Now showing 1 - 10 of 11
- PublicationApplication of hemp-lime renders to improve insulation of wallsThis paper measures the variation in the thermal transmittance of solid brick walls triggered by the application of hemp-lime renders in an effort to enhance the insulating properties of building fabrics. Six trial renders with different proportions of hemp and lime were fabricated and two selected based on their workability and adhesion. The renders were applied to solid brick walls and their thermal transmittance measured using the hot box method. Thermal imaging was used to control thermal bridges in the masonry assemblies. The results were compared with a control brick wall with no render. When compared to commercial mixes such diathomite and expanded polystyrene, it was seen that the hemp-lime renders display similar thermal properties that qualify them as good insulators. The results evidenced that the application of a hemp-lime render can halve the thermal transmittance of a solid brick wall. The renders investigated notably increase the resistance to heat transfer in the brick wall. Render 5 (a 1.25: 1 -hemp: NHL3.5 mix applied in a 21 mm depth) nearly doubles the thermal resistance and halves the thermal transmittance of the wall, reducing the U-value from 6.99 to 3.65 W/m2K therefore doubling the insulation provided by the solid brick wall.It was also noted that the 21 mm hemp-lime renders also improve the thermal properties of stone walls however, the improvement is not as notable as in the solid brick walls. Though it was noted that a render twice the thickness (40 mm) would greatly improve the thermal performance of the stone walls reducing U-values by c.40%. The outstanding insulating ability of air gaps was exposed by including a 20 mm gap between the renders and the wall: when the hemp-lime renders were applied on a metal lath or mesh set with a 20 mm gap off the wall, the U-values of the walls lower by over 30%. Also, it was demonstrated that the hemp-lime renders improve the thermal performance of solid walls to a much greater extent than cavity walls.
- PublicationDesign and manufacture of a precast PCM enhanced concrete cladding panel for full scale performance monitoringThe overall aim of this study is to develop innovative precast cladding panels for the renovation of Europe’s existing building stock thereby improving their energy performance. Using the mass of a building to store heat and/or cold can reduce the demand on the auxiliary heating and/or cooling systems and hence reduce the overall energy demand of the building. Previous laboratory research has shown that the incorporation of phase change materials (PCMs) into concrete enhances its thermal storage capacity by up to 50%. However in a real application where a PCM-concrete composite material is used in a building to store thermal energy, the effectiveness of the PCM depends on many variables including the form of construction and local climate conditions. In this research study a precast cladding panel formed with PCM enhanced concrete has been developed and manufactured. In order to observe the performance of the PCM-concrete composite panels in a full scale scenario, three demonstration huts have been constructed and instrumented to record internal thermal behaviour. Monitoring of the data is ongoing and shows that the effectiveness of the PCM varies with the seasons. Data recorded during the summer period highlighted that the internal temperature may not drop low enough during the night to solidify the PCM and discharge the stored heat. A further test in which passive ventilation was provided during the night proved to be an effective method of addressing this issue. It is expected that this long term study will enable recommendations to be made on the seasonal benefits of using PCM-concrete to enhance the energy performance of buildings located in climate conditions similar to Ireland. The results of the data analysis will inform a refinement of the panel design prior to installing the panels at a school in the UK which currently has an overheating problem.
- PublicationSubmission to the Public Consultation on the Review of Part L (Conservation of Fuel and Energy for Buildings other than Dwellings) 2017This submission is a contribution to the Review of Part L (Conservation of Fuel and Energy for Buildings other than Dwellings) 2017, which have "the overall objective of improving the energy and carbon performance of new buildings other than dwellings and to transpose the EU requirement for nearly zero energy buildings and major renovations, without imposing a disproportionate burden on industry in terms of bureaucracy or costs".
- PublicationOperational and embodied energy analysis of 8 single-occupant dwellings retrofit to nZEB standardIn 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 pre- and 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 results of the 8 similar buildings exhibit a wide variance of operational energy consumption while the embodied energy is (by nature of the calculation) consistent. The average estimated primary energy requirement for the buildings was 674 kWh/(m2ᐧyear) pre-retrofit and 38 kWh/(m2ᐧyear) post-retrofit while the average measured primary energy requirement for space heating and hot water alone was 119 kWh/(m2ᐧyear) – ranging from 74 to 167 kWh/(m2ᐧyear) for the 8 houses. The embodied energy of the materials and technologies used to retrofit the buildings was 676 kWh/m2. Despite the building performing worse than expected, desirable primary energy and carbon paybacks of 2.0 and 6.1 years were achieved respectively. These positive payback periods are largely due to the very poor operational performance of the buildings pre-retrofit.
- PublicationWhat is a sustainable or low impact concrete?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 concretes have higher embodied energies but due to their high strengths less material is used, giving them a low environmental impact advantage over standard concrete materials. However, claims that these concretes are many multiples less impactful is widely inaccurate, and misleading promotion. In a similar vein, this work also questions the claims of carbon negativity of popular bio based concretes, such as hemp-lime. Investigation of the means of carbon sequestration and the difficulties in its quantification are discussed. More realistic estimates of the energy embodied of hemp-lime are used for calculation of the embodied energy, and carbon, for walls sized appropriate to low energy architecture.
- PublicationDevelopment and testing of a sandwich panel with UHPC and PCM concrete layersPrecast 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 behaviour illustrated the role of the shear connector in allowing composite action to occur.
- PublicationPost Occupancy Analysis of nZEB implementation via the PH standardBuilding regulations are currently under development across Europe in advance of the implementation of the nearly Zero Energy Buildings (nZEB) standard at national member state level. However, when revising the national building regulations to improve energy efficiency, few examples exist of the monitored performance of such dwellings, making informed decision-making difficult. This paper reports on the monitored performance of nZEB compliant dwellings which were built to the Passive House (PH) Standard. It finds that the PH bedroom CO2 concentrations are significantly better than in houses built to the current building regulations which use natural ventilation.
- PublicationAn assessment of the thermal storage capacity of hemp-lime using the Transient Performance Ratio methodMany claims are made regarding the superior thermal performance of high heat capacity materials under the general heading of thermal mass. However, the benefits of thermal mass are poorly quantified in existing literature. These issues often become more important in the case of biobased materials, where thick, monolithic wall construction leads to a stronger connection between a building's structure and the indoor environment. New materials include hemp-lime concrete, which offers a combination of structural, thermal and hygroscopic properties that make it suitable for incorporation into the building envelope. Hemp-lime has long been proposed to offer excellent thermal mass performance, yet this impact is poorly quantified in existing literature. This paper uses the Transient Energy Ratio (TER) method, developed by these authors, to compare the performance of hemp-lime concrete walls with traditional solid wall and cavity wall constructions.
- PublicationRecorded energy consumption of nZEB dwellings and corresponding interior temperatures: Initial results from the Irish nZEB101 projectIreland is mandating the unprecedented mass market deployment of low-energy dwellings via the near Zero Energy Buildings (nZEB) standard, from 1 January 2021 due to the EU wide Energy Performance of Buildings Directive (EPBD). This is among the first academic papers to provide recorded energy and temperature data for nZEB compliant dwellings in Ireland. It reports on initial results of the www.nZEB101.ie Post Occupancy Evaluation project, the objective of which is to uncover key nZEB design and operations lessons, to aid the next iteration of the country's building regulations. This paper reports on the analysis of winter temperatures and the energy consumption of 17 nZEB compliant dwellings, each of which have been monitored for at least a 12 month period. While analysis of further properties is needed to further validate the findings, key findings to date include significantly higher than expected interior temperatures and energy consumption, and a usage profile which is significantly different from the assumptions in the DEAP National energy rating software.
- PublicationFinite Element Analysis of Thin Precast Concrete Sandwich PanelsThe 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.