being equal (same climate, same needs).
Energy conservation measures in hotels have to be carefully selected in order not to endanger the
quality of the services provided. On the other hand, there is no need to waste energy. Accordingly, priority
should be given to control energy use in guest rooms, for example, using simple controls to turn of the airconditioning system when windows are open or the popular room key-cards to ensure that practically all
electrical appliances are turned off when guestrooms are unoccupied. Depending on the hotel category,
electrical energy consumption may range between 12-18% of the total energy consumption and upto 40%
of the total electrical energy consumption. Outdoor lighting for decoration and safety purposes should be at
reasonable levels. Automatic operating timers or motion sensors can easily control the hours for artificial
lighting outdoors or in corridors.
Figure 7. Annual total energy consumption per unit floor area in Hellenic hotels.
Hot water consumption, for sanitary use, services and kitchens, varies according to the hotel category.
A five star hotel requires around 150 litters per guest per day, while a three star hotel 90 litters per guest per
day. Total energy consumption for hot water may represent as much as 15% of total energy consumption.
Average annual energy consumption may reach 1500-2300 kWh per room. Flat plate solar collectors can be
used to cover a significant part of the energy demand for sanitary and pool water heating, and if combined
with absorption chillers, can also be used for cooling.
The use of solar collectors and heat recovery from the cooling system (i.e. recover waste heat from
cooling towers as useful energy) can also be used to reduce energy consumption for service hot water and
swimming pool water heating. Additional savings result from improved cooling tower efficiency and
reduced operating hours. For a representative size hotel of 800 beds, the average annual energy savings
potential from solar collectors can reach 640 kWh/m2 of collector area. Annual energy savings can reach
350 MWh from the solar collectors, 40 MWh from the heat recovery in the cooling equipment, 12 MWh
from using excess heat of the cooling system to heat the pool water, and additional savings of 43 MWh as a
result of the reduced cooling tower operation time.
CONCLUSIONS
A number of decision support methodologies and software have been developed or are under
completion within the framework of European projects. The software can be used to perform a fast but yet
comprehensive building audit and diagnosis of an existing residential, office or hotel building, including
the building’s envelope construction, technical installations and equipment, indoor quality, and to assess
the potential for energy and natural resource savings. The tools address a multitude of issues and enable the
user to assess different scenarios during a building refurbishment project or even to determine priorities for
a large stock of buildings. Having this information it is possible to expedite the decision making process,
identifying where and how to invest and the means to combine common renovation works with energy
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C.A. Balaras, E. Dascalaki, S. Kontoyiannidis
Decision Support Software for Sustainable Building Refurbishment. ASHRAE TRANSACTIONS, Vol. 110, Part 1, pp. 592-601,
ASHRAE Annual Winter Meeting, 25-28 January, Anahaim, USA (2004).
conservation measures. This can improve the financial aspects of RUE and RES techniques and systems
and make it easier to implement. However, the software are not expert systems, but rather provide all the
necessary tools and support the user to make well targeted and justified global decisions, at the early stages
of a project.
The audit scheme is well organized and cuts down significantly the time required to perform an audit,
perform calculations and produce results. In addition, they do not require a large number of auditors with
expertise in different disciplines to perform the audits and analysis, thus cutting down the necessary
manpower. Further developments are underway to adapt the existing methodologies and software for
buildings with other uses, like hospitals, schools etc.
ACKNOWLEDGMENTS
EPIQR for apartment buildings was developed in the frame work of a European project coordinated by
BRE, U.K. and was partly financed by the European Commission (D.G. Research) in the JOULE
programme (JOR3-CT96-0044). INVESTIMMO also for apartment buildings (http://investimmo.cstb.fr) is
an ongoing European project coordinated by CSTB, France and is partly financed by the European
Commission (D.G. Research) in the GROWTH programme (G1RD-CT-2000-00371). TOBUS for office
buildings (http://tobus.cstb.fr) was coordinated by CSTB, France and was partly financed by the European
Commission (D.G. Research) in the JOULE III programme (JOR3-CT98-0235). XENIOS for hotels
(http://www.meteo.noa.gr/xenios) is an ongoing European project coordinated by NOA, Hellas and is
partly financed by the European Commission (D.G. for Energy & Transport) in the ALTENER programme
(AL-135/2001).
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