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Chapter 4: Energy Efficiency Improvement in Traditional Buildings - The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site

Chapter Four: Energy Efficiency Improvement in Traditional Buildings
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
Chapter Four: Energy Efficiency Improvement in Traditional
4.1 - Introduction
This chapter aims to identify the measures and solutions which have been developed to
specifically address the energy efficiency upgrading of traditional buildings, namely the
constraints posed by their heritage value. This was performed through the analysis and
revision of the literature and available case studies addressing specifically the energy efficiency
improvement in traditional buildings.
The framework of energy efficiency improvement for traditional buildings and the specific
measures to address it are discussed, with special focus being put on the constraints posed by
this type of building. This includes connecting several aspects of this field of research, namely
the economic and social framework involving these typologies, the thermal performance of
traditional buildings, their construction systems, the consequences for the heritage after
introducing these measures and the current developments in technical research dealing with
the energy efficiency of buildings, which can further be applied to Oporto’s traditional
4.2 - Energy Efficiency in Traditional Buildings
The approach to improve the energy efficiency of existing buildings through refurbishment is
similar to the general buildings' framework explored in the previous chapter. The main
differences reside in the pre-existing physical conditions, which are unchangeable (site location
and building orientation), and the necessity of dealing with the occupants’ behaviour, which is
usually accounted for in the design of new buildings. In being part of the existing stock,
traditional buildings share this approach. Additionally, their specificity leads to the necessity of
considering further factors: the cultural heritage values and the performance of traditional
construction systems.
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
4.2.1 Existing Buildings Energy Efficiency Approach
The framework proposed by Erlandsson and Levin comprises the sub-systems ‘physical
building’ and ‘housing’, which can be compared to the ‘hardware’ and ‘software’ concepts of
information technologies (2005). The first relates to the building itself and all its components,
while the second refers to a building's services and occupants' behaviour. A similar approach is
proposed by Richarz et al. dividing energy efficiency upgrades in two complementary lines:
constructions and installations (2007).
Addressing the building simulation, Hensen and Lamberts (2011) presented a division in sub-
systems, which dynamically interact and influence energy efficiency in buildings (figure 6). This
adds the actions of the occupants and the environmental conditions of the building site to
previous approaches. It is worth mentioning that the division proposed in the building services,
separates the equipment (lighting, appliances) from the HVAC system. This division is not
consensual, being also usual to find these sub-systems under the building installations or
services. This separation is not crucial, as these systems are dependent on the occupants'
control and on their level of efficiency. However, this separation makes sense when dealing
with existing buildings due to the variable costs involved in the upgrade of the equipment (soft
measures) and of the HVAC systems (hard measures).
Figure 6 Dynamic
interactions of sub-
systems in buildings
in Hensen and
Lamberts (2011, p.2)
The building framework described by Brand, divides building and services systems into layers
(figure 7), relating them to their possible timescales of change and simultaneously stressing
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
the adaptive capacity of traditional buildings. The building is disaggregated into structure, skin
and space plan, while facilities are divided into services and stuff. All these layers are described
according to their usual cycle of replacement: structure - 30 to 300 years; skin - 20 years;
services - 7 to 15 years; space plan - 30 years; stuff - widely variable. Accordingly, services and
stuff are the most feasible layers to be upgraded, followed by skin, which corresponds to the
building envelope. Under the management of change it is also possible to affirm that these
layers are widely accepted as the major targets for the energy efficient retrofit of buildings.
Figure 7 - Building layers of change in Brand (1994, p.13)
Richarz specifically addressed the energy efficiency upgrade in existing buildings, concluding
that renewing the installations can be the most effective way of achieving it (2007). Insulation
is also pointed out as a highly effective solution. The same author argues for the use of passive
measures in order “to activate or re-activate natural, self-regulatory processes in the building”
(2007, p.21). It is also stressed that these measures work well in temperate climates, as they
focus on natural ventilation and lighting, and take advantage or improve the existing thermal
The Recast Directive (EC, 2010) proposes several scales to address energy efficiency: technical
building system, building, building envelope, building unit (house) and building element. These
are complemented with local renewable energy production at superior scales, like the
neighbourhood or the district.
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
Table 12 presents a synthesis of the energy efficiency approaches identified in the literature,
showing both the building framework approach and the possible scales of intervention. This
allows for pointing out the necessity of addressing energy efficiency upgrade in traditional
buildings through these scales, based on the feasibility of their execution (affordability and
ownership) crossed with their effectiveness in achieving energy savings (return of investment
and carbon cuts). Furthermore, the comparison between the measures applicable at individual
unit (home) and at building scale (e.g. insulation and renewables) should be taken into account
to evaluate the improvements and obtain an overall scenario of potential cuts in energy and
CO2 emissions.
In terms of the implementation of the solutions, it is also important to consider a ‘fabric-first
approach’, which means that “renewable energy sources should always come second to
insulating a building and making it airtight. Without these measures, occupiers won’t receive
the benefits from their renewable energy and micro-generation installations” (National
Refurbishment Centre, 2012, p.10). The Building Research Establishment advocates the same
in the refurbishment of their Victorian terrace case study, establishing a three steps approach:
fabric first, then heating and hot water and finally renewables (BRE, 2012).
Conclusively, it is possible to affirm that the approach for an energy efficiency upgrade in
traditional buildings has to be directed towards the improvement of their envelope
performance, technical systems efficiency and the occupants' behaviour, and must be
complemented with the introduction of RES. Furthermore, it should be approached from
various levels of intervention, in order to make it affordable for the households. The four
components are interrelated and inextricably linked; however, for traditional buildings the
envelope upgrade is the most sensible aspect, because it is subject to major heritage
constraints. At the same time, its performance is crucial for the overall performance of the
building, thus also posing the greatest technical challenges in its improvement. Similarly, the
introduction of renewables has to be considered in respect of the visual consequences it
causes to the building and to the historic city image.
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
Table 12 Compared building approach framework
4.3 Improvement of Traditional Buildings Energy Efficiency
Using the defined framework it is possible to draw up an approach for the energy efficiency
improvement of traditional buildings based on three complementary levels: the building’s
physical elements, the housing (services, equipment and occupants) and the energy
Erlandsson and
Levin, 2005
Richarz et al. ,
Hensen and
Lamberts, 2011
Brand, 1994
Energy Efficiency
Directive Recast,
AdEPorto, 2010 Restart Project , 1996
Main facade
Building Envelope
Exterior windows
and doors
Gable facade
Partition wall
Space Plan
Building Unit
Building Element
HVAC System
Technical building
Physical Building
Temperature space
Central HVAC system
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
production (renewables). They can further be divided into systems and sub-systems, providing
the possibility of addressing independent improvement measures (table 13).
Table 13 Traditional buildings improvement framework proposed
Level System Sub-system building level home level
Solutions Implementation
Common area
Roof and Loft
Main facade
Gable facade
Party wall
Glazing (exterior
windows and
Interior space
Partition wall
Interior doors
and windows
DWH, Heating,
Cooling and
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
Moreover, the elements to be improved are addressed by two scales of possible
implementation: building and home. These levels are based both on the cost and on the
consent procedures necessary to implement the solutions, which are aggravated in Portugal by
the complex legal tenancy framework. A similar situation is identifiable for the improvement of
the communal areas of the Scottish Georgian tenements, where any work must have the
consent of all tenants (Changeworks, 2008). Hence, the focus must be set on the measures
addressing the building unit or the building elements, which allow a direct action without the
necessity of engaging all tenants or the building owners. Moreover, these measures are usually
more affordable, consequently increasing their feasibility.
At the same time, it is necessary to consider the possibilities posed by the local energy
production. The heritage constraints posed by the historic cityscape limit their application.
However, the district systems can be used to overcome such a situation, by concentrating the
energy production and consequently minimising the impact. An example of this is the future
RUTE (Thermal Energy Urban Network), which envisages the use of tri-generation from natural
gas in Oporto’s urban core to provide combined cooling, heat and power to large consumers,
while simultaenously reducing the losses in energy distribution by 30% (Cardoso, 2011;
Fernandes, 2009). If this was applied to domestic consumers as well, it could help reducing the
environmental footprint of Oporto’s traditional buildings with a reduced risks for heritage
damaging. However, district scale is not in the scope of this research, so the subject will not be
developed here.
4.3.1- Solutions for Traditional Buildings
The English Heritage developed a toolkit which identifies gradual stages of measures based on
the cost and easiness of their implementation in the traditional buildings residential sector
(2011). These stages range from easy savings (‘soft measures’) to long term planning (‘hard
measures’) as shown in table 14. The first type is based mainly on lifestyle enhancements, both
by improving the household’s behaviour and by using more efficient equipment. In what can
be considered a second level, it proposes the general draught-proofing and ‘easy insulation’ of
some building elements, which should be considered before carrying out ‘hard measures’. The
maintenance and improvement of traditional windows and doors is further encouraged in
order to maintain the character and appearance of traditional buildings. It consists either of
draught-proofing the frame or in the installation of secondary glazing. ‘Easy insulation’
addresses the building systems and the elements which are reachable by the interior and
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
whose insulation poses no negative visual consequences. Inversely, the long term measures
can be both costly and difficult to implement, as they involve construction work. They can be
planned in advance and may be considered if in-depth refurbishment is to be undertaken.
This framework of solutions seems consensual in the literature and summarises the research
promoted by BRE, English Heritage, Historic Scotland and SPAB, based on UK case studies from
the pre-1919 built stock, covering Georgian, Victorian and Edwardian houses (Cartwright et al.,
2011; Changeworks, 2008; Drewe and Dobie, 2008; Ferguson, 2011; Pickles et al., 2012; Rye et
al., 2012; Yates, 2006)
. This literature is crucial, because it represents the most solid corpus
of research, developed along a consistent period (since the 1990’s until now) and is based both
on scientific experiments and case studies. At the same time, the type of buildings in question
reveals a certain formal similarity with Oporto’s traditional buildings (with Georgian design
influence), which is further discussed in Chapter Six.
Table 14 Residential traditional buildings energy efficiency toolkit in (English Heritage, 2011)
- See table 16.
level category Measures
appliances s tandby nulling
lights turned off
lower heating temperature
higher efficiency
lower temperatures in clothes washing
less water boiling
introduction of controls for radiators and boiler
use of intelligent thermostats
smart energy metering
use of low-energy lamps
motion detectors for external lighting
boiler maintenance
introduction of fuel efficient boiler
use of biomass heating
heavy curtains
‘sausage dogs’
frame draught-proofing
installation of secondary glazing
floors and chimneys
roof and loft (by the interior)
systems (hot water tank and piping system)
insulation of the building envelope roofs and walls
insulation of floors suspended or solid
solar thermal
hydro power
air or ground heat pump
Introduction of renewables
easy insulation of some building elements
easy s avings
(‘soft measures’)
general draught-proofing of doors and
long term
planning (‘hard
lifestyle enhancements
home appliances upgrade and better use
heating controls and energy metering
improved lighting
energy efficient heating
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
Table 15 Solutions framework
Level System Sub-system
English Heritage, 2011
(´soft measures')
English Heritage, 2011
(´hard measures')
Drewe and Dobie, 2008 Changeworks, 2008 Yates, 2006 Richarz et al. , 2007 Rye et al., 2012 AdEPorto, 2010 Restart P roject, 1996
Cartwright et al. , 2011
and Fergu son, 2011
Roof insulati on from inside
Roof insulati on from outside
Loft insulation Loft insulation Loft insulation
Exterior insul ation Composite external insul ation
External insul ation with
ventil ation cavity
Party wall insul ation
Draught-proofing doors and
Draught-proofing doors and
Draught-proofing windows
Weatherstripping of windows
and doors
Set a maximum of free-
cooling rate
Draught-stripping and seal
on windows.
Secondary glazing
Draught-stripping on
Double glazing or secondary
Double or secondary glazing
Introduce double glazing in
existing frames
Double glazing in wood
Double or triple glazing
Keepi ng traditional
windows, doors and shutters
Maintaining traditional
Maintaining traditional
Maintenance or introduction of
inner shutters
Secondary glazing in skyl ight
Double or triple glazing in
Ground floor insulation Draught-proofing floors Ground floor insulation Ground floor insulation Ground floor insulation
Floors insul ation Suspended floors insul ation
Floor insulation (confining with
unheated spaces)
Central biomass pel let
boile r
air-to-air and air-to-wate r
source heat pumps
Solar thermal
Solar thermal
Solar thermal
Solar thermal
Energy produ ction
Micro-generation (wi nd,
photovoltaic, sol ar
thermal, hydro power
and heat pumps ground
and air)
temperature space control
programmer, room thermostat
and thermostatic radiator valves
Lifestyl e (nulling stanby,
turning off li ghts, turning
down the thermostat)
Room thermostats
Heating controls & energy
Smart metering
Natural lighting
Home appliances
Efficie nt appliances
A-rated energy efficie ncy
Lightin g
Efficie nt lighting
Efficie nt lighting
Low energy lamps
Easy insulation (tank and
Heat recovery
Mechanical ventilati on with heat
Mechanical ventilati on with heat
Condensing combination
boile r with a mechanical
heat save device
Controlled ventilation system
Natural cross ventilation
Natural ventil ation
Energy efficient heating
Gas central heating with
condensing boiler
LPG-fired condensi ng boiler (hot
water and space heating)
Central HVAC system
Partition wall insulation
Interior doors an d
Building services
DWH, Heating,
Cooling and
Energy efficient heating
Floors insul ation
General draught-proofing
Partition wall
Low-cost draught-proofing
(heavy curtains, portie re,
shutters, sausage dogs)
Partition wall insulation
Skylight improvement
High light transmissi on, low
solar gains, low refl ectance
glass in skyli ght
Interior space
Draught-proofing floors
Adding insulation to
Floor insulation (confining
with unheated spaces)
Glazing (exterior
windows and
Glazed eleme nt
improveme nt
External insul ating
External insul ating
Gable facade insulati on
Other facades external
insulati on
General draught-proofing
including chimneys
Interior insul ation (ex terior wall
dry lining insulation)
Dry lining insulation
Dry lining insulation
Main facade insulation
Interior insul ation of main
Main facade dry lining
insulati on
Roof insulati on
Roof insulati on
Roof insulati on
Roof insulati on
Main facade
Draught-proofing chimneys
Adding wall insulation
Wall insulation
Dry lining insulation
Building Envelope
Roof and Loft
Interior insul ation (roof and
Re-roofing incorporating
insulati on
Top floor insulati on
Roof insulati on
Gable facade
Party wall
Draught lobby
insulate d porch
Physical Building
Common area
Draughtproofing entrance
draught sealing of front doors
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
Table 16 Traditional buildings energy efficiency case studies in the United Kingdom
Cartwright et al., 2011 and
Ferguson, 2011
Changeworks, 2008 Restart, 2000 Energy Saving Trust, 2010
Pilot Case s tudy 1 Case study 2 Case study 3
Case Study and demonstration
Case study
Light refurbishment case
Test wall
Georgian Tenement in World Heritage Edinburgh (test in
a stair of 9 flats - 1820)
usual energy effici ent measures
in solid wall ho uses
Four-storey ten ement in
Greenock, Scot land (1996)
Nelson Housing Mar ket Regeneration
Scheme (2006)
The Flagship Home P roject, Beaufort
Gardens, London
The Nottin gham Ecohome (2000)
BRE Victorian Terr ace - Watford
Recommended solut ions Rector y, Ampermoching (1724; 2001-2002)
The Firs, Riddlecombe,
Devon (2012)
Mill House, Drewsteignto n,
Devon (2012)
Lister Housing Co-op erative, Lauriston Place,
Edinburgh (2007-2008)
CRUARB Office, Rua da Font e Taurina, Oporto
Sheffield EcoTerr ace (2009)
loft insulation
150 mm mineral wool loft insulation
between joists , 50 mm laid over
re-laying the roofs and the insul ating of the
roof spaces
Addition of a floor with high ins ulated roof
Roof insulation above the ceil ing: 400 mm of Warmcell
recycled newspaper insul ation above and between the
ceiling joists
mineral wood and sheep's wool
Roof insulation from insid e: waterproofing covering
natural or mineral fibers betwee n the rafters, vapour
barrier, second layer of insulation and fi nish
Roof insulation along slope of rafters: 300 mm of blown
Warmcell insulation in a plywood we b
heat phase-change materials in ceil ing
Roof insulation from outside when re-roofing:
waterproofing covering, insul ataion layer, second
natural or mineral fibers betwee n the rafters, vapour
barrier and finish
Natural cross ventilation of unheated roof space
Additional work: Re-roofe d re-using most of old slates;
Installed breathable unde rlay to protect insulation;
Extended verge overhang for future ex ternal insulation
Top most floor insulation: fill ing void space between
joists with natural or mineral fibe rs or loose fill
material (cellul ose flakes), vapour barrier (plastic
sheeting or buildin g paper), second layer of insulation
if necessary and floorboard
loft insulation betw een the joists with mine ral wool,
vapour barrier
Loft insulation - 300mm of insulation
insulated dry lini ng to external
Plaster removed. External wall – 50
mm expanded polystyrene
insulation – plasterboard
dry lining
Internal insulation: 2 × 50 mm zero odp phenolic foam
laminate boards (This was applied to the front el evation so
that the external appearance could be maintained)
Main facade internal insulation:
aerogel, polyurethane foam and
polyisocyanurate insulati on (PIR)
Internal insulation wi th upgrade of existing single
glazing: insulation material place in the wall (rigidPS
foam, mineral wool, mine ral foam, rigid PUR foam,
calcium silicate sheets) , vapour barrier, finish. Points
necessity to insulate i nternal partition 500mm when
joining the exte rnal wall, and insulation of timbe r
joists floors support in exte rnal walls (PUR spray foam).
Secondary bouble galzing added
Internal insulation in granite
external wall: gypsum ski m (3mm),
plasterboard (12.5mm), air gap
(25mm), PIR (polyisocyanurate)
board (100mm) + existing wall
external insulati ng render
use of traditional materials and original
design features for the chimney stacks which
are in keeping with the peri od of the houses
External insulation: 140 mm expanded polystyrene board
and a Sto render system. The thermal performance of the
walls has been improved by 860%
North facade external insulati on:
Expanded Polystyrene (EPS)
External insulation (i n conjugation with new double
glazing window): composite system (insulation board
with rendering system)
External insulation composite system (60-140mm)
External insulation li me
render 40mm
External insulation wi th ventilation cavity (conjugated
with new double glazi ng window): create double
framework of rails to support cladding; two level s of
insulation betwe en rails, possible coveri ng of system
withn boards, cladding material
secondary glazing
Replacement timber window s with
double glazing (22 mm air gap) and
draught sealing
fitting traditional doubl e glazed sash
windows to improve energy ef ficiency
double glazed window s in the rear elevation
The house would originall y have had single glazing – double
glazed u-PVC windows were inherited and no secondary
glazing. Two north facing sets of French windows were tripl e
glazed, krypton fill ed with two low e coats
Double and triple glazed framing New double glazing windows New double glazed wi ndows
Existing wood double glaze d
Secondary glazing (slim li ne) reducing U value to 2.0
secondary glazing in the front elevati on Secondary double glazing Introduction of folden wooden shutters internally Shutters refurbishment
Weatherstripping of windows and doors: sel f-adhesive
strip (DIY but limited durabili ty), grooves in frame and
standard sealing profiles
Draughtproofing - reducing air changes per hour from 2.5-3
(usual in sash windows) to 0.4
Introduce double glazing in ex isting frames
ground floor insulation
Solid ground floor: Excavated down and laid damp proof
membrane horizontally and verticall y to above ground level;
150 mm polystyrene with 50 mm edge upstands; 100 mm
concrete slab
Insulation of floors to unheated space
Suspended ground floor insul ation: mineral wool,
vapour barrier
Ground floor insulation
Suspended ground floor: 100 mm of sheep’s wool betwee n
the joists and 60 mm ofinsulating wood fibre board (Gutex)
beneath the joists. A breather membrane over the Gutex
Floor insulation (21mm of insulating material and 9mm of
particle board - u value of 0.25)
Second floor: Existing floorboards taken up and the joi sts
strengthened; Loose Rockwool placed betw een joists for
sound insulation (shoul d have used sheep’s wool but not
readily available at the time); 3 mm Regupol sheet made of
recycled rubber and cork over joists for impact noise
reduction; Existing boards replaced and suppleme nted with
additional reclaimed boards to enlarged the floor area
General draught-proofing
partition wall
Composite board comprising 12.5
mm wallboard and 19 mm extruded
polystyrene fitte d internally
draught sealing of front doors of
replacement of front doors and rainwater
Replacement of some of the ex isting u-PVC doors with fsc
gas central heating with
condensing boiler
Gas fires, gas fired central heating
from back boiler, programmer, room
thermostat and thermostatic
radiator valves
Two condensing boilers were i nstalled to
provide communal heating to all the units but
with each tenant having radiators and
programmable controls
Central biomass pelle t boiler
LPG-fired condensing boil er (hot water and space
New 'A' rated condensing boilers
Air source heat pump
air-to-air and air-to-water source heat
Condensing combination boil er with a
mechanical heat save device
factory insulated hot water
Back boiler, 135 litre hot water tank
with 80 mm factory applied
Solar panels were install ed on the roof to
supply part of the building’s hot water with a
heat recovery ventilation syste m
4 m2 flat plate solar panel contributes 50% to annual hot
water; wood-fired boil er for central heating and hot water
top-up; 1100 litre accumulator stores and distributes hot
water to the radiators and domestic use; It was planned to
install one or two 1 metre diameter wind turbine s (this is no
longer the case as it would not generate viable amounts in
this area; Renewable energy and low energy construction
has saved £800 to £1000 a year
Solar thermal Sol ar thermal
controlled ventil ation system kitchen and bathroom extract fans
Mechanical ventilation with heat recovery
unit per floor
Both bathrooms and both kitchens have heat recovery fans
which save up to 80% of airborne heat. Whole house heat
recovery mechanical ventilati on
Mechanical ventilation with heat
Mechanical ventilation with heat recovery
Lighting an d
All low energy lamps and A-rated energy
efficiency appli ances
Low energy lighting (CFL's 23W); smart metering; energy
district heating system based on a biomass
install a new front door and create an insulated porch
The potential environme ntal impact could be
further reduced by combining the use of
carbon neutral technology with a planned re-
use of construction materials suppleme nted
by low environmental imp act traditional
materials such as lime mortars, insulation
made from sheep’s wool or newspaper, and
Over time, the u-PVC wi ndows will be replaced as the
glazing units fail (doubl e glazed or secondary glazing)
energy cut by 67%/year and CO2 emissions
cut by 63%/year
The overall energy savings are 75% in terms of costs and 85%
in terms of tonnes of CO2 emitted
4% improvement in U-value
of external wall
87% improvement in U-value of
external wall
The annual energy cost of each flat were reduced by na
average of £175 (some cases up to £400); The annual CO2
emissions of each flat were reduced by na average of 1
tonne (some cases up to 2.4 tonnes)
Simulated: (20% savings in heating, 20% savings in
cooling, 40% saving in lighting
less 76% of CO2 emissions; less ele ctricity consumption
of 60% and less gas of 81%
after the work was completed the houses
national home energy rating (NHER)
increased from approximately 3.0 to 9.0.
The annual energy consumption of each flat were reduced
by na average of 5000kWh (some cases up to 12000kWh); The
annual CO2 emissions of each flat were reduced by na
average of 1 tonne (some cases up to 2.4 tonnes)
Simulated: (7 MWh heating, 13 MWh cooling, 20 MWh
lighting against simil ar non refurbished 13 MWh
heating, 19 MWh cooling, 32 MWh lighting)
Less 67% in running costs
Internal Con struction Improv ements
partition and
Buildings Systems
Future improv ements
Yates 2006
Richarz et al. , 2007
Rye et al. 2012
Building Env elope
Roof and loft
Exterior walls
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
By crossing the framework for the improvement of traditional buildings presented in table 13,
with the specific solutions identified in the literature reviewed, it was possible to produce a
table that confirms the solutions framework presented above, and details it with the effective
measures taken in diverse case studies (table 15). From these solutions it is possible to
highlight the envelope insulation, the glazing upgrade and the introduction of renewables as
the most effective for improving the energy efficiency of traditional buildings. As such, these
measures will be further addressed below. Furthermore, the upgrade of the communal spaces
and the cost-effectiveness of the solutions, which are subjects that need to be evaluated in the
energy efficiency upgrade of Oporto's traditional buildings, are also reviewed.
The use of external insulation is acknowledged to be the most effective, as it takes advantage
of the high thermal mass that is usual with traditional buildings (Ferguson, 2011; Richarz et al.,
2007). However, its use in the building envelope is considered the major challenge for
improvements to traditional buildings, for both the technical and the heritage constraints
posed, as pointed out in several of the reviewed case studies (table 16). The BRE research
conducted on several Victorian examples, supports this by pointing out the problems posed by
the insulation of solid walls (Yates, 2006). The improvements tested were made by addressing
the envelope’s insulation at several scales (roof, walls and glazing) and by paying careful
attention to the consequences this had for the buildings’ authenticity. This ‘case-by-case’ basis
is the most commonly applied approach for assessing the visual impact of the solutions and to
verify the heritage disruption caused.
The use of natural insulation, such as mineral and natural fibres or hemp batts, is pointed out
to be more adequate for traditional buildings. It is normally more expensive than petro-
chemical materials, but it absorbs and lets out moisture and allows the traditional construction
to continue breathing (Changeworks, 2008; Curtis, 2008; Drewe and Dobie, 2008; English
Heritage, 2011; Yates, 2012). Richarz et al. underline the difference between the measures
executed from the interior or from the exterior of the building, putting emphasis on the use of
scaffolding which represents a substantial increase in the total cost (2007).
Moreover, the same authors reviewed the type of insulation available for each approach,
stating that flexible materials (e.g. mineral or natural fibres), are more suitable for inner
insulation than rigid boards, as they can easily be inserted into the construction voids. These
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
factors confirm that natural and flexible insulation solutions are the most viable for the energy
efficiency upgrade of traditional buildings.
In the specific case of Oporto it is important to stress the dimensional problem posed to the
feasibility of insulation due to the reduced interior dimensions of spaces and/or by the limited
thickness available on the main facades due to the granite stone carving whose plan should
not be surpassed. Consequently, the insulation thickness reveals to be an important parameter
to consider in the implementation of the solutions. The local climate allows the use of reduced
insulation thicknesses when compared to North European countries, but even so the available
space is still constricted
. The use of dry lining insulation is additionally limited by the usually
existing relation of the wall with the ceiling stucco, which must be preserved. The use of slim
insulation materials may be considered to overcome the visual and dimensional effects of the
intervention. Hence, it is possible to consider the use of two recent materials: aerogel
insulation and phase change materials (PCM), i.e. materials which store or release heat when
changing their phase (solid to liquid and vice versa). However, as pointed out by Cartwright et
al., the use of less conventional materials poses two major restrictions: their high initial cost
and the lack of knowledge in their application, which leads to longer times of execution and
consequent higher costs (2011).
The incorporation of microencapsulated PCM in plaster was studied in Portugal by Silva et al.
(2008) and Monteiro et al. (2005), both pointing out its potential for energy efficiency. In these
experiments 25% of PCM
was incorporated in the final layer of plaster covering the inner face
of exterior walls. The results revealed that the room maximum temperature was reduced by
28% and the room minimum temperature was increased by 6%, without using any heating or
cooling equipment (Monteiro et al., 2005). This 1 mm thick PCM layer improved the wall
thermal mass significantly and, with an additional cost of 1€ per square meter of the total
render cost, it seems to be a high potential solution to be used in the upgrade of the thermal
performance of traditional buildings
. The analogous research undertaken by Lucas measured
- The AdEPorto et al. study (2010), addressing the energy efficiency improvement of Oporto's traditional
buildings, admits the possibility of using the minimal insulation thickness of 50mm in external walls, which may be
increased until 100mm for obtaining the best results. Similarly, the roof insulation may use thicknesses varying from
70mm until 160mm.
- This ratio proved to be the best in terms of balancing the mechanical stability of the plaster with their thermal
- The BRE Victorian terrace experimental project also incorporated PCM insulation into the ceiling tiles of the
presentation room, with no results available yet (BASF, 2010).
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
a variation of 4 to 5°C between a wall with PCM plaster and a reference wall. The author
highlights that it enabled achieving the thermal comfort temperatures with a reduced use of
energy (2011). Additionally, the work undertaken by Zamalloa et al. in Spain during the
summer of 2008, showed that the use of the PCM insulation increased the thermal inertia of a
wall, thus reducing the cooling demand up to 30% (2009). These results confirm how PCM
insulation can play a relevant role in the passive cooling of buildings, increasing of comfort and
saving energy.
The approach towards roof insulation is also consensual in literature, and is considered in
conjunction with the loft space (Changeworks, 2008; Drewe and Dobie, 2008; English Heritage,
2011; Richarz et al., 2007; Yates, 2006). If the space under the roof is not inhabited the
insulation is placed on the floor which permits cross ventilation of this space (cold roof). If it is
used for living, the insulation is then placed directly in the roof, either by re-roofing and
placing insulation on the exterior, or by incorporating it between the rafters (warm roof).
The upgrade of the traditional external windows and doors also needs to be carefully
considered in order to avoid the disruption of the overall building character. The approaches
that have proven to be the most successful are based on upgrading the glass (by the insertion
of double glazing if the frame design allows it) or by the introduction of secondary glazing,
which is usually a more viable measure with several successful examples among the reviewed
literature (Changeworks, 2008; Curtis, 2008; Yates, 2006). From these examples, the Slimline
secondary glazing applied in a Scottish pilot study deserves a special mention for its
reversibility (Changeworks, 2008). The authors argue that the secondary glazing is usually less
intrusive, but it must be conjugated with the original windows design.
Furthermore, the literature stresses that the use of ‘low-cost’ measures (draught-proofing,
curtains and inner shutters) allows enhancing the performance of the glazing systems
(Changeworks, 2007; Drewe and Dobie, 2008; English Heritage, 2011). Addressing this
objective, Richarz et al. introduced internal folding wooden shutters in upgrading a German
traditional building with the aim of improving its thermal efficiency (2007).
Associated both with the roof and the glazed elements of the buildings, updating skylights is
also addressed in the case studies. Their improvement is similar to the approach used in
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
windows and focuses on the replacement of single by double glazing, the introduction of
secondary glazing (Changeworks, 2008), and the upgrading of glass for high light transmission,
low solar gains and low reflectance (Restart Project, 2000).
Communal spaces
Like in the Georgian tenements of Scotland, the skylights in Oporto are inserted on the top of
the building’s communal space where the staircases are located. This raises the problem of the
upgrade of such spaces, which was addressed in the Changeworks report (2008). Known in the
Scottish tenements as the ‘stairwell’ or ‘close’, it allows for heat to escape. The proposed
improvement of these spaces is based on three complementary measures: insulation, lighting
and recycling of heat (Changeworks, 2008). The insulation consists mainly of draught-proofing
the flats and building entrance doors. The building's main entrance can benefit from the
installation of a second door creating a ‘draught lobby’, which allows the retention of heat. The
similarity between Oporto’s traditional buildings makes this a possible measure to be taken
into account when addressing their comprehensive upgrade. At the same time, the use of low
energy lighting and the installation of a mechanical pump and piping system to recover heat
from the roof space into the communal areas, which can then benefit from this ‘free’ heat, are
advocated. However, as it is also stressed in the report that this is only viable when integrated
in major refurbishment works (Changeworks, 2008). The same applies to any measure
addressing the retrofit of the building's exterior, due to the high cost involved in such
construction work, which is escalated by the necessity of using scaffolding.
The data compiled by Changeworks (2008) clearly shows how measures which are construction
intensive have a high payback period and are hardly likely to be undertaken by tenants or
owners with lower incomes (table 17). From the table it is possible to confirm that small house
improvements are more effective, with the additional advantage of having the possibility of
being executed on a Do-It-Yourself (DIY) basis, reducing the costs and the payback period.
Inner space measures, such as the insulation of suspended timber floors and lofts or the
building’s general draught-proofing, are also widely pointed out in literature as effective for
energy efficiency upgrading of traditional buildings (table 15). This is confirmed by their
payback time, in particular if they are executed without using a contractor. The retrofit of the
building systems and the improvement of the occupants’ behaviour, are similar to the ones
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
previously discussed and usually do not present negative consequences for the traditional
buildings’ fabric, which allows to classify them as ‘heritage friendly’. The upgrade of equipment
and systems is highly variable, depending on the initial investment made, which can cover just
a simple upgrade (insulation on the water tank or piping) up to the complete renovation.
Table 17 Payback periods from typical energy efficiency measures in (Changeworks, 2008, p.26)
This framework of low and hard cost measures is also supported by Portuguese research. The
study undertaken by Afonso identified that a period of 13 years is necessary in order to
achieve the payback of the investment made for the building’s energy efficiency improvement
(2009). Further, it points out that if this upgrade is inserted in the building’s total
refurbishment, it requires only an additional investment of 10%. Similar results were obtained
by Veiga, who identified a payback period of 12 years and confirmed the additional cost of 10%
for improving the building's thermal performance under an overall refurbishment process
The introduction of renewables is widely pointed out as a positive measure to compensate the
energy consumption of buildings. Their use is proposed in some of the case studies identified,
with precedence being given to the solar thermal systems (table 15 and table 16). However,
their use in the historic environment is not consensual, as it has been revealed to be disturbing
for the site character. English Heritage promoted research on this subject and analysed the
Measure Cost (£) Annual savings (£) Payback period
Hot water tank insulation (800mm
12 20 c. 6 months
Hot water pipework insulation 10 10 1 year
Suspended timber floor insulation 90 (DIY) 45 2 years
250 (DIY) 110 c. 2 years
500 (contractor) 4 to 5 years
Cavity wall insulation 500 90 c. 5 years
90 (DIY) 20 c. 5 years
200 (contractor) c. 10 years
Solid wall insulation (50mm
plasterboard laminates, or battens,
insulation and plasterboard)
From 42/m2300
Depend on property
Double glazing (seal units) 3,000 90 20+ years
Loft insulation (270mm)
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
introduction of micro-generation from renewable sources, covering wind, solar thermal,
photovoltaic, and biomass energy, in traditional buildings (English Heritage, 2006; English
Heritage, 2008c; English Heritage, 2010a; English Heritage, 2010b; English Heritage, 2012). A
similar but more detailed perspective is given by Changeworks for Scottish traditional buildings
(2009). The major conclusion provided by this source stresses that renewables can be
introduced but safeguarding a building’s significance must always be met and the visual
consequences of the ‘intrusion’ must be carefully considered in each individual case.
4.3.2 - Traditional buildings energy efficiency upgrade in Portugal
In Portugal, the energy efficiency of traditional buildings has often been addressed in research,
but concrete case studies are scarce. Further, the approach is mainly technical, driven by the
attempt to comply with the thermal regulation for buildings.
Driven by this objective, the Portuguese Energy Agency (ADENE) promoted research
addressing the retrofit of existing residential buildings, focusing basically on dwellings built in
the past five decades (Anselmo et al., 2004). Therefore, with the exception of pitched roofs,
this research does not cover traditional buildings and their construction systems. Nonetheless,
referring to the example of Oporto it points out that addressing the roof insulation is more
effective in terms of cost-benefit analysis than insulating exterior walls.
The larger bulk of research addressing this subject in Portugal was developed by the
universities’ engineering departments, which may justify the focus on the technical approach
undertaken (Afonso, 2009; Craveiro, 2008; Cupido, 2000; Jardim, 2009; Rocha, 2008). Based on
the dynamic thermal simulation of a traditional building, Afonso concluded that to achieve the
desired level of comfort, the top floor and the attic require the major thermal loads, while the
middle floors present a very similar performance (2009). Additional research also points out
the discrepancy between the thermal loads calculated, when using the static method inserted
in the thermal regulation, and the dynamic modelling made by software, which presented
lower values (Veiga, 2011).
Some of this scholarly research addressed very detailed aspects of the construction systems of
traditional buildings and their thermal performance improvement. Santoss research
addressed traditional pitched roofs, identifying mineral wool as the most effective insulation
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
solution for the majority of the cases (2009). The reversibility of the solutions in order to avoid
damaging the heritage value of buildings is also stressed by this research.
The 1996’s Restart project was a pioneer study in addressing the energy efficiency of Oporto's
traditional buildings (Resetnet, 2010). The Oporto RESTART Project - Porto - Rehabilitation
Process in the Historical Centre- was integrated in the urban regeneration process taking
place in the World Heritage area of the Historic Centre. This experimental project addressed
the adaptive reuse of a building to host the Oporto Municipal technical body for the historic
centre - CRUARB’s (Restart Project, 2000). The central strategy was based on the use of natural
lighting, taking advantage of the central skylight and upgrading its glass characteristics. The
building insulation was also central in the intervention, addressing the roof, partition walls and
floors in non-heated zones. External walls were insulated from the interior to avoid conflicting
with the building’s character. The project also promoted natural ventilation, but the thermal
comfort was, however, mainly provided by a central HVAC system.
The guidance promoted by AdEPorto et al. presents a holistic and very experience-based
approach to the energy efficiency improvement of Oporto’s traditional buildings (2010). The
study was also monitored by the Portuguese Heritage Institute (IGESPAR) in order to assess the
solutions from the heritage conservation perspective. Methodologically, this work applies the
most proven solutions to Oporto's traditional buildings to achieve the thermal performance
levels required by the regulation. The occupants' behaviour or the appliances' efficiency are
disregarded in the study, which addresses mainly the fabric and the systems. The approach
focussed on the improvement of the overall building envelope, divided into exterior wall,
glazed elements and roof (AdEPorto et al., 2010). The report stresses the particularity of the
facades of Oporto’s traditional buildings, where the glazed area is usually superior to the
opaque, which adds a high relevance to the retrofit of windows and French doors. Aligning
with the previously reviewed literature, the exterior walls were divided into main and gable
facades and grouped with the according possible insulation approaches. These are respectively
dry lining and exterior insulation with independent cladding and air cavity. The proposed roof
insulation is similar to the one presented by Richarz et al. (2007), consisting of the insertion of
flexible materials between the rafters and of a vapour barrier layer to avoid condensation.
When possible, it is recommended to upgrade the glazed elements (double glazing or
introduction of secondary glazing, including in the skylight). It is also recommended to use
traditional inner wood shutters, as advised in the reviewed best practice case studies. The
introduction of solar thermal panels is also promoted in order to reduce the energy demand
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
and comply with the regulations. Aiming to minimise their visual impact, the design guidance
stipulates that the panels should cover less than 10% of the total roof area, be mounted
directly on the slope and parallel to the ridge. However, even if this reduces their impact, it is
important to point out that the visual contrast between the black panels and the red roofs tiles
is likely to disturb the image and character of the Historic Centre if applied on a large scale.
This situation is aggravated by the sloping topography of the city, which allows seeing the
historic centre roofscapes from above at several points, as shown in figure 8.
Figure 8 Oporto historic centre roofscapes as seen from the Cathedral hill
4.4 Heritage in Energy Efficiency Improvement of Traditional Buildings
In the past ten years the UK’s heritage bodies have promoted several studies in the field of
refurbishment of traditional and historic buildings in order to meet current day standards. The
most recent concern is directed at climate change and sustainability in general (Cassar, 2005;
English Heritage, 2008a; English Heritage, 2008b), and energy efficiency in particular, following
the EPBD translation into the UK national regulation (Changeworks, 2008; Drewe and Dobie,
2008; English Heritage, 2007; GHEU, 2007; Pickles et al., 2011; Wood and Oreszczyn, 2004).
Further, these studies reinforce the necessity of minimising the disturbance to the existing
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
fabric and of promoting reversible solutions when upgrading for energy efficiency in traditional
buildings (Drewe and Dobie, 2008).
The concern posed by the application of the European thermal regulations in the historic
environment, drove ICOMOS France to publish an official declaration (2008) and to organise a
conference to discuss this subject with Euromed Heritage (2010). The results specifically stress
the necessity to preserve the authenticity of traditional buildings, which are less protected and
subjected to suffer damaging change during the renovation processes to achieve the
regulation standards. Once more, the emphasis is put on the external insulation of buildings as
the major challenge and risk for traditional buildings, as proven by the results presented by the
Graz case study
Overall, it is possible to affirm that the concern posed by the traditional buildings upgrade to
address energy efficiency seems consensual among the conservation community. This concern
can be summarised into the need of applying compatible technical systems to traditional
buildings, which perform differently from modern ones, preserving at the same time their
authenticity. However, a methodological approach balancing the weight of heritage with
energy efficiency was not identified. Yates advocates the necessity of establishing a
‘conservation limit’ and developed a methodology for dealing with it (2006; 2011). The method
proposed is mainly based on the intervention criteria established in the international heritage
charters and on the professional’s practice. Special emphasis is put on avoiding changes to the
fabric and aesthetic appearance of the properties, but no specific method for achieving this is
provided. The research promoted by the English Heritage and Historic Scotland bases its
assessment on the conservation principles, but without clearly defining the assessment
methodology (Baker, 2010; Changeworks, 2008; Curtis, 2008; Drewe and Dobie, 2008; English
Heritage, 2011; Historic Scotland, 2012). May and Rye stress the necessity of developing a
“systemic approach (…) regarding the assessment and retrofit of traditional buildings” (2012,
p.7). They recommend the investigation of further methods and propose guidance for the
management of change, implementing the usual three colours system (green, amber, red) for
grading the impact of the solutions (2012). Even if the process of impact assessment was not
straightforwardly defined, this study effectively presents the most comprehensive approach
identified. The Oporto research and guidance are focused mainly on the technical aspects
- The Federal Office for Historic Monuments in Vienna uses a colour system for grading the energy upgrade
intervention. It is based in the three traffic lights in a very similar way to the previously reviewed in Chapter two.
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
(Cupido, 2000), merely addressing the heritage aspect on a common sense approach as
avoiding to damage the appearance of buildings (AdEPorto et al., 2010; Restart Project, 2000).
From this framework it is possible to conclude that an integrated method for addressing
heritage in energy efficiency improvement processes is still needed.
Table 18 Energy efficiency improvements and their heritage consequences in traditional buildings
Based on the framework of solutions previously approached and on the levels of intervention
identified, it was possible to categorise these solutions accordingly to the consequences they
Level S ystem Sub-system Solutions buildin g level home level Compatible Neutral Intrusive Disruptive
Dry lining insulation oo
exteri or insulation oo
General draughproofing oo
Create insulated porch oo
exteri or insulation o o
Inner insul ation o o o
Dry lining insulation o o o
exteri or insulation o o o
Dry lining insulation o o o
exteri or insulation o o
Party wall Dry lining insul ation o o o
draughproofing o o
Inner shutters o o
Double glazing o o
Secondary glazing o o
draughproofing o o
Double glazing o o
Low emissiv ity glass o o
draughproofing o o o
Insulation o o o
Partition wall Insulation oo
draughproofing oo
Double glazing o o
Improve eff iciency oo
Piping insulation oo
Tank insulation oo
Thermostats oo
Natural ventil ation o o o
Low energy lamps o o
Natural lighting oo
Appliances Improve efficiency oo
Stand-by null ing o o
Decrease heating temp. o o
Smart metering o o
Temperature control oo
Solar thermal oo o
Solar photovoltaic oo o
Micro-wind oo o
Biomass o o o
Heat pumps oo
Gable facade
Glazing (exterior
windows and
Energy production
Building services
DWH, H eating,
Cooling and
Heritage Consequences
Solutions Implementation
Physical Building
Common area
Building Envelope
Roof and Loft
Main facade
Interior space
Interior doors
and windows
Chapter Four: Energy Efficiency Improvement in Traditional Buildings
pose to the cultural significance of traditional buildings. This can be defined in the same way
ICOMOS proposed the heritage impact assessment discussed in chapter two (2005; 2011). A
similar code of colours was applied to assess an initial impact of the measures identified. The
blue colour represents the neutral solutions, while green stands for the compatible solutions
which pose no special consequences in their implementation. The solutions under the yellow
group are most likely to be compatible, but this must be confirmed in detail. The intrusive
solutions, which are disruptive and must be avoided, are represented under the red colour.
The scheme in table 18 presents this framework which is provisionally fulfilled. This proposal
will be further analysed in chapters six and seven, where it will be applied to the specific
characteristics of Oporto’s traditional buildings.
4.5 - Conclusions
The approach to upgrade the energy efficiency of traditional buildings is consensually based on
two major areas which can be called ‘hardware’ (the buildings fabric and all the physical
related elements) and ‘software’ (building services, equipment and household behaviour). Also
stressed is the priority given to the improvement of the energy conservation of the envelope,
which further enhances any behavioural or equipment upgrade that otherwise may turn out to
be ineffective. The introduction of renewables must come afterwards and be handled carefully
in order to avoid damaging the historic city’s significance.
Also consensual is the approach for traditional buildings energy efficiency improvement found
in the literature, with special focus on the consistent research produced in the United Kingdom
covering Georgian, Victorian and Edwardian architecture. This framework is also organised
under several upgrade levels, according to the easiness and the feasibility of the
implementation of the diverse solutions, which are crucial to take into account when dealing
with rented buildings.
It was also verified that the different approaches covering the integral building refurbishment
or performed at home level, highly influenced by the economic feasibility of the solutions.
Regarding the ownership framework of Oporto's traditional buildings and the economic
constrains of the households, the focus must likely be set on the solutions that address the
home level and may be executed by the tenants themselves and thus have a high potential of
The investigation of energy efficiency measures in the traditional buildings in Oporto World Heritage Site: Joaquim Flores
The most usual and effective measure to improve energy efficiency in buildings, is widely
pointed out in literature to be the insulation of the envelope. At the same time, the envelope
is also the most vulnerable element of traditional buildings, as heritage constraints limit the
changes it can be subject to, both at building and site scale.
The specific measures identified to deal with the energy efficiency refurbishment of traditional
buildings can be summarised as follows:
- Use of ‘low cost’ solutions (draught-proofing, curtains and inner shutters);
- Improvements in the insulation and draught-proofing of the building envelope (roof,
walls, floor, windows and doors);
- Taking advantage of high thermal mass and increased use of passive solutions (natural
lighting, solar gains, natural ventilation);
- Promotion of local energy production from renewables (solar thermal, solar PV, micro-
wind, biomass boilers and heat pumps);
- Promotion of efficient district transformation of energy (co-generation);
- Using the most efficient possible heating, ventilation, air conditioning (HVAC) and
lighting systems;
- Increasing the households’ awareness of efficient and optimised use of energy in
dwellings (smart-metering);
The solutions identified were further crossed with the consequences they posed to the
significance of traditional buildings and coded into a four colours scheme. This must be
confirmed in chapter six and seven, when addressing specifically Oporto’s traditional buildings.
Moreover, this overall scheme will be the base for performing the building simulations in
chapter eight.
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