Artikkel i Teknisk Ukeblad om vedovner i passivhus. Artikkelen er skrevet av Mona Sprenger

Abstract

There is an increasing interest in development of coupled multi-layer window structures. This is to optimize thermal properties and to develop systems with a better climate protected solar shading system. The risk of condensation on the inside of the exterior glass layer in a multi-layer window structure might be a challenge and is often questioned. The risk of condensation will depend on both window properties and indoor and outdoor climate conditions. The air gap between the inner and outer part have to be ventilated with outdoor air to give the window a "drying out" capacity. The U-value of the window and the moisture condition in the air gap both depend on the ventilation of the air gap. Reducing the ventilation improves the U-value, but increases the time of desiccation.Net long-wave radiation from the glass surface to the atmosphere during cloudless night-time will cause exterior glass temperatures lower than the outdoor air temperature, and hence increase the risk of condensation on both sides of the exterior glass. The aim of this work has been to assess for which climate conditions there will be a risk of condensation on the exterior glass layer and what might be the optimal ventilation of the outermost air gap. Simulations of the temperature on the exterior surface of the glazing including the long-wave radiation during night-time have been done and compared to measurements. An assessment has been made studying the risk of condensation and the drying out rate for climate conditions for two locations in Germany. A spreadsheet-based model calculating the U-value of a multilayer glazing unit according to ISO 15099 [1] has been further developed including airflow from exterior openings through the air gap.

The main purpose of this book, Hygrothermal, Building Pathology and Durability, is to provide a collection of recent research works to contribute to the systematization and dissemination of knowledge related to construction pathology, hygrothermal behaviour of buildings, durability and diagnostic techniques and, simultaneously, to show the most recent advances in this domain. It includes a set of new developments in the field of building physics and hygrothermal behaviour, durability approach for historical and old buildings and building pathology vs. durability. The book is divided in several chapters that are a resume of the current state of knowledge for benefit of professional colleagues, scientists, students, practitioners, lecturers and other interested parties to network.

The application of manufactured nanomaterials provides not only advantages resulting from their unique properties but also disadvantages derived from the high energy use and CO2 burden related to their manufacture, operation, and disposal. It is therefore important to understand the trade-offs of process economics of nanomaterial production and their associated environmental footprints in order to strengthen the existing advantages while counteracting disadvantages. This work reports the synthesis, characterization, and life cycle assessment (LCA) of a new type of superinsulating materials, nano insulation materials (NIMs), which are made of hollow silica nanospheres (HSNSs) and have great flexibility in modifying their properties by tuning the corresponding structural parameters. The as-prepared HSNSs in this work have a typical inner pore diameter of about 150 nm and a shell thickness of about 10–15 nm and exhibit a reduced thermal conductivity of about 0.02 W/(m K) because of their size-dependent thermal conduction at the nanometer scale. The energy and raw material consumption related to the synthesis of HSNSs have been analyzed by the LCA method. The results indicate that the recycle of chemicals, up-scaling production, and use of environmentally friendly materials can greatly affect the process of environmental footprints. New synthesis routes for NIMs with improved thermal performance and energy and environmental features are also recommended on the basis of the LCA study.

Sammendrag

Denne rapporten beskriver resultatene fra et prosjekt hvor vi har gjennomgått og diskutert erfaringer fra et utvalg utbyggingsprosjekter i Norge hvor man har hatt spesielt høye ambisjoner med hensyn til
energibruk og klimagassutslipp. Prosjektets målsetning er å bidra til økt kunnskap om gode løsninger for utforming av bygninger og energiforsyning for fremtidens boligområder, samt danne underlag for en
veileder til bruk i planleggingsprosessen. Hovedkonklusjonen er at det er behov for mer kunnskap og veiledningsmateriale om hvordan man kan integrere dette tidlig i planprosessen. Følgende punkter er
spesielt viktige:

•  Fokus på integrert, tverrfaglig prosjektering fra tidligfase.
• Formulering av konkrete krav/målsetninger i tidligfase.
• Undersøkelse av tilgjengelighet og leveransebetingelser for lokal, fornybar energi, samt muligheter for utveksling mot energinettet.
• Utforming av bygningsmassen med hensyn til varmetap, utnyttelse av solenergi, dagslys og materialbruk med lavt klimagassutslipp.
• Beregning av energi, effekt og klimagassutslipp, samt inneklima fra tidligfase og gjennom prosessen.
• Vurdering av ulike energiforsyningsløsninger i tidlig planfase, og innhenting av kunnskap om driftsforhold og leveringssikkerhet.