Richard O'Hegarty - Academia.edu (original) (raw)

Papers by Richard O'Hegarty

Proponents of Passivhaus and nZEB often emphasise a 'fabric first approach' to ensure optimum env... more Proponents of Passivhaus and nZEB often emphasise a 'fabric first approach' to ensure optimum envelope design, and by extension highest building energy performance. The energy performance of two similar walls, of two separate nZEB-compliant dwellings, are assessed in this paper. The walls have similar construction details, consisting of a layer of 200 mm of mineral wool on the exterior side and a block construction on the interior. The walls are investigated by comparing theoretical and in-situ conductance values while also estimating the embodied energy of both walls. The study found that, although the walls were of similar design and the test was conducted using the same methodology (in accordance with ISO 9869-1), that there was a significant different between the in-situ performance of both walls. One wall performed only slightly worse than the design value while the other performed more than two times worse. This research extrapolates on the findings by comparing theoretical heat loss scenarios with both wall types and calculates A) the potential building energy performance for both walls and B) the carbon and energy payback for the insulation used to achieve such high performance. The results demonstrate the importance of good practice in construction of the building envelopes and in the manufacturing, robustness and quality control of the various building components.

The Europe Union needs to reduce its carbon emissions. To achieve the proposed 55% emission reduc... more The Europe Union needs to reduce its carbon emissions. To achieve the proposed 55% emission reduction target by 2030 it has embarked on a Renovation Wave which aims for more, and deeper, building renovation. Considering this ambition and the scale of the challenge, there remains a surprising paucity of documented post occupancy evaluation studies of deep retrofit projects, particularly those related to the new nZEB standards and of group housing schemes. This paper reports on the post-retrofit performance of a community of 12 single story, one bedroom social houses located in the southeast of Ireland, occupied by retired and elderly tenants. The deep retrofit works included the upgrade of the building fabric, ventilation and heating, all with a view to transforming the living standards of the occupants. They in turn responded, when surveyed, with near unanimous satisfaction. The upgrade and the addition of onsite microgeneration ensured these houses were transformed from lowly F and G national building energy ratings (BER) to A rated homes as calculated by the national energy rating software, DEAP. However, a performance gap is reported between the expected A performance (<75 kWh/m 2 /yr) and the actual performance, with some homes consuming more than twice the predicted energy, while in one extreme case the mean winter indoor temperatures are more than 7°C above the operating temperatures assumed by the DEAP software. The higher than expected indoor temperatures are directly correlated with the higher than expected energy consumption, consumed by a heat pump which in itself exhibited inefficiencies in operation. This post occupancy evaluation, post retrofit, provides evidence therefore of high occupant satisfaction, but a satisfaction based on significant energy 'underperformance'. This case study provides evidence and insights that can help guide future retrofit practices as Ireland progresses towards the transformation of its building stock to near Zero Energy Buildings (nZEB). It also opens up serious questions around the aims and expectations of our national nZEB standard and generates some key insights into the energy consumption of nZEB dwellings and the assessment methods necessary to measure them accurately.

CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to ... more CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to numerically investigate the performance of a thin Precast Concrete Sandwich Panel (PCSP) proposed for building retrofit. Standard precast concrete sandwich panels, constructed of steel reinforced concrete, are physically heavy and have significant thicknesses. A thin precast concrete over-cladding sandwich panel is presented in this paper which combines the state-of-the-art in ultra-high-performance concrete, carbon fibre shear reinforcement and vacuum insulation to allow for a slimmer design while abiding by thermal and structural constraints. Another precast concrete re-cladding sandwich panel is also referred to in this paper which uses phase change materials (PCM) in a thicker inner wythe to enhance the thermal storage properties of the concrete. The panels are modelled, and their structural integrity is investigated, using finite element techniques. The aim of the analysis is to pro...

CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018, Aug 30, 2018

CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to ... more CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to numerically investigate the performance of a thin Precast Concrete Sandwich Panel (PCSP) proposed for building retrofit. Standard precast concrete sandwich panels, constructed of steel reinforced concrete, are physically heavy and have significant thicknesses. A thin precast concrete over-cladding sandwich panel is presented in this paper which combines the state-of-the-art in ultra-high-performance concrete, carbon fibre shear reinforcement and vacuum insulation to allow for a slimmer design while abiding by thermal and structural constraints. Another precast concrete re-cladding sandwich panel is also referred to in this paper which uses phase change materials (PCM) in a thicker inner wythe to enhance the thermal storage properties of the concrete. The panels are modelled, and their structural integrity is investigated, using finite element techniques. The aim of the analysis is to provide an insight into the limiting parameters of these thin precast concrete claddin elements. The analysis has highlighted the concrete wythe thickness and the insulation stiffness as two important performance parameters.European Commission Horizon 202

Buildings, 2022

New energy-efficiency regulations have been established and applied in many Gulf countries to imp... more New energy-efficiency regulations have been established and applied in many Gulf countries to improve building energy performance. Thermal bridging reduces the building envelop performance, and this is not a focus of these regulations. This paper investigates the concrete construction of residential housing in hot climates and identifies more sustainable concrete construction methods. Both experimental and numerical methods are used to identify the impact of thermal bridging. Using finite element analysis, the impact of solar radiation on a building’s thermal bridging was analyzed. It is identified as an essential element for accurate modelling of bridging across concrete in a hot climate. The FE model was evaluated against monitored data and assessed using common statistical indicators. The results show that the heat loss across uninsulated cast in situ structural elements is more than double the heat loss across portions of insulated walls. Moreover, neglecting solar radiation on ...

A theoretical approach has been used to evaluate the performance of facade integrated solar colle... more A theoretical approach has been used to evaluate the performance of facade integrated solar collectors based on the physical collector parameters such as absorber plate absorptance, transmittance of the glazed cover plate and insulation thickness. A 1D steady state model, based on the Hottel Whillier Bliss equation, was employed to determine the effect of changing paramete rs to me et facade integration criteria. Buildings account for 40% of the final energy consumption in Europe (1), Over half of this energy use is associated with building heating, cooling and domestic hot water (DHW) demands (2) . This energy is predominantly provided through the burning of fossil fuels, which can be reduced through the implementation of renewable energy systems. Solar thermal systems, for building applications, make use of an area on the building's envelope to install the solar collectors, which in turn, absorb the solar radiation and convert it to useful heat for the building's heating a...

The 35th Passive and Low Energy Architecture (PLEA) Conference, Coruna, Spain, 1-3 September 2020

In line with the Energy Performance of Buildings Directive, Irish dwellings are being retrofit to... more In line with the Energy Performance of Buildings Directive, Irish dwellings are being retrofit to near Zero Energy Building (nZEB) standards with a number of the deep energy retrofits classified as A-rated. As a result of the low operational energy, the embodied energy share of an nZEB's life cycle energy is significantly increased. Therefore, to obtain a holistic picture of the change in energy profile of buildings, the embodied energy of the material added to achieve that low performance should also be taken into account. This paper presents results from a case study of 8 single-occupant terrace bungalows retrofit to nZEB standard. The preand post-retrofit operational performance is first estimated using the Irish Dwelling Energy Assessment Procedure (DEAP). The post-retrofit operational performance of the space heating and domestic hot water heating system is also measured over a year. The embodied energy is estimated by way of embodied carbon/energy calculations. Monitored r...

Precast concrete sandwich panels provide a thermally efficient alternative to conventional brick ... more Precast concrete sandwich panels provide a thermally efficient alternative to conventional brick and mortar construction and improve the energy efficiency of existing buildings. This project comprised the design and testing of a sample re-cladding panel composed of a phase change material (PCM) in the concrete inner wythe (for thermal efficiency) and a thin ultra-high performance concrete (UHPC) outer wythe, joined compositely using a C-grid shear connector. Six different concrete mixes were prepared and structurally tested in compression and flexure. A concrete sandwich panel was cast using two of the best performing mixes and subsequently tested in three-point bending to investigate its flexural performance. The strongest PCM and UHPC concretes had average compressive and flexural strengths of 25MPa and 5.1MPa, and 121MPa and 9.2MPa respectively. The 900mm span panel tested in flexure reached its serviceability limit at 10kN, with ultimate peak load occurring at 97kN. Post-peak be...

This paper compares a range of new and proposed 'greener' concretes and evaluates their e... more This paper compares a range of new and proposed 'greener' concretes and evaluates their environmental impact via quantification of their embodied energy. These new concretes are further compared with bio based concretes so as to develop a broad picture of the relative environmental impact of the increasing array of concretes now available to building designers. Some uses, advantages and disadvantages of each type are discussed. Particularly the quantity and volume of concrete material for each specific use case is considered for comparison of the embodied energy for a square meter of building envelope structure. Results show that bio based concretes have considerably lower impact than standard concretes, as exhibited by much lower embodied energies per kilogram of material. However, those values documented in only a few studies, and further repeatedly referenced in the wider literature, are approximate at best and sometimes inaccurate. Ultra high performance and geopolymer c...

Journal of Building Engineering, 2021

Abstract High Performance Concrete (HPC) when reinforced with fibres (HPFRC) is often presented a... more Abstract High Performance Concrete (HPC) when reinforced with fibres (HPFRC) is often presented as an environmental improvement on typical reinforced concrete given that its higher strength means less material is required to resist the same forces. However, to achieve these high strengths, considerable proportions of cement, superplasticisers and discontinuous fibres are typically needed, all of which are manufactured using carbon-intensive processes. This article investigates the feasibility of HPFRC as a sustainability improvement on typical reinforced concrete for facade applications by developing novel low carbon HPFRC mixes and carrying out an embodied carbon analysis of a concrete cladding element constructed of those developed mixes. The environmentally improved HPFRC include coarse aggregates (to reduce cement paste volume), non-corrosive fibres (to eliminate the risk of corrosion) and a high dosage of supplementary cementitious material (to again minimise the cement content). Compressive strengths of 100 MPa and pre-cracking flexural strengths above 8 MPa were achieved. Importantly it was also found that the inclusion of resin coasted glass and basalt fibres (2.3% by volume) resulted in deflection hardening behaviour under flexural loading conditions. An environmental investigation found that the embodied carbon of a precast concrete facade can be reduced by 50% when using the presented fibre reinforced high performance concrete in place of typical reinforced concrete cladding.

Journal of Structural Integrity and Maintenance, 2021

ABSTRACT The traditional means of using precast concrete sandwich panels are restrictive in terms... more ABSTRACT The traditional means of using precast concrete sandwich panels are restrictive in terms of applications, where thick wythes result in heavy panels which are often unsuitable in retrofitting domestic and commercial buildings. As concrete sandwich panel technology has evolved to make it more widely accessible, recent research work has demonstrated that it is possible to achieve thermally efficient partial composite action within a thin wythe panel provided non-conductive shear connectors are used. This paper examines high performance recycled aggregate concrete in heavily insulated non-load-bearing panels for retrofitting domestic and commercial buildings. A series of concrete mixes were tested to develop one which would be more sustainable than the widely accepted standard mixes for wythes. Different 220 mm thick concrete sandwich panels were tested consisting of 20 mm thick fibre-reinforced recycled aggregate concrete wythes and a 180 mm layer of XPS insulation. Unconnected and shear connected panels were tested in flexure in a displacement control test. The effects of composite action and post-cracking toughness were examined and it was concluded that a shear connected panel comprising sustainable thin recycled aggregate concrete wythes enclosing a thick layer of insulation is a feasible product to use for light high-performance sandwich panels.

Energy and Buildings, 2021

Abstract In-situ U-value monitoring of building envelopes are investigated in this article by rev... more Abstract In-situ U-value monitoring of building envelopes are investigated in this article by reviewing past studies and monitoring the performance of highly insulated building envelopes. Specific past research studies have concluded both over- and underperformance of the building fabric when measured in situ. This current research has found that when analysing all studies and results over the full range of envelope U-values together there is no evidence of over- or underperformance. However, when highly insulated envelopes (U-values

Energy and Buildings, 2021

Abstract Electrical energy usage in Saudi Arabia is high (∼300 TWh/yr) and is increasing (>5%/... more Abstract Electrical energy usage in Saudi Arabia is high (∼300 TWh/yr) and is increasing (>5%/yr). The residential building sector is responsible for approximately half of the total electricity usage. Past studies have shown that up to 70% of the electric energy used in buildings in Saudi Arabia is consumed in the air conditioning of internal space. This study investigates this significant cooling requirement, particularly concerning the building envelope in typical detached villa housing. The paper concludes that walls formed using insulated concrete blocks only, as is common in Saudi Arabia, do not ensure compliance with the minimum requirements of the Saudi Code 2018. Thermal bridging of the building’s envelope, which is currently not given due focus in the code, undermines the performance further. Bridging caused by the mortar joints between blocks, and by the cast concrete structural elements, increases the thermal transmittance through the envelope by a factor of two, relative to a non-bridged insulated concrete block wall. Simplified methods for thermal bridging calculation are referenced in the Saudi code, and these are evaluated here with reference to a detailed finite element study. Modelling studies show that the neglection of thermal bridging could underpredict building energy load by approximately 54 kWh/m2/yr – from 139 to 85 kWh/m2/yr. A 55 mm thick continuous external insulation layer is proposed to improve the performance considerably, reducing the wall-averaged thermal transmittance from 1.27 W/(m2·K) to 0.34 W/(m2·K) and hence achieving compliance with the latest building code.

Journal of Green Building, 2020

Embodied energy is a measure of the energy used in producing, transporting and assembling the mat... more Embodied energy is a measure of the energy used in producing, transporting and assembling the materials for a building. Operational energy is the energy used to moderate the indoor environment to make it functional or comfortable—primarily, to heat or cool the building. For many building geometries, the walls make the most significant contribution to the embodied energy of the building, and they are also the path of greatest heat loss or gain through the fabric, as they often have a greater surface area than the roof or floor. Adding insulation reduces the heat flow through the wall, reducing the energy used during operation, but this adds to the embodied energy. The operational energy is not only a function of the wall buildup, but also depends on the climate, occupancy pattern, and heating strategy, making an optimisation for minimum overall energy use non-trivial. This study presents a comparison of typical wall construction types and heating strategies in a temperate maritime cl...

Construction and Building Materials, 2021

d Techrete, Ireland h i g h l i g h t s A thin precast concrete sandwich panel design is presente... more d Techrete, Ireland h i g h l i g h t s A thin precast concrete sandwich panel design is presented. The challenges associated with achieving the thin design are discussed. The structural performance of thin panel iterations is experimentally measured. The thermal performance of the panel design is calculated.

Proponents of Passivhaus and nZEB often emphasise a 'fabric first approach' to ensure optimum env... more Proponents of Passivhaus and nZEB often emphasise a 'fabric first approach' to ensure optimum envelope design, and by extension highest building energy performance. The energy performance of two similar walls, of two separate nZEB-compliant dwellings, are assessed in this paper. The walls have similar construction details, consisting of a layer of 200 mm of mineral wool on the exterior side and a block construction on the interior. The walls are investigated by comparing theoretical and in-situ conductance values while also estimating the embodied energy of both walls. The study found that, although the walls were of similar design and the test was conducted using the same methodology (in accordance with ISO 9869-1), that there was a significant different between the in-situ performance of both walls. One wall performed only slightly worse than the design value while the other performed more than two times worse. This research extrapolates on the findings by comparing theoretical heat loss scenarios with both wall types and calculates A) the potential building energy performance for both walls and B) the carbon and energy payback for the insulation used to achieve such high performance. The results demonstrate the importance of good practice in construction of the building envelopes and in the manufacturing, robustness and quality control of the various building components.

The Europe Union needs to reduce its carbon emissions. To achieve the proposed 55% emission reduc... more The Europe Union needs to reduce its carbon emissions. To achieve the proposed 55% emission reduction target by 2030 it has embarked on a Renovation Wave which aims for more, and deeper, building renovation. Considering this ambition and the scale of the challenge, there remains a surprising paucity of documented post occupancy evaluation studies of deep retrofit projects, particularly those related to the new nZEB standards and of group housing schemes. This paper reports on the post-retrofit performance of a community of 12 single story, one bedroom social houses located in the southeast of Ireland, occupied by retired and elderly tenants. The deep retrofit works included the upgrade of the building fabric, ventilation and heating, all with a view to transforming the living standards of the occupants. They in turn responded, when surveyed, with near unanimous satisfaction. The upgrade and the addition of onsite microgeneration ensured these houses were transformed from lowly F and G national building energy ratings (BER) to A rated homes as calculated by the national energy rating software, DEAP. However, a performance gap is reported between the expected A performance (<75 kWh/m 2 /yr) and the actual performance, with some homes consuming more than twice the predicted energy, while in one extreme case the mean winter indoor temperatures are more than 7°C above the operating temperatures assumed by the DEAP software. The higher than expected indoor temperatures are directly correlated with the higher than expected energy consumption, consumed by a heat pump which in itself exhibited inefficiencies in operation. This post occupancy evaluation, post retrofit, provides evidence therefore of high occupant satisfaction, but a satisfaction based on significant energy 'underperformance'. This case study provides evidence and insights that can help guide future retrofit practices as Ireland progresses towards the transformation of its building stock to near Zero Energy Buildings (nZEB). It also opens up serious questions around the aims and expectations of our national nZEB standard and generates some key insights into the energy consumption of nZEB dwellings and the assessment methods necessary to measure them accurately.

CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to ... more CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to numerically investigate the performance of a thin Precast Concrete Sandwich Panel (PCSP) proposed for building retrofit. Standard precast concrete sandwich panels, constructed of steel reinforced concrete, are physically heavy and have significant thicknesses. A thin precast concrete over-cladding sandwich panel is presented in this paper which combines the state-of-the-art in ultra-high-performance concrete, carbon fibre shear reinforcement and vacuum insulation to allow for a slimmer design while abiding by thermal and structural constraints. Another precast concrete re-cladding sandwich panel is also referred to in this paper which uses phase change materials (PCM) in a thicker inner wythe to enhance the thermal storage properties of the concrete. The panels are modelled, and their structural integrity is investigated, using finite element techniques. The aim of the analysis is to pro...

CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018, Aug 30, 2018

CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to ... more CERI 2018 and ITRN Conference, Dublin, Ireland, 29-30 August 2018The purpose of this study is to numerically investigate the performance of a thin Precast Concrete Sandwich Panel (PCSP) proposed for building retrofit. Standard precast concrete sandwich panels, constructed of steel reinforced concrete, are physically heavy and have significant thicknesses. A thin precast concrete over-cladding sandwich panel is presented in this paper which combines the state-of-the-art in ultra-high-performance concrete, carbon fibre shear reinforcement and vacuum insulation to allow for a slimmer design while abiding by thermal and structural constraints. Another precast concrete re-cladding sandwich panel is also referred to in this paper which uses phase change materials (PCM) in a thicker inner wythe to enhance the thermal storage properties of the concrete. The panels are modelled, and their structural integrity is investigated, using finite element techniques. The aim of the analysis is to provide an insight into the limiting parameters of these thin precast concrete claddin elements. The analysis has highlighted the concrete wythe thickness and the insulation stiffness as two important performance parameters.European Commission Horizon 202

Buildings, 2022

New energy-efficiency regulations have been established and applied in many Gulf countries to imp... more New energy-efficiency regulations have been established and applied in many Gulf countries to improve building energy performance. Thermal bridging reduces the building envelop performance, and this is not a focus of these regulations. This paper investigates the concrete construction of residential housing in hot climates and identifies more sustainable concrete construction methods. Both experimental and numerical methods are used to identify the impact of thermal bridging. Using finite element analysis, the impact of solar radiation on a building’s thermal bridging was analyzed. It is identified as an essential element for accurate modelling of bridging across concrete in a hot climate. The FE model was evaluated against monitored data and assessed using common statistical indicators. The results show that the heat loss across uninsulated cast in situ structural elements is more than double the heat loss across portions of insulated walls. Moreover, neglecting solar radiation on ...

A theoretical approach has been used to evaluate the performance of facade integrated solar colle... more A theoretical approach has been used to evaluate the performance of facade integrated solar collectors based on the physical collector parameters such as absorber plate absorptance, transmittance of the glazed cover plate and insulation thickness. A 1D steady state model, based on the Hottel Whillier Bliss equation, was employed to determine the effect of changing paramete rs to me et facade integration criteria. Buildings account for 40% of the final energy consumption in Europe (1), Over half of this energy use is associated with building heating, cooling and domestic hot water (DHW) demands (2) . This energy is predominantly provided through the burning of fossil fuels, which can be reduced through the implementation of renewable energy systems. Solar thermal systems, for building applications, make use of an area on the building's envelope to install the solar collectors, which in turn, absorb the solar radiation and convert it to useful heat for the building's heating a...

The 35th Passive and Low Energy Architecture (PLEA) Conference, Coruna, Spain, 1-3 September 2020

In line with the Energy Performance of Buildings Directive, Irish dwellings are being retrofit to... more In line with the Energy Performance of Buildings Directive, Irish dwellings are being retrofit to near Zero Energy Building (nZEB) standards with a number of the deep energy retrofits classified as A-rated. As a result of the low operational energy, the embodied energy share of an nZEB's life cycle energy is significantly increased. Therefore, to obtain a holistic picture of the change in energy profile of buildings, the embodied energy of the material added to achieve that low performance should also be taken into account. This paper presents results from a case study of 8 single-occupant terrace bungalows retrofit to nZEB standard. The preand post-retrofit operational performance is first estimated using the Irish Dwelling Energy Assessment Procedure (DEAP). The post-retrofit operational performance of the space heating and domestic hot water heating system is also measured over a year. The embodied energy is estimated by way of embodied carbon/energy calculations. Monitored r...

Precast concrete sandwich panels provide a thermally efficient alternative to conventional brick ... more Precast concrete sandwich panels provide a thermally efficient alternative to conventional brick and mortar construction and improve the energy efficiency of existing buildings. This project comprised the design and testing of a sample re-cladding panel composed of a phase change material (PCM) in the concrete inner wythe (for thermal efficiency) and a thin ultra-high performance concrete (UHPC) outer wythe, joined compositely using a C-grid shear connector. Six different concrete mixes were prepared and structurally tested in compression and flexure. A concrete sandwich panel was cast using two of the best performing mixes and subsequently tested in three-point bending to investigate its flexural performance. The strongest PCM and UHPC concretes had average compressive and flexural strengths of 25MPa and 5.1MPa, and 121MPa and 9.2MPa respectively. The 900mm span panel tested in flexure reached its serviceability limit at 10kN, with ultimate peak load occurring at 97kN. Post-peak be...

This paper compares a range of new and proposed 'greener' concretes and evaluates their e... more This paper compares a range of new and proposed 'greener' concretes and evaluates their environmental impact via quantification of their embodied energy. These new concretes are further compared with bio based concretes so as to develop a broad picture of the relative environmental impact of the increasing array of concretes now available to building designers. Some uses, advantages and disadvantages of each type are discussed. Particularly the quantity and volume of concrete material for each specific use case is considered for comparison of the embodied energy for a square meter of building envelope structure. Results show that bio based concretes have considerably lower impact than standard concretes, as exhibited by much lower embodied energies per kilogram of material. However, those values documented in only a few studies, and further repeatedly referenced in the wider literature, are approximate at best and sometimes inaccurate. Ultra high performance and geopolymer c...

Journal of Building Engineering, 2021

Abstract High Performance Concrete (HPC) when reinforced with fibres (HPFRC) is often presented a... more Abstract High Performance Concrete (HPC) when reinforced with fibres (HPFRC) is often presented as an environmental improvement on typical reinforced concrete given that its higher strength means less material is required to resist the same forces. However, to achieve these high strengths, considerable proportions of cement, superplasticisers and discontinuous fibres are typically needed, all of which are manufactured using carbon-intensive processes. This article investigates the feasibility of HPFRC as a sustainability improvement on typical reinforced concrete for facade applications by developing novel low carbon HPFRC mixes and carrying out an embodied carbon analysis of a concrete cladding element constructed of those developed mixes. The environmentally improved HPFRC include coarse aggregates (to reduce cement paste volume), non-corrosive fibres (to eliminate the risk of corrosion) and a high dosage of supplementary cementitious material (to again minimise the cement content). Compressive strengths of 100 MPa and pre-cracking flexural strengths above 8 MPa were achieved. Importantly it was also found that the inclusion of resin coasted glass and basalt fibres (2.3% by volume) resulted in deflection hardening behaviour under flexural loading conditions. An environmental investigation found that the embodied carbon of a precast concrete facade can be reduced by 50% when using the presented fibre reinforced high performance concrete in place of typical reinforced concrete cladding.

Journal of Structural Integrity and Maintenance, 2021

ABSTRACT The traditional means of using precast concrete sandwich panels are restrictive in terms... more ABSTRACT The traditional means of using precast concrete sandwich panels are restrictive in terms of applications, where thick wythes result in heavy panels which are often unsuitable in retrofitting domestic and commercial buildings. As concrete sandwich panel technology has evolved to make it more widely accessible, recent research work has demonstrated that it is possible to achieve thermally efficient partial composite action within a thin wythe panel provided non-conductive shear connectors are used. This paper examines high performance recycled aggregate concrete in heavily insulated non-load-bearing panels for retrofitting domestic and commercial buildings. A series of concrete mixes were tested to develop one which would be more sustainable than the widely accepted standard mixes for wythes. Different 220 mm thick concrete sandwich panels were tested consisting of 20 mm thick fibre-reinforced recycled aggregate concrete wythes and a 180 mm layer of XPS insulation. Unconnected and shear connected panels were tested in flexure in a displacement control test. The effects of composite action and post-cracking toughness were examined and it was concluded that a shear connected panel comprising sustainable thin recycled aggregate concrete wythes enclosing a thick layer of insulation is a feasible product to use for light high-performance sandwich panels.

Energy and Buildings, 2021

Abstract In-situ U-value monitoring of building envelopes are investigated in this article by rev... more Abstract In-situ U-value monitoring of building envelopes are investigated in this article by reviewing past studies and monitoring the performance of highly insulated building envelopes. Specific past research studies have concluded both over- and underperformance of the building fabric when measured in situ. This current research has found that when analysing all studies and results over the full range of envelope U-values together there is no evidence of over- or underperformance. However, when highly insulated envelopes (U-values

Energy and Buildings, 2021

Abstract Electrical energy usage in Saudi Arabia is high (∼300 TWh/yr) and is increasing (>5%/... more Abstract Electrical energy usage in Saudi Arabia is high (∼300 TWh/yr) and is increasing (>5%/yr). The residential building sector is responsible for approximately half of the total electricity usage. Past studies have shown that up to 70% of the electric energy used in buildings in Saudi Arabia is consumed in the air conditioning of internal space. This study investigates this significant cooling requirement, particularly concerning the building envelope in typical detached villa housing. The paper concludes that walls formed using insulated concrete blocks only, as is common in Saudi Arabia, do not ensure compliance with the minimum requirements of the Saudi Code 2018. Thermal bridging of the building’s envelope, which is currently not given due focus in the code, undermines the performance further. Bridging caused by the mortar joints between blocks, and by the cast concrete structural elements, increases the thermal transmittance through the envelope by a factor of two, relative to a non-bridged insulated concrete block wall. Simplified methods for thermal bridging calculation are referenced in the Saudi code, and these are evaluated here with reference to a detailed finite element study. Modelling studies show that the neglection of thermal bridging could underpredict building energy load by approximately 54 kWh/m2/yr – from 139 to 85 kWh/m2/yr. A 55 mm thick continuous external insulation layer is proposed to improve the performance considerably, reducing the wall-averaged thermal transmittance from 1.27 W/(m2·K) to 0.34 W/(m2·K) and hence achieving compliance with the latest building code.

Journal of Green Building, 2020

Embodied energy is a measure of the energy used in producing, transporting and assembling the mat... more Embodied energy is a measure of the energy used in producing, transporting and assembling the materials for a building. Operational energy is the energy used to moderate the indoor environment to make it functional or comfortable—primarily, to heat or cool the building. For many building geometries, the walls make the most significant contribution to the embodied energy of the building, and they are also the path of greatest heat loss or gain through the fabric, as they often have a greater surface area than the roof or floor. Adding insulation reduces the heat flow through the wall, reducing the energy used during operation, but this adds to the embodied energy. The operational energy is not only a function of the wall buildup, but also depends on the climate, occupancy pattern, and heating strategy, making an optimisation for minimum overall energy use non-trivial. This study presents a comparison of typical wall construction types and heating strategies in a temperate maritime cl...

Construction and Building Materials, 2021

d Techrete, Ireland h i g h l i g h t s A thin precast concrete sandwich panel design is presente... more d Techrete, Ireland h i g h l i g h t s A thin precast concrete sandwich panel design is presented. The challenges associated with achieving the thin design are discussed. The structural performance of thin panel iterations is experimentally measured. The thermal performance of the panel design is calculated.