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Assessing the impact of climate change on energy retrofit of alpine historic buildings: consequences for the hygrothermal performance


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Climate change will affect future hygrothermal performance of buildings. This could lead to higher risks regarding energy optimization, thermal comfort and historic building conservation depending on the local climate, building construction and retrofit solutions adopted. This paper explores the risks brought by climate change on a typical residential historic building of South Tyrol. The results obtained show that, although the climate warming will reduce the future heating energy demand, an improvement of buildings’ energy performance will still be necessary to increase sustainability and ensure their continued use. Natural ventilation would suffice to prevent overheating in the studied location, but a further analysis is needed for warmer alpine regions. Regarding the moisture-related risks for the historic construction, mould growth should be considered when retrofitting a wooden wall and frost damage should be carefully studied in the case of sandstone walls.
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IOP Conference Series: Earth and Environmental Science
Assessing the impact of climate change on energy retrofit of alpine
historic buildings: consequences for the hygrothermal performance
To cite this article: L. Hao et al 2020 IOP Conf. Ser.: Earth Environ. Sci. 410 012050
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Assessing the impact of climate change on energy retrofit of
alpine historic buildings: consequences for the hygrothermal
L. Hao1,2, D. Herrera1, A. Troi1, M. Petitta1, M. Matiu1 and C. Del Pero2
1 Eurac Research, Bolzano, Italy
2 Department of architecture, built environment and construction engineering,
Politecnico di Milano, Italy
Corresponding author:
Abstract. Climate change will affect future hygrothermal performance of buildings.
This could lead to higher risks regarding energy optimization, thermal comfort and
historic building conservation depending on the local climate, building construction and
retrofit solutions adopted. This paper explores the risks brought by climate change on a
typical residential historic building of South Tyrol. The results obtained show that,
although the climate warming will reduce the future heating energy demand, an
improvement of buildings’ energy performance will still be necessary to increase
sustainability and ensure their continued use. Natural ventilation would suffice to
prevent overheating in the studied location, but a further analysis is needed for warmer
alpine regions. Regarding the moisture-related risks for the historic construction, mould
growth should be considered when retrofitting a wooden wall and frost damage should
be carefully studied in the case of sandstone walls.
1. Introduction
The severity and impact of climate change has been rigorously assessed in scientific literature.
According to IPCC’s (Intergovernmental Panel on Climate Change) Fifth Assessment report [1], the
increase of global surface temperature by the end of 21st century is expected to exceed 2.6 - 4.8
compared to 1986-2005 in the most pessimistic scenario. Together with this temperature increase,
extreme climate events are expected to occur more frequently. For instance, the length, frequency and
intensity of heat waves1 might increase in large parts of Europe, Asia and Australia. It is also likely that
“extreme precipitation events will become more intense and frequent in many regions” [1]. The EEA
(European Environment Agency) also confirmed this tendency [2]. However, the changes among
different regions will not be uniform. For instance, precipitation will likely decrease in many mid-
latitude regions while increase in other regions. Studies carried out in Alpine context have confirmed
serious challenge of climate change. The 2018 South Tyrolean Climate Report [3] indicates that the
temperature increase during summer periods will be up to 5℃ under the most pessimistic scenario by
2100. Besides the temperature increase, extreme precipitations will become more frequent in this Alpine
Increased temperatures and changed rain patterns might have great impacts on historic buildings in
terms of energy use, indoor climate and moisture safety of buildings’ envelope. When combined with
retrofit solutions, several risks could threat the conservation and efficiency of historic buildings [4]:
1) Inadequate sizing of HVAC systems leading to energy inefficiency or discomfort.
2) Unsuited retrofit solutions and occupant behaviour combined with increased temperatures in
summer might weaken the original passive cooling strategies and exacerbate the risk of overheating.
3) Moisture related risks are likely to increase if more extreme precipitations are found in
combination with retrofit interventions that limit the drying capacity of walls.
1 Heat waves are excessively hot periods that last for several days or longer, which will cause the overheating of human body.
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The retrofit of historic buildings is gaining an increasing attention in Europe. In fact, historic
buildings constitute a considerable share of building stocks in Europe where more than 14% of existing
buildings were built before 1919, 12% were built between 1919 and 1945 [5], and more than 40% were
built before 1960 [6]. Most of these historic buildings have not undergone any energy retrofit. It is
estimated that the retrofit of European building stock constructed before 1945 could save up to 180 Mt
of CO2 within 2050 [5] and improve the thermal comfort of occupants. However, considering the
possible risks highlighted above, there is a need to investigate further aspects like the specific role of
thermal mass and natural ventilation in alpine historic buildings and their combined effect with a
changing climate. Additionally, the relationship between moisture dynamics in historic buildings, rain
pattern changes and retrofit solutions should be evaluated on regional basis. In conclusion, retrofit
solutions should be defined based on aforementioned knowledge and a clear awareness of future risks
to maximise energy efficiency, occupant thermal comfort and ensure a proper building conservation.
2. Methodology
The results presented in this study are based on numerical simulations carried out on a reference building
designed to be representative of Alpine historic residential buildings. Buildings performance is
simulated and compared before and after retrofit, analysing possible retrofit interventions, as well as in
present and future scenarios, using plausible forecasted future climatic conditions. In this paper,
building’s performance is assessed according to three parameters: energy demand, indoor comfort and
moisture safety of the envelope.
2.1. Reference building construction
The geometry of the reference building is based on (i) the results of the TABULA [7] dataset, for Italy
(Climate region E) and the province of Salzburg (Austria), (ii) the database and design guidelines
proposed by CasaClima for the province of Bolzano (Italy) [8], and a study of the building stock in the
Alpine region of Val Passiria (Italy) [9]. The building, a two-storey single family house with a living
room on the ground floor and three bedrooms on the first floor and a total conditioned area of 180 m2,
could be deemed a typical residential house of the Alpine region. Details of the geometry are presented
in Figure 1.
Figure 1 Geometry and construction of the reference building
The building construction and the retrofit solutions are defined based on literature and summary of
current practice in South Tyrol [10-12]. The building is constructed with stone masonry walls and
wooden pitched roof without any insulation. The main façade of the building (living room and
bedrooms) is oriented to the south, with timber framed windows and single glazing. The considered
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retrofit solutions are: 1) internal application of insulation on external walls, 2) roof and 3) ground floor,
as well as 4) substitution of single glazed windows with double glazing. Details of the original
construction and retrofit solutions are presented in Figure 1.
2.2. Future climate data
In order to assess future climatic conditions we used data from EURO-CORDEX initiative which
provide high-resolution regional climate change simulations [13]. Within EURO-CORDEX initiative,
the global climate projections from CMIP52 were dynamically downscaled for the European domain,
and here two Representative Concentration Pathways (RCPs), RCP4.5 and RCP8.5, were used. These
pathways represent two different scenarios, respectively intermediate scenario and business-as-usual
In the present study, we used the outputs of EURO-CORDEX: five general circulation models
(GCMs) and regional climate models (RCMs) combinations. In detail, they are CNRM-CM5 with
RCA4, IPSL-CM5A-MR with WRF381P, and EC-Earth (three different initial conditions: EC-Earth-
r3i1p1, r12i1p1, r3i1p1) with HIRHAM5, RCA4 and RACMO22E. These five global models are forced
by RCP4.5 and RCP8.5 respectively. Therefore, ten climate projections are established (5 GCM-RCM
combinations, and for each 2 emission scenarios RCP4.5 and RCP8.5). The model data have been bias-
corrected and downscaled for the city of Toblach in South Tyrol, Italy, using quantile mapping. Toblach
is selected with the consideration of its abundant precipitation, which may threat conservation of historic
buildings. Time series were extracted for precipitation, air temperature, humidity, wind speed, wind
direction and solar radiation. The daily meteorological time series were further disaggregated to hourly
data by open-source MEteoroLOgical observation time series DISaggregation Tool (MELODIST), see
Förster K et al. [14].
The climate projections of final ten models are compared with observed station data of Toblach, and
finally model IPSL-CM5A-MR-8.5 is adopted in this preliminary study considering its consistency with
observation data in term of temperature and precipitation. In the simulation, present scenario is defined
with the time span from 2011 to 2017, the longest time period available in the observational data set.
The time span of future scenario is from 2094 to 2100.
2.3. Computational tool and numerical models
2.3.1. Energy demand and indoor climate calculation models. Energy demand and indoor climate are
calculated using EnergyPlus 8.7.0 [15]. The heating energy demand for the building under climate and
retrofit scenarios is calculated on the basis of the temperature set point during heating period, while
indoor temperature and relative humidity (RH) in summer are calculated in free floating conditions,
without any mechanical cooling system.
The assumptions and variables used for the simulations are reported in Table 1. The occupancy,
lighting and electric appliances profiles are based on 2014 Building America House Simulation
Protocols [16]. Airtightness of the building envelope before retrofit is defined according to literature
review: 10 ac/h, at 50 Pa. In the literature, the average infiltration rate of 53 historic houses from Estonia,
Finland and Sweden is 8.43 ac/h, at 50 Pa [17]. In UK, the infiltration rate of 471 houses rages from 9.9
to 16.5 ac/h. When restricting the construction year from pre 1900 to 1949, the infiltration rate rages
from 10.5 to 16.5 ac/h [18]. The value after retrofit is defined according to CasaClima standard (A): 1.5
ac/h, at 50 Pa [8]. Ventilation rate is defined according to UNI 10339: 1995, based on an average
ventilation level of residential buildings with normal level of expectation. The ventilation rate is
calculated according to the occupants and area of the room in reference building. A scenario with
additional natural ventilation was also established to test the ability of night cooling in mitigating indoor
overheating. It is modelled by simplified ventilation calculations in EnergyPlus’s Wind and Stack Open
Area model. When the natural ventilation is trigged, the opening area of the window is defined as 50%
2 The fifth phase of the Climate Model Intercomparison Project
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Table 1 Assumptions and variables used for the simulations
Heating period
September 15thApril 15th
Heating set point
Occupants, lighting and
equipment profiles
Defined based on 2014 Building America House Simulation Protocols [16]
Infiltration rate -before retrofit
10 ac/h, at 50 Pa
Infiltration rate - after retrofit
1.5 ac/h, at 50 Pa [8]
Ventilation profile
Defined based on UNI 10339: 1995
Ventilation profile
additional ventilation
Wind and stack open area model
2.3.2 Moisture dynamic models. The hygrothermal performance of the retrofitted wall is calculated by
means of numerical simulation with Delphin 6.0. This simulation tool has been validated on several
aspects comparing predictions with measurements and tested in numerous studies [20-24].
Both the characteristics of the wall construction and internal and external climates have a significant
influence on the hygrothermal performance of the envelope. Table 2 presents the defined wall
characteristics and boundary conditions. Wind-driven rain (WDR) is the main source of the moisture
influencing the moisture dynamic across the wall. WDR is calculated according to EN 15927-3 [25],
where the wall annual index is an important parameter estimating the quantity of water impacting a wall
of any given orientation. It takes into account the topography, local sheltering and the type of building
and wall [25]. In the simulated reference building, the wall annual index is defined with following
assumptions: the reference building located in a farmland with boundary hedges (Terrain category II),
on flat ground, and it is a freestanding building with a distance of obstruction over 60 m.
Table 2 Parameters and values used in the hygrothermal simulations
Input parameter
Input distribution
Wall conditions
Wall orientation (degree from North°)
90 (East)
Wall annual index
Reduction coefficient of WDR
Outdoor boundary condition
Heat conduction
Convective heat conduction exchange coefficient: 12 [W/m2K]
Effective heat conduction exchange coefficient: 12 [W/m2K]
Vapour diffusion mass transfer coefficient
7.5e-09 [s/m]
Solar absorption coefficient
Long-wave emissivity
Indoor boundary condition
DIN EN 15026/WTA adaptive indoor climate model
Surface heat transfer coefficient
Convective + radiative: 8 [W/m2K]
Surface vapour diffusion coefficient
5e-06 [s/m]
2.4. Assessment models
2.4.1 Indoor comfort assessment. Indoor comfort is assessed according to EN 15251 [26], which defines
the comfort temperature range in free running buildings as a function of the outdoor temperatures. The
approach in the standard is valid for dwellings where occupants can adapt the indoor thermal conditions
through window operation or clothing arrangement. Thus, the assessment is carried out in the living
room during the occupied hours where occupants could apply adaptive actions.
2.4.2 Frost damage assessment. In this study, the risk of frost damage is identified when two criteria are
met: a) temperature is below freezing point of water in pores and b) the degree of saturation (S) reaches
to critical degree of saturation (Scrit). In Vereecken et al.’s risk assessment [27], the freeze-thaw point is
assumed to be -2℃. Different materials have different tensile strength, and so the degree of saturation
that will lead to frost damage varies. In the present study, the critical value of granite in South Tyrol is
set to 80%, and critical saturation ration of sandstone is equal to 60% according to C. Franzen’s study
[28]. The critical saturation ratio of plaster is set to 30% according to WTA 6-5 [29].
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2.4.3 Mould risk assessment. This study uses the VTT model to assess the risk of mould growth. The
model was established to measure mould growth primarily on wood and organic materials [30, 31], and
was extended to other materials [32]. It is generally used in research [33, 34].
Mould growth will occur when RH ≥ RHcrit, where RHcrit is a function of temperature, RH and time.
Mould growth and decay rates relate to temperature, material type, and surface quality. Depending on
the mould growth initial condition and growth rate, Mould Growth Index (MGI) represents the condition
between no-mould and 100% mould coverage. In this study, the surface of wood fibreboard is defined
as sensitive to mould growth and growth rate shows significant relevant decline, and climate board is
defined as medium resistant to mould growth and growth rate shows relatively low decline. Mould risk
is assumed to exist when MGI exceeds 1 [32].
3. Results and discussion
3.1. Present and future climate comparison
When comparing the annual temperature distribution in present and future scenarios, a general
increase is noticeable (Figure 2): the average value raises 3.76℃. However, temperature increase is not
constant throughout the year (Figure 3). The maximum increase appears in winter months with an
average rise of 5.85, whereas in summer, the average increase is 2.06℃. Besides average values of
temperature, the daily temperature gradient is an important indicator in defining the potential of night
cooling. Figure 4 shows the distribution of daily temperature difference during present and future
scenarios. The maximum temperature difference decreases, as well as the interquartile range showing a
reduction in the temperature difference between the maximum and minimum daily values.
In winter, the increase of external temperature implies a reduction in heating energy demand, while
in summer, a temperature rise may cause indoor overheating. Moreover, due to the drop of daily
temperature difference in summer, night cooling effect may be weakened.
The total amount of annual rain increases from 865 mm in present scenario to 993 mm in future
scenario (Figure 5), while the annual rain event number decreases from 137 to 131 meaning that the
amount of rainfall per event will increase considerably. The distribution of events’ duration in future
will remain similar. These changes in the rain patterns might lead to higher rain flux on the wall surface.
Thus, there may be more water absorbed into the wall which limiting the drying process of the wall.
Figure 2 Annual temperature distribution of
present and future scenarios
Figure 3 Average monthly temperature in present
and future scenarios
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Figure 4 The distribution of daily temperature
difference of summer months in present and
future scenarios
5 Annual precipitation amount and event
number in present and future scenarios
3.2. Energy consumption
Figure 6 shows the average annual heating demand of the reference building in different scenarios.
When comparing the energy demand between present and future scenarios, it could be seen that the
energy demand in future decreases by 26% in un-retrofitted scenarios and 30% in retrofitted scenarios.
This decrease may be explained as a consequence of the increase of outdoor temperature in future
scenario that will lower the heating demand in any case. A higher relative reduction of energy demand
is reported in the case of retrofitted buildings. This is possibly due to the ability of the insulated building
to better preserve heat coming from internal loads that when combined with increased external
temperature results in lower energy needs.
When retrofit solutions are applied, heating energy demand in both time scenarios (present and
future) is dramatically reduced. Future scenario exhibits a slight advantage over the present scenario:
the retrofit action achieves 86.4% energy saving in future scenario comparing to 85.6% in present
scenario. This result shows that also with increased external temperature, retrofit interventions is still an
effective way to improve energy efficiency.
Figure 6 Average annual heating energy
consumption of whole building in kWh for
retrofitted/un-retrofitted and present/future
7 Average annual heat loss
due to
nfiltration during the
heating period in
retrofitted and present/future
(relative contribution to heating
demand is shown as percentage)
Figure 7 shows the average annual heat loss due to infiltration during the heating months. Infiltration
results in a significant energy loss comparing to total heating energy consumption in all scenarios (on
average more than 35% of the heating energy demand). Retrofit solutions can effectively reduce this
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infiltration by improving the airtightness of the envelope and cut more than 75% of the energy loss in
present and future scenarios. However, the relative weight of energy losses due to infiltration increase
in retrofit scenarios. This may due to the reduced share of energy losses across the envelope.
3.3. Indoor thermal comfort
Indoor thermal comfort is assessed according to the adaptive comfort model in EN 15251. As
aforementioned, the assessment is carried out on living room where the occupants could apply adaptive
action during the occupancy. In addition, the assessment method is applicable: when 10< Θrm <30℃ for
upper limit and 15 < Θrm < 30℃ for lower limit without mechanical cooling systems [35]. Where Θrm is
running mean outdoor temperature. Due to the relatively cold summer in Toblach (Figure 3), the
applicable hours are only a fraction of the summer period. As shown in Figure 8, the average applicable
hours increased from 1290 hours in present scenario to 1520 hours in future scenario. This increase
reflects outdoor temperature increase.
When comparing comfort conditions before and after retrofit (Figure 8), there is an obvious change
from under-heating to overheating state. The results show that retrofit interventions contribute to indoor
overheating not only in future but also in present scenario. However, the overheating caused by the
retrofit interventions could be easily relieved with an additional natural ventilation. When an extra
ventilation plan is added, the overheating hours decrease and the indoor environment stays within a
comfortable range most of the time.
When comparing different time scenarios, the overheating rate in retrofitted buildings grows from
present to future scenarios. This is a direct consequence of the temperature rise in the future. On the
other side, un-retrofitted building’s comfort level worsens in the opposite direction: under-heating. The
increase in under-heated hours in the future relates to the unequal increase of outdoor and indoor
temperature. The median value of running mean outdoor temperature increase from 15.8 to 18.0
(2.2℃), while the median value of the indoor operative temperature increase from 17.7 to 18.5℃
(0.7℃). Since the comfort criteria in adaptive method is defined according to outdoor temperature as a
linear relationship, the increase of the neutral temperature will be higher than the increase of indoor
8 Average annual comfort level in retrofitted/un-retrofitted and present/future scenarios,
according to EN 15251 category 2 criteria for buildings without mechanical cooling systems
3.4. Envelope hygrothermal safety
Three internal insulation systems are compared with respect to their hygrothermal performance: 1) wood
fiberboard3 (vapour open system), 2) wood fiberboard with vapour barrier (vapour tight system) and 3)
3 The wood fibreboard is produced by Pavatex.
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calcium silicate board4 (vapour open & capillary active system). These three insulation systems are
coupled with three wall constructions: 1) granite wall, 2) sandstone wall and 3) wooden wall (pine).
These three wall constructions are the most commonly found in South Tyrol. The properties of the
insulation materials and wall materials are presented in Table 3. In addition, the sd-value of the vapour
barrier used in the simulation is 7.72m.
Table 3 Properties of main construction materials
λdry [ W/mK ] ρ [kg/m³] Cp [J/kg·K]
µdry [ - ] θpor[m³/m³]
silicate board
To assess the hygrothermal risks, three Assessment Points (AP) are defined: A. High relative
humidity in the interface between the insulation and historic plaster, B. Mould risk between the
insulation and historic plaster, and C. Frost in the outer historic plaster and 0.5 cm into the wall (Figure
9). To optimise the computational resources, the hygrothermal models are 1-D models (as showed in
Figure 9) that simplify the wall construction as a sequence of homogeneous layers.
Figure 9 Risk assessment points and example of Delphin simulation model
3.4.1 Condensation risk. RH in the uninsulated wall is mainly depending on indoor RH, and it is
relatively low both in present and future scenarios: below 70% for all three wall constructions. However,
when climate change is combined with additional insulation, the condition worsened in stone masonry.
With vapour open system (wood fibreboard), condensation appears both in granite wall and sandstone
wall (in both present and future scenarios) (Figure 10). However, the total condensation hours decrease
in future scenarios (e.g. condensation hours of granite wall decrease from 59.6% to 43.2%). With vapour
tight system, RH increases with time, which reflects the accumulation of moisture in wall due to the
limiting effect of vapour barrier to dry inwards. (Figure 10) Even though there is no liquid water
4 The calcium silicate board is produced by Calsitherm Silikatbaustoffe GmbH.
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accumulated during the simulated period, it could be presumed in later years. With vapour open &
capillary active system, there is no condensation in the wall and the fluctuation pattern of RH is similar
to the vapour open system, i.e. no accumulation phenomenon observed. Regarding the wooden walls,
RH increases in future scenario but does not show condensation risk with any of the three insulation
Figure 10 Relative humidity in masonry walls with vapour retard and vapour tight insulation system
3.4.2 Mould risk. No risk of mould growth was found on any of the uninsulated walls. However, with
the addition of internal insulation, the risk of mould appearance increased considerably in the future
climate scenarios. With vapour open system, the mould index of granite wall and wood wall in present
scenario are very low while it will exceed 1 in future scenario. (Figure 11) For wood wall, the mould
index in future is higher than 2 implying there will be more than 10% coverage of mould on surface.
With vapour tight system and vapour open & capillary active system, there will be mould risk in wood
wall in future scenario. The decline of mould on wood material is significant, but the damage caused by
mould risk is still probable due to the increased rain quantity in future.
Figure 11 Mould index in granite and wood wall with internal insulation
3.4.3 Frost damage. Both the application of internal insulation and change of precipitation in future will
raise the saturation rate. However, climate change has larger impacts: the saturation ratio reaches to Scrit
due to the extreme rain events. The saturation ratio of retrofitted granite wall could stay below critical
saturation ratio in present and future scenarios. Retrofitted sandstone wall is safe from frost damage in
present but suffers frost risk in future scenario. The saturation ratio will exceed or be close to critical
saturation ratio in future scenario when there is severe rain (Figure 12). The saturation curve results of
retrofitted sandstone walls are similar independently of the insulation system. For the external plaster,
the application of insulation systems does not increase the saturation ratio. The external plaster of both
granite and sandstone wall will be in frost risk in present and future (Figure 13). However, the saturation
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ratio surpasses the critical value more frequently in the future, which implies an urgent need for better
solutions to protect the historic facade.
Figure 12 Saturation ratio
of retrofitted sandstone
wall (assessed at AP-C1)
Figure 13 Saturation ratio of external plaster
(assessed at AP-C2)
4. Conclusion
The performance of a representative Alpine historic residential building is assessed in terms of energy
use, indoor comfort and moisture safety of the envelope under present and future climatic scenarios. The
assessment has considered different configurations of wall constructions as well as different possible
retrofit interventions.
The results of the simulations demonstrated that the retrofit interventions could significantly improve
energy efficiency of historic buildings in both present and future scenarios. Future temperature increase
does not compromise the effectiveness of thermal insulation.
A change in climate together with retrofit interventions will result in higher risk of indoor
overheating. However, at least in studied case study, this could be effectively reduced by additional
natural ventilation. In alpine region, the multifarious terrain results in diverse climate, and studied
location has a rather cold climate. Therefore, indoor comfort should be studied before adopting any
retrofit solutions.
Climate change and retrofit interventions will also impose moisture related risks to the conservation
of historic envelopes. Several solutions that are applied currently often could lead to risks in future. For
instance, mould risk is reported in future granite wall with wood fibreboard, as well as wood wall with
all three studied insulation systems. Future risk of frost damage is also present in insulated sandstone
wall. Retrofit solutions should be carefully studied for compatibility with local building materials and
In conclusion, the present study verified that historic buildings are vulnerable to the changes imposed
by climate and retrofit interventions. However, this paper, as a preliminary study, still presents several
limitations that should be further studied. For further studies, 1) different future climate projections
should be used to have a better understanding of future climate change; 2) different alpine locations
should be studied considering the wide climate variations; 3) building performance should be assessed
not only in “far” future (around 2100), but also in “near” future (around 2050), which is more instructive
for retrofit practices.
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... This is especially the case when precipitation loads are also projected to increase. Further, Hao et al. studied mould growth, interstitial condensation and freeze-thaw damage in interior insulated historical Alpine buildings [16]. Sahyoun [20]. ...
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Previous studies show that climate change has an impact on the damage risks in solid masonry facades. To conserve these valuable buildings, it is important to determine the projected change in damages for the original and internally insulated cases. Since historical masonry covers a wide range of properties, it is unknown how sensitive the climate change impact is to variations in different parameters, such as wall thickness, brick type, etc. A factorial study is performed to determine the climate change impact on freeze-thaw risk, mould growth and wood decay in solid masonry in Brussels, Belgium. It is found that the critical orientation equals the critical wind-driven rain orientation and does not change over time. Further, the freeze-thaw risk is generally decreasing, whereas the change in mould growth and wood decay depends on the climate scenario. Knowing the brick type and rain exposure coefficient is most important when assessing the climate change impact. For freeze-thaw risk and wood decay, it is found that simulating one wall thickness for the uninsulated and one insulated case is sufficient to represent the climate change impact. Finally, the effects of climate change generally do not compensate for the increase in damage after the application of internal insulation.
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Transient building energy simulations are powerful design tools that are used for the estimation of HVAC demands and internal hygrothermal conditions of buildings. These calculations are commonly performed using a (often dated) typical meteorological year, generated from past weather measurements excluding extreme weather conditions. In this paper the results of multiyear building simulations performed considering coupled Heat and Moisture Transfer (HMT) in building materials are presented. A simple building is simulated in the city of Udine (Italy) using a weather record of 25 years. Performing a multiyear simulation allows to obtain a distribution of results instead of a single number for each variable. The small therm climate change is shown to influence thermal demands and internal conditions with multiyear effects. From this results it is possible to conclude that weather records used as weather files have to be periodically updated and that moisture transfer is relevant in energy and comfort calculations. Moreover, the simulations are performed using the software WUFI Plus and it is shown that using a thermal model for the building envelope could be a non negligible simplification for the comfort related calculations.
Durability has been an issue in the construction sector from its early development; and the majority of durability failures are found to be moisture related, due to bad construction and design practices, poor maintenance, or inappropriate operation and usage of the building. Since condensation is the main cause of such problems, it is essential to understand its effects on the overall building envelope, including corrosion of metallic elements, and the consequent risk to structural integrity and reduction of thermal performance. This chapter investigates the issues around durability, explores moisture-related durability risks, and explains the various mathematical models that designers can use to predict or analyse the hygrothermal behaviour of building elements.
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Historic buildings account for more than one quarter of Europe’s existing building stock and are going to be crucial in the achievement of future energy targets. In order to ensure their endurance, conservation compatible solutions are needed. Nevertheless, some alteration in the climate is already certain and therefore the impact of climate change on retrofitted historic buildings should be considered in terms of occupants’ comfort, heritage conservation, and energy performance. Inappropriate interventions might weaken the potential of original passive climate adaptive system, such as thermal mass and night cooling, leading to higher risks of overheating. Similarly, retrofit solutions will change the moisture dynamics of historic envelopes, which might lead to moisture damages when combined with more extreme precipitation events. This paper reviews recent literature that provides evidence of climate change’s impact on retrofitted buildings, reveals potential future risks, and thereby throws light on new factors influencing the retrofit decision-making process.
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Meteorological time series with 1 h time steps are required in many applications in geoscientific modelling. These hourly time series generally cover shorter periods of time compared to daily meteorological time series. We present an open-source MEteoroLOgical observation time series DISaggregation Tool (MELODIST). This software package is written in Python and comprises simple methods to temporally downscale (disaggregate) daily meteorological time series to hourly data. MELODIST is capable of disaggregating the most commonly used meteorological variables for geoscientific modelling including temperature, precipitation, humidity, wind speed, and shortwave radiation. In this way, disaggregation is performed independently for each variable considering a single site without spatial dependencies. The algorithms are validated against observed meteorological time series for five sites in different climates. Results indicate a good reconstruction of diurnal features at those sites. This makes the methodology interesting to users of models operating at hourly time steps, who want to apply their models for longer periods of time not covered by hourly observations.
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Old buildings that represent and maintain historic values often have poor indoor conditions and energy efficiency. The aim of this work was to evaluate the influence of building structures on airtightness and energy performance of certain historic building types. In this study on-site measurements, dynamic simulation and questionnaires were used. Significant differences between the levels of the airtightness of the historic houses exist in the studied region. No statistically significant correlation was found between the structure types and the envelope tightness. The typical air leakage places of the studied houses were at the junctions of the envelope structures. Measured air exchange rates indicated that the level of ventilation is insufficient in some of the houses while some are too leaky. If the airtightness of the naturally ventilated house is improved, the acceptable ventilation rate has to be guaranteed. Tightening the envelope and moving from natural to mechanical ventilation was the most effective way to improve the indoor conditions and energy performance.
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Is it reasonable to invest -thoughts and money -in the energy refurbishment of historic buildings? This paper quantifies the potential impact in terms of climate protection and enhanced living conditions – looking not only at exemplary listed buildings, but more generally historic "cityscapes". Statistics reveal that 14% of EU-27 building-stock dates before 1919, other 12% between 1919 and 1945 (with considerable national differences), corresponding to 30 resp. 55 million dwellings and 120 million Europeans living there. With information on climatic regions and building performance a heating-demand of 855 TWh corresponding to more than 240 Mt CO 2 can be estimated. Refurbishment can save 180 Mt CO 2 within 2050 (3.6 % of 1990's EU-27-emissions), while bringing indoor comfort increases (higher surrounding temperatures, less draughts, ...) and energy-costs decrease. Finding conservation-compatible solutions enhances therefore long-term-conservation and sustainable management of our towns.
The article presents the possibilities of using hemp fiber as a loose-fill insulation material. The article presents the results of research concerning raw hemp fiber obtained from the Polish crop of industrial hemp of Białobrzeskie variety. The analysis involved evaluation of thermal conductivity in function of bulk density and air permeability, the properties important for insulation materials. The results of laboratory investigation were used to create the numerical simulation models of heat transfer in the frame wall partitions filled with hemp fibers. The study showed that with the increase of bulk density, the thermal conductivity and air permeability of material decrease. The obtained lambda values are comparable with the characteristic values for conventional thermal insulation materials. The results of heat transfer and temperature distribution reveal that hemp fibers characterize with strongly air permeance, what affects on the need for additional barriers against air filtration.
The scope of the annex has been to develop and provide decision support data and tools for energy retrofitting measures. A suggested risk management process is presented. Requirements on general guidelines, which can speed up the decision process and at the same time raise awareness for the associated risks, are suggested. A guideline for the retrofitting of a cold attic developed based on a probabilistic risk assessment method is demonstrated, which includes energy use, life cycle cost and functional performance.
Technical Report
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Interior insulation is often the only possible post-insulation technique to improve the thermal performance of single leaf masonry walls. As a result of potential damage patterns such as frost damage, interstitial condensation and mould growth however, there is often some reluctance to adopt this technique. To fully exploit the capacity for energy savings offered by interior insulation while avoiding hygrothermal failure, a reliable risk assessment is extremely important. This requires a probabilistic approach, since the uncertainty of all influencing parameters might result in widely varying results.