In insulated structures, air voids and cracks allow for airflows driven by temperature differences, i.e., natural convection. The airflow paths often exist in structures built with bad workmanship, but sometimes even with the best workmanship they are difficult to avoid. Air paths within new types of loose-fill insulation may also occur. For horizontal structures, critical channel flow Rayleigh numbers can be identified for the onset of convection.
A technique for improving the thermal performance of lightweight steel- and wood-framed building assemblies is introduced in this paper. In this approach, rigid extruded insulation material is applied only to the framing members themselves (studs, plates, doubles, headers, etc.), effectively creating a composite member composed of insulation and structural framing. The depth of the envelope cavity is thereby extended by an amount that is equal to the thickness of the rigid insulation employed.
The effect of wall material configuration on dynamic thermal performance is analyzed for six typical wall configurations. Due to different arrangements of concrete and insulation layers, these walls present a wide range of dynamic thermal properties. Newly developed thermal structure factors are used in selection and thermal analysis of these walls. A simple one-room model of the building exposed to diurnal periodic temperature conditions is analyzed to give some basic information about the effect of wall material configuration on thermal stability of the building.
This paper outlines the methods and results of a four-year project that measured heat flows through two uninsulated slab-on ground floors on nominally wet soils. One floor was on peat soil, the other on clay, and water table depths were 0.5 m to 1.0 m through most of the year. Heat fluxes were measured over the whole floor using heat flux transducers (HFT) at the concrete floor surface, and temperatures were measured by thermocouple, continuously for four years. The soil conductivities and soil temperatures were measured daily at 11 positions near one edge of the floors.
Condensation phenomena on internal surfaces of buildings are becoming recurrent eventualities in contemporary buildings, particularly in residential buildings. Despite the general belief, this accumulation of water on walls is not mainly due to mass migration from outdoor to indoor, but to a modification of behavioural approaches of people, especially referring to the preferred air temperature.