Building Airtightness Research Articles

Assessing overheating risk and thermal comfort in state-of-the-art prototype houses that combat exacerbated climate change in UK

There is growing evidence that terraced houses—thermally lightweight, well insulated, naturally ventilated with three exposed wall surfaces—are at risk of overheating, especially in south-eastern England. The aim of this study is to evaluate the building performance and develop a reliable building simulation, which will be employed in the second phase of the study: developing affordable and feasible passive design strategies to support the energy-efficient building systems of the construction industry. This paper reports on the results from the first phase of the study where a quantitative methodology, including indoor and outdoor environmental monitoring, in-situ measurements and building simulation modelling, was adopted. The performance of a case study was modelled and simulated via employing Integrated Environmental Solutions (IES) software suite.The results from the base-case were analysed according to the adaptive thermal comfort of Chartered Institution of Building Services Engineers (CIBSE) Technical Memorandum 52 guidelines: The Limits of Thermal Comfort—Avoiding Overheating in European Buildings. The spaces studied within the case study house were observed to exceed the acceptable limits of thermal comfort; particularly, the large bedroom within this zone exceeded the upper limit for overheating up to 11 h daily. Furthermore, the results from the monitoring study indicate a high risk of summertime overheating across all the case study settings, especially during short-term peaks in outdoor temperatures. The main reasons for the problematic thermal performance were identified as well-insulated and fully air-tight building fabric, the lack of sufficient ventilation through the living spaces and excessive heat gains through the composite cladding material.

Influence of Building Air Tightness on Energy Consumption of Ventilation System in Nearly Zero Energy Residential Buildings

Building air tightness increased quickly in recent years as nearly zero energy buildings concept gradually drawn more attentions from the industry. Ventilation system plays an important role for the indoor air quality control in residential buildings with good air tightness. The energy consumption of the ventilation system is a significant part of the overall energy consumption of low energy residential building. The influence of the building air tightness on the energy consumption of ventilation system was not addressed sufficiently in previous studies. This paper analyses the quantitative relations between building air tightness, energy recovery efficiency and ventilation system control strategy. A mathematical model of the heating and cooling energy consumption in residential buildings is proposed, which takes building air tightness, energy recovery efficiency and control strategy of ventilation system as major input parameters. Equivalent COP of ventilation energy recovery system is proposed as an energy efficiency index of the ventilation system. It can be used as a criterion to decide the optimal design parameters of nearly zero residential buildings in different climate conditions.

Transition from n50 to actual air exchange dependent on climatic conditions

The knowledge of the air flow and air exchange in the building is critical both on the design and operation stage of the building. Infiltration of air interferes with the mechanical ventilation and determines the proper functioning of the natural ventilation system, still commonly used in the standard buildings. The building airtightness can be described by n50 parameter, however it does not specify the real air exchange in natural conditions. According to the simple procedure of the standard EN ISO 13789, factor n50 may be easily converted to the monthly averaged air change rate. However, it is difficult to accept the same value of air change rate in any month of a year, as it is often done in the certification procedures. More precise, climate dependent conversion procedures have been elaborated in USA, but they were developed for the specific local building technology and local climate conditions. This paper presents the results of the preliminary measurements conducted in a single family house in Poland, built in a heavy-weight technology. The real air exchange rate was measured in various climatic conditions by means of gas tracing method, with CO2 as the tracer gas, in order to prove a relationship between the enhanced procedure and the external conditions. Acceptable agreement between the results of the measurement and model calculations was obtained. Based on the preliminary results, the authors determined the more realistic influence of the enhanced algorithm on the ventilation energy demand. The use of the simplified model resulted in case of the analyzed object in 15% overestimation of the ventilation thermal losses.

Optimizing production efficiencies of hot water units using building energy simulations - Trade-off between Legionella pneumophila contamination risk and energy efficiency

The energy needed for domestic hot water represents an important share in the total energy use of well-insulated and airtight buildings. One of the main reasons for this high energy demand is that hot water is produced at temperatures above 60°C to mitigate the risk of contaminating the hot water system with Legionella pneumophila. However, this elevated temperature is not necessary for most domestic hot water applications, and has a negative effect on the efficiency of hot water production units. A simulation model has been developed which proposes an alternative to this constant 60°C by predicting the Legionella pneumophila concentration dynamically throughout the hot water system. Based on this knowledge, a hot water controller is added to the simulation model that sets a lower hot water comfort temperature in combination with heat shocks. In this paper, the simulation model is used to estimate the energy saving potential in a case study building, at the level of the heat production system by reaching higher production efficiencies. Three different production units, namely an electric boiler, heat pump and solar collector have been investigated. The controller is expected to become an alternative for the current, energy intensive, high temperature tap water heating systems.

Evidence based residential ventilation: sizing procedure and system solutions addressed by REHVA Residential Ventilation Task Force

Wider application of heat recovery ventilation in residential buildings brings attention to knowledge and regulatory gaps which call for research and other actions. In many technical questions there is no consensus in national regulations of EU Member States (MS). This applies for instance for air flow rates, i.e. how much ventilation is needed, restrictions of the use of some heat exchangers types, connection of cooker hoods to ventilation system and placement of exhaust air devices. While European standards are well detailed in these aspects for non-residential ventilation, there is very limited information available for residential ventilation systems. Recent European Guidebook REHVA GB No 25 has made an attempt to collect evidence based best practice technical solutions and design principles for residential ventilation. In this paper a recent evidence and common assumptions behind REHVA airflow rate selection procedure is discussed. Best practice solutions and open research questions related to cooker hood connection to heat recovery and compensation to enable balanced operation of ventilation in an airtight building are analyzed. The paper summarizes existing evidence in these questions and defines open research questions for future residential ventilation research agenda.

A Simplified Methodology to Estimate Energy Savings in Commercial Buildings from Improvements in Airtightness

Air leakage through the envelope of commercial buildings in the United States accounts for approximately 6% of their energy use. Various simulation approaches have been proposed to estimate the impact of air leakage on building energy use. Although approaches that are based on detailed airflow modeling appear to be the most accurate to calculate infiltration heat transfer in simulation models, these approaches tend to require significant modeling expertise and effort. To make these energy savings estimates more readily available to building owners and designers, Oak Ridge National Laboratory, the National Institute of Standards and Technology, the Air Barrier Association of America, and the US Department of Energy (DOE) are developing a user-friendly online calculator that applies a detailed airflow modeling approach to examine energy savings due to airtightness in commercial buildings. The calculator, however, is limited to 52 US cities and a few cities in Canada and China. This paper describes the development of an alternative, simplified method to estimate energy savings from improved airtightness. The proposed method uses the same detailed approach for hourly infiltration calculations as the online calculator but it expands the ability to estimate energy savings to all US cities using hourly outdoor air temperature as the only input. The new simple regression model-based approach was developed and tested with DOE’s standalone retail prototype building model. Results from the new approach and the calculator show good agreement. Additionally, a simple approach to estimate percent energy savings for retrofitted buildings was also developed; results were within 5% of the energy saving estimates from the online calculator.

Airtightness of residential buildings in the Continental area of Spain

Infiltration plays a relevant role regarding the energy performance of buildings. Many European countries have already established standards which aim to limit the energy waste through the envelope following the European Energy Performance of Buildings Directive guidelines. However, in Mediterranean countries there is still a lack of knowledge in this field. An extensive study has been carried out in order to characterize the air leakage through the envelope of the existing housing stock in the Continental climate area of Spain. Results of 129 dwellings tested, including different typologies and periods of construction, are shown. Blower door tests were performed, and thermal imaging was used to locate leakage paths. Single-family dwellings were found to be more airtight than apartments, given that the mean air permeability rate at 50 Pa (q50) was 5.4 m3/h·m2 and 6.8 m3/h·m2 respectively. The mean air change rate at 50 Pa (n50) was 6.1 h−1 for single-family dwellings and 7.1 h−1 for multi-family housing. Nevertheless, great dispersion of results and extreme values were found. In addition, the influence of several construction characteristics on permeability results was assessed.

Overpressure induced by fires in airtight buildings

The need for sustainability and smaller ecological footprint leads to the construction of more airtight building envelopes with better thermal insulation in order to reduce the pollution and increase the energy efficiency, according to the Energy Performance of Buildings Directive (EPBD 2010/31/EU).The specific fire hazards possibly associated with such structures raised questions amongst fire community in Belgium. Consequently, in 2010 the Belgian Ministry of Interior funded a study about the fire hazards possibly associated with Passive Houses in comparison to traditional houses. The University of Mons and ISSeP used zone modelling for investigating how much the characteristics of a passive house such as airtightness, ventilation and thermal insulation could affect the fire development. A significant difference in pressure rise (due to thermal expansion of fumes) was observed because of the airtightness in the passive house. However, due to a lack of validation from experimental data at large scale, the scientific monitoring committee of the project decided to not mention the potential problem that the forces of pressure could block the occupants during a certain period due to inwards-opening doors.It was decided in 2015 to build a full-scale experimental facility in the region of Mons with the support of the KCC centrum and the Régie Provinciale du Hainaut. This facility was designed with the support of the Ghent University. The inner dimensions of the construction are the same as the inner dimensions of a 40-foot shipping container, but the outer shell consists of 20 cm concrete blocks and the inner shell is made of plaster board. The volume is divided into two rooms, which simulate two different rooms of a passive house. In one room air is extracted, while in the other one fresh air is supplied.In this study, we present the tests carried out in this facility by burning pallets stack and wood cribs. Two different ventilation duct configurations were tested: one with mechanical ventilation on, the other with the ducts closed with an airtight metal cap (the mechanical ventilation being off). Measurements were made for gas pressure, mass loss rate, gas temperature, volumetric flow rate in the ducts and for some tests O2, CO2, CO and THC concentrations were also quantified. Over pressure peaks from 850 to 2035 Pa were measured without mechanical ventilation (ducts closed), while values from 420 to 750 Pa were observed with the mechanical ventilation on. Both the reverse flow of the fan supplying fresh air and the extra flow rate of fumes in the extraction duct due to the overpressure inside the apartment were not sufficient to prevent overpressure inside the rooms. These tests confirm there may be problems of overpressure in very airtight houses such as passive houses in case of fire. Especially, the occupants may not succeed in escaping during a period of several minutes due to the impossibility to open inward opening doors. This experimental study confirms the observations carried out during the reconstruction of the fire which occurred during the night of the 5 February 2013 in an passive apartment in Cologne, the occupant being blocked for about 2 minutes.This experimental campaign was also used for validating the zone model CFAST predictive capability. The way to take into account the effective leakage which depends on the overpressure inside the building as well as the mechanical ventilation in CFAST for obtaining satisfactory simulation results are briefly presented in this paper. The use of validated software could be helpful to take into account the fire-induced overpressure in confined dwellings in fire safety design.

Energy and defrosting contributions of preheating cold supply air in buildings with balanced ventilation

Residential wastewater is a constant and available source for saving energy. This paper mainly investigated the possibility of utilizing wastewater heat to reduce ventilation heat load. Swedish residential buildings are to a significant extent served by mechanical ventilation with heat recovery (MVHR) systems. MVHR in airtight buildings has greatly reduced ventilation heat loads, especially in cold climate countries such as Sweden. However, cold outdoor air might lead to frost formation in heat recovery exchangers which increases the energy use. Therefore, this study focused on reducing the defrosting need by preheating the incoming cold outdoor air to MVHR during the coldest days. The effects of preheating the incoming air to MVHR on ventilation heat load and annual ventilation heating demand were also studied. It was found that the heat recovery efficiency of MVHR is the most decisive factor in rating the performance of the combined system with an air preheater. Contributions of the studied air preheater to annual energy savings were negligible. On the other hand, the reduction of the initial defrosting need was significant. The obtained results showed that the defrosting need in a building located in central Sweden in two cases of an MVHR system equipped with a rotary heat exchanger/plate heat exchanger was eliminated/reduced to one-third. The defrosting need was reduced by 50% in northern Sweden for both cases.

Inwards Doors Blocked by Fire Induced Overpressure in Airtight Apartment: a Real Case in Germany

Nowadays, construction requirements and practices are rapidly moving towards more airtight building envelopes, thermal insulation and energy saving according to the Energy Performance of Buildings Directive. In such structures, one might wonder if there are specific risks in case of fire. Some fatal accidents during the intervention of fire brigades were reported in the past due to a backdraft phenomenon in airtight and insulated renovated apartment. However, the occupants of better insulated and sealed buildings can also be exposed to news kinds of hazards. This paper presents the fire that occurred in an apartment in Germany on the 5 February 2013. This fire broke out during night in an apartment in a newly renovated building to meet the passive standard. Awakened by the noise of the flames, the occupant of the apartment quickly noticed that a fire had just broken out in his living room. After an unsuccessful attempt at fire extinction, he decided to abandon his dwelling. Unfortunately, the inwards-opening door to reach the outside via the corridor turned out to be completely blocked. After an interminable waiting period estimated by the investigators of nearly two minutes the occupant was finally able to open the bedroom door leading to the balcony where he was rescued by the emergency services and escaped with burns. After some investigations and based on fire simulations results from CFAST modeling, it was concluded that the door were blocked due to the fire induced overpressure.From this real fire case there is no doubt about the capacity of the building structure to withstand high levels of overpressure, the integrity of the sealing of the passive house being not deteriorated in the first moments of the fire. This new fire hazard has to be taken into account in the fire safety design of confined dwellings.

Emissions and treatment of VOCs emitted from wood-based construction materials: Impact on indoor air quality

Concerns about insulation properties, bio-sourcing and recyclability of construction products promote the use of wood-based materials. Recent studies about indoor air quality in new constructions evidenced negative impacts of such material emissions on indoor air quality (IAQ). Efforts made on building air tightness to save energy promoted indoor pollutant confinement, encouraging the deployments of air treatment systems to improve IAQ. First, this study aims at characterizing wood-based material emissions in a real scale environment. Second, it aims at assessing the ability of widespread air treatment processes to address this specific IAQ problematic. Regarding emissions, a quantitative inventory of VOCs emitted by wood-based products is proposed. Terpenes and carbonyl VOCs (OVOCs) are the typical identified and quantified species. Concentration profiles of VOC and depletion rates are determined under environmental conditions. Then, the behaviors of two air treatment devices are addressed. It evidenced that the abatement of emitted VOCs not only depends on the chemical structure of the VOC but also on the conception of the device. Regarding terpenes, the devices induce noticeable but contrasted conversion rates. Moreover, possible sorption and transient secondary emissions of primary terpenes are evidenced. Regarding OVOCs, contrasted behaviors are observed between VOCs containing more than 4 carbon atoms compared to lighter ones. These behaviors still question the generation of lighter OVOCs as photocatalytic side-products, even in real scale environments. The proposed experimental approach gives a new insight and allows effective conclusions on sources and sinks of VOCs in a built environment.

A Review of the Physics and the Building Science which Underpins Methods of Low Energy Storage of Museum and Archive Collections

ABSTRACT The need to keep things cool for durability should be the single most powerful influence on storage design. The simplest temperature control is to moderate the outside temperature by a combination of thermal insulation and heat capacity. The low energy storage building is a lightweight, thermally insulated, airtight building put on top of an uninsulated floor slab laid directly on the ground. The thermal insulation is calculated to even out the daily temperature cycle but to allow an annual temperature cycle which is about half the amplitude, but much smoother, than the annual temperature cycle outside. The winter temperature inside will nearly always be above ambient and so will maintain a moderate RH without need for either humidification or dehumidification. The temperature inside in summer will be below ambient and thus will force dehumidification of the infiltrating air. However, the airtightness of the building allows intermittent dehumidification with low energy consumption, less than one kWh/m3 per year. There now exist enough buildings designed on this principle to reassure curators that highly valued collections can be stored in a space with a gentle temperature cycle and with an RH stability as good as air-conditioning usually achieves.

A study on variation laws of infiltration rate with mechanical ventilation rate in a room

Mechanical ventilation system is commonly used or recommended to supply the outdoor fresh air for both centralized and non-centralized air-conditioning buildings. ASHRAE requires a positive pressure (i.e., zero infiltration rate) for mechanically ventilated rooms. In fact, positive pressure is difficult to be maintained under poor building airtightness or low mechanical ventilation rates. When the positive pressure is not achieved, the existence of air infiltration brings two problems—the outdoor air pollutants infiltrating indoors and the excessive fresh air cooling/heating load. In order to solve the above problems, air purifiers can be used to remove the indoor pollutants, and the mechanical ventilation rate should be reduced to prevent the excessive ventilation. Therefore, in order to determine the Clean Air Delivery Rate (CADR) for the air purifier and to calculate the amount of mechanical ventilation that should be reduced, the influence of mechanical ventilation on the room infiltration rates must be figured out. This study investigates the variation laws of the infiltration rate with the mechanical ventilation rate, and then theoretically deduces the relational expressions between the two rates for stack effect and wind dominant ventilation models. The theoretical derivations were validated by tests in actual rooms. From a practical perspective, this study can be used to improve the indoor environment and ventilation rates for mechanically ventilated rooms, demonstrated by the case study.

東京都で生息が確認されたネッタイトコジラミ

We conducted a nationwide bedbug surveys in 2016–2017. A total of 101 specimens from 19 prefectures was collected in the investigations. Cimex hemipterus was recorded for the first time in Tokyo in 2016. The species was found in a highly air-tight building, with a constant elevated room temperature therefore, possibly providing an overwintering habitat. The results suggested that C. hemipterus abundance increased in various parts of Japan, with an increase of both Japanese and other tourists.

Methodology for the Study of the Envelope Airtightness of Residential Buildings in Spain: A Case Study

Air leakage and its impact on the energy performance of dwellings has been broadly studied in countries with cold climates in Europe, US, and Canada. However, there is a lack of knowledge in this field in Mediterranean countries. Current Spanish building regulations establish ventilation rates based on ideal airtight envelopes, causing problems of over-ventilation and substantial energy losses. The aim of this paper is to develop a methodology that allows the characterization of the envelope of the housing stock in Spain in order to adjust ventilation rates taking into consideration air leakage. A methodology that is easily applicable to other countries that consider studying the airtightness of the envelope and its energetic behaviour improvement is proposed. A statistical sampling method has been established to determine the dwellings to be tested, considering relevant variables concerning airtightness: climate zone, year of construction, and typology. The air leakage rate is determined using a standardized building pressurization technique according to European Standard EN 13829. A representative case study has been presented as an example of the implementation of the designed methodology and results are compared to preliminary values obtained from the database.

The influence of construction and material solutions on the level of air tightness in single energy buildings

This publication focuses on the assessment of the impact of structural solutions of single-family buildings with an increased energy standard on their air-tightness level. The first part presents the threats resulting from the low tightness of the building. To formulate the conclusions, quantitative and qualitative casing tightness tests of existing single-family energy-efficient buildings were carried out. Construction and material solutions used in buildings were also analysed. The obtained results indicate that there is no impact of the building structure on its level of air tightness.

Durability evaluation of adhesive tapes for building applications

In the building sector, various adhesive materials are experiencing an increased usage for sealing of overlaps and joints between most commonly used building materials, around penetrations, pipes and windows for increasing the moisture tightness and the airtightness of buildings. Among the adhesive materials are adhesive tapes that are used to ensure adequate airtightness of a building and thus must be able to withstand severe environmental conditions without significant long-term deterioration. Durability test methods are needed to evaluate whether the tapes fulfill their performance requirements for the service life of the whole building. However, there is a lack of reliable test methods and evaluation procedures for tapes used for building applications. This study was performed to evaluate tape durability testing and evaluation methods, which hence form a basis for further improvements of the existing methods.

Assessing the overheating risks in Italian existing school buildings renovated with nZEB targets

Energy retrofit projects following nearly zero-energy buildings (nZEB) requirements often pay a little attention to Indoor Environmental Quality of the building. This aspect is extremely important in school buildings, as they are frequented mostly by young people, who are affected more by a healthy environment. In this context, starting from a reference case, overheating risks in existing school buildings considered for energy renovation were investigated through TRNSYS 16. Four building configurations were evaluated (existing, nZEB, nZEB with external shadings, nZEB with external shadings and night ventilation) and the influence of several parameters was taken into account (climate, orientation, building level). The aim of this paper is to understand if nZEB standards applied to Italian school buildings guarantee good indoor thermal conditions and which building configuration can be more advantaged by these standards. Furthermore, even if overheating risk is qualitatively recognized in insulated and air tight buildings, quantitative assessments are still missing for the Italian building stock. The intent of this research is to provide preliminary data on this topic in order to lead to a more conscious choice of retrofit strategies as a compromise between energy performances and indoor environmental quality.

改修集合住宅の気密性能と温熱空気環境に関する研究 その1 気密性能と換気量予測

改修集合住宅の気密性能と温熱空気環境に関する研究 その1 気密性能と換気量予測

改修集合住宅の気密性能と温熱空気環境に関する研究 その2 被験者実験時における温熱環境

改修集合住宅の気密性能と温熱空気環境に関する研究 その2 被験者実験時における温熱環境