Indoor air quality and ventilation in modern airtight homes

Since the 1990s the push to reduce energy use in buildings has been escalating, driven latterly by the increasingly pressing global need to reduce levels of the greenhouse gas emissions from building that are so devastating to our climate. But the hasty adoption of new ways of doing things can often mean mistakes are made simply because of a lack of hands-on experience with the emerging systems being promoted. The viewing of ‘innovation’ as a good thing in the quest for better building can sometimes have unintended consequences, some of which can leave architects wide open to litigation. One of the most contentious areas amongst many involved in the building industry is the trend towards increasingly ‘Airtight Buildings’, often reinforced by emerging Building Regulations. In this article we address some of those ‘Airtight’ concerns and proffer advice on the subject gleaned from recent research, much of which was assimilated and undertaken for a doctoral thesis by Grainne McGill at Queen’s University, Belfast. What architects need is sufficient confidence in their ‘water-tight’ reasons for making related design detail decisions that even if they do fail they will have been deemed to have acted with due care and diligence and not held responsible for subsequent construction failures. We hope the following article will help them understand the issues involved, and point the way to reasonable and professionally competent solutions that will boost that confidence in the rapidly changing building markets of today

Technologically dependent ventilation in a temperate climate- A UK case study

A fundamental shift in sustainable design thinking and practice has occurred over the last few decades. In particular, the increasing application of heat recovery ventilation (MVHR) is changing the way we envisage the home environment. Instead of passive, adaptive spaces, there is an increasing trend towards the creation of airtight envelopes, where dependence is placed on technological devices to condition the interior environment. This dependence however presents a number of challenges and risks that are of particular concern in a social housing context. This paper discusses the inherent challenges of technologically dependent ventilation in airtight housing in a temperate climate in Scotland. A door-to-door survey was conducted in 36 homes which investigated occupant behaviour and perceptions of ventilation in their home. The study identified issues with occupant use and control of ventilation, with particular concerns relating to the perception of MVHR systems

Building Performance Evaluation of a Retrofitted Dwelling in Scotland

It is estimated that 80% of the 2050 building stock already exists and given targets of an 80% reduction of greenhouse gas emissions by 2050, there is a clear need to develop and evaluate retrofitting strategies that reduce energy consumption whilst achieving resilient and healthy indoor environments. This paper presents the results of a building performance evaluation of a retrofitted, Passivhaus certified dwelling in the Orkney Islands (Scotland) during the heating season. The study involved testing of the Mechanical Ventilation with Heat Recovery (MVHR) system, sound assessments, U-Value measurements, energy monitoring, a thermographic survey and indoor environmental monitoring over a three week period. The dwelling had sought to address some ventilation issues identified in other projects by the inclusion of carbon dioxide sensors as part of the MVHR control strategy. The thermal performance of the building envelope and sound level measurements of the MVHR system satisfied the Passivhaus minimum requirements, with acceptable indoor environmental quality observed throughout the monitoring period. However, the results highlighted concerns regarding energy and noise of the MVHR system in boost mode and identified some thermal weaknesses at window seals, and maintenance of the MVHR system in a social housing context. The findings of this study can be used to highlight potential problems and good practice, with the aim of reducing the gap between design intentions and measured performance in future retrofit projects

Health Effects of Modern Airtight Construction: Research Needs and Future Directions

In response to the challenges of climate change, a global shift in building standards and practices is currently underway. In the UK and Ireland, this has been evidenced through substantial improvements of thermal performance and airtightness in new-build and retrofitted dwellings. Whilst improvements in fabric performance should lead to health benefits (particularly for households in fuel poverty), there is now growing concern that the practice of increasing airtightness and limiting ventilation to reduce heat loss may result in indoor air quality problems. These concerns have been exacerbated by reduced space standards, the use of new untested building materials and products, the increasing reliance on mechanical ventilation in new-build housing and the growing housing shortage in the UK. However, while awareness of the risks of increasing airtightness on indoor air quality in housing is growing, there remains a significant lack of evidence of the potential health implications. Research of this nature requires a fundamental understanding of the complex interplay between the climate, building design, occupant behaviour, air quality, toxicology and health

Place, Time and Architecture: The Growth of New Traditions

Space, Time and Architecture is intended for those who are alarmed by the present state of our culture and anxious to find a way out of the apparent chaos of its contradictory tendencies. So wrote the Swiss Modernist Sigfried Giedion (1941, p.vi) introducing the first edition of his pioneering and influential history to the background and cultural context in which modern architecture and urban planning grew and flourished. He stated there that: History is not a compilation of facts, but an insight into a moving process of life. In the Charles Eliot Norton Lectures Giedion gave at Harvard University in 1938–1939 he endeavoured to bring some order and understanding to the development of Modernism in the context of the great buildings and cities of the world, even as many were being blown to pieces in Europe during the Second World War. Eighty years later, as the destruction of great monuments of civilization continues in very different parts of the world, we are using this special issue of the Architectural Science Review, as a modest homage to the significance of his great work. We are also exploring ways out of the apparent chaos of the contradictory tendencies of our own age. The following papers focus on how architectural solutions relate to the people they serve and the places they are built in now and how they will perform in the different future we are so much better able to predict today

Post occupancy analysis of nZEB implementation via the PH standard

Building regulations are currently under development across Europe in advance of the implementation of the nearly Zero Energy Buildings (nZEB) standard at national member state level. However, when revising the national building regulations to improve energy efficiency, few examples exist of the monitored performance of such dwellings, making informed decision-making difficult. This paper reports on the monitored performance of nZEB compliant dwellings which were built to the Passive House (PH) Standard. It finds that the PH bedroom CO2 concentrations are significantly better than in houses built to the current building regulations which use natural ventilation. KEYWORDS: IAQ, CO2, Passive House, nZEB, Cardon Dioxid

Ventilation Performance and Hygrothermal Conditions in New-build UK Housing

Providing a high quality indoor environment is important to protect occupant’s health and well-being, particularly in the home where we spend a significant amount of time. This paper explores indoor environmental conditions in mechanically and naturally ventilated new-build low-energy housing in the UK. Indoor air temperature, relative humidity and carbon dioxide data were collated and analysed from 53 dwellings across 20 different new-build demonstration projects (consisting of public and private developments). The results raise concerns regarding ventilation performance in new-build homes, particularly homes with natural/mechanical extract ventilation (MEV). Significantly less variation of temperature and relative humidity levels were observed in homes with balanced mechanical ventilation with heat recovery systems (p=<0.001), suggesting these systems may help to provide a more stable indoor hygrothermal environment. Average indoor air relative humidity levels were consistently higher in MVHR dwellings. The findings suggest that the type of ventilation strategy can play a significant role in regulating indoor relative humidity and air temperature in new- build thermally efficient homes

Building Performance and End-user Interaction in Passive Solar and Low Energy Housing Developments in Scotland

In the UK housing sector, changes to building regulations have raised standards for fabric performance, bringing about a demand for affordable, low energy housing. Housing Associations have been at the forefront of adopting these measures, but as owners of long term rented stock it is important for them to understand and evaluate the performance of both ‘as-built’ and ‘as-occupied’ dwellings. This paper describes a detailed evaluation of three new-build social housing demonstration projects located in Glasgow (Scotland). The study included occupant surveys in each scheme, fabric testing and detailed monitoring of environmental conditions, energy consumption, and evaluation of occupancy behaviours in eight dwellings. A particular focus of this paper is the ventilation performance as the homes are ventilated differently using natural, mechanical extract and mechanical heat recovery methods. The results showed a wide discrepancy of energy consumption and poor levels of ventilation, particularly in bedrooms. Causes of this included the design and installation of the ventilation provision but occupant interaction with the systems was also a significant factor. Two sites included sun-spaces that, despite having good potential for preheat ventilation and drying spaces, were underperforming. The study highlights significant impacts of the complex interactions between heating and ventilation systems, and the apparent need for more effective ventilation strategies and systems in bedroom spaces, but also improved strategies for end-user understanding of, and interaction with, both mechanical systems and natural ventilation opportunities. The papers aims to provide robust and credible evidence on which to base critical regulatory and design decisions on the most effective means of ventilating low carbon social housing in Britain

Indoor air quality and thermal environment assessment of Scottish homes with different building fabrics

The ongoing climate change and policies around it are changing how we design and build homes to meet national carbon emission targets. Some countries such as Scotland are adopting higher-energy-efficient buildings as minimum requirements in the building regulations. While net zero homes might be more energy-efficient and emit fewer operational carbon emissions, we have yet to fully understand the influence on the indoor environment, particularly on indoor air quality (IAQ) and thermal comfort. This study compares the IAQ of three homes in Scotland with equal internal layouts and designs but different building fabrics. The homes represent the minimum Scottish building regulations (2015), the Passivhaus standard and the Scottish 'Gold Standard'. Temperature, relative humidity, PM2.5 and total volatile organic compounds (tVOC) were measured at five-minute intervals for seven months and compared to occupants' subjective responses to the IAQ. All three homes had temperatures above the recommended thresholds for overheating. Measured hygrothermal conditions were within the ideal range 66.4% of the time in the Passivhaus, 56.4% in the Gold Standard home and 62.7% in the control home. Measured IAQ was better in homes with higher energy efficiency, particularly tVOC. For instance, indoor PM2.5 in the Passivhaus were 78.0% of the time below the threshold, while in the standard home the figure was 51.5%, with a weak correlation with outdoor PM2.5 (Passivhaus: B rs = 0.167, K rs = 0.306 and L rs = 0.163 (p < 0.001); Gold: B rs = −0.157, K rs = 0.322 and L rs = 0.340 (p < 0.001); Control: B rs = −0.111, K rs = 0.235 and L rs = 0.235 (p < 0.001)). TVOCs in the Passivhaus were 81.3%, while in the control home they were 55.0%. While the results cannot be generalised, due to the small sample, this study has significant policy implications, particularly in Scotland, exhibiting the importance of IAQ in current building legislation and sustainable assessment methods

Indoor Air Quality Assessment of Latin America’s First Passivhaus Home

Sustainable building design, such as the Passivhaus standard, seeks to minimise energy consumption, while improving indoor environmental comfort. Very few studies have studied the indoor air quality (IAQ) in Passivhaus homes outside of Europe. This paper presents the indoor particulate matter (PM2.5), carbon dioxide (CO2), and total volatile organic compounds (tVOC) measurements of the first residential Passivhaus in Latin America. It compares them to a standard home in Mexico City. Low-cost monitors were installed in the bedroom, living room, and kitchen spaces of both homes, to collect data at five-minute intervals for one year. The physical measurements from each home were also compared to the occupants’ IAQ perceptions. The measurements demonstrated that the Passivhaus CO2 and tVOC annual average levels were 143.8 ppm and 81.47 μg/m3 lower than the standard home. The PM2.5 in the Passivhaus was 11.13 μg/m3 lower than the standard home and 5.75 μg/m3 lower than outdoors. While the results presented here cannot be generalised, the results suggest that Passivhaus dwellings can provide better and healthier indoor air quality in Latin America. Further, large-scale studies should look at the indoor environmental conditions, energy performance, and dwelling design of Passivhaus dwellings in Latin America