Cool Roofs

Studies on urban heat island (UHI) have been more than a century after the phenomenon was first discovered in the early 1800s. UHI emerges as the source of many urban environmental problems and exacerbates the living environment in cities. Under the challenges of increasing urbanization and future climate changes, there is a pressing need for sustainable adaptation/mitigation strategies for UHI effects, one popular option being the use of reflective materials. While it is introduced as an effective method to reduce temperature and energy consumption in cities, its impacts on environmental sustainability and large-scale non-local effect are inadequately explored. This paper provides a synthetic overview of potential environmental impacts of reflective materials at a variety of scales, ranging from energy load on a single building to regional hydroclimate. The review shows that mitigation potential of reflective materials depends on a set of factors, including building characteristics, urban environment, meteor- ological and geographical conditions, to name a few. Precaution needs to be exercised by city planners and policy makers for large-scale deployment of reflective materials before their environmental impacts, especially on regional hydroclimates, are better understood. In general, it is recommended that optimal strategy for UHI needs to be determined on a city-by-city basis, rather than adopting a “one-solution- fits-all” strategy.

Cool materials are characterized by having a high solar reflectance r – which is able to reduce heat gains during daytime - and a high thermal emissivity ε that enables them to dissipate the heat absorbed throughout the day during night.
Despite the concept of cool roofs - i.e. the application of cool materials to roof surfaces - is well known in US since 1990s, many studies focused on their performance in both residential and commercial sectors under various climatic conditions for US countries, while only a few case studies are analyzed in EU countries.
The present thesis work aims at analyzing the thermal benefits due to their application to existing office buildings located in EU countries. Indeed, due to their weight in the existing buildings stock, as well as the very low rate of new buildings construction, the retrofit of office buildings is a topic of great concern worldwide.
After an in-depth characterization of the existing buildings stock in the EU, the thesis gives an insight into roof energy balance due to different technological solutions, showing in which cases and to what extent cool roofs are preferable.
A detailed description of the physical properties of cool materials and their availability on the market provides a solid background for the parametric analysis carried out by means of detailed numerical models that aims at evaluating cool roofs performance for various climates and office buildings configurations.
With the help of dynamic simulations, the thermal behavior of representative office buildings of the existing EU buildings stock is assessed in terms of thermal comfort and energy needs for air conditioning. The results, which consider several variations of building features that may affect the resulting energy balance, show how cool roofs are an effective strategy for reducing overheating occurrences and thus improving thermal comfort in any climate. On the other hand, potential heating penalties due to a reduction in the heat fluxes passing through the roof are taken into account, as well as the aging process of cool materials.
Finally, an economic analysis of the best performing models shows the boundaries for their economic convenience.

Cool materials are characterized by having a high solar reflectance r –
which is able to reduce heat gains during daytime - and a high thermal
emissivity 􀄰 that enables them to dissipate the heat absorbed throughout
the day during night.
Despite the concept of cool roofs - i.e. the application of cool materials
to roof surfaces - is well known in US since 1990s, many studies focused
on their performance in both residential and commercial sectors under
various climatic conditions for US countries, while only a few case studies
are analyzed in EU countries.
The present work aims at analyzing the thermal benefits due to their
application to existing office buildings located in EU countries. Indeed, due
to their weight in the existing buildings stock, as well as the very low rate of
new buildings construction, the retrofit of office buildings is a topic of great
concern worldwide.
After an in-depth characterization of the existing buildings stock in the
EU, the book gives an insight into roof energy balance due to different
technological solutions, showing in which cases and to what extent cool
roofs are preferable.
A detailed description of the physical properties of cool materials and
their availability on the market provides a solid background for the
parametric analysis carried out by means of detailed numerical models
that aims at evaluating cool roofs performance for various climates and
office buildings configurations.
With the help of dynamic simulations, the thermal behavior of
representative office buildings of the existing EU buildings stock is
assessed in terms of thermal comfort and energy needs for air
conditioning. The results, which consider several variations of building
features that may affect the resulting energy balance, show how cool roofs
are an effective strategy for reducing overheating occurrences and thus
improving thermal comfort in any climate. On the other hand, potential heating penalties due to a reduction in the incoming heat fluxes through
the roof are taken into account, as well as the aging process of cool
materials.
Finally, an economic analysis of the best performing models shows the
boundaries for their economic convenience.

Heat island refers to the temperature increase in urban areas compared to rural settings, intensifying the cooling energy consumption of buildings. Roofs constitute a major part in urban areas, hence cool roof coverings contribute to mitigate heat island. Heat island is an ...

A cool roof reflects the sun’s heat and emits absorbed radiation back into the atmosphere at a higher rate than standard materials. They reduce the amount of heat held and transferred to the building below, keeping the building cooler and at a more constant temperature.

This research has collected 12 months of primary data on buildings in Melbourne and extended that with modeling for industrial, commercial and residential buildings. Sensitivity was carried out for insulation levels, shading, pitch and paint colour.

The motive of undertaking this project “cool
roofs technology” discusses the various technical and design
considerations as applicable for a composite climate. The
primary intent of “cool roof technology” is to reduce the
amount of energy (heat) absorbed by a roof surface and
maintain the temperature of upper floors in building in
summer season. The manual addresses architects, engineers,
and other building professionals are responsible for the
performance and construction of buildings. The direct and
indirect benefits and energy savings potential of cool roofs,
its helps to reduce the urban heat island, global warming,
local air temperature and creates a more comfortable and
healthier environment.

Cool roofs are effective solutions to counter the overheating of building roofs, inhabited spaces below and urban areas in which buildings are located thanks to their capability of reflecting solar radiation. Nonetheless, the relatively low surface temperatures that they induce can cause condensation of humidity and leave the surface wetted for large part of the day, thus promoting the growth of bacteria, algae and other biological fouling; this can cause a quick decay of the solar reflective performance. Biological growth is countered by surface treatments, which, however, may be toxic and forbidden in many countries and may also vanish quickly. It can also be countered by lowering the thermal emittance and thus decreasing heat transfer by infrared radiation to the sky and the consequent night undercooling, but this can decrease the performance of cool roofs. An alternative approach, which is analyzed in this work, is to embed in the first layer below the cool roof surface a phase change material (PCM) that absorbs heat during the daytime and then releases it in the nighttime. This can increase the minimum surface temperatures, thus reducing the occurrence humidity condensation and also the biological growth. In this work, preliminary results on the coupling of a cool roof surface with a PCM sublayer are presented, being obtained by theoretical investigation on commercial materials and taking into account the time evolution pattern of the environmental conditions.

Modern residential roofs in Malaysia mainly employ red and brown roof tiles due to aesthetic factors and the ability of the roof surface to reflect or retard heat transfer is typically not considered the main priority. The present article reveals the findings of a study on the effect of roof tile colour on heat conduction transfer through roof tiles and ceiling boards, roof-top surface temperature and cooling load. Findings suggest that the selection of white roof tiles significantly reduces the peaks of heat conduction transfer and roof-top surface temperature as well as the values of heat conduction transfer and roof-top surface temperature throughout diurnal profiles, which consequently reduces hours of indoor thermal discomfort and use of air-conditioners in indoor spaces. A decline in peak roof-top surface temperature of up to 16.00 °C that results in annual energy savings of up to 13.14% can be achieved when the roof tile colour is changed from red to white. Further research on the development of solar-reflective paint or coating products that can significantly increase the solar reflectance values of non-white roof tiles are essential to overcome issues related to maintenance difficulties and lack of preference among house buyers towards white roof tiles.

Building energy efficiency has become a key research issue in the last years,
given the huge energy requirement of the construction sector and the potential for energy
saving. In particular, passive solutions such as natural materials are always appreciated for
their intrinsic high thermal performance and low environmental impact. In this view,
natural stones represent a good solution as building envelope covering or city pavements.
This paper concerns the experimental characterization of several gravel coverings for roofs
and urban paving in terms of their albedo characteristics. A cheap and local natural high
reflectance stone is chosen, which common use is as aggregate for concrete. The purpose
of the work is to study its intrinsic cooling potential. To this aim, the in-field albedo of
gravel samples is measured with varying grain size of the same natural stone named
“Bargiolina”. These in-field measurements are compared to in-lab measurements about
solar reflectance and thermal emissivity. The analysis shows a significant variation of the
albedo with varying grain size of the same stone. Both in-lab and in-field measurements
agree that the stone with the smallest grain size, i.e. thin sand, has the best optic-thermal
performance in terms of solar reflectance (62%). This feature results in the reduction of the
surface temperature when exposed to solar radiation. Moreover, a natural mixed stone is
compared to the high reflectance stone, demonstrating that the chosen “Bargiolina”
presents an intrinsic cool behavior. Therefore, this natural, low-cost, low impact and high
performance material could be successfully applied as cool roof or cool paving, for its
passive cooling contribution and its potential for reducing urban heat islands.

The high rate of heat transfer through the residential roof assembly aggravates the condition of indoor thermal discomfort. Bulk insulation can be installed in the assembly to improve thermal performance. However, although it can efficiently reduce diurnal heat transfer from the outdoor environment into the indoor space through the roof assembly, it can also suppress nocturnal heat transfer in the opposite direction. Alternatively, high-albedo roof tiles employ cool colors to reflect heat at the roof surface, whereas bulk insulation hinders the conduction of heat through the roof assembly. In light of the potential of high-albedo roof tiles and bulk insulation in reducing heat transfer, thermal-energy performance of an urban pitched residential roof assembly, which adopted varying configurations of high-albedo roof tiles and bulk insulation under a hot, humid climate, was evaluated. Energy savings were generated, which were 15.13% when the change from a conventional to a high-albedo...

Increasing surface reflectivity in urban areas can decrease ambient temperature, resulting in reducing photochemical reaction rates, reducing cooling energy demands and thus improving air quality and human health. The weather research and forecasting model with chemistry (WRF-Chem) is coupled with the multi-layer of the urban canopy model (ML-UCM) to investigate the effects of surface modification on urban climate in a two-way nested approach over North America focusing on Sacramento, Houston, and Chicago during the 2011 heat wave period. This approach decreases the uncertainties associated with scale separation and grid resolution and equip us with an integrated simulation setup to capture the full impacts of meteorological and photochemical reactions. WRF-ChemV3.6.1 simulated the diurnal variation of air temperature reasonably well, overpredicted wind speed and dew point temperature, underpredicted relative humidity, overpredicted ozone and nitrogen dioxide concentrations, and underpredicted fine particular matters (PM 2.5). The performance of PM 2.5 is a combination of overprediction of particulate sulfate and underprediction of particulate nitrate and organic carbon. Increasing the surface albedo of roofs, walls, and pavements from 0.2 to 0.65, 0.60, and 0.45, respectively, resulted in a decrease in air temperature by 2.3 • C in urban areas and 0.7 • C in suburban areas; a slight increase in wind speed; an increase in relative humidity (3%) and dew point temperature (0.3 • C); a decrease of PM 2.5 and O 3 concentrations by 2.7 µg/m 3 and 6.3 ppb in urban areas and 1.4 µg/m 3 and 2.5 ppb in suburban areas, respectively; minimal changes in PM 2.5 subspecies; and a decrease of nitrogen dioxide (1 ppb) in urban areas.

Urban surfaces modification as increasing the albedo is a mitigation strategy to counter the effects of urban heat islands and thus decrease ambient temperature and photochemical reaction rates. Here, the effects of increasing surface reflectivity assessed applying a multi- layer urban canopy model coupled to Weather Research and Forecasting model with chemistry. The temporal and spatial distribution of pollutants over North America simulated during 2011 heat wave period. The reflectivity of roofs, walls, and roads are increased from 0.2 by 45%, 40%, and 25%, respectively. Simulated showed that the average daily maximum air temperature decreased by 0.7 oC in urban areas. The maximum decrease in 24-h averaged particulate matters (PM2.5) and ozone (O3) concentrations are approximately 5% (2.2 μg/m3) and 2% (5.2 ppbv), respectively. This relatively minor variation in pollutant concentrations comparing to the base case scenario is due to a decrease in planetary boundary layer height because of albedo enhancement.

The intensification of the Urban Heat Island effect (UHI) is a problem that involves several fields: the construction sector is strictly related with this phenomenon, and new adequate solutions can significantly mitigate its amplitude.
In particular, roofs are the envelope components of buildings most directly engaged with solar gains, so any mitigation strategy should involve the design process of these components.
To this purpose cool materials, i.e. materials which are able to reflect a large amount of solar radiation and keep surfaces cooler, have been deeply analyzed in the last years both at building and urban scales, showing their benefits especially for hot climates. However, also green roofs represent a possible way to cope with UHI, but their design process requires taking into account many variables that are strictly related with the local climatic conditions.
In this context, the present paper proposes a comparison between cool roofs and green roofs for several Italian cities that are representative of different climatic conditions. In search of the most effective solution, the answers may be different depending on the perspective that leads the comparison.

Passive strategies for environmental sustainability and energy reduction in construction industry are becoming increasingly important in both the scientific community and the industrial world. Particularly, cool roofs showed acknowledged contribution in cooling energy saving and reducing urban overheating phenomenon, such as urban heat island. Additionally, high albedo strategy has shown also promising benefits from a global scale perspective, by counteracting global warming measured by means of CO2eq emissions' offset. In this view, the present research work combines experimental, numerical, and analysitical analysis approaches with the purpose of estimating the environmental and energy impact of the application of cool clay tiles over the roof of a residential area with single family buildings located in central Italy, where a continuous monitoring setup has been operating since 2010. The multiscale and multipurpose investigation demonstrated a global year-round CO2 emission compensation by more than 700 tons, of which the 15% is produced by the passive cooling contribution at building scale and the remaining part is produced by the climate mitigation technique. The work therefore showed that local energy saving strategies must be combined with larger scale models for performing an exhaustive environmental analysis.

Installation of stone wool as thermal insulation in the roof assembly can be adopted to store heat in the living space, if the building is exposed to cold weather, and, inversely, to retard heat from entering the living space, if it is exposed to hot weather. In spite of the effectiveness of stone wool as a roof insulation material, during installation, it can cause irritation to the skin and can be hazardous to the lungs. Therefore, incorporation of stone wool with other materials to form a rigid board, without compromising its effectiveness as a roof insulation material, is imperative. Strength properties of a stone-wool-fibre-reinforced high density polyethylene (HDPE) composite roof insulation material were studied. Granular silica aerogel, which possesses an ultra-low thermal conductivity, was added as filler to reduce the thermal conductivity of the composite. Hot compression moulding was performed to prepare samples of the composite with varying silica aerogel content of 0, 1, 2, 3, 4, and 5 wt. %. Findings suggest that 2 wt.% is the optimum silica aerogel content as it resulted in the highest flexural strength and modulus, which is 24.4 MPa and 845.85 MPa, respectively, even though it reduced the tensile strength and modulus by 10% and 4.45% respectively, relative to 0 wt. %, which can be considered as inconsequential. Higher silica aerogel content above 2 wt. % may result in poor interfacial adhesion and low compatibility to the stone wool fibre and HDPE, which further reduces the tensile and flexural strengths and moduli of the composite.

Cool roofs represent an acknowledged, relatively simple and low cost strategy to reduce cooling energy demand of buildings and mitigate urban heat island phenomena. The purpose of this paper is to study the coupled passive-active effect produced by such a technology , where the active effect consists of the cool roof capability to decrease the suction air temperature of heat pump external units, when these units are located over the roof. This “cooling” benefit produces an extra-increase of the energy performance of the heat pump in cooling mode, given that it produces the decrease of the temperature lift between the source and the output. In order to study this twofold effect, an industrial building with an office area located in Rome, Italy, was continuously monitored in summer 2012. The main results showed that the cool roof allows to decrease the roof overheating up to 20°C. The office indoor air temperature also decreased, even if the same set-point temperature was kept constan...

The albedo of urban roofs and surfaces has a major role in determining the thermal-energy performance of buildings. Therefore, “cool” materials with high solar reflectivity and thermal emissivity could substantially affect energy saving potential given their ability to reduce the cooling energy need, especially during summer. This study deals with the experimental analysis of the thermal-optical properties of an innovative cool membrane for buildings’ roof. This material consists of a waterproof polyurethane-based membrane with high elasticity. Laboratory measurements were carried out, with the purpose of determining the optic-energy properties and the “cool roof” behavior of both the already commercialized and the optimized membranes, which were prepared in order to maximize the cooling potential in terms of direct indoor benefits and indirect urban benefits. The optimization was carried out by increasing specific components, i.e., rutile TiO2 and hollow ceramic microspheres, as observed to be effective in optimizing this potential. After the in-lab experimental campaign, an in-field monitoring campaign was carried out, in order to measure the reflection properties of the membranes when exposed to different weather conditions. The final purpose consisted of the evaluation of the reflection capabilities’ variation for each membrane, i.e., the ratio between measured global reflected and incoming radiation, in order to estimate its effect when applied to buildings in realistic conditions.

Increasing surface reflectivity in urban areas can decrease ambient temperature, resulting in reducing photochemical reaction rates, reducing cooling energy demands and thus improving air quality and human health. The weather research and forecasting model with chemistry (WRF-Chem) is coupled with the multi-layer of the urban canopy model (ML-UCM) to investigate the effects of surface modification on urban climate in a two-way nested approach over North America focusing on Sacramento, Houston, and Chicago during the 2011 heat wave period. This approach decreases the uncertainties associated with scale separation and grid resolution and equip us with an integrated simulation setup to capture the full impacts of meteorological and photochemical reactions. WRF-ChemV3.6.1 simulated the diurnal variation of air temperature reasonably well, overpredicted wind speed and dew point temperature, underpredicted relative humidity, overpredicted ozone and nitrogen dioxide concentrations, and und...

Modern residential roofs in Malaysia mainly employ red and brown roof tiles due to aesthetic factors and the ability of the roof surface to reflect or retard heat transfer is typically not considered the main priority. The present article reveals the findings of a study on the effect of roof tile colour on heat conduction transfer through roof tiles and ceiling boards, roof-top surface temperature and cooling load. Findings suggest that the selection of white roof tiles significantly reduces the peaks of heat conduction transfer and roof-top surface temperature as well as the values of heat conduction transfer and roof-top surface temperature throughout diurnal profiles, which consequently reduces hours of indoor thermal discomfort and use of air-conditioners in indoor spaces. A decline in peak roof-top surface temperature of up to 16.00 °C that results in annual energy savings of up to 13.14% can be achieved when the roof tile colour is changed from red to white. Further research o...

Silica aerogel possesses an ultra-low thermal conductivity by virtue of its nano-structure. Owing to the fragility of monolithic aerogel, the development and production of aerogel-based insulation materials involve the incorporation of granular aerogel with other materials to form composite materials. In the present study, the application of silica-aerogel-incorporated composite cement paste as render on the roof-top surface is coupled with the installation of a novel silica-aerogel-incorporated composite insulation board below the roof tiles. Control and silica-aerogel-incorporated samples of the composite cement paste and insulation were prepared. Thermal conductivity and strength tests were performed on the samples. A simulation study was performed on a Building Information Model subjected to a tropical climate to project the resultant impact of the cement render coupled with the insulation board on the thermal-energy-efficiency of the roof. For optimization of thermal and strength performances, silica aerogel contents of 4 wt.% and 3 wt.% were selected for the cement render and insulation board, respectively. The projected annual cooling load and energy savings revealed that the application of a 20-mm cement render, coupled with the installation of a 100-mm thick insulation board, is recommended as the optimum roof configuration.

Silica aerogel possesses an ultra-low thermal conductivity by virtue of its nano-structure. Owing to the fragility of monolithic aerogel, the development and production of aerogel-based insulation materials involve the incorporation of granular aerogel with other materials to form composite materials. In the present study, the application of silica-aerogel-incorporated composite cement paste as render on the roof-top surface is coupled with the installation of a novel silica-aerogel-incorporated composite insulation board below the roof tiles. Control and silica-aerogel-incorporated samples of the composite cement paste and insulation were prepared. Thermal conductivity and strength tests were performed on the samples. A simulation study was performed on a Building Information Model subjected to a tropical climate to project the resultant impact of the cement render coupled with the insulation board on the thermal-energy-efficiency of the roof. For optimization of thermal and strength performances, silica aerogel contents of 4 wt.% and 3 wt.% were selected for the cement render and insulation board, respectively. The projected annual cooling load and energy savings revealed that the application of a 20-mm cement render, coupled with the installation of a 100-mm thick insulation board, is recommended as the optimum roof configuration.

Humans have been thinking of making a comfort zone for their living environment since the beginning, to do so they have no ways except using their surrounding environment. This is known as one the first human actions for sustainable development. The ways that natives of each region have used to create an environment for developed life over the years. These methods have also become the culture of the region besides improving the lives of native people and have created a sense of belonging for them. Hence, green roofs are considered as one of the first and oldest of these methods. The green roofs can be built in different ways according to the place being used. These methods were specific to places that could be created based on native plants, materials available, and the culture of the region. The green roof technology can be considered as a solution for today’s poor environmental conditions of cities through reducing greenhouse gas, improving human health, and ecosystem. This book investigated the traditional green roofs in different regions of the world and also different impacts that these kinds of roof can have on the surrounding environment. This book aims to create a scientific background for the use of local pattern of each region as a potential solution for the problems of the region and the similar regions through introducing modern and traditional green roofs. Results and investigations can prepare grounds for researchers to express their ideas to build new green roofs.

1. Introduction
Usually everything around human is called environment [1]. The environment is consisted of a set of data that create reality. Set of perceptions that human acquires from the fact, forms objectivity. Objectivity varies in different humans. Different people can have different perceptions from environment.
Mental constant is a factor that contributes objectivity to be unit in a group of people. Having understood the environment and created objectivity humans will adapt it with their mental constant. In addition, whenever this adaptation happens, identity and sense of belonging will take place in the person. Unlike its name, mental constant can be composed of all the human senses. Perhaps a certain type of sound, smell, contexture, or view would remind a common message for a set of human beings that would not mean the same for others. Nevertheless, it can be said that we create a series of schemas or key words in mind when we are dealing with the environment, and we remember the event with reference to these key words. There are factors that bind us with the environment and culture. These factors are called environmental mechanisms which is consisted of a set of specific culture environmental factors (manufactured and non-manufactured), or taken from a culture, which human recognizes it as a symbol or sign. Each area has specific and clarified elements of culture and identity that have been developed throughout the history. A history that continually expresses these symbols as its particular identity, like the fingerprint of a person.
To create a new construction, considering spirit of the place was of high importance in traditional context of each region. Each place, as a living organism, has its own unique spirit that manufactured building, as new data, should be able to exchange information with the old data. New manufactured buildings’ non-compliance with the spirit of the place can make the place a sick existence that its organs are incompatible with each other and with its nature.
Different construction cultures through many years according to different reactions of people to their climate, regularly will become a symbol for that region.
As a result, the geographical location of that place will be recognized with these symbols. In addition to the physiological comfort which these symbols cause in the climate, it also creates a sense of belonging to the inhabitants of this region. It prepares the inhabitants for displaying consistent behaviors with the norms of the region as well. Due to the reason that people observe the same codes and sings in their private homes (with all those memories and backgrounds), they can also observe them in a larger scale of neighbor, neighborhood, and city.
As a result, in a larger scale, they do not consider themselves outside of their own home. Therefore, the same sense of belonging, which is the cause of peace, providing service, and controlling their own home affairs, will make sense in a scale larger than home.
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The high rate of heat transfer through the residential roof assembly aggravates the condition of indoor thermal discomfort. Bulk insulation can be installed in the assembly to improve thermal performance. However, although it can efficiently reduce diurnal heat transfer from the outdoor environment into the indoor space through the roof assembly, it can also suppress nocturnal heat transfer in the opposite direction. Alternatively, high-albedo roof tiles employ cool colors to reflect heat at the roof surface, whereas bulk insulation hinders the conduction of heat through the roof assembly. In light of the potential of high-albedo roof tiles and bulk insulation in reducing heat transfer, thermal-energy performance of an urban pitched residential roof assembly, which adopted varying configurations of high-albedo roof tiles and bulk insulation under a hot, humid climate, was evaluated. Energy savings were generated, which were 15.13% when the change from a conventional to a high-albedo roof surface was performed, and 17.00% when the installation of bulk insulation was performed on the high-albedo roof assembly.

Installation of stone wool as thermal insulation in the roof assembly can be adopted to store heat in the living space, if the building is exposed to cold weather, and, inversely, to retard heat from entering the living space, if it is exposed to hot weather. In spite of the effectiveness of stone wool as a roof insulation material, during installation, it can cause irritation to the skin and can be hazardous to the lungs. Therefore, incorporation of stone wool with other materials to form a rigid board, without compromising its effectiveness as a roof insulation material, is imperative. Strength properties of a stone-wool-fibre-reinforced high-density polyethylene (HDPE) composite roof insulation material were studied. Granular silica aerogel, which possesses an ultra-low thermal conductivity, was added as filler to reduce the thermal conductivity of the composite. Hot compression moulding was performed to prepare samples of the composite with varying silica aerogel content of 0, 1, 2, 3, 4, and 5 wt. %. Findings suggest that 2 wt.% is the optimum silica aerogel content as it resulted in the highest flexural strength and modulus, which is 24.4 MPa and 845.85 MPa, respectively, even though it reduced the tensile strength and modulus by 10% and 4.45% respectively, relative to 0 wt. %, which can be considered as inconsequential. Higher silica aerogel content above 2 wt. % may result in poor interfacial adhesion and low compatibility to the stone wool fibre and HDPE, which further reduces the tensile and flexural strengths and moduli of the composite.