Influence of Wood Properties and Building Construction on Energy Demand, Thermal Comfort and Start-Up Lag Time of Radiant Floor Heating Systems

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.

Effect of Wood Properties and Building Construction on Thermal Performance of Radiant Floor Heating Worldwide

“…The same authors [26], in an experimental analysis under laboratory conditions of four types of wood flooring based on heating start-up and shutdown cycles, reported that wood flooring maintained a high temperature for longer periods once the heating source was removed. Similar results were found in the previous study by the present authors [29], where they analysed the thermal performance of 60 radiant wooden floors for the climate of Madrid and 216 dwellings. In many situations, wooden flooring with high thermal resistance was found to deliver higher comfort levels at a slightly lower energy demand than granite floors.…”

“…This article enlarges the study performed in the previous research by Ruiz-Pardo et al [29] by extending its scope from dwellings in Madrid, Spain, to include others in 28 cities in which there is a high likelihood of using the heating systems selected according to the Köppen-Geiger classification. The aim was to evaluate the possible effect of the thermal properties of wood, in combination with building characteristics and climate, on the thermal performance of radiant wooden flooring, and to compare it with a highly conductive natural stone floor.…”

“…The simulation model used was presented in the article by Ruiz-Pardo [29], which performed a transient coupled simulation of the building and radiant floor heating. The radiant floor heating was modelled with an experimentally validated detailed model based on the response factor method, and the building using a resistance-capacity (RC-network) model.…”

“…A total of 216 different dwellings in each city were simulated, these being the same as in the previous article by Ruiz-Pardo [29], with the difference of including the overall heat transfer coefficient (U-value) of the outer enclosures, since in the previous article these values were approximated for Madrid. In the present study, because different climates are considered, appropriate U-values must be selected for each one.…”

Effects of wet treatment on bonding strength and electrothermal performance of electrothermal plywood bonded with emulsion polymer‐isocyanate adhesive

“…Wooden heating floors have become a widely adopted indoor heating approach because they offer the advantages of comfort, space saving, partition heating, and uniform temperature distribution. [1][2][3] Electric heating elements, including heating cables, [4] hot water pipes, [5] and electrothermal films, [6] are essential parts of the wooden heating floor systems. Scalable, flexible, and film-like carbon fiber paper has a heating temperature range of 30-250 C and an electric-to-radiant power transfer efficiency of more than 97%, making it promising for the application of electric heating elements.…”