Roger G. Marchand

A Logical Extension of the ASTM Standard E96 to Determine the Dependence of Water Vapour Transmission on Relative Humidity

It is well known that the water vapour transmission properties of hygroscopic building materials depend on the local relative humidities(rh). Traditionally, the ASTM Standard E96 specifies only two conditions of rh. The dry cup method in the standard corresponds to a mean rh of 25 % and the wet cup to 75 %. This information is not enough to describe the behaviour of the material through the entire range of rh. European standards have already proposed an extension of the existing standard to address this issue. ASTM standard should follow this change. A logical extension of the E96 standard to include the effect of rh on water vapour transmission properties has been proposed and is being discussed by one of the C16 Committee Task Groups. This paper presents the application of the proposed extension to several common building materials. The details include the operating principles of a constant temperature-rh chamber and the effects on the test results, of the vapour resistance offered by still air inside the cup, the surface resistances and buoyancy. The experimental data were used to critically assess the above effects. The data as well as the analyses of the data are expected to provide guidance to refine the existing ASTM Standard.

Moisture Diffusivity of Cellulose Insulation

Test specimens of blown cellulose insulation were placed in contact with water to initiate an isothermal moisture intake process in which liquid water was allowed to enter freely against gravity into the specimens. The transient moisture distribution in the specimens was determined using the gamma-ray attenuation method over a period of 10 days. The results indicate that, as with most porous systems, the specimens first establish a characteristic water retention curve and then undergo a unique secondary moisture transport process. This paper presents the experimental data from the investigation. The data were used to derive information on the moisture diffusivity of cellulose insulation, in relation to the secondary mois ture transport process undergone by the test specimens.

Control strategies for lighting and ventilation in offices: effects on energy and occupants

Participants (N=126) spent a day in a full-scale office laboratory, completing questionnaires and standard office tasks. Some participants experienced typical constant lighting and ventilation conditions, whereas others were given personal control over the dimming of lighting in their workstation and over the flow rate of air from a ceiling-based nozzle in their workstations. Half of the participants, some with personal control and some without, were exposed to environmental changes typical of demand—response load shedding in the afternoon: workstation illuminance was reduced by 2% per minute, and ambient air temperature increased by ∼1.5°C over a 2.5 hour period. Results showed that personal environmental control improved environmental satisfaction. Personal control over lighting led to an average energy reduction of around 10% compared to a typical fixed system; participants with personal control also reduced flow rate compared to the constant condition. Use of each control type averaged two—three control actions per person per day, which dropped to less than one control action per person per day in a longer-term pilot study (N=5) conducted in the same space. Load shedding had some small negative effects for occupants, but in practice is unlikely to create substantial hardships, and is a reasonable response to peak power emergencies.

Preferred Surface Luminances in Offices, by Evolution

Forty participants viewed a series of greyscale images of a typical non-daylit, open-plan partitioned office, and rated them for attractiveness. The image was projected onto a screen at realistic luminances and 54 percentof full size. The images in the series were geometrically identical, but the luminances of important surfaces were independently manipulated. Initially, the combinations of luminances were random, but as the session continued, a genetic algorithm was used to generate new images that generally retained features of prior images that were rated most highly. As a result, the images presented converged on an individuals preferred combination of luminances. The results demonstrated that this technique was effective in reaching a participants preferred combination of luminances. There were significant differences in room appearance ratings of the most attractive image compared to other images, and the differences were in the expected direction. Factor analysis of ratings of the most attractive images revealed a factor structure with some similarity to that obtained when people rated real office spaces. Furthermore, preferred luminances were similar to those chosen by people in real settings, as was the variation in preferences between individuals. Finally, subjective ratings of brightness, uniformity and attractiveness were significantly related to luminances in the image.

Calibration of a Heat Flow Meter Apparatus

A series of calibration measurements was done on a 600 mm × 600 mm heat flow meter apparatus. Several specimens of medium density glass fiber in sulation and expanded polystyrene insulation were used as transfer standards. The thickness of these transfer standards varied from 25 to 160 mm. The mean tempera ture varied from 0 to 40°C and the temperature difference across the insulation spec imens varied from 10 to 40 K. Measurements included cases in which the ambient temperature of the test assembly was either maintained within 1 K of the mean tem perature, or those with only edge insulation, and an enclosure for the whole test assembly in order to reduce the edge heat losses. A total of 91 sets of measurements were made. Each set of measurements included two sub-sets, one for the warmer(hot) plate and the other for the colder(cold) plate and each sub-set included a heat flow transducer output and the temperatures on either side of the transducer assembly. For 90 out of the 91 sets of measurements, the steady state heat flux across the specimen was correlated, with a standard deviation of 2%, to a simple linear rela tion between the average transducer output and the average of the surface tempera tures of the two transducer assemblies.