Abstract:Building more air-tight dwellings is having a deleterious impact on indoor air quality. In a range of recently completed dwellings CO2 concentrations were measured in occupied bedrooms at unacceptable concentrations (occupied mean peak of 2317ppm and a time weighted average of 1834ppm range 480 -4800ppm). Such high levels confirm that air tight dwellings with only trickle ventilators as the 'planned' ventilation strategy do not meet the standards demanded by the Building Regulations. Reducing ventilation rates to improve energy efficiency and lower carbon emissions, without providing a planned and effective ventilation strategy is likely to result in a more toxic and hazardous indoor environment, with concurrent and significant negative long term and insidious impacts on public health. Furthermore, the methodology underpinning the current regulations cannot be considered as creditable. Any researchers operating in this field require to recognise that dwellings have internal doors. (6) and Crump et al (7) , who called for further investigations to ascertain 'healthy' ventilation rates. This was partially addressed in a recent study (8) commissioned by the Scottish Government, "The effect that increasing air-tightness may have on air quality within dwellings". In this study air tightness and air change rates were measured in a mid-terrace dwelling (Garston, Watford) under a variety of conditions and the published report concluded that dwellings built to 5m 3 /m 2/ /hr@50Pa provide air change rates roughly in line with the CIBSE (9) recommendation of 8l/s per person. BRE test results 2.1In a mid-terrace dwelling, with an air tightness reduced to 6m 3/ /m 2 /hr@50Pa with standard trickle vents fitted on all windows, ventilation rates were measured at 0.7 to 1.3ach -1 on the upper floor (equating to 37-69 l/s), and 0.4 to 0.6 ach -1 on the ground floor (equating to 21-32 l/s). Measurements of CO 2 concentrations (released from a mechanical source) did not provide any cause for concern and settled at circa 1000ppm in the living room and 600ppm in bedrooms. 2.2 3.2The living room and double bedroom were repeatedly pressure tested with the MHVR system outlets/inlets sealed and the system disconnected from the power supply. By progressively increasing the opening area of an additional vent in the tarpaulin, the target air leakage/infiltration rate of 5m 3 /m 2 /hr@50 Pa was achieved. The rooms were then re-occupied Four data sets were collected over two 24hours occupied periods. The initial set measured CO 2 , temperature and humidity -with the MHRV system disabled -between 1800-2200hrs in the living room and 2300-0700hrs in the master bedroom The second two data sets measured the same parameters with the MHRV system re-activated. ResultsGraph 1:Living room MHRV disabled Graph 2: Bedroom MHRV disabled 4. Discussion 4.1 When the living room door is closed and the room occupied by 2 adults and 3 children, CO 2 levels climbed at a rate of 514ppm/hour, peaking at just over 2600ppm. At this time the children star...

The need to reduce carbon emissions and fuel poverty has led to increased building envelope air tightness, intended to reduce uncontrolled ventilation heat losses. Ventilation strategies in dwellings still allow the use of trickle ventilators in window frames for background ventilation. The extent to which this results in “healthy” Indoor Air Quality (IAQ) in recently constructed dwellings was a concern of regulators in Scotland. This paper describes research to explore this. First a review of literature was conducted, then data on occupant interactions with ventilation provisions (windows, doors, trickle vents) gathered through an interview-based survey of 200 recently constructed dwellings, and measurements made on a sample of 40 of these. The main measured parameter discussed here is CO2 concentration. It was concluded after the literature review that 1000 ppm absolute was a reasonable threshold to use for “adequate” ventilation. The occupant survey found that there was very little occupant interaction with the trickle ventilators e.g., in bedrooms 63% were always closed, 28% always open, and in only 9% of cases occupants intervened to make occasional adjustments. In the measured dwellings average bedroom CO2 levels of 1520 ppm during occupied (night time) hours were observed. Where windows were open the average bedroom CO2 levels were 972 ppm. With windows closed, the combination of “trickle ventilators open plus doors open” gave an average of 1021 ppm. “Trickle ventilators open” gave an average of 1571 ppm. All other combinations gave averages of 1550 to 2000 ppm. Ventilation rates and air change rates were estimated from measured CO2 levels, for all dwellings calculated ventilation rate was less than 8 L/s/p, in 42% of cases calculated air change rate was less than 0.5 ach. It was concluded that trickle ventilation as installed and used is ineffective in meeting desired ventilation rates, evidenced by high CO2 levels reported across the sampled dwellings. Potential implications of the results are discussed.

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.