Control of moisture and heat flow through building enclosure assemblies is a critical component of overall building performance. This thesis shows that significant drying of moisture in wall assemblies is possible and that ventilation of cladding significantly increases the rate of drying in some assemblies without having detrimental impact on the enclosures thermal performance. A review found that thermal and moisture buoyancy, wind pressure gradients and mechanical equipment drive ventilation airflow. This ventilation flow can theoretically increase the effective water vapour permeance and thermal conductivity. Ventilation has the potential to increase outward drying through relatively impermeable claddings at the low flows expected to occur in service. The impact on thermal conductance is much less. A methodology for assessing the complicated airflow resistance characteristics of lap sidings was developed and applied to a representative vinyl siding. Field drying studies showed that the sample tested is well ventilated. Field brick veneer clad wall samples were also tested for system airflow resistance over a range of driving pressures. Theoretical predictions under-estimated the measured flow rate for given steady driving air pressures. Measurements of naturally driven cavity air speeds and smoke pencil testing showed that flow rates were commonly occurring that would in theory significantly affect the hygrothermal performance of the walls. This was confirmed with field drying studies. A field drying study of east-facing test wall with vinyl siding and brick veneer cladding was conducted in Waterloo, Ontario, Canada. Significant amounts of drying and inward moisture redistribution were measured. Wall sheathing dried quickly in hot summer conditions but in some cases significant inward driven moisture flow occurred. In cool and cold weather the wall dried more slowly and much less moisture moved inward. Increased cladding ventilation significantly increased drying rates and reduced internal wall assembly moisture levels. It was concluded that cladding ventilation acts to increase the effective vapour permeance of cladding and to reduce solar driven inward vapour drives. The use of spun bonded polyolefin sheathing membrane in lieu of #15 asphalt impregnated felt was found to improved hygrothermal performance in the test walls. The difference observed was concluded to be due to the higher vapour permeance of the spun bonded polyolefin and may not hold for wall assemblies with lower permeance sheathings (e. g. oriented strand board and foam plastic). Walls clad with vinyl siding dried faster than those clad with brick veneer. It was concluded that the vinyl siding is a well ventilated cladding system.

In recent years the U. S. and Canada have seen a steady increase in energy consumption. The U. S. in particular uses 25% more energy than it did 20 years ago. With declining natural resources and an increase in fuel costs, it has become important to find methods of reducing energy consumption, in which energy conservation in space heating and cooling has become a widely researched area. One method that has been identified to reduce the energy required for space heating is the use of radiant panels. Radiant panels are beneficial because the temperature set points in a room can be lowered without sacrificing occupant comfort. They have therefore become very popular in the market. Further research, however, is required to optimize the performance of these panels so energy savings can be realized. <br /><br /> An analytical model has been developed to predict the panel temperature and heat output for perimeter radiant panel systems with a known inlet temperature and flow rate, based on a flat plate solar collector (RSC) model. As radiative and convective heat transfer coefficients were required to run the model, an analytical analysis of the radiative heat transfer was performed, and a numerical model was developed to predict the convective heat transfer coefficient. Using the conventional radiative heat exchange method assuming a three-surface enclosure, the radiative heat transfer could be determined. Numerically, a correlation was developed to predict the natural convective heat transfer. <br /><br /> To validate the analytical model, an experimental analysis was performed on radiant panels. A 4m by 4m by 3m test chamber was constructed in which the surrounding walls and floor were maintained at a constant temperature and the heat output from an installed radiant panel was measured. Two radiant panels were tested; a 0. 61m wide panel with 4 passes and a 0. 61m wide panel with 8 passes. The panels were tested at 5 different inlet water temperatures ranging from 50°C to 100°C. <br /><br /> The RSC model panel temperature and heat output predictions were in good agreement with the experimental results. The RSC model followed the same trends as that in the experimental results, and the panel temperature and panel heat output were within experimental uncertainty, concluding that the RSC model is a viable, simple algorithm which could be used to predict panel performance.

Much of the existing commercial building stock is aging and will be in need of upgrades now or within the next twenty years. Typically, enclosure retrofits consist of adding insulation to the exterior or interior of the existing façade. In this thesis, an alternative solution is examined, whereby a glass façade is added to the exterior of the existing building, forming a double façade. For historic buildings, this could preserve and protect the existing façade without completely covering it up. For outdated buildings, this could modernize the existing façade, giving it the all-glazed appearance that is currently so popular among architects. Regardless of the retrofit motive, it is important to be able to quantitatively compare retrofit solutions to make informed design decisions. As such, building simulation can be an important design tool. At present, there is no available simulation tool that can easily and accurately model a double façade; therefore, a double façade (DoFa) model was developed to fill this gap. A spreadsheet-based, lumped model was created and validated using current complex fenestration models and limited experimental data. Further experimental data is required to validate all aspects of the model. Results showed that the DoFa model can achieve accurate results; however, further development is needed to predict optical properties of venetian blinds and convective coefficients for natural airflow in double façade cavities. The model was used to compare double façades to traditional glazing systems. Results indicated that double façades can perform comparably to double glazing with outdoor shading in summer, and triple glazing in winter. However, the results are only valid for the tested glazing systems. In a second application, the DoFa model was modified to simulate an entire enclosure to compare a double façade retrofit to more traditional retrofit strategies. Results suggested that a double façade provides a good improvement in winter performance, though summer overheating is a concern. For the case study examined, a double façade would have performed better than the chosen retrofit of replacing the windows with double glazing and indoor shading, without insulating the opaque components. The DoFa model can be very useful in creating double façade preliminary design and operation strategies. At present, the DoFa model is an instantaneous, stand-alone tool. Further development is needed to pair the DoFa model with whole building energy simulations.

Control of moisture and heat flow through building enclosure assemblies is a critical component of overall building performance. This thesis shows that significant drying of moisture in wall assemblies is possible and that ventilation of cladding significantly increases the rate of drying in some assemblies without having detrimental impact on the enclosures thermal performance. A review found that thermal and moisture buoyancy, wind pressure gradients and mechanical equipment drive ventilation airflow. This ventilation flow can theoretically increase the effective water vapour permeance and thermal conductivity. Ventilation has the potential to increase outward drying through relatively impermeable claddings at the low flows expected to occur in service. The impact on thermal conductance is much less. A methodology for assessing the complicated airflow resistance characteristics of lap sidings was developed and applied to a representative vinyl siding. Field drying studies showed that the sample tested is well ventilated. Field brick veneer clad wall samples were also tested for system airflow resistance over a range of driving pressures. Theoretical predictions under-estimated the measured flow rate for given steady driving air pressures. Measurements of naturally driven cavity air speeds and smoke pencil testing showed that flow rates were commonly occurring that would in theory significantly affect the hygrothermal performance of the walls. This was confirmed with field drying studies. A field drying study of east-facing test wall with vinyl siding and brick veneer cladding was conducted in Waterloo, Ontario, Canada. Significant amounts of drying and inward moisture redistribution were measured. Wall sheathing dried quickly in hot summer conditions but in some cases significant inward driven moisture flow occurred. In cool and cold weather the wall dried more slowly and much less moisture moved inward. Increased cladding ventilation significantly increased drying rates and reduced internal wall assembly moisture levels. It was concluded that cladding ventilation acts to increase the effective vapour permeance of cladding and to reduce solar driven inward vapour drives. The use of spun bonded polyolefin sheathing membrane in lieu of #15 asphalt impregnated felt was found to improved hygrothermal performance in the test walls. The difference observed was concluded to be due to the higher vapour permeance of the spun bonded polyolefin and may not hold for wall assemblies with lower permeance sheathings (e. g. oriented strand board and foam plastic). Walls clad with vinyl siding dried faster than those clad with brick veneer. It was concluded that the vinyl siding is a well ventilated cladding system.

In recent years the U. S. and Canada have seen a steady increase in energy consumption. The U. S. in particular uses 25% more energy than it did 20 years ago. With declining natural resources and an increase in fuel costs, it has become important to find methods of reducing energy consumption, in which energy conservation in space heating and cooling has become a widely researched area. One method that has been identified to reduce the energy required for space heating is the use of radiant panels. Radiant panels are beneficial because the temperature set points in a room can be lowered without sacrificing occupant comfort. They have therefore become very popular in the market. Further research, however, is required to optimize the performance of these panels so energy savings can be realized. <br /><br /> An analytical model has been developed to predict the panel temperature and heat output for perimeter radiant panel systems with a known inlet temperature and flow rate, based on a flat plate solar collector (RSC) model. As radiative and convective heat transfer coefficients were required to run the model, an analytical analysis of the radiative heat transfer was performed, and a numerical model was developed to predict the convective heat transfer coefficient. Using the conventional radiative heat exchange method assuming a three-surface enclosure, the radiative heat transfer could be determined. Numerically, a correlation was developed to predict the natural convective heat transfer. <br /><br /> To validate the analytical model, an experimental analysis was performed on radiant panels. A 4m by 4m by 3m test chamber was constructed in which the surrounding walls and floor were maintained at a constant temperature and the heat output from an installed radiant panel was measured. Two radiant panels were tested; a 0. 61m wide panel with 4 passes and a 0. 61m wide panel with 8 passes. The panels were tested at 5 different inlet water temperatures ranging from 50°C to 100°C. <br /><br /> The RSC model panel temperature and heat output predictions were in good agreement with the experimental results. The RSC model followed the same trends as that in the experimental results, and the panel temperature and panel heat output were within experimental uncertainty, concluding that the RSC model is a viable, simple algorithm which could be used to predict panel performance.

Firefighters often arrive at structures in which the state of fire progression can be described as ventilation-controlled or under-ventilated. This means that inside the enclosure the pyrolyzed fuel has consumed most, if not all of the available oxygen, resulting in incomplete combustion. Under-ventilated (fuel rich) combustion is particularly dangerous to occupants because of the high yield of toxins such as carbon monoxide and to firefighters because once firefighters enter the structure and introduce oxidizer, the environment can rapidly change into a very dangerous, fast burning condition. The fuel load in many compartment fires would support a several megawatt fire if the fire were not ventilation controlled. In the process of making entrance to the fire compartment, firefighters will likely provide additional ventilation paths for the fire and may initiate firefighting tactics like positive pressure ventilation to push the hot flammable combustion products out of the attack pathway. Forced ventilation creates a strongly mixed flow within the fire compartment. Ventilation creates a complex fluid mechanics and combustion environment that is generally not analyzed on the scale of compartment fires. To better understand the complex coupling of these phenomena, compartment scale non-reacting and reacting experiments were conducted. The experiments, which were conducted at The University of Texas at Austin’s fire research facility, were designed to gain insight into the effects of ventilation on compartment thermal characteristics. Computational models (low and high order) were used to augment the non-reacting and reacting experimental results. Though computationally expensive, computational fluid dynamics models provided significant detail into the coupling of buoyantly driven fire products with externally applied wind or fan flow. A partially stirred reactor model was used to describe strongly driven fire compartment combustion processes because previously there was not an appropriate low dimensional computational tool applicable to this type of problem. This dissertation will focus on the experimental and computational characterization of strong vent flows on single room enclosure fires. / text

In recent years several high-profile building fires have highlighted shortcomings in the way we design for the complex interaction of structures and fire. These weaknesses appear to arise from a combination of gaps in knowledge of some of the more intricate aspects of compartment fire dynamics and from limitations in the engineering applications developed to date from hitherto established fundamentals. In particular the One Meridian Plaza Fire (1991), the Madrid Windsor Tower Fire (2005) and the Lakanal House Fire (2009) have emphasised the need for further study in the field of post-flashover compartment fires and the often consequent external fires that emerge from the compartment openings. External fire plumes impinge upon the structural façade, causing added structural stress, and often result in external fire spread and secondary ignition in upper level compartments. Hence a better understanding of the effect had by the internal compartment fire on the development of external flaming and the insult of the plume to its surroundings is beneficial for Structural Engineers, Fire Protection Engineers and Emergency Response Personnel alike. This research explores existing correlations, identifies their limitations and proposes a simplified methodology that links key parameters found to govern the internal post-flashover compartment fire to the heat flux potentially imposed on the exterior façade. Existing correlations addressing the effect of compartment fires on the insult to the external structure have largely been compiled by Law and are summarised in the form of a design manual for bare external structural steel [1]. Formulated in the 1970s, these correlations are based on the combined findings of several different experimental tests devised to investigate component phenomena of compartment fires and external flaming, forming an analytical model which is mostly empirical in nature. The methodology is convoluted and has several inherent assumptions which give rise to various limits of applicability however it is currently still used in structural-fire design, but best known as Annex B of both Eurocodes 1 and 3 [2,3]. As part of the present research, full-scale fire tests are conducted in situ, in a highly instrumented high-rise building, to provide high-resolution measurements of several internal compartment fire characteristics during a post-flashover fire in a modern, realistically-furnished compartment. External high resolution instrumentation in the main test also provides detailed measurements of the external flaming and distribution of heat flux incident on the façade. The tests provide realistic benchmark scenario data for comparing physical measurements against the analytical Law Model, the difference in which allows for an evaluation of the assumptions used in the model, which are often defined as ‘conservative’ in nature from the perspective of structural design. A detailed sensitivity study of the main input parameters in the Law Model allows for the identification of parameters of pivotal influence on the resultant heat flux incident on the plane of the external façade. Analysis of the Law Model and its underlying experimental basis also enables the identification of several limits of applicability of the model. Combined, these assessments show the analytical model can be stripped of unnecessary complexity and a Simplified Model is proposed with clear bounds of applicability. The proposed model describes the distribution of heat flux to the façade above a compartment opening and features only parameters of key importance, where low-dependency parameters are grouped into associated error bars. This results in a model that can be applied in the design of several building components that fall in the plane of the façade, such as structural elements, façade cladding and window arrangements. Its ease of implementation renders the model more widely accessible to different factions of the Fire Engineering Community. Furthermore, analysis of the Law Model identifies further parameters of potential importance that have, as of yet, not been addressed. A preliminary investigation conducted using Computational Fluid Dynamics (CFD) tools shows that variation in some parameters – that are not individually accounted for in the Law Model – may influence the compartment fire conditions, the consequent external flaming and the resultant external heat exposure. Therefore, it is recommended that further comprehensive experimental research be conducted into the potential influence of the identified parameters.

Much of the existing commercial building stock is aging and will be in need of upgrades now or within the next twenty years. Typically, enclosure retrofits consist of adding insulation to the exterior or interior of the existing façade. In this thesis, an alternative solution is examined, whereby a glass façade is added to the exterior of the existing building, forming a double façade. For historic buildings, this could preserve and protect the existing façade without completely covering it up. For outdated buildings, this could modernize the existing façade, giving it the all-glazed appearance that is currently so popular among architects. Regardless of the retrofit motive, it is important to be able to quantitatively compare retrofit solutions to make informed design decisions. As such, building simulation can be an important design tool. At present, there is no available simulation tool that can easily and accurately model a double façade; therefore, a double façade (DoFa) model was developed to fill this gap. A spreadsheet-based, lumped model was created and validated using current complex fenestration models and limited experimental data. Further experimental data is required to validate all aspects of the model. Results showed that the DoFa model can achieve accurate results; however, further development is needed to predict optical properties of venetian blinds and convective coefficients for natural airflow in double façade cavities. The model was used to compare double façades to traditional glazing systems. Results indicated that double façades can perform comparably to double glazing with outdoor shading in summer, and triple glazing in winter. However, the results are only valid for the tested glazing systems. In a second application, the DoFa model was modified to simulate an entire enclosure to compare a double façade retrofit to more traditional retrofit strategies. Results suggested that a double façade provides a good improvement in winter performance, though summer overheating is a concern. For the case study examined, a double façade would have performed better than the chosen retrofit of replacing the windows with double glazing and indoor shading, without insulating the opaque components. The DoFa model can be very useful in creating double façade preliminary design and operation strategies. At present, the DoFa model is an instantaneous, stand-alone tool. Further development is needed to pair the DoFa model with whole building energy simulations.

Thesis (J.C.L.)--Catholic University of America, 1990. / Includes bibliographical references (leaves 49-52).

Once dominant, longleaf pine forests of the southeastern United States have been modified by 97 percent, resulting in several animal species being listed as endangered and threatened. Pine plantation silviculture (tree plantings) now occupies half of the original longleaf range where several animal species of conservation concern have experienced recent local population declines. In North America, the accepted practice of pine plantations is to plant pines densely in rows for wood production. Given that land use is considered a primary local driver for the 30% of amphibian species currently at risk of extinction, and planted pine is predicted to expand coverage by 2020, sustainable land management will require integrating ecological and economic goals, including conservation objectives. To understand how amphibian species characteristic of longleaf pine forest are affected by planted pine forestry, it is necessary to understand how associated shifts in habitat structure associated with aging pine stands influence species composition across a wide geographic area, especially populations of rare species. The purpose of this dissertation is to examine how forest structure (natural regeneration vs plantation) affects amphibian species composition and occupancy of small isolated wetlands embedded within the forest. Particular emphasis is placed on assessing several potential causal mechanisms of regional declines in amphibian species. This study was performed on Florida public forests where active forest management is a potential conservation tool and historic populations of rare amphibians occur. Sites where occupancy was assessed included: Goethe State Forest, Ocala National Forest, Jennings State Forest, Saint Marks National Wildlife Refuge, and Apalachicola National Forest. Withlacoochee State Forest was used for examining potential causal mechanisms of amphibian declines because of close proximity of reference condition forest to planted pine. Chapter One of this dissertation uses Objective Based Vegetation Monitoring (OBVM) metrics to quantify differences in forest habitat structure surrounding study sites (among planted pines and naturally regenerated second growth pine) and relationships between vegetation metrics. Increased basal area of planted pine resulted in decreased canopy openness and a significant decrease of ground cover, especially wiregrass. Serenoa repens petiole counts and percent cover of woody shrubs also significantly decreased wiregrass cover, and variance partitioning indicated that the effects of woody shrub invasion and pine basal area on wiregrass were independent on public forests. Absence of bare ground because of pine needle litter was a significant predictor of wiregrass absence in a zero-inflated negative binomial model (ZINB). ZINB predictions for wiregrass cover along a gradient of pine basal area and woody shrub abundance demonstrated the importance of habitat management for native groundcover on public forests. OBVM metrics were often positively correlated within the canopy, subcanopy, and groundcover categories. Chapter Two presents the results of site occupancy modeling comparing the presence of 10 species of amphibians in planted pine and naturally regenerated forest, focusing on the influence of canopy and groundcover habitat structure on occupancy of individual amphibian species. Amphibian species of greatest conservation need (SGCN) in Florida adapted to xeric soils, i.e. the gopher frog (Lithobates capito) and striped newt (Notophthalmus perstriatus), were found where basal tree areas were below 10.3 m2/ha, and a mesic amphibian SGCN, the ornate chorus frog (Pseudacris ornata), was found at pine basal areas up to 13.1 sq. m2/ha. All SGCN were found at sites with average woody shrub cover below four percent, and litter cover below 80 percent. Wiregrass cover was higher than four and six percent per m2 at sites with L. capito and N. perstriatus, respectively. Of 33 site detections for SGCN, only three sites had < 2.5 m2 wiregrass cover. Only one species, the pinewoods treefrog (Hyla femoralis), was more common on planted pine stands, and both Lithobates sphenocephala and L. grylio had constant probability of occupancy regardless of forest type. Percent wiregrass cover was a significant predictor of occupancy for five species, particularly for State listed species L. capito and N. perstriatus, suggesting it may be a useful indicator of habitat quality for longleaf-dependent amphibians. Chapter Three focuses on experimental release of juvenile southern toads into two types of terrestrial enclosures to independently determine if amphibian movement and desiccation is determined by forest management. Movement enclosures consisted of four 50 m x 2.5 m unidirectional runways joined at the center to determine movement rate, distance, and behavior among forests of varying habitat structure. Movement rates were relatively consistent among forest types and positively related to rainfall, which itself did not vary among forests. Canopy closure and ground slope were predictors of behavior as toads move preferentially toward canopy openings and negative slopes, particularly when in planted pine habitat. Ten desiccation enclosures, each 15 cm diameter by 45 cm tall, were used to determine water loss and survival of toads for up to 72 hours. The proportional water loss from toad bodies was significantly related to ambient soil moisture at enclosures, with moisture consistently less at planted pines sites in xeric soil, suggesting a potential source of mortality for species specialized to sandhills. Juvenile survival was particularly low at sandhills planted with pine where dry duff replaced native groundcover and likely prevented successful water conservation behavior. The results of these studies suggest that land management decisions related to planted pine forests will determine the species composition at embedded isolated wetlands for both rare and common amphibians. As natural disturbance regimes that limit woody shrub invasion are replaced by plantation silviculture tree plantings that further decrease light transmittance, native groundcover is reduced to greater extent than stands allowed to naturally regenerate following past timber harvest. Current and predicted expansion of pine plantation will particularly limit occupancy for amphibian SGCN endemic to sandhills, where planting dense pines lowers ambient soil moisture and juvenile survival. The vegetation metrics presented will allow land managers to guide forests toward conservation goals, to predict suitability of forests for amphibian species, and enhance success when repatriation efforts are needed. The significant relationship of amphibian occupancy to sensitive herbaceous vegetation (wiregrass) highlights that greater emphasis on forest groundcover is needed where amphibian SGCN occur and that cumulative impacts of forest management on native groundcover should be considered.