No abstract

Radiant floor heating is becoming increasingly popular in cold climates because it delivers higher comfort levels more efficiently than conventional systems. Wood is one of the surface coverings most frequently used in radiant flooring, despite the widely held belief that in terms of thermal performance it is no match for higher conductivity materials if a high energy performance is intended. Given that the highest admissible thermal resistance for flooring finishes or coverings is generally accepted to be 0.15 m2K/W, wood would appear to be a scantly appropriate choice. Nonetheless, the evaluation of the thermal performance of wooden radiant floor heating systems in conjunction with the building in terms of energy demand, thermal comfort, and start-up period, has been insufficiently explored in research. This has led to the present knowledge gap around its potential to deliver lower energy consumption and higher thermal comfort than high-thermal-conductivity materials, depending on building characteristics. This article studies the thermal performance of wood radiant floors in terms of three parameters: energy demand, thermal comfort, and start-up lag time, analysing the effect of wood properties in conjunction with building construction on each. An experimentally validated radiant floor model was coupled to a simplified building thermal model to simulate the performance of 60 wood coverings and one reference granite covering in 216 urban dwellings differing in construction features. The average energy demand was observed to be lower in the wood than in the granite coverings in 25% of the dwellings simulated. Similarly, on average, wood lagged behind granite in thermal comfort by less than 1 h/day in 50% of the dwellings. The energy demand was minimised in a significant 18% and thermal comfort maximised in 14% of the simulations at the lowest thermal conductivity value. The vast majority of the wooden floors lengthened the start-up lag time relative to granite in only 30 min or less in all the dwellings. Wood flooring with the highest thermal resistance (even over the 0.15 m2K/W cited in standard EN 1264-2) did not significantly affect the energy demand or thermal comfort. On average, wood flooring lowered energy demand by 6.4% and daily hours of thermal comfort by a mere 1.6% relative to granite coverings. The findings showed that wood-finished flooring may deliver comparable or, in some cases, higher thermal performance than high-conductivity material coverings, even when their thermal resistance is over 0.15 m2K/W. The suggestion is that the aforementioned value, presently deemed the maximum admissible thermal resistance, may need to be revised.

Accuracy in moisture content measurement is of great importance in the assurance of wood product quality and is necessary to meet administrative and normative requirements. Improving the accuracy of resistance-type moisture meters, and meeting the normative demands of their annual calibration, requires the use of optimised curves relating electrical resistance to moisture content for the most commercially important wood types. The Samuelsson model, adjusted by linear regression techniques, was used to describe the relationship between the electrical resistance and moisture content of seven boreal and three tropical hardwoods available on the Spanish market. The curves produced can be used to predict the moisture contents of these hardwoods via the measurement of their electrical resistance with an error of just ± 1.0%. These curves should also prove of great use in the calibration of wood resistance-type moisture meters.Key words: moisture meter; xylohygrometer calibration; calibration curves; Samuelsson model. ResumenDeterminación de curvas para la estimación del contenido de humedad de diez maderas de frondosas mediante medidas de resistencia eléctrica La precisión en la medida del contenido de humedad juega un papel fundamental no solo en el aseguramiento de la calidad de los productos de la madera sino, también, en el cumplimiento de las exigencias normativas y administrativas que gravitan sobre los productos. Para ser capaces de mejorar la precisión de la medida tomada por los xilohigrómetros de resistencia y cumplir con las exigencias normativas de calibración anual de los equipos, es necesario obtener curvas optimizadas que relacionen la resistencia eléctrica con la humedad en las maderas de mayor importancia comercial.El modelo de Samuelsson, Log[Log(R) + 1] = a.h + b, ajustado mediante técnicas de regresión lineal, fue usado para describir la relación existente entre la resistencia eléctrica de la madera (R) y el contenido de humedad (h) de siete maderas de frondosas boreales y tres de frondosas tropicales comercialmente disponibles en el mercado español. Las curvas obtenidas pueden ser usadas para la predicción del contenido de humedad de dichas maderas, con un error máximo de ± 1.0%, mediante la medición de su resistencia eléctrica. Estas curvas serían también de interés para la calibración de medidores de humedad de madera por resistencia eléctrica. Palabras

No abstract

The relationship between the log of the electrical resistance (ER; measured using pin electrodes) and the moisture content (MC) have not been reported in any form of cork. That is important for the cork stoppers industry because it should help in the design and verification of more precise devices for measuring cork moisture content. In this study, using linear regression techniques, different regression models of the type log(Log(R) + 1) = axh+b were derived to describe the relationship ERMC, that was measured using pin electrodes on two types of cork stoppers [natural (N) and agglomerate(AG)]. The results obtained show that in the models proposed, the moisture content of AG cork stoppers can be estimated with an error of ± 0.3%, while that of N stoppers can be estimated with an error of 0.5%. Neither the geographical origin of the N corks nor the surface treatment to which the AG corks were subjected significantly affected the proposed models.Therefore, the moisture content of cork stoppers could be measured at the industrial scale using electrical resistancetype moisture meters.