Global warming due to increased emissions of CO2 has lead to more focus on decreasing energy consumption and greenhouse gas emissions caused by buildings. In Norway balanced ventilation with heat recovery is the most recommended solution for a low-emission building. However, a minority claims that a naturally ventilated house can be equally sustainable.

To find out more about which concept is more sustainable, a model building with natural ventilation is compared to the same building with balanced ventilation in several cases. These are calculated in the computer-program SIMIEN, mainly with Oslo-climate. A sensitivity analysis of several parameters is also done.

The calculations indicate that the total greenhouse gas emissions in a lifetime perspective from a house with natural ventilation can be as low as from a house with balanced ventilation. A typical Norwegian passive house heated with electricity seems to have higher greenhouse gas emissions than a naturally ventilated house with 50% of the space heating covered by biofuel.

A naturally ventilated house with pre-heating of air in a earth heat exchanger, and reduced air change rate at daytime when people are out, can have equally low global warming potential as a typical passive house, when both have electric heating.

This indicates that natural ventilation, especially in a concept with wood-pellets, or district heating, can achieve very low total greenhouse gas emissions.

Summary

Single-crystalline sodium tungsten bronze (Na-WO₃) nanorods with typical diameters of 10–200 nm and lengths of several of microns were prepared via hydrothermal synthesis. X-ray diffraction data showed that the as-prepared Na-WO₃ nanorods crystallize in a hexagonal structure (space group P6 / mmm) with unit cell parameters a = 7.3166(8) Å and c = 3.8990(8) Å, and elongate along the <001> direction. The Na-WO₃ nanorods had a mean chemical composition of Na_0.18WO_3.09·0.5H₂O. The Na-WO₃ nanorods exhibited a typical cathodic coloration related to proton insertion, indicating their potentials in electrochromic smart window applications.

Monodisperse polystyrene (PS) spheres with controllable size have been synthesized by a straight forward and simple procedure. The as-synthesized PS spheres have a typical diameter ranging from ~180 nm to ~900 nm, where a reduced sphere size is obtained by increasing the polyvinylpyrrolidone (PVP)/styrene weight ratio. The PS spheres function as sacrificial templates for the fabrication of hollow silica nanospheres (HSNSs) for thermal insulation applications. By modifying the silica coating process, HSNSs with different surface roughness are obtained. All resulting HSNSs show typically a thermal conductivity of about 20 mW/(mK), indicating that the surface phonon scattering is probably not significant in these HSNS samples.