Pitched Roof Research Articles

Ventilated pitched roof with forced ventilation and flow homogenizer device: testing and performance assessment

Ventilated tile roofs are common objects in the construction sector of Italy. A preferred type is characterized by a ventilated air space between the upper tile layer and the roof structure below. The air enters through openings at the gutters level, flows up below sheathing in the air space along the pitch and is finally discharged through openings along the ridge. This setup, which leaves the room below the roof sealed and habitable, allows removing the heat brought by the absorbed solar radiation thanks to the flow that is established by natural ventilation in the air space. However, its actual performance is often weak and also unpredictable due to continuously changing buoyancy forces. Nonetheless, a permanent and adequate flow can be ensured even through a relatively thin air space and for whichever irradiance and wind conditions by forced ventilation: a properly designed fan can provide the desired flow rate by extracting the air after this is collected along the ridge by a manifold. A thorough design and manufacturing of the manifold is needed, however, to avoid a highly inhomogeneous flow, which would follow the easiest path and leave most of the pitch practically unventilated. As an alternative, a throttling shutter parallel to the ridge has been proposed to progressively choke the flow entering the manifold through parallel climbing ducts as the fan is approached, possibly allowing onsite adjustment after installation. In this work the solution, developed by means of a small scale test bed, is illustrated in details and some methods to assess the performance are presented.

Palace of the Earl of Padul, Granada (Spain). A Milestone in A Crossroad

The Palace of the Counts of Padul is the most emblematic building of Padul, Province of Granada in Spain, being one of the most remarkable of the region of the Valley of Lecrín. It is a building of undoubted historical value, declared of Cultural Interest, maximum level of protection of the Spanish legislation in historical heritage. In spite of this and being a symbol of Padul, citizen ignorance is generalized about its importance. It is a building of the first part of the XVII century. D. Antonio de Aróstegui y Zazo (knight of the Santiago order and a secretary of Felipe III) was its developer. He gives the building a noble character with an unusual design for this shire. It has an L shape floor, two floors and two squared towers standing out a third floor covered by a pitched roof. Load-bearing walls of masonry not carved stones, with carved stones corners. Deck built with logs, and bricks, and wooden roof truss. Looking like a solid simple house of civil architecture at the beginning of the Baroque style. Analysing the urban morphology of Padul, the uniqueness and large area of the plot that it occupies with respect to the rest of the urban plot is verified. It is also remarkable its relative position with respect to the historical roads that crossed here: The real road that came from Granada heading to the Alpujarras, and leading to Motril and the road that starting in Malaga crossed through Alhama and arrived at Padul. It is clear then, the function that had as a control post, having been a necessary passage towards the Lecrín Valley, the Alpujarras and the Mediterranean coast. Immediately after its declaration in 1981 as a National Monument, and despite this, it suffered an unfortunate intervention which has been maintained until today and that the City of Padul wants to revert with its acquisition. It is in this situation in which the invitation of the council government to the University of Granada is produced so that the students of Final of Grade Projects of the School of Building Engineering have it as a real object to work. By focusing our attention on this building, it is intended to preserve its valuable heritage, showing its history, proposing technical solutions that help to preserve its values, and finally, to make the Casa Grande popular for the residents of Padul and all visitors.

Evaluation of thermal properties of insulation systems in pitched roofs

The article outlines the basic requirements for pitched roof insulation systems. The analysis of the properties of thermal insulation materials used in insulation systems was conducted. It is substantiated that the thermal resistance of such structures on the surface of the roof is formed taking into account the thermal conductivity of thermal insulation, thermal conductivity of wooden rafters and heat loss through the leakiness of joints and mounting devices. An assessment was made of the effect of loads of various types on the heat-insulating layer, namely: the effect of the air flow in the ventilated gap; the movement of the vapor-air mixture in the material; condensation of water vapor and penetration of drip liquid; exfiltration of air at the joints of the plates and on the surfaces of contact with the supporting structures. The expediency of using products on the basis of unstitched polyethylene foam in the construction of pitched roofs with a wooden roof system, taking into account the advantages and features of this material, as well as taking into account the possibility of creating a seamless insulating shell, is substantiated.

PRINCIPLES AND CONCEPTS IN DESIGNING TROPICAL-SHORE SETTLEMENT IN ESTUARY ECOSYSTEM CASE STUDY: WERIAGAR DISTRICT, BINTUNI BAY

Weriagar District is located in estuary area and is prone to land loss, due to river and coastal erosion. Without any prevention efforts, Weriagar land might be disappear due to erosion on coastal and riverside. The Shore Housing Improvement Program was developed in 2014 to improve the environment, housing and settlement in Weriagar District. Based on the preliminary site observation and further site survey, the program continued in conducting in-depth analysis consists of house assessment method prior to concept select matrix development, in which design criteria were obtained. The results from analysis phase shows that it is necessary to design a house and settlement that can fulfil the needs of indigenous people, both functionally and aesthetically. Functionally, the house is designed to provide spaces for both private and public needs of the family. It can be used either as a family private space or as a public gathering space between family and their neighbours. Aesthetically, houses’ architectural form is designed to identify the locality of Weriagar District. The houses’ design feature highlighted in using local material, rainwater harvesting system, high pitched roof feature as a response to hot-humid climate and elevated-floor feature as response to tidal condition in estuary area.

Lower extremity kinematics of cross-slope roof walking

Working conditions of residential roofers expose them to a unique sloped environment. The purpose of this study is to determine in what way traversing across a sloped/roof surface alters lower extremity kinematics of the upslope and downslope legs compared to level walking. College aged males negotiated across a pitched (26 degrees) roof segment during which lower extremity three-dimensional kinematics were calculated. One foot was higher on the slope and one was lower for the duration of cross slope walking. Overall, cross-slope walking on a 26 degree roof significantly altered 77% of the measured lower extremity variables compared to level self-selected pace walking. The data suggest that roof pitch incite significant differences in crossslope walking of the kinematics in the lower extremity between the upslope and down slope limbs when compared to level surface walking. These alterations could temporarily alter proprioception which may in turn lead to increased falls and musculoskeletal injury, though further study is needed.

Performance of thin-film BIPV as double sloped pitched roof in buildings of Malaysia

ABSTRACTSolar energy in built environments became more popular in the recent years emerging as building integrated photovoltaics (90° façade and 0° roof BIPV). However, in most cases, residential buildings have varying roof pitches instead of 0° roof. In this context, it is significant to assess the energy output and performance of double-sloped pitched roof thin-film BIPV at different angles and orientation. Results show that the performance of the BIPV inclined at 15° and east orientation is better among the other orientation and angles.

Geographical variation in energy yields of rooftop photovoltaic projects in Australia

ABSTRACTPrecise estimation of rooftop-received solar energy is essential for the efficient energy generation of photovoltaic (PV) projects and the development of energy policies. Conventional measurements usually adopt light detection and ranging (LIDAR) data, which can only be extracted from existing buildings, to estimate the solar radiation potential of building rooftops in a region. This research establishes a pixel-based estimation method for investigating the effects of different geolocations on energy output and yield distributions of rooftop PV systems by formulating estimation equations for the SketchUp platform. Based on the proposed alorighm, the solar radiation on a certain cell of a shadow map is mathematically formulated for each pixel unit. A building model derived from a typical Australian house with flat and pitched roofs is then chosen as a case study in this paper. The potential electrical energy from the rooftop PV systems is then measured and analysed considering solar radiation potentials in different geographical positions. This study will benefit commercial and individual energy investors in the efficient use of renewable energy sources through the accurate prediction of radiation-based energy yields and the identification of areas that can provide high energy revenues on building roofs for different geolocations.

Optimizing Structures with Semi-Rigid Connections Using the Principle of Virtual Work

In this paper, the virtual work optimization method (VWOM) has been generalised to consider structures with semi-rigid connections. The VWOM is an automated method that minimizes the mass of a structure with a given geometry, multiple deflection criteria and load cases, while adhering to Design code requirements. In the optimization process, members are selected from a discrete database to meet all strength and stiffness criteria. Connections are modelled using rotational springs, allowing some moment transfer. The rotational stiffness of each connection can be varied form rigid to pinned. The example of a pitched roof frame is used to explain the method. Two case studies are considered: (i) a three-storey two-bay and (ii) a four-storey three-bay office building. The VWOM produced results up to 26.7% lighter than results in the literature. Furthermore, the structures were optimized for a range of rotational stiffness, where all connections in the structure were assumed to have the same rotational stiffness. Characteristic jumps in the optimized mass versus rotational stiffness were observed.

Energy Demand Reduction in Nearly Zero-Energy Buildings by Highly Efficient Aluminium Foam Heat Exchangers

The capability periodically to store and release the latent heat of phase transition during melting and solidification of Phase Change Materials (PCMs) has been currently the main subject of interest with regard to cost reduction efforts for cooling, heating of interiors and Domestic Hot Water (DHW) necessary for the operation and maintenance of adequate thermal comfort in new modern as well as old renovated residential buildings. The main principle of PCMs facilities to reduce significantly the energy consumption in the building industry of the future is based on the ability of thermo-active heat exchangers to absorb and later to dissipate into the surroundings excessive heat which can be easily obtained from renewable sources (e.g. solar energy, geothermal heat, etc.) directly in a building or in its immediate vicinity. Smart interior tiling and furnishing systems can provide high energy efficiency by stabilizing the room temperature at a level ensuring sufficient thermal comfort basically governed by the thermal conductivity and heat exchange area between ceiling (respectively also wall and floor if necessary) heat exchangers (radiators) and the heat storage medium in the form of PCMs. Unfortunately, most conventional building materials, e.g. aerated concrete, bricks, gypsum, ceramic tiles, etc. are particularly characterized by very low thermal conductivity, which disadvantages them to be used for these purposes. However, highly porous metallic material such as aluminium foam prepared by powder metallurgy [10, 11] is on the contrary excellently heat conductive, which predisposes it to be used for light-weight design of supporting structure of very energy efficient indoor as well as outdoor thermo-active heat exchangers for building industry of the future. This contribution points to the possibility to apply aluminium foam for both the novel innovative roofing system to cover pitched roofs and the interior ceiling panels, with the minimum energy demands for maintaining the sufficient thermal comfort in future nearly Zero-Energy Buildings (nZEBs).

A parametric study of the effect of roof height and morphology on air pollution dispersion in street canyons

We investigate the effect of conventional pitched roofs on ventilation and pollution in street canyons using Computational Fluid Dynamics and a parametric approach. We studied parallel street canyons with several street morphologies, created by assigning a set of streets with pitched roofs, and varying their pitch and arrangement for three different height-to-width aspect ratios. The distribution of flow properties and pollution concentrations within the street canyons are examined and the effect of different parameter combinations is assessed. We find the relationship between these properties and the street morphology to be complex and case specific.For most morphologies, the pitched roofs lead to higher average pollution concentrations, and in some cases to pollution hotspots near emission sources especially on the leeward side. The pitched roofs are rarely beneficial to ventilation of the street canyons, but a few roof arrangements lead to reduced concentrations on the windward side. Roof slope is shown to significantly relate to both average pollution concentrations and their distribution inside the street; in some street geometries more than others. The results have implications for pedestrian and residential pollution exposure, and for conservation of building facades on historical buildings.

Methodology for the service life prediction of ceramic claddings in pitched roofs

Currently, the built heritage presents clear signs of degradation, requiring in some situations an urgent intervention. The majority of defects can be avoided or mitigated at the design and execution stages, but the designers and stakeholders often neglect the maintainability of the buildings and components, thus compromising their performance and durability. It is thus necessary to adopt an integrated approach during the buildings life cycle, evaluating their performance over time, the influence of the degradation agents and mechanisms on their durability and service life, and the adoption of cost-effective maintenance strategies. In this sense, it is crucial to use quantitative information related with the performance of building components over time. This study intends to respond to this need by proposing a methodology for the service life prediction of pitched roofs’ ceramic claddings, which are the most common type of roofing system adopted in Portugal and in many countries around the world. These elements are one of the most vulnerable in a building, more exposed to the degradation agents, and with a higher incidence of defects. The method proposed is validated based on a visual inspection campaign, performed in 85 buildings and 146 claddings located in Portugal, with a total area of 43,991.6 m2. Various degradation patterns are established based on the roofs’ characteristics, evaluating their influence on the roof claddings’ service life. The proposed methodology allows obtaining coherent results, providing relevant information regarding the pitched roofs ceramic claddings’ service life, aiding the adoption of rational and integrated maintenance strategies.

Chemically and size-resolved particulate matter dry deposition on stone and surrogate surfaces inside and outside the low emission zone of Milan: application of a newly developed "Deposition Box".

The collection of atmospheric particles on not-filtering substrates via dry deposition, and the subsequent study of the particle-induced material decay, is trivial due to the high number of variables simultaneously acting on the investigated surface. This work reports seasonally resolved data of chemical composition and size distribution of particulate matter deposed on stone and surrogate surfaces obtained using a new method, especially developed at this purpose. A "Deposition Box" was designed allowing the particulate matter dry deposition to occur selectively removing, at the same time, variables that can mask the effect of airborne particles on material decay. A pitched roof avoided rainfall and wind variability; a standardised gentle air exchange rate ensured a continuous "sampling" of ambient air leaving unchanged the sampled particle size distribution and, at the same time, leaving quite calm condition inside the box, allowing the deposition to occur. Thus, the "Deposition Box" represents an affordable tool that can be used complementary to traditional exposure systems. With this system, several exposure campaigns, involving investigated stone materials (ISMs) (Carrara Marble, Botticino limestone, Noto calcarenite and Granite) and surrogate (Quartz, PTFE, and Aluminium) substrates, have been performed in two different sites placed in Milan (Italy) inside and outside the low emission zone. Deposition rates (30-90μgcm-2month-1) showed significant differences between sites and seasons, becoming less evident considering long-period exposures due to a positive feedback on the deposition induced by the deposited particles. Similarly, different stone substrates influenced the deposition rates too. The collected deposits have been observed with optical and scanning electron microscopes and analysed by ion chromatography. Ion deposition rates were similar in the two sites during winter, whereas it was greater outside the low emission zone during summer and considering the long-period exposure. The dimensional distribution of the collected deposits showed a significant presence of fine particles in agreement with deposition rate of the ionic fraction. The obtained results allowed to point out the role of the fine particles fraction and the importance of making seasonal studies.

Point thermal bridges of insulated pitched roof structures

The current demands on building insulation are continuously increasing. It is understood that the lower the heat transfer coefficient of a particular part of a construction is, the greater the importance of systemic thermal bridges. This article compares the individual systems of insulation of pitched roofs in terms of the heat transfer coefficient. The focus is on the size of the point thermal bridges in rafter thermal insulation systems and determines their impact on increasing the overall heat transfer coefficient. However, it should be noted that point thermal bridges are individually very small and combined only contribute to 2% of the overall heat transfer coefficient of parts of a structure.

Insulation systems for buildings and structures based on expanded polyethylene

Insulation systems for buildings and structures imply the use of efficient thermal insulation products based on mineral wool, expanded polystyrene, expanded polyurethane, etc. For a long time, products from non-cross-linked expanded polyethylene were used as insulation for pipelines, reflective insulation, protection against air infiltration, etc. Modern technologies and engineering solutions allowed widening the field of application of non-cross-linked expanded polyethylene (NXLPE) as a construction insulation material. In particular, we can consider a complex of insulation systems for walls, floors and a pitched roof, which allows to form a fully insulating shell of a low-rise building, e.g. a cottage. The novelty of the patented technology Tepofol® and that of the material concerned in comparison with the known solutions is the development of a rolled material based on NXLPE (20 to 150 mm thick) with a lock joint, as well as the technology of seamless connection of individual heat-insulating cloths. The rolls of NXLPE are mechanically fixed to the frame and connected with the lock. One of the advantages of expanded polyethylene, which only few insulating materials possess, is the possibility of forming seamless insulating shells. The article considers a number of insulation systems based on the use of products from expanded polyethylene. In particular, these are the systems of insulation of the walls of frame buildings, the insulation of floors, as well as the insulation of logistics facilities and hangars.

Urban and regional heat island adaptation measures in the Netherlands

The urban planner's role should be adapted to the current globalised and over-specialised economic and environmental context, envisioning a balance at the regional scale, apprehending not only new technologies, but also new mapping principles, that allow obtaining multidisciplinary integral overviews since the preliminary stages of the design process. The urban heat Island (UHI) is one of the main phenomena aff ecting the urban climate. In the Netherlands, during the heat wave of 2006, more than 1,000 extra deaths were registered. UHI-related parameters are an example of new elements that should be taken into consideration since the early phases of the design process.

Local loss coefficients inside air cavity of ventilated pitched roofs

Pitched roofs with a ventilated air cavity to avoid snow melt and ensure dry conditions beneath the roofing are a widely used construction in northern parts of Europe and America. The purpose of this study has been to determine pressure losses at the inlet (eaves) and inside the air cavity consisting of friction losses and passing of tile battens. These results are necessary to increase the accuracy of ventilation calculations of pitched roofs. Laboratory measurements, numerical analysis as well as calculations by use of empirical expressions have been used in the study. A large difference in the local loss coefficients depending on the edge design and height of the tile batten was found. The local loss coefficients of the round-edged tile battens were approximately 40% lower than the local loss coefficients of the sharp-edged tile battens. Furthermore, the local loss factor increased by increasing height of the tile batten. The numerical analysis was found to reliably reproduce the results from the measurements.

Principles and concepts in designing tropical-shore settlement in estuary ecosystem, case study: Weriagar District, Bintuni Bay

Weriagar District is located in estuary area and is prone to land loss, due to river and coastal erosion. This paper will describe about tropical-shore settlement design and house design in estuary area. The results from analysis phase shows that it's necessary to design a house and settlement that can fulfil the needs of indigenous people, both functionally and aesthetically. Functionally, the house is designed to provide spaces for both private and public needs of the family. It can be used either as a family private space or as a public gathering space between family and their neighbours. Aesthetically, house’ architectural form is designed into that identifies the locality of Weriagar District. The houses’ design feature highlighted in using local material, rainwater harvesting system, high pitched roof feature as response to hot-humid climate, and elevated-floor feature as response to tidal condition in estuary area. The houses design also considered daily activity pattern and community culture, including appropriate structure, construction, and material availability. The expected result was that the settlement improvement and house design would meet suitable standards and needs of inhabitants in Weriagar District.

Urban and regional heat island adaptation measures in the Netherlands

Urban and regional heat island adaptation measures in the Netherlands

Experimental analysis of an innovative tile covering for ventilated pitched roofs

This study investigates the thermal and fluid-dynamic behaviour of two ventilated roofs equipped with a new tile shape in comparison with a standard Portuguese tile. The novel tile shape was designed to improve the air permeability of coverings, thus producing a further above sheathing ventilation (ASV) enhancement as proposed in the ongoing LIFE HEROTILE European project, in which original roof tiles with innovative sidelock and headlock patterns have been designed, produced and are now under testing with real operating conditions. The heat transfer in the different roof layers and the ASV fluid flow have been experimentally analysed by means of a dedicated real scale mock-up. The results of the preliminary testing period are presented in this paper, they are referred to a first period with open eaves and to a second one in which eaves were closed to observe the only effect of tile air permeability. The data analysis shows that the ASV is strictly linked to the external wind conditions and grants better performances in HEROTILE roof. Moreover, the new tile design produces a significant increase of the ASV, so that better thermal performances are achievable in reducing solar heat gain during hot periods. As a consequence, the mock-up with HEROTILE ventilated roofs need less energy for air conditioning and allows high energy saving when compared with the standard one.

Technical – Economic Research for Passive Buildings

A newly constructed passive house must save 80 % of heat resources; otherwise it is not a passive house. The heating energy demand of a passive building is less than 15 kWh/m2 per year. However, a passive house is something more than just an energy-saving house. This concept involves sustainable, high-quality, valuable, healthy and durable construction. Features of a passive house: high insulation of envelope components, high-quality windows, good tightness of the building, regenerative ventilation system and elimination of thermal bridges. The Energy Performance of Buildings Directive (EPBD) 61 requires all new public buildings to become near-zero energy buildings by 2019 and will be extended to all new buildings by 2021. This concept involves sustainable, high-quality, valuable, healthy and durable construction. Foundation, walls and roofs are the most essential elements of a house. The type of foundation for a private house is selected considering many factors. The article examines technological and structural solutions for passive buildings foundation, walls and roofs. The technical-economic comparison of the main structures of a passive house revealed that it is cheaper to install an adequately designed concrete slab foundation than to build strip or pile foundation and the floor separately. Timber stud walls are the cheapest wall option for a passive house and 45-51% cheaper compared to other options. The comparison of roofs and ceilings showed that insulation of the ceiling is 25% more efficient than insulation of the roof. The comparison of the main envelope elements efficiency by multiple-criteria evaluation methods showed that it is economically feasible to install concrete slab on ground foundation, stud walls with sheet cladding and a pitched roof with insulated ceiling.