Roof Windows for Passive Houses – What Can Be Improved?

In general, skylights and roof windows in pitched roofs ca n be described as the critical components of buildings concerning heat losses, risk of surface condensation, increased risk of overheating of rooms behind etc. This is very sensible task especially for passive house solutions. The paper informs about studies analyzing the importance of these relatively small areas in the building envelope and more detailed in pitched roof of a passive house. One of the key problems is the position of roof window within the pitched roof construction. Second part of the paper comments results of detailed analysis of thermal performance for different combination of frame type and glazing. These studies are performed hand in hand with development works. It is documented that such approach ca n lea d to promising results, reducing the thermal transmittance of roof window to 0.7 – 0.5 W/(m2K). If we consider the real roof window quality including the thermal couplings due to window installation such thermal transmittance stays safely bellow 0.9 W/(m2K)

Experimental investigations of wooden beam ends in masonry with internal insulation: results contrasting three years of the experiment

This paper deals with hygro-thermal performance of wooden beam ends embedded in masonry walls with lime-cement plaster applied on the external side. Three different insulation systems are attached on the internal side of masonry. The real scale experiment has been monitored for three consecutive years. Microclimatic conditions in joist pockets were assessed by VTT mold growth index. The paper shows the influence of two changes of boundary conditions on the microclimate in joist pockets. First, moisture load on the internal side of building enclosure was increased (24 °C, 60 % in winter 2016/2017 instead 20 °C, 50 % in winter 2015/2016). Then, the artificial short-time rain event brought liquid water onto the external surface of building enclosure in July 2017. The rain intensity was chosen so as to mimic the intensive summer thunderstorm. The increase of water vapor concentration in the air on the internal side led to suitable conditions for mold growth in unsealed joist pockets of a vapor open insulation system. On contrary, microclimate in sealed joist pockets in both vapor open and vapor closed insulation systems stayed in acceptable levels with no mold growth. The artificial rain event significantly changed the hygro-thermal performance of joist pockets. Drying season was shortened and the relative humidity in joist pockets overtook the time profile of external relative humidity

Assessment of the BIPV potential at the city of Prague and their effect on the built environment

This work highlights the BIPV potential in two urban areas with different characteristics at the city of Prague. Representative building blocks were selected and CitySim software tool was used for the assessment of the hourly irradiation profiles on each surface over one year period. Considering appropriate irradiation thresholds, suitable surfaces were then quantified. Integration criteria are discussed and suitable BIP V applications are proposed considering not only energy performance but also their impact on the quality of built environment. Results indicated that only 5.5% of the total area can be used in Vinohrady and 13.7% in Jizni Mesto contributing on average by 32% and 31% on the hourly electricity demand respectively

“Near-to-Zero-Energy Floor” in a Campus Building from 1971

AbstractIn 2013, a campus building in Prague, built more than 40 years ago, was partially refurbished. Its old curtain wall with very poor performance was completely removed and replaced by a new element façade of significantly higher quality, which meets today's recommendations concerning the energy efficiency. The comfort requirement was satisfied partially – the effect of overheating was almost entirely eliminated without the need of mechanical cooling. It was still necessary to improve the quality of ventilation. Therefore, a study on the possibility and effects of installing an additional ventilation system was conducted. As a pilot project, a complex solution of one selected floor was implemented. This solution is described and commented upon in this paper

Optimization of Processing Parameters of Medium Density Fiberboard Using Response Surface Methodology for Multiwalled Carbon Nanotubes as a Nanofiller

In the present work, medium density fiberboard (MDF) panels were produced using multiwalled carbon nanotubes (MWCNT) reinforced urea formaldehyde resin. Response surface methodology was employed to optimize the relationship between the three variables, viz. pressing time, percentage of UF resin and percentage of MWCNT, used in the fabrication of MDF, and the influence of variables on the internal bonding (IB) and modulus of rupture (MOR) was studied. The optimum conditions based on the IB strength were determined as 8.18 % of UF resin, pressing time of 232 s, and MWCNT of 3.5 %. Similarly, the optimized conditions for MOR are also reported in this paper

Hygro-thermal performance of wooden beam ends: experimental investigations of uninsulated and internally insulated brick wall

Wooden floors were traditionally used in brick apartment houses built at the turn of 20th century in many European cities. Thermal renovation of such houses often involves thermal insulation at interior side of external walls. Internal insulation makes microclimate in the vicinity of wooden beam ends colder and more humid. The real-scale experiment involving a part of wooden floor connected to a 30 cm thick masonry wall was monitored for two consecutive years. Measured data were used to compare microclimate in sealed and open joist pockets. Joist pockets were either placed in the masonry wall with plaster on both sides or placed in the same masonry wall insulated on the interior side (vapour open thermal insulation system). The measured results indicate that the sealing tape alone is not sufficient to keep the relative humidity in joist pockets below 85 % in cold climate and under high internal moisture load. The paper concludes that reasonable trade-off between thermal efficiency, thermal comfort and moisture safety is difficult to reach for masonry with internal insulation and wooden floors. Sealing provisions complemented by tempering of joist pockets are considered as two key technical measures for reliable hygro-thermal performance of wooden beam ends in full-brick masonry with interior thermal insulation in cold temperate climate

Studies on internal surface heat transfer in the window area

In this paper reporting preliminary results from the ongoing research, heat transfer phenomena at window surfaces and adjacent areas of the building envelopes are studied. In the first step, in-situ observation of balcony door based on indirect estimation of temperature distribution close to window surface was carried out by means of infrared imaging (IR). In the second step, more advanced full-scale experiments were performed in a well-insulated laboratory testing room with floor heating, equipped with one window, under well controlled steady-state conditions. A combination of IR with particle imaging velocimetry (PIV) was used here with extra focus on situation close to the window frame at window sill. In such areas the reduced heat transfer by convection can be observed. As a consequence, the condensation risk free situation there seems not to be always guaranteed even by high performing building components despite the results of standard heat transfer calculations used in design practice