Sheffield City Council in the UK identified some dwellings of non-standard construction that needed to be refurbished. The refurbishment mainly involved applying insulation and rendering to the exterior surfaces of external walls and replacing old windows. The main aims of the refurbishment for the Council were to improve the condition and appearance of the dwellings and reduce conductive heat loss through the fabric.
This paper discusses how ventilation and air distribution can have a positive or negative impact on chemical, biological and radiological agents entering buildings, on their movement within the buildings and on their removal. It also points out the key role played by the envelope airtightness of the building and its pressurization as a security tool.
In developed countries, the concentrations of indoor pollutants are very similar to those outdoors. 3 basic strategies are proposed to reduce occupant exposure to indoor contaminants : 1. Building air tightening and pressure management2. Ventilation and air filtration3. Contaminant removalIn poor countries, the use of advanced ventilation and filtration techniques is not feasible at all, natural ventilation may be one of the more effective solutions
A manufactured home has been installed on the NIST campus for ventilation, energy andindoor air quality studies. The primary purposes of the facility are to study mechanicalventilation requirements for U.S. manufactured homes and to investigate the systems used tomeet these requirements. In addition, the building will be used to investigate moisture issues,indoor air quality impacts of combustion appliances, and VOC emissions from buildingmaterials and furnishings. The first phase of this multiyear effort has focused on airtightness,system airflows and air change rates.
The airtightness of a building envelope impacts upon the magnitude of uncontrolled air leakage and associated ventilation energy losses. A building's airtightness can be assessed using a steady state fan pressurisation technique. This paper describes a study on the largest building in the UK ever to have had its airtightness tested. Power law regression analysis revealed a good correlation between flow rate into the building and observed pressure differentials.
To better quantify the impact of different window opening models in comparison to ventilation techniques a multizone ventilation model, incorporating the CO2-production of the inhabitants, was developed, using Comis-Transys. The reference model represents a free-standing dwelling in which infiltration is the only source of fresh air. Through a series of simulations natural ventilation systems (standard, user controlled or CO2-based demandcontrolled), air-tightness techniques and/or window opening models (deterministic or stochastic) are added.
With the application of part L2 of the Building Regulations in the UK, new buildings with excessive air leakage have no longer been acceptable. All new commercial and public building over 1000 m2 must be tested for airtightness. An air permeability formula measures the envelope of walls, roof and ground floor area. This paper explains why bother about air leakage, and what desginers and constructors must do, and how the testing for airtightness should be carried out. The essential message is : build tight - ventilate right.
Increasing emphasis on energy-efficiency has many jurisdictions enacting stricter energy codes. Yet, these same green building codes typically do not adequately address ventilation when a building envelope is designed to both minimize infiltration/exfiltration and maximize thermal efficiency. Our company investigated an apartment complex in Southern California, U.S.A. that was designed 25% more thermally efficient than required by State Code. Within months of occupancy, the first complaints of biological growth at windows and closets occurred.
This paper asks questions about what is the right tightness and a warns against too tight tightness guidelines.The author gives advice :- A tight building envelope should reduce average natural infiltration (due to wind and temperature) to 0.05 to 0.1 air change per hour.- A tight building envelope should contain the desired air pressure field.- A building envelope should not be too tight because of the unbalanced airflows that can create excessive levels of depressurization.
The author explains that too tight building envelopes can cause bad operation of atmosperically vented combustion systems (e.g. gas water heaters) in case of of unintended depressurization of the building, for example with large exhaust fans and dirt filters. He considers that airtightness requirements of standards are often too severe. He proposes a building airtightness of 2 to 6 air changes per hour at 50 Pa for warm climates and 1.5 to 4 for cold climates, buildings with atmospherically vented combustion appliances being at the high end of the range or higher.
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