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Measurements of Temperature Dependency on Thermal Insulation Thickness in Ventilated Attics

The main objective of this paper is by measurements to investigate whether increased thermal insulation thickness reduces the temperature in ventilated attics. With lower heat flux through the ceiling in the winter, the theory is that the temperature in the attic decreases and consequently the relative humidity increases which may cause mold growth. While some simulations support this theory, others do not. To test the theory in practice, measurements were performed in 29 dwellings, mainly older single family houses with ventilated attics and insulation thicknesses varying between 150 and 600 mm (6“ and 23“). The temperature was measured for more than one year in the attic, the living space below and outdoors. All measured attics were ventilated as recommended in guidelines; i.e. with openings at the top and the bottom. The measurements in the attics showed high dependency on the outdoor temperature, while indoor temperature and the thickness of insulation were not significant. Consequently, the thermal insulation thickness alone cannot explain possible increasing mold problems. However, extra insulation in attics may obstruct the ventilation openings and therefore, reduce the ventilation rate. Measurements of ventilation rates in non-problematic and moldy attics should therefore be the next step

Towards moisture safe ventilated cold attics - Monitored conditions in a full-scale test building

Existing building stock in Europe accounts for approx. 40% of the total energy consumption. Upgrading the thermal insulation of the existing buildings is an important measure to reduce heat losses through the building envelope. In some cases, increasing the thermal resistance of the construction may compromise the hygrothermal performance of the retrofitted construction. In particular, if vapour barrier is necessary for the good performance and it is practically difficult, if not even impossible, to install a well-sealed air- and vapour tight layer. To investigate the robustness of the hygrothermal performance of ventilated cold attics – with or without a vapour barrier – a monitoring campaign in a full-scale test building was set up. Also role of number of other parameters like moisture buffering capacity of the insulation material and thermal resistance was investigated. This paper presents part of this measuring campaign, which includes conditions both in the attic space and inside the insulation layer. The monitored data covers a period with two winters. The results show that it in temperate climate is practically indifferent for the hygrothermal performance of the monitored, well-ventilated attics with air-tight ceilings whether there is a vapour barrier or not and if the insulation material has moisture buffering capacity or not

Timing of Latest Eocene Molluscan Extinction Patterns in Mississippi

Molluscs removed from 12 bulk samples of the Yazoo Formation (upper Eocene), exposed in a quarry at Cynthia, Mississippi, are similar in com- position and diversity to those found in the underlying upper Eocene Moodys Branch Formation, when dif- ferences in outcrop area are considered (74% of the Yazoo species are also found in the Moodys Branch). This suggests there was no significant extinction during the late Eocene (at the P15/P16 biozone boundary) as has been reported for planktic foraminifera. Only 11.4% of the species from the Yazoo extend into the Oligocene Red Bluff Formation, suggesting a large molluscan extinction at or near the Eocene-Oligocene boundary. The presence in the lowermost Red Bluff of an assemblage with a relatively high diversity dominated by suspension-feeding bivalves suggests that the molluscan fauna had recovered from the extinction by the earliest Oli- gocene

Naticid Gastropod Prey Selectivity Through Time and the Hypothesis of Escalation

The hypothesis of escalation posits that biologic hazards such as predation have increased during the Phanerozoic. Previously, a survey of drilling frequencies in the Cretaceous and Paleogene of the North American Coastal Plain suggested an episodic pattern of escalation within the naticid gastropod predator-prey system. This study examines escalation from the perspective of naticid prey selectivity. If escalation occurred within the system, less selectivity of prey may be apparent in the Paleogene compared to younger assemblages. We test this hypothesis for four Eocene Coastal Plain assemblages. Contrary to predictions, intraspecific prey size selectivity was well developed for nine of eleven bivalve prey species. Drillhole size (indicating predator size) correlated significantly with prey size, especially for successful drillholes. Few incomplete or nonfunctional drillholes occurred, except within corbulid species. Interspecific prey selectivity was less developed than for Neogene or Recent assemblages. Naticid prey preferences predicted by cost-benefit analysis were consistent with actual drilling frequencies only for the Bashi Marl Member of the Hatchetigbee Formation (Alabama). In the Piney Point Formation of Virginia, all prey items were drilled at equivalent frequencies, despite their different cost-benefit rankings. Upper Lisbon (Alabama) and Moodys Branch (Mississippi and Louisiana) assemblages showed limited agreement with preferences predicted by cost-benefit analysis. Prey selectivity thus appears less developed in the Paleogene compared to the Neogene and Recent, in accordance with the hypothesis of escalation

Evolution of the Naticid Gastropod Predator-Prey System: An Evaluation of the Hypothesis of Escalation

Previous work has suggested that escalation may have characterized the history of the naticid gastropod predator-prey system, based on apparent increases in drilling frequencies and the occurrence of antipredatory aptations among prey. We evaluate this hypothesis based on a comprehensive survey (over 40,000 specimens) of predation on molluscs from the Upper Cretaceous through lower Oligocene formations within the U.S. Gulf and Atlantic Coastal Plain. Patterns in drilling of both bivalve and gastropod prey are complex. Drilling frequencies were relatively low in the Cretaceous but increased sharply above the Cretaceous-Tertiary boundary, remaining high until the late Eocene. Following a significant decline near the Eocene-Oligocene boundary, drilling frequencies increased to a moderate level in the Oligocene. Contrary to our prediction based on the hypothesis of escalation, no temporal trend of increasing stereotypy of drillhole site occurred. However, significant increases in prey effectiveness (indicated by the incidence of incomplete drillholes and multiply bored shells) occurred between the Cretaceous and Oligocene. This pattern characterizes entire faunas as well as individual prey taxa that were consistently heavily drilled (turritellid gastropods and corbulid bivalves)

Spatial Variation of Naticid Gastropod Predation in the Eocene of North-America

Although, the fossil record of naticid gastropod drilling has played an important role in the controversy over predator-prey evolution, little is known about variation of drilling frequencies within single horizons or how predation patterns are influenced by environmental variables. Without an understanding of spatial variation in drilling, temporal patterns in drilling are difficult to interpret. We surveyed 27,554 specimens of molluscs from the Cook Mountain interval (upper middle Eocene) and Jackson Group (late Eocene) of the U.S. Gulf and Atlantic Coastal Plain to document spatial variation in naticid drilling frequencies. The Jackson Group assemblages from the Moodys Branch and Yazoo formations were sampled along a depth gradient in order to compare drilling frequencies to environmental variables within a single climatic zone. There was a statistically significant difference between drilling frequency of the inner to middle shelf Moodys Branch Formation (mean = 8.3%) and the outer shelf Yazoo Formation (mean = 21.2%; chi square = 49.58, P ≪ 0.001), but there was no significant bathymetric trend in drilling frequencies among the five assemblages of the Moodys Branch. Drilling frequency was not related to substrate type within the Moodys Branch. Drilling, however, was correlated with species diversity of Moodys Branch assemblages (r = 0.50, P \u3c 0.01). Drilling frequency was significantly correlated with the percentage of naticids in each assemblage (r = 0.77, P \u3c 0.001) and the percentage of certain prey species of the bivalve families Lucinidae and Corbulidae, and the gastropod families Turritellidae and Hipponicidae (r = 0.80, P \u3c 0.001). These preferred species represented 40% of the naticid victims, but only 16% of the assemblages. Cook Mountain assemblages represented marine inner to middle shelf environments from Virginia, Alabama, Louisiana, and Texas. Naticid drilling frequencies of the entire molluscan fauna ranged from 6.8-38.7% with a mean of 22%. In the Cook Mountain, three preferred species (of the families Turritellidae, Lucinidae, and Noetiidae), representing 24% of the total individuals, accounted for 44% of the drilled individuals. As in the Moodys Branch Formation, Cook Mountain assemblages showed a significant correlation between relative abundance of preferred species and drilling frequency of samples (r = 0.585, P \u3c 0.05). The dependence of naticid drilling on the availability of preferred prey species indicates a possible behavioral inflexibility in naticid predation patterns. The Virginia Cook Mountain fauna exhibited significantly greater drilling frequencies (mean = 30.3%, n = 4 samples) than did the Gulf Coast assemblages (mean = 18.0%, n = 11 samples; Mann-Whitney U-test, P \u3c 0.01). This result is consistent with a trend found by some previous workers of an equatorward decrease in naticid drilling