Mutagenicity assay of emission extracts from wood stoves: comparison with other emission parameters

The emission from wood stoves of several types of air pollutants has been measured under standardized burning conditions with emphasis on the amount of organic compounds and determination of the mutagenic activity with the Salmonella/microsome assay. The study corroborates earlier findings that conventional wood stoves can be a significant source of hydrocarbon and tar compounds in the ambient air. The emission of mutagenic compounds comprise both compounds requiring mammalian activation and compounds which are active in the test without exogenous activation. The mutagenicity tests show that nitroaromatic compounds are present in wood stove emissions, although the emission of nitrogen oxides is low. A wood stove constructed using the downdraft principle emitted much less hydrocarbons and tar, less mutagenic components and slightly less carbon monoxide than conventional wood stoves.     

Electrical savings by use of wood pellet stoves and solar heating systems in electrically heated single-family houses

This study investigates how electrically heated single-family houses can be converted to wood pellets- and solar heating using pellet stoves and solar heating systems. Four different system concepts are presented and system simulations in TRNSYS evaluate the thermal performance and the electrical savings possible for two different electrically heated single-family houses. Simulations show that the electricity savings using a wood pellet stove are greatly affected by the level of comfort, the house plan, the system choice and if the internal doors are open or closed. Installing a stove with a water-jacket connected to a radiator system and a hot water store has the advantage that heat can be transferred to domestic hot water and be distributed to other rooms. Such systems leads to that more electricity can be replaced, especially in houses having a traditional plan. Though it is unnecessary to have too many radiators connected to a stove with a low fraction of energy heating the water jacket. Today's most common control strategy for stoves (the on/off-control) results in unnecessarily high emissions. A more advanced control varying the heating rate from maximum to minimum to keep a constant room temperature reduces the number of starts and stops and thereby the emissions.     

Optimisation of ceramic heat storage of stoves

In order to optimise the efficiency of tile stoves with a thermal capacity of up to 10 kW using wood logs, an important task is to investigate the heat storage of such firing systems used for space heating. For a basic understanding of heat transfer and heat storage behaviour, experiments as well as numerical simulations were carried out. Within the framework of these investigations, two different types of tile stoves were tested: a single-walled stove without an air gap and a double-walled stove with an air gap. Findings show that the air gap influences the heat storage behaviour causing a smooth surface temperature distribution and a decline in efficiency on the other hand. In order to avoid this negative effect, variations of the width of the air gap, ceramic mass, material and length of the flue gas tube were carried out. To remedy the deficiencies of the double-walled design, an extension of the length of the flue gas tube by 10–14% is necessary. Dense chamotte also allow double-walled tile stoves with the same efficiency as single-walled stoves using standard chamotte.     

Controlling building indoor temperature and reducing heating cost through night heating electric stove

This paper investigates the use of massive electric stove as a thermal storage in order to reduce the heating cost associated with maintaining indoor comfort condition in building. The control of electric stove takes advantage of low night-time electrical rate by shifting heating loads from day-time to night-time. A general numerical modelling of thermal behaviour of building envelope, electric stove and indoor air under the condition of outdoor variation is presented in detail. The resultant non-linear system of the heat balance equations, partial differential equations, is solved numerically. Besides the modelling work, attention is put on the control of electric stove’s night heating in such way that the stove-stored energy is released during day-time without sacrifice of indoor comfort. A simple control algorithm is given. Model applications show that the night heating with a proper size massive electric stove as a building thermal storage is cost-effective for buildings with night electrical rate benefit, while maintaining a comfortable indoor temperature in the building. Simulation also illustrates that up to 28% heating cost saving can be obtained compared with conventional direct heating.     

Analysis of wood burning stoves as a supplemental heat source

The use of wood burning stoves as a supplemental residential heat source is examined. Three common types of wood burners are considered: the wood stove, the wood boiler, and the Franklin‐combination stove. The analysis focuses upon three main areas: cost, energy and environmental effects. Indications are that the large scale use of wood as a fuel source is a viable alternative to conventional energy sources in regions having ample forest resources and relatively low population densities.     

New equipment for testing steady and transient thermal performance of multilayered building envelopes with PCM

Thermal properties of the different building envelopes, such as thermal transmittance in steady state, heat storage capacity and dynamic thermal responses, must be taken into account during the design phase of buildings. The evaluation and measurement of these parameters in multilayered samples are difficult because of the irregular morphology of the used materials and the difficulty in providing the well-controlled environment needed for the measurements. A new equipment has been designed to measure the thermal response and heat capacity of composite walls of different materials simulating real building envelopes.The equipment presented in this paper was used to test the improvement in the thermal response of a building envelope due to the incorporation of PCM. This study is focused on wood structural panels attached to a gypsum board, which is either impregnated or not with PCM. The four edges of the composite sample are properly insulated to ensure one-dimensional heat flow. The two faces of the sample are exposed to controlled environments heated and cooled by copper coils with thermo stated water supplied by water baths. The measured surface heat fluxes at both surfaces of the sample and temperature distribution in the sample provide accurate assessment to thermal mass and dynamic response of the composite wall, while the steady state measurements provide an accurate estimate of its effective thermal transmittance.     

An inverse hygrothermal model for multi-zone buildings

The dynamic hygrothermal behaviour of existing buildings can be characterized using data-driven models that are established via system identification techniques. However, most of the time the identification problem is difficult to solve for multi-zone buildings due to high dimensionality of the model and poor excitation in the training data. In addition, building thermal and moisture dynamics are coupled and simultaneous identification of the coupled model is challenging. This paper presents a simplified one-way coupled inverse model to capture the building thermal and moisture dynamics where the impact of space moisture on the building thermal response is neglected. This simplification enables the thermal and moisture sub-models to be estimated sequentially which reduces the computation complexity and improves model identifiability. Both thermal and moisture sub-models adopt a physically based approach in which moisture interactions between different zones are neglected while the inter-zonal thermal interactions are captured. A 3-step procedure is developed to reduce the problem dimension in identifying the thermal sub-model. As a case study, the overall approach was applied to model a medium-size commercial building with nine thermal zones from measured data and the estimated models were validated for different periods of time during a cooling season.     

Mathematical model of heat transfer and feasibility test of improved cooking stoves in Bangladesh

Improved cooking stoves (ICSs) advance the cooking system significantly in Bangladesh. However, the comparative performance analyses of ICSs of Bangladesh are not available in the literature. In this study, heat loss through the stoves was investigated by using ANSYS simulation. From the simulation result, it was found that the average temperature of the wall of ICSs was less than the conventional stove. The maximum thermal efficiencies of some ICSs were found 30%, which is better than other conventional stoves. In addition to this, a feasibility study of ICSs has been carried out by considering cost, greenhouse gas emission and effectiveness of the ICSs. Taken all into consideration, this study would contribute to the literature for further improvement of the stove and guide the consumer to select the appropriate ICS.     

Radiant floors integrated with PCM for indoor temperature control

The control of indoor thermal comfort in buildings through thermal inertia during the summer season plays a fundamental role in the design of energy efficient buildings, especially in the Mediterranean climate. In fact, lightweight, highly insulated buildings cannot provide the necessary mass to buffer thermal gains. Phase change materials (PCM) have been used to provide lightweight building components with the required thermal inertia without increasing their overall mass. So far the integration of PCM into lightweight piped radiant floors for the control of thermal comfort during summer cooling regimes has not been investigated. This paper reports the development of a lightweight piped radiant floor prototype with an integrated PCM layer aimed at buffering internal gains at constant temperature during summer cooling regimes without affecting its winter warming capacity. Both the construction of the laboratory specimens and the development of the optimized finite element models are detailed and the assessment of the floor performance in a simulated room is discussed.     

Performance of EN ISO 13790 utilisation factor heat demand calculation method in a cold climate

The applicability of the utilisation factor method EN ISO 13790 is studied in modern Finnish buildings in the cold climate of Finland. The heat-demand results of EN ISO 13790 are compared against a validated dynamic simulation tool. It is shown that, with the default values of the numerical parameters of the utilisation factor, EN ISO 13790 gives in Finnish conditions as much as 46% higher or 59% lower heat demand of the building compared to the simulation tool, depending on the type of the building and its thermal inertia. The results of EN ISO 13790 can be calibrated for the residential buildings with the correct selection of the numerical parameters for Finnish conditions. With the new values of the parameters, the results are in good agreement in most cases; however, the maximum difference between the methods remained 29% for highly insulated residential buildings. For office buildings, heat demand was strongly underestimated in all the cases by the monthly method EN ISO 13790 regardless of the values of the parameters. The results of the study indicate that the monthly method EN ISO 13790 with new determined numerical parameters is reasonably applicable for residential buildings, but not applicable for office buildings. Therefore, the other methods of prEN 13790, i.e., simple hourly or detailed simulation methods, should be used for office buildings.     

Coarse particulate matter and airborne endotoxin within wood stove homes

Emissions from indoor biomass burning are a major public health concern in developing areas of the world. Less is known about indoor air quality, particularly airborne endotoxin, in homes burning biomass fuel in residential wood stoves in higher income countries. A filter‐based sampler was used to evaluate wintertime indoor coarse particulate matter (PM_10‐2.5) and airborne endotoxin (EU/m³, EU/mg) concentrations in 50 homes using wood stoves as their primary source of heat in western Montana. We investigated number of residents, number of pets, dampness (humidity), and frequency of wood stove usage as potential predictors of indoor airborne endotoxin concentrations. Two 48‐h sampling events per home revealed a mean winter PM_10‐2.5 concentration (± s.d.) of 12.9 (± 8.6) μg/m³, while PM_2.5 concentrations averaged 32.3 (± 32.6) μg/m³. Endotoxin concentrations measured from PM_10‐2.5 filter samples were 9.2 (± 12.4) EU/m³ and 1010 (± 1524) EU/mg. PM_10‐2.5 and PM_2.5 were significantly correlated in wood stove homes (r = 0.36, P < 0.05). The presence of pets in the homes was associated with PM_10‐2.5 but not with endotoxin concentrations. Importantly, none of the other measured home characteristics was a strong predictor of airborne endotoxin, including frequency of residential wood stove usage.     

Impacts of stove/fuel use and outdoor air pollution on chemical composition of household particulate matter

Biomass combustion for cooking and heating releases particulate matter (PM_2.5) that contributes to household air pollution. Fuel and stove types affect the chemical composition of household PM, as does infiltration of outdoor PM. Characterization of these impacts can inform future exposure assessments and epidemiologic studies, but is currently limited. In this study, we measured chemical components of PM_2.5 (water-soluble organic matter [WSOM], ions, black carbon, elements, organic tracers) in rural Chinese households using traditional biomass stoves, semi-gasifier stoves with pelletized biomass, and/or non-biomass stoves. We distinguished households using one stove type (traditional, semi-gasifier, or LPG/electric) from those using multiple stoves/fuels. WSOM concentrations were higher in households using only semi-gasifier or traditional stoves (31%-33%) than in those with exclusive LPG/electric stove (13%) or mixed stove use (12%-22%). Inorganic ions comprised 14% of PM in exclusive LPG/electric households, compared to 1%-5% of PM in households using biomass. Total PAH content was much higher in households that used traditional stoves (0.8-2.8 mg/g PM) compared to those that did not (0.1-0.3 mg/g PM). Source apportionment revealed that biomass burning comprised 27%-84% of PM_2.5 in households using biomass. In all samples, identified outdoor sources (vehicles, dust, coal combustion, secondary aerosol) contributed 10%-20% of household PM_2.5.     

Entwicklung eines Flächenschätzverfahrens zur Abschätzung von Bauteilflächen als Grundlage für die energetische Bewertung von Wohngebäuden

Development of a simplified method to estimate the thermal envelope area of residential buildings. A calculation procedure for the estimation of the area of building envelope components has been developed. Based on the statistical evaluation of the data records of more than 4, 000 residential buildings the analyses gave mean values for the area of walls, windows, roofs and cellar ceilings and their dependency of the following basic factors: the area of living space, the number of heated storeys, the number of adjoining buildings. When applying the estimation procedure only these basic factors have to be collected.     

Performance analysis of the building envelope: A case study of the Main Hall,Shinawatra University

The envelope of the Main Hall, Shinawatra University has been designed to provide protection from energy gain. According to initial estimates, the Main Hall could achieve an overall thermal transfer value (OTTV) of 10.16 W/m², which is four times lower than those recommended by the Thai national standard. This study aims to evaluate the actual energy performance of the Main Hall building envelope using field measurements and simulations. The air temperature, surface temperature, and relative humidity were measured at frequent intervals, both indoors and outdoors. Hourly average meteorological data for insolations were utilized in order to calculate the solar gain by light transmission. Based on the empirical data, the energy fluxes through the envelope on eight different orientations were simulated and the average value was found within 7% of the estimated OTTV. Using the same empirical data for the outdoor condition, simulations of other common types of building envelope in Thailand were carried out for comparison. The results of the analysis show that the Main Hall's lightweight and highly insulated building envelope outperforms other commonly used heavyweight envelopes in preventing building energy gain in the hot-humid climate of Thailand. Although the use of the lightweight and highly insulated envelope helps reduce the operating and investment costs of the air conditioning system as well as the cost of building structure, it also increases the investment cost of the envelope substantially. However, the life cycle cost analysis (LCCA) reveals that the life cycle cost (LCC) of the Main Hall envelope is the most economical, and the increased investment cost of the Main Hall envelope requires a discounted payback period of only 3–5 years, depending on the envelope types used in the comparison. Furthermore, it should be noted that greater savings and a more favorable pay back period could be obtained if this highly energy efficient envelope is applied to other typical buildings, especially high-rise structures in urban areas.     

Rapid on-site evaluation of thermal comfort through heat capacity in buildings

A simple, straightforward procedure to estimate the effective thermal mass of a building is established. Basic measurements of inside and outside temperatures are shown to exhibit several common characteristics, so that a single value for the effective thermal inertia can be derived. A relationship between the delay in the internal temperature to attain a maximum value with respect to the ambient, and the temperature amplitude attenuation inside the building, is found to exist, and its dependence on maximum outside temperature is explored. This procedure is shown to be useful to rapidly classify buildings or dwellings according to the effectiveness of the participation of its thermal mass in damping extreme temperatures, such as those found in regions with dry climates. The procedure hereby proposed has also been useful to estimate the relevance of thermal mass of a given building in power savings in HVAC.     

Gekoppelte Simulation zur Spezifikation von Heiz‐ und Kühlkörpern

Combined thermal building simulation for advanced heating and cooling specification. Modern concepts of buildings and rooms require a rethinking concerning conventional solutions for heating or cooling of buildings. But often it is not possible to quantify, whether a new idea is worthwhile because of missing sharpness of simple assessments. Therefore a programming system for combined thermal building simulation and indoor air flow calculation, mainly developed and successfully applied by the authors is extended by a highly resolved model for heating and cooling devices. In that way it is possible to model the specification of radiators in a test chamber or under operating conditions. In addition, the effect of cooling by radiators can be investigated. The approaches for modelling will be explained in short and some selected results are presented and discussed.     

A Pilot Study to Measure Indoor Concentrations and Emission Rates of Polycyclic Aromatic Hydrocarbons

Sampling and analytical methods for gas- and particulate-phase polycylic aromatic hydrocarbons (PAH) in indoor air were evaluated in a controlled field study. Using 12-h, 25-m³ samples, gas-phase PAH were collected on XAD-4 resin and analyzed by GC-MS, and particulate-phase PAH were collected in filters and analyzed for by HPLC with fluorescence detection. Tests were conducted in homes and office buildings without active combustion sources and with gas stoves, wood stoves and cigarette smoking as controlled sources. Indoor concentrations, outdoor concentrations and air-exchange rates were simultaneously measured. The precisions of the concentrations were evaluated using collocated sample pairs collected indoors and outdoors. Net emission rates were calculated for the gas-phase PAH. Net emissions of these compounds were measured in buildings without active combustion sources. Environmental tobacco smoke was identified as a significant source of both gas- and particulate-phase PAH.     

现代木结构建筑在上海

现代木结构建筑以其与生俱来的生态性特点在居住及其他使用等诸多方面的优势越来越明显。代表着当今建筑现代化趋势的木结构建筑也逐渐进入大上海，并得到了稳定的发展。总结木结构建筑在上海地区实践的经验，对它的价值在我国这样一个曾经是长期使用传统木结构建筑的国家被重新认识，无疑具有重大意义。