Thermal rehabilitation of
buildings
MASTER ERASMUS MUNDUS
WAVES/MEAECS
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
COURSE: Acoustic and Energetic Rehabilitation
Strategies
TOPIC: ENERGETIC REHABILITATION OF
BUILDININGS
GENERAL THEORY AND TERMINOLOGY
Andreia Pereira
E-mail: apereira@dec.uc.pt
Department of Civil Engineering
University of Coimbra
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Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
PORTUGUESE REALITY
(EXAMPLE)
Source: The future in efficiency and sustainability of buildings, Paulo Santos , ADENE, 2022
2
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
PORTUGUESE REALITY
Source: The future in efficiency and sustainability of buildings, Paulo Santos , ADENE, 2022
3
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
PORTUGUESE REALITY
4
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
PORTUGUESE REALITY
Source: The future in efficiency and sustainability of buildings, Paulo Santos , ADENE, 2022
5
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
PORTUGUESE REALITY
Source: The future in efficiency and sustainability of buildings, Paulo Santos , ADENE, 2022
6
Thermal rehabilitation of
buildings
PORTUGUESE REALITY
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Thermal transmittance
Source: The future in efficiency and sustainability of buildings, Paulo Santos , ADENE, 2022
7
Thermal rehabilitation of
buildings
PORTUGUESE REALITY
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Opportunities to improve energy efficiency
Source: The future in efficiency and sustainability of buildings, Paulo Santos , ADENE, 2022
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Thermal rehabilitation of
buildings
General theory and therminology
Energy Efficiency in buildings
1.1 - Thermal comfort in buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.2 - Heat and mass transfer phenomena
1.3 - Thermal transmittance of opaque elements
1.4 - Thermal bridges
1.5 - Thermal transmittance of windows
1.6 - Thermal transmission of elements in contact with the ground
1.7 - Heat transfer coefficient by transmission
1.8 – Heat transfer by ventilation
1.9 – Solar energy transmission through glazing systems
1.10 – Thermal inertia
1.11 – Building envelope
1.12 – Building surface condensation and rehabilitation strategies
1.13 – Technical systems
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Thermal rehabilitation of
buildings
1.1 – Thermal comfort in buildings
THERMAL CONFORT DEPENDS ON SEVERAL FACTORS
Environmental factors:
- Air temperature
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
- Radiation
The combined effect of these factors will define the degree
of comfort or thermal discomfort felt by people.
- Air flow (wind)
- Moisture
Human factors:
- Metabolism (Level of physical activity)
- Clothes
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Thermal rehabilitation of
buildings
1.1 – Thermal comfort in buildings
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Thermal balance
MVHR – Mechanical Ventilation with heat recovery
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Thermal rehabilitation of
buildings
1.1 – Thermal comfort in buildings
THERMAL CONFORT IN BUILDINGS
•
Which parameters can we control in the design stage of a building?
- Air temperature
- Surfaces temperature
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- Relative humidity (The ratio of water vapor in the air to the maximum amount of water vapor the air
can hold at a particular temperature)
- Ventilation
•
How can we control these parameters in the design stage of a building?
-
Stabilize temperature– use thermal mass (thermal inertia), thermal insulation and bioclimatic
guidelines in the design of the building (e.g orientation, layout and location, window shading)
-
Stabilize surface temperature- use thermal insulation, applied continuously
-
Guarantee a minimum ventilation – through natural ventilation, mechanical ventilation, mixed
ventilation
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Thermal rehabilitation of
buildings
1.1 – Thermal comfort in buildings
CLIMATE
•
EXAMPLE: PORTUGAL
Classification Köppen-Geiger
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•
In most of the mainland territory the climate is temperate
continental, Type C, checking the subtype Cs (A
temperate climate with dry summer) and the following
varieties:
•
Csa, Warm temperate climate (C) with dry (s) and hot
summer (b)
•
Csb, Warm temperate climate (C) with dry (s) and mild
summer.
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Thermal rehabilitation of
buildings
1.1 – Thermal comfort in buildings
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INSIDE THE BUILDING
•
EXAMPLE: PORTUGAL
•
Which reference values are considered to be comfort conditions in dwelling?
Portuguese legislation assumes the following reference indoor environment conditions (set point
temperatures):
- Winter season – Tair = 18ºC (HR=50%) e Rph ≥ 0,5 ren./h (air renovations per hour)
- Summer season – Tair = 25ºC (Rph ≥ 0,6 ren./h)
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Thermal rehabilitation of
buildings
1.2 - Heat and mass transfer phenomena
- Heat transfer between two points of an element acours when there is a diference of temperatures;
-
Heat transmission is always in the direction of the element with the highest temperature to the one
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with the lowest temperature;
-
Heat transfer is done with energy conservation, that is, the amount of heat that the hottest
element gives is always equal to the amount of heat that the coldest element receives;
Three different heat transmission mecanisms:
- Condution (1)
- Convection (2)
- Radiation (3)
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Thermal rehabilitation of
buildings
1.2 - Heat and mass transfer phenomena
Heat Transfer by conduction
Heat is transferred that way between solids at different temperature in
contact with each other and between points at different temperature
within the same solid.
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Fourier´s law

Thermal conductivity (W/mºC)
Q Heat flow (W)
Area (m )
A
Temperature (ºC)
T
Q / A Heat flux (W/m )
Exterior
(Te)
Interior
(Ti)
2
T1
T2
2
T / x
Temperature gradient ( ºC/m)
x / 
Thermal resistance (m2ºC/W)
L
With Ti > Te
(Winter)
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Thermal rehabilitation of
buildings
1.2 - Heat and mass transfer phenomena
Heat transfer by conduction
Exterior
(Te)
Interior
(Ti)
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T1
T2
L
Com Ti > Te
(Winter)
Materiais
 / L - Thermal resistance (m2ºC/W)

(W/mºC)
Steel
50
Concrete
2
Ceramic
0,69
Granite
2,8
Extruded
polystyrene (XPS)
0,037
Rockwool
0,040
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Thermal rehabilitation of
buildings
1.2 - Heat and mass transfer phenomena
Heat transfer by convection
Heat transmission between fluid and surface due to fluid flow
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Newton´s law for coolling:
Heat flux by convection (W)
Thermal transmittance by convection (W/m2ºC)
Tf
Transmission surface (W/m2ºC)
Surface temperature (ºC ou K)
Ts
Temperature of the fluid (ºC or K)
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Thermal rehabilitation of
buildings
1.2 - Heat and mass transfer phenomena
Radiation
Heat transmission between two bodies that emit and absorb
electromagnetic radiation
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Stefan-Boltzmann law:
Heat flux by radiation (W)
Emissivity of the emitting surface
Transmission area
Stefan – Boltzmann Constant
Temperature od the radiating element and of the receiving element
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building elements
Global heat transfer assuming one directional flux and steady state regime
Thermal transmittance
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U
1
Rsi   Ri  Rse
External surface resistance
Rse 
1
hconv ,e  hrad ,e
Element thermal resistance
Q  UA  Ti  Te 
ISO 6946 - Building components and building elements - Thermal
resistance and thermal transmittance - Calculation methods
Ri 
Li

Internal surface resistance
Rsi 
1
hconv ,i  hrad ,i
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Global heat transfer assuming one directional flux and steady state regime
Thermal transmittance
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U
1
Rsi   Ri  Rse
The values under “horizontal” apply to heat flow
directions ±30° from the horizontal plane
ISO 6946 - Building components and building elements - Thermal
resistance and thermal transmittance - Calculation methods
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Evaluation of the thermal conductivity of homogeneous materials
(W/mºC)
Standards:
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EN12667, EN12664, EN12939
Methods:
Guarded hot plate (ISO 8302)
Heat Flow Meter (ISO 8301)
- Tabulated values – ISO 10456
- Manufacturers
Ri 
Li

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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Evaluation of the thermal conductivity of homogeneous materials (W/mºC) – Influence
of thickness
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XPS (Values of Danosa manufacturer)
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Common thermal insulation materials
Rigid sprayed
Polyurethane foam =>
≈ 0.040 W/(mºC)
Mineral wool (high
density) =>
≈ 0.040 W/(mºC)
Agglomerated
polyurethane foam =>
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≈ 0.040 W/(mºC)
Agglomerated
expanded cork=>
Rigid polyisocyanurate foam
(P.I.R.)
≈ 0.023 a 0.03 W/(mºC)
≈ 0.045 W/(mºC)
Expanded
Polystyrene(EPS) =>
≈ 0.040 W/(mºC)
Thermal insulation plaster
≈ 0.05 a 0.07 W/(mºC)
Cellular concrete or with
Extruded Polyestyrene
(XPS) =>
≈ 0.035 W/(mºC)
lightweight aggregates =>
≈ 0.15 a 0.30 W/(mºC)
… others
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Thermal conductivity of homogeneous materials
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(ITE 50 – LNEC)
…
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Thermal resistance of non- homogeneous layers (W/mºC)
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Evaluation of the thermal resistance of
elements/components (m2ºC/W)
Heat flux is not
unidirectional!!!
-
Simplified methods (ISO 6946)
-
Numerical methods (ISO 10211)
-
Experimental methods: “Hot Box” method (ISO
12567-1)
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Thermal resistance of non- homogeneous layers (ITE 50 LNEC)
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THERMAL RESISTANCE OF PORTUGUESE SINGLE BRICK WALLS
R (m2ºC/W)
THERMAL RESISTANCE OF PORTUGUESE DOUBLE BRICK WALLS
R (m2ºC/W)
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Thermal resistance of non- homogeneous layers (ITE 50 LNEC)
THERMAL RESISTANCE OF PORTUGUESE SINGLE BRICK WALLS
R (m2ºC/W)
There are other manufacturers that display
solutions with better results : Ex.
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Thermal resistance of non- homogeneous layers (ITE 50 LNEC)
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Thermal resistance of slabs
with pre-stressed beams with
ceramic bricks (m2ºC/W)
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Thermal resistance of unventilated air layers with high emissivity surfaces (ISO 6946):
- An unventilated air layer is one in which there is no express provision for air flow through it.
- An air layer having no insulation between it and the external environment, but with small openings to the external environment,
shall also be considered as an unventilated air layer if these openings are not arranged so as to permit air flow through the
layer and they do not exceed:
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- 500 mm2 per metre of length (in the horizontal direction) for vertical air layers, and
- 500 mm2 per square metre of surface area for horizontal air layers.
The values under “horizontal”
apply to heat flow directions
±30°
from the horizontal plane.
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Thermal resistance of a well ventilated air layer with high emissivity surfaces (ISO 6946):
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- Well-ventilated air layer is one for which the openings between the air layer and the external
environment are equal to or exceed:
- 1 500 mm2 per metre of length (in the horizontal direction) for vertical air layers;
- 1 500 mm2 per square of metre of surface area for horizontal air layers.
The total thermal resistance of a building component containing a well-ventilated air layer shall be
obtained by disregarding the thermal resistance of the air layer and all other layers between the air
layer and external environment, and including an external surface resistance corresponding the
corresponding value of Rsi from Table 7 may be used.
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Telha cerâmica
Example:
Consider the following figure of a building and
determine
the
thermal
transmistance
of
Desvão fortemente ventilado
U4
the
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constructive solutions U1, U2, U3 e U4
1
U *
Rse   Ri  Rsi
Laje em betão armado com
0,20 m de espessura
Exterior
U3
Reboco interior com
1,5 cm de espessura
Tijolo de 0,07 m
U2
Viga em betão armado com 0,25 m
de espessura
Reboco exterior com 2 cm de espessura
Caixa de estores em XPS (4 cm de espessura
na face interior e 3 cm na face exterior)
Reboco interior com 1,5 cm de espessura
Alvenaria de
tijolo de 0,15 m
U1
Alvenaria de
tijolo de 0,11 m
Interior
Isolamento térmico em XPS com
4 cm de espessura (+2 cm cx. ar)
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance of building opaque elements
Adicional data:
Material or element
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Screed (Concrete with EPS aggregates)
Plaster
mortar with 2000 kg/m3
Reinforced concrete
Thermal insulation mat. (XPS)
Hollow ceramic brick with 0,11m
Hollow ceramic brick with 0,15m
Hollow ceramic brick with 0,07m
Plasterboard
Ceramic material
Thermal
condutivity, 
(W/mºC)
0,28
0,18
1,3
2
0,037
0,25
0,6
2
Thermal resistance Rt (m ºC/W)
0,27
0,39
0,19
-
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Thermal rehabilitation of
buildings
1.3 - Thermal transmittance of building opaque elements (elements with ventilated coatings)
=> consider Rsi in the exterior side (but not consider Ri of the exterior coating)
Does not include the
exterior coating
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If the exterior linning is airtight
then:
Include exterior
coating
Ventilated Wall
If the exterior linning is
airtight then:
Traditional
roofs
Include exterior
coating
It does not include the
roof tile
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance building opaque elements
Global heat transfer assuming one directional flux and steady state regime
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Temperature diagram
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Thermal rehabilitation of
buildings
1.3 – Thermal transmittance building opaque elements
 In most zones of building envelope, heat transfer may be
assumed unidirectional
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U [W/(ºC.m2)]
x area
Exterior
(Te)
Interior
(Ti)
 In certain zones of the building envelope or at corners or
junctions the heat flux can be bidimensional or even
tridimentional
Ψ [W/(ºC.m)] x lenght
Com Ti > Te
(Winter season)
Interior
(Ti)
Exterior
(Te)
With Ti > Te
(Winter season)
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
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Thermal bridge is a localised area of the building envelope where the heat flow is different (usually
increased) in comparison with adjacent areas. This is typically where there is either a break in the
insulation, less insulation or the insulation is penetrated by an element with a higher thermal
conductivity.
The effects of thermal bridges are:
•Altered, usually decreased, interior surface temperatures; in the worst case this can lead to
moisture penetration in building components and mould growth.
•Altered, usually increased, heat losses.
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Material (planar) thermal bridges
Shutter boxes
Beam
LTB
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PTB
PTB
Column
Portuguese thermal code defines a
requirement for these elements:
Ushutter box≤ 0.9 W/(ºC.m2)
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Material (Planar) thermal bridges – PORTUGUESE
EXAMPLE
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Corrections before 2006
?
Corrections after 2006 (changes
in thermal requirements)
Ubeam, Column ≤ 0.9 W/m2ºC
Column
U ≤ Umax
Beam
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Material (Planar) thermal bridges – PORTUGUESE
EXAMPLE
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Concrete shutter box
Shutter box in concrete with insulation improvement
performed in its interior (thermal and acoustic)
EPS shutter box
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Strategy to reduce thermal and acoustic
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Repeating thermal bridges / Point
U≈0.5
bridges
U≈0.7
Lightweight partitions (ex. between conditioned and unconditioned spaces)
Roof in sandwish solution
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Linear thermal bridges (LTB)/geometrical thermal bridge - is a localised
area of the building envelope where the heat flow is different (usually increased) in
comparison with adjacent areas, located in the junctions between elements (where it is
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not possible to measure a area, but it is possible to measure a lengh)
LTB
MTB
Zones with LTB:
-
Walls
-
Floors
-
Roofs
-
Windows
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
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Linear thermal bridges (LTB) –construction details for portuguese construction
Junction between facade wall
and intermediate floor
Junction between two
vertical walls
Junction between facade and
roof
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Linear thermal bridges (LTB) –construction details for portuguese construction
?
?
Junction between the facade and balcony
com varanda
Junction between the facade
and the shutter box
Junction between facade and
openings
Junction between facade and floor
over unconditioned space
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Lineal thermal transmittance (for LTB) – W/mºC
 (W / m2 º C )
Calculation performed according to:
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•
Numerical Calculation (expected uncertainty 5%)
The linear thermal transmittance, Ψ, shall be calculated in accordance with ISO 10211.
•
Thermal bridges catalogs (expected uncertainty of 20%)
Calculation performed according to the ISO 14683 - Linear thermal
transmittance — Simplified methods and default values
•
Default values (expected uncertainty of 50%)
Calculation performed according to the ISO 14683 - Linear thermal
transmittance — Simplified methods and default values
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
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Lineal thermal transmittance (for LTB) – Example of a catalog
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Lineal thermal transmittance –
Example of default values
Table 07 – Tabulated values of the linear
thermal transmittance Ψ [W/(m.ºC)]
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(portuguese legislation / –DL n101-D2020)
Insulation system of the wall
Insulation in Insulation in Insulation in
the interior
the exterior the air-gap
Type of connections
Façade with ground floor
Façade with floor
over exterior or
Insulation
unconditioned space
bellow floor
0.80
0.75
0.70
0.55
0.80
0.75
Insulation
over the
floor
Façade with intermediate floor (1)
0.10
0.50
0.34
0.60
0.15 (2)
0.50 (3)
0.60
0.10 (4)
0.60
0.70
0.55
0.60
1
0.80
1
0.10
0.40
0.50
0.10
0.10
0.10
0.25
0.25
0.25
0.30
0.30
0.30
Façade with balcony (1)
Façade
Insulation bellow roof
with roof
slab
Insulation over roof
slab
Using the catalog =>0.39 and 0.82 W/(ºC.m) Two vertical walls with salient angle
Using default values => 2x0.5=1.0
Façade with windows
(1) The value in table relate to half of the
loss caused by the connection.
(2) (3) (4) Increase when there is a
suspended ceiling in: (2) 25%; (3) 50%; (4)
70%.
Insulation
is in
contact
with
window
Insulation
does not
contact
window
Zone of blind box
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
Direct heat transfer coefficient by transmission to the external environment:
H ext  Ui . Ai   j .L j W /º C 
j
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i
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Thermal rehabilitation of
buildings
1.4 – Thermal bridges
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Example
Consider the façade represented in the following figure.
Assume that the façade length is 10m, that the temperature
gradient between the indoor and outdoor environment is 20ºC,
that the beam bead has a height of 0.25m and that the
thermal transmission coefficients of the double brick wall and
the plane thermal bridge are respectively 0.55W/(m2ºC) and
0, 72W/(m2ºC).
Evaluate the total heat transfer through
the facade.
Junction between
facade and roof
Junction between facade
wall and intermediate
floor
Junction between facade
wall and ground floor
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
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Components
Wood
Aluminium
PVC
Without and with thermal break –
Two profiles connected with
polyamida material
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
Heat gains and losses through windows
There are 3 types of energy flows through glazed spans:
•
“Non-solar" heat transfer– related with transmission in the
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form of conduction, convection and radiation;
•
Solar gains in the form of radiation;
• Ventilation and infiltration heat transfer
(air exchanges).
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
Factors that influence thermal transmittance
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- Glass (thickness, airgap, gas inside the airgap,
presence of low emissivity coatings, sealants
material)
- Frame
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
Glass
low emissivity coatings
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Solar energy spectrum is composed of different parts determined by their wavelength:
- Ultraviolet (UV) light –responsible for burning the skin and materials fading
- Visible light
- Infrared (IR) light – transmitted as heat into a building
Low-E coatings have been developed to
minimize the amount of ultraviolet and
infrared light that can pass through glass
without compromising the amount of visible
light that is transmitted.
https://glassed.vitroglazings.com/topics/low-e-demonstration
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
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Glass
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
Glass
If calculated, the double glass with air gap would be:
1
0.04  0.006 / 1  0.17  0.006 / 1  0.13
 2.84 W /(m 2 º C )
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UW 
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Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
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i) Default values => ITE 50 - LNEC
For:
- Wood windows
- Aluminium windows (with or without thermal
breack )
- PVC windows
Window with shutter
U wdn 
Un Uw
2
Window without shutter
=>
56
Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
ii) Detailed calculation (ISO 10077)
For “detailed calculation” how
can we obtain the coefficients?
iii) Experimental methods (ISO 12567-1 - Hot box)
Hot box
In this case the Uw refers only to the tested (i.e
with the dimensions and composition tested)
57
Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
For “detailed calculation” how
can we obtain the coefficients?
Glass:
ii) Detailed calculation (ISO 10077)
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Windows frame:
Linear thermal transmittances for current windows (ISO 10077-1:2010)
In the majority of the situations a
default value of Ψ is considered,
assuming the default values given
in the ISO10077-1:2010
58
Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of
windows
Calculation for each window type and
configuration
Calculation based on tabled values
(manufacturer):
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Uf , Ug e Ψ
Average day-night
Blinding devices allow to increase
thermal resistance
ISO 10077-1
Types of protection
Window with blinding
system activated
Metal rulers blinds
Window without
blinding system
activated
Ruler shutters on
wood or plastic without
foam filling
Ruler shutters on
plastic with foam filling
Opaque wood covers
ΔR
(m2°C/W)
0.09
0.12
0.13
0.14
59
Thermal rehabilitation of
buildings
1.5 – Thermal transmittance of windows
Example
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Consider the window of the following figure:
a) Calculate the thermal transmission coefficient of the
window, taking into account the following data:
Exterior dimensions
Total area, Aw (m2)
Glazing area (Ag)
Frame Area (Af)
Visible perimeter of the glazing
Thermal transmittance of the frame (W/m2°C)
1. 23 mX1.48m
1.82
1.15
0.67
6.36
2.5
Thermal transmittance of the glass (W/m2°C)
1.1
Linear thermal transmittance (W/m°C)
0.11
With "watertight" blind situated outside, even
disregarding the contribution of the material of
the blind=>
UW 
1.15 1.1  0.67  2.5  6.36  0.11
 2.00 W /( m 2 º C )
1.15  0.67
60
Thermal rehabilitation of
buildings
1.6 – Ground thermal transmittance
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Calculation is performed according to:
Exterior or
unconditioned
space
ISO 13370- Thermal performance of buildings – Heat
transfer via the ground – Calculation method
•
Detailed modelling
•
Simplified calculation
•
Default values
61
Thermal rehabilitation of
buildings
1.6 – Ground thermal transmittance
Steady-state ground heat transfer coefficient
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
H g  U bf . A  U bw .P. z
 W/ºC
is the average depth of the
basement floor [m]
Thermal
is the length of the wall in
transmittance of the
contact with the soil [m]
buried floor
(W/m2ºC)
Surface area of the floor,
measured in the interior
(m2)
Surface area of the floor, measured in the
interior (m2)
B’ – Chracteristic dimension
Ap – Ground floor area of the floor slab
P – Perimeter of the floor slab
62
Thermal rehabilitation of
buildings
1.6 – Ground thermal transmittance
Thermal transmittance of buried floors – Example of default values
Table 3 – Thermal transmittance of buried floors with or without continuous insulation, Ubf [W/m2ºC]
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Rf – Thermal resistance of all floor
layers except for thermal surface
resistances, [m2.ºC)/W]
For z≤0,5m and Rf<0,5 =>
Ubf=1,15xU(Rf=0,5)
For z>0,5m and Rf<0,5 =>
Ubf=1,10xU(Rf=0,5)
63
Thermal rehabilitation of
buildings
1.6 – Ground thermal transmittance
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Thermal transmittance of buried walls – Example of default values
64
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
According to the EN ISO 13789 (Thermal performance of buildings — Transmission and ventilation
heat transfer coefficients — Calculation method) the overall heat transfer coefficient is given by:
 W/ºC
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
H T  H D  H g  HU
HD
- Direct heat transfer coefficient by transmission to the
external environment:
Hg
- Steady state heat transfer coefficient by
transmission to the ground:
HU
- Steady state heat transfer through
unconditioned spaces
HU
HU
HD
Hg
65
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
Direct heat transfer coefficient by transmission to the external environment:
H D  Ui . Ai   j .L j
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
i
j
HU
HD
Hg
HU
66
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
Steady state heat transfer coefficient by transmission to the ground:
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
H g  U bf . A  U bw .P. z
 W/ºC
is the average depth of the
basement floor [m]
Thermal
is the length of the wall in
transmittance of the
contact with the soil [m]
buried floor
2
(W/m ºC)
Surface area of the floor,
measured in the interior
(m2)
Thermal
transmittance of the
buried wall
(W/m2ºC)
HU
HD
Hg
HU
67
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Steady state heat transfer through unconditioned spaces


HU  btr ,U  Ui . Ai   j .L j 
j
 i

btr,U - adjustment factor of the heat transfer between
the conditioned and unconditioned spaces with value
btr,U≠1 if the temperature of the unconditioned room is
not equal to the temperature of the external
environment
HU
HD
Hg
HU
68
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
Steady state heat transfer through unconditioned spaces
btr,u - adjustment factor
- Depends on the degree of ventilation of
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
the space
btr ,U V ,Ventilation, Ai / Au 
Default values– EN ISO 13789
Connections and openings
permanently open
Connections well-sealed and unopened
elements (ventilation)
69
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
Steady state heat transfer through unconditioned spaces
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
btr,u - adjustment factor
- Building with 5 floors;
-2 apartments and a common walkpath in each floor;
- Common circulation has all the connections between elements
well sealed, without ventilation openings permanently open;
- hight : 2.40 m.
70
Thermal rehabilitation of
buildings
1.7 – Heat Transfer Coefficient by transmission
Steady state heat transfer through unconditioned spaces
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
btr,u - adjustment factor
71
Thermal rehabilitation of
buildings
1.8 – Heat Transfer by ventilation
It is necessary to evaluate the ventilation rate Rph and guarantee a minimum value (Portuguese requirement
a RPH ≥ 0.4)
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Natural ventilation
Mechanical ventilation
72
Thermal rehabilitation of
buildings
1.8 – Heat Transfer by ventilation
Examples of Acoustic performances of ventilation grids
Standard autoregulable Grids
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Natural ventilation
Acoustic autoregulable Grids
With silencer
73
Thermal rehabilitation of
buildings
1.8 – Heat Transfer by ventilation
It is necessary to evaluate the ventilation rate Rph and guarantee a minimum value (Portuguese requirement
a RPH ≥ 0.5)
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Natural ventilation
74
Thermal rehabilitation of
buildings
1.8 – Heat Transfer by ventilation
- Air permeability measures a glazed unit’s ability to prevent air from passing through.
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
- It is measured on a scale of class 1 to class 4.
- Class 4 is the highest level of prevention.
- Testing a glazed unit for air permeability is essential.
- Air permeability is also important for acoustic performance of windows.
75
Thermal rehabilitation of
buildings
1.9 – Solar energy transmittance of the glazing system
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Solar transmittance of the glass: ratio of solar heat gain through a
window to the solar radiation striking the outer surface, for a given
incidence angle (usually perpendicular to the glazing surface) – a
solar transmittance of 0,3 (or 30%) decreases in 70% the heat solar
gains .
gV 
Solar radiation transmitted
Solar radiation incident
Solar energy transmittance is also called solar
heat gain coefficient or solar factor
In general the majority of the manufacturers display the value of g and U:
Solar control
coating reflects the
heat from the sun
back to the
environment
76
Thermal rehabilitation of
buildings
1.9 – Solar energy transmittance of the glazing system
Fator solar do vidro para uma incidência normal ao vão, g,vi
-
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
-
Manufacturer
Default values (ex: Portuguese thermal
regulation)
Calculation using the method provided in the
standard EN 410
77
Thermal rehabilitation of
buildings
1.9 – Solar energy transmittance of the glazing system / Solar protections
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
SOLAR FACTOR OF THE
GLAZING WITH SOLAR
PROTECTIONS- g Tvc
78
Thermal rehabilitation of
buildings
1.9 – Solar energy transmittance of the glazing system / Solar protections
Besides the solar factor of
the glass it is necessary to
consider the influence of
the prototections such as
shutters or element
shading devices.
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
overhangs
F0 – Shading provided by
overhangs
Fh – Shading
provided by
landscape features )
Blinds or louvers
Ff – Shading provided
by vertical fins
79
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.10 – Solar energy transmittance of the glazing system / Solar protections
The effect of shading devices can be assessed using:
- Sun path diagrams
-
Default values
-
Computer modelling
80
Thermal rehabilitation of
buildings
1.10 – Thermal inertia
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Thermal inertia of the building: it is the capacity of the building to absorb heat in its structure
(walls, slabs, etc.) during the hottest periods and release it when it is colder, keeping the
interior temperature more stable throughout the day (it cools down when air temperature is
higher and heats when air temperature is lower).
Evolution of exterior and interior temperatures in a building
81
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.10 – Thermal inertia
- Linings with thermal resistance
82
Thermal rehabilitation of
buildings
Color of the facade
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.10 – Thermal inertia
83
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.11 – Building envelope
84
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.11 – Building envelope
Floor
Ceiling
85
Thermal rehabilitation of
buildings
1.12 – Building surface condensation
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Building surface condensation / Associated Pathologies
86
Thermal rehabilitation of
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
1.12 – Building surface condensation
Without condensation
With condensation
Condensation in thermal bridges
87
Thermal rehabilitation of
buildings
1.12 – Building surface condensation
Inside buildings, the cooling takes place in a localized manner near the facings of the exterior
walls, particularly in areas where there are thermal bridges, which can be detected by infrared
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
thermography.
Example of T and HR measurements using a
thermohygrometer
inside a room with
Fluxo de calor
widespread condensation on walls and
clothing =>
88
Thermal rehabilitation of
buildings
1.12 – Building surface condensation
Evaluating surface condensation
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Compare internal surface temperature with dew temperature
Fluxo de calor
If outdoor and indoor temperatures remain constant and heat flow is unidirectional => The heat flux
passing from the interior to the exterior environment is equal to the heat flux passing in any
intermediate layer of the wall
89
Thermal rehabilitation of
buildings
1.12 – Condensation in buildings/
Rehabilitation strategies
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Thermography is a very useful tool in detection of
this and other manifestations of humidity presence
Eliminate condensation phenomenon
 Increase ventilation
 Reduce water vapor production
 Room heating
 Thermal insulation reinforcement
Repair of affected zones (with molds)
 washing and sterilization or simple water wash;
 Perfect drying;
 Fungicide application;
 Brushing extraction of the fungicide product (3
days later)
 General painting of the surface (or, at the limit,
the replacement of the covering).
90
Thermal rehabilitation of
buildings
1.12 – Condensation in buildings/
Rehabilitation strategies
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
- Applying thermal insulation
91
Thermal rehabilitation of
buildings
1.12 – Condensation in buildings/ Rehabilitation strategies
Correction of thermal bridges in the facade
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
LTB
?
At least with reinforced
plaster, but….
More eficient solutions => Placing insulation in the exterior face of the walls
ETICS -External Thermal Insulation
Composite System
Ventilated facade
92
Thermal rehabilitation of
buildings
1.12 – Condensation in buildings/ Rehabilitation strategies
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Correction of thermal bridges in the facade
External thermal insulation with rigid independent coating plates and airgap (ventilated)
93
Thermal rehabilitation of
buildings
1.12 – Condensation in buildings/ Rehabilitation strategies
Correction of thermal bridges in the facade
Parede de suporte
Argamassa de colagem
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Placa de isolamento térmico em EPS
 ≈ 0.04 W/(ºC.m2)
Bucha de fixação mecânica da placa de isolamento
1ª camada de argamassa de base
Fluxo de calor
Armadura em fibra de vidro
2ª camada de argamassa de base
 ≈ 0.05 a 0.07 W/(ºC.m2)
Primário de regularização
=> Require more
Acabamento colorido
thickness to obtain more
thermal insulation
ETICS -External Thermal Insulation
Composite System
Single wall with insulation applyed
in the exterior face– lightweight
thermal insulation mortars (applyed
using projection)
94
Thermal rehabilitation of
buildings
1.13 - Technical systems
Systems for heating water
Term.
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
• Gas water heater
• Electric Termoacumulator
Cal4
• Gas wall boiler (Cal1), gas floor boiler (Cal2), diesel floor
boiler (Cal3) and pellet boiler (Cal4).
Cal1
Cal2
•
Cal3
Through heat pump, eventually associated with geothermy
• Solar thermal systems
•
Central Production Facilities
95
Thermal rehabilitation of
buildings
1.13 - Technical systems
Technical installations in current
buildings
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
Heating of sanitary water
Environment heating/cooling
96
Thermal rehabilitation of
buildings
1.13 - Technical systems
Cal1
Cal2
Boilers
(for heating of sanitary water, for heating
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
environment or for both)
•
Gas wall boiler (Cal1)
•
Gas floor boiler (Cal2)
•
Diesel floor boiler (Cal3)
•
Pellet boiler (Cal4)
•
Wood-burning boiler (Cal5)
Cal4
Cal3
Cal5
97
Thermal rehabilitation of
buildings
Renewable Energy Technical Systems
Mestrado Integrado em Engenharia Civil – Acústica Aplicada
(Mandatory for all new building and major rehabilitations, with rare exceptions)
Solar thermal collectors
Photovoltaic panels (for
electricity production)
Other renewable
energies…
Boilers pellets or wood
Wind turbine (for electricity
production)
98