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air tightness

Pressure testing a very large building : theory and practice

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.

Impact of residential natural ventilation and air-tightness techniques on the energy loss and indoor air quality

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.

Unravelling airtightness

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.

Using forced ventilation to mitigate mold growth in existing multi-family housing

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.

Building airtightness. How tight is tight enough ?

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.

Building airtightness : how tight is tight enough ?

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.

Development of a simplified dwelling airtightness measuring device : IMPEC

Studies on buildings’ airtightness have shown that several issues can arise from uncontrolled airflow leakages in buildings (e.g., higher energy cost, thermal comfort and health of occupants, building components and equipment preservation). Indeed, the ne

Interstitial condensation due to air leakage: A sensitivity analysis.

This paper presents an approach to evaluate the sensitivity of a roof design to condensation problems, given the uncertainty to achieve continuity of airtightness in practice. The approach consists of a repeated number of simulations with a 2D heat, air and vapour transfer model to predict the variation in roof moisture performance due to various discontinuities in roof geometry. The set of discontinuities is calibrated by comparing measuring data of roof airtightness to simulation results.

Cost-effectiveness of increasing airtightness of houses.

Air infiltration through the exterior envelope of a residential building impacts significantly on the heating energy consumption and cost, especially in a cold climate such as Montreal's. Therefore to renovate existing houses to the level of new well-built houses in terms of airtightness will lead to a reduction of the heating energy costs. By considering the life-cycle energy consumption and the initial cost of renovation, and the CO2 tax credits, the paper estimates the cost-effectiveness of this type of renovation.

The impact of airtightness on system design.

States that 80% or more of infiltration is due to the many imperfections designed into the building envelopes. Discusses the problem and the role of ANSI/ASHRAE Standard 62-1999.

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