Exhaust air heat recovery in buildings

The market evolution of domestic exhaust air heat pumps since 1979 in Sweden is described. Some information is also given about the German market. Technologies of different exhaust air heat pumps systems are shown and results of several monitoring projects in Sweden are summarized : they show for houses built in the 1980's an electricity consumption of 90 to 130 kWh/m2/year (including domestic hot water and household electricity), depending on the thermal characteristics of the building envelope. The energy savings thanks to the exhaust air heat pump are about 30%.

Airborne microbial contaminants in indoor environments. Naturally ventilated and air-conditioned homes.

The study compared the atmospheric burden of viable particulates in the interiors of condominium homes with central air conditioning with that of the typically more open type of naturally ventilated Hawaiian residence. Enumeration of the numbers and types of respirable fungi and bacteria inside were done using Andersen microbial air samplers. To evaluate the impact of the air conditioning system on indoor air quality the results were compared with those obtained outside the homes.

House-dust mites and associated environmental conditions in Danish homes.

Describes and investigation of house-dust mites in 96 Danish homes with one or more members with asthma. All the homes were measured for air exchange rates, humidity and temperature. The study found a positive correlation between indoor air humidity and mite concentration and an inverse correlation between house-dust mite concentration and indoor air exchange. House-dust mite concentration was higher in the houses with mite-allergic persons. In 76% of the homes the concentration was above the proposed limit of 10 mites/0.1 g dust. This was so in 48% of the non-allergic homes.

The relationship between airborne acidity and ammonia in indoor environments.

Forty seven residential buildings were monitored for indoor acid aerosol, nitric acid and ammonia concentrations over a summer in State College, Pennsylvania. Questionnaires were also distributed for information on occupant behaviour. The paper discusses the relationship between ammonia and concentrations of aerosol strong acidity and HNO3 in the buildings. The indoor outdoor relationship was also analysed. High indoor NH3 levels were found and low acid levels. Mass balance models that included an NH3 neutralisation term were found to predict indoor acid concentrations reasonably well.

Cost-effectiveness of increasing airtightness of houses.

Air infiltration through the exterior envelope of a residential building impacts significantly on the heating energy consumption and cost, especially in a cold climate such as Montreal's. Therefore to renovate existing houses to the level of new well-built houses in terms of airtightness will lead to a reduction of the heating energy costs. By considering the life-cycle energy consumption and the initial cost of renovation, and the CO2 tax credits, the paper estimates the cost-effectiveness of this type of renovation.

The use of natural ventilation and air conditioning for houses in warm-humid climates.

There are important benefits to come from using passive techniques as opposed to artificial cooling. They may not be sufficient to provide thermal comfort throughout the year in wet tropical areas, however. Few experiments have been performed on the thermal performance of buildings using a mixed-running strategy in warm-humid climates. The paper attempts to demonstrate that a possible dual-mode integrated operation can be used for such locations.

Natural ventilation of the housing in hot and humid climates: some suggestions for the design of urban blocks.

The study aimed to identify the behaviour of wind in the type of urban blocks usually found in cities in tropical climates. The results presented here were obtained in colonial type areas. The authors' approach was to establish a relationship between the clusters of buildings and the evidence of overpressures or low-pressure in proximity to the openings of occupied spaces. A prominent physical feature of natural ventilation is the maximal difference of pressure between windward and leeward building facades.

Validation of multizone IAQ modelling of residential-scale buildings: a review.

Empirical validation studies of the application of multizone indoor air quality models to residential-scale buildings are reviewed here. The focus is on empirical verification efforts. Models have also been subjected to analytical verification and inter-model comparisons. Not many of the empirical verifications reported statistical analyses of the comparison between measurements and predictions. Additional statistical analyses have been performed and reported if sufficient data were available in the literature. Measurement uncertainty was not dealt with in most of the published reports.

The management of the individual heating systems in housing. From field studies to specific parameters for projects.

Individual heating systems have become more and more common in Italy in recent years, as a result of the development of a methane gas network and of general housing renovation. The research proposed some field studies to analyse the indoor climate for improving the heating system and indoor climate. Aims to correct the management of the heating systems to improve housing quality and occupant comfort.

A Building America prototype home packed with HVAC features.

Describes the features of a prototype home designed for a large builder in Michigan, USA, and the results of a series of DOE-2.1E energy simulations performed to assess the impact of various energy efficient aspects. The new features included: improvements to the thermal envelope and mechanical equipment; use of structurally insulated panels (SIPs) for the envelope; high performance, low-E argon-filled windows; a smaller, more efficient boiler; passive cooling design via a central stairwell with operable skylight; a unique mechanical ventilation system that can be scheduled and zoned.

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