airtightness

The improvement of air tightness in existing residential buildings could be triggered from the desire for better indoor comfort conditions and the expected reduction of cost for space heating. While the improvement of comfort sensation could not be easily understood from the building owner, the reduction of cost for space heating is much easier.

Laboratory measurements have been performed to investigate the airtightness of clamped joints in the wind- and vapour layers. Air leakage was measured immediately after mounting with moisture content of the wooden members at approximately 17 weight %, and after drying down to approx. 7 weight %. It was found that screws as fasteners provided better airtightness than nails. Center distance of 600 mm resulted in general higher air leakages than shorter center distances like 300 mm or 150 mm.

This paper analyses approaches for setting airtightness requirements whether in voluntary or regulatory schemes. We have classified approaches for upper limits into two major types: default values and minimum requirement. Lessons learnt from existing schemes where minimum requirements have been enforced show that the scheme to justify a given airtightness level is one fundamental ingredient in terms of market impact.

We have developed a simple model to estimate ductwork leakage and heat conduction losses in steady-state conditions for a balanced ventilation system. Implemented in a spreadsheet, it allows us to calculate their impact on heat recovery efficiency consistently with EN 15241 without the need for a dynamic simulation tool. One case study shows that the global heat recovery of a balanced ventilation system with a nominal heat recovery of 80% can be reduced to less than 50% if the ductwork leakage and thermal resistance are poor.

Implementation of the European Energy Performance of Buildings Directive (EPBD) introduced the first legal airtightness regulations into the 2008 Polish Building Codes. Unfortunately these provisions are currently not sufficiently precise or developed in relation to testing procedures to ensure appropriate airtightness. Generally there is a low level of awareness, experience and knowledge among architects, designers, investors, contractors and there are no certification requirements imposed for measurement companies.

Although standards for single-zone air leakage tests are widely used, there are no existing standards for several multi-zone cases including: 1) testing air leakage between adjacent zones or 2) testing leakage to the outside from a single unit in a multi-zone building. While a range of test procedures have been used to determine inter-zone leakage using fan-pressurization, the accuracy of the methods can vary significantly. Using field measurements and simulations, we compared the uncertainty in the leakage between two adjacent zones for different measurement and calculation methods.

This paper describes two recent applications of aerosol sealing techniques in buildings for improving indoor air quality and reducing energy required for heating, cooling, and ventilation. One application applies a commercially-available duct sealing technology, which has typically been used in single-family applications, to large-building exhaust systems. The initial leakage rates, percent leakage sealed, and issues encountered are presented for several large buildings.

In 1998, NIST published a review of commercial and institutional building airtightness data that found significant levels of air leakage and debunked the "myth" of the airtight commercial building (Persily, 1998). Since then, NIST has expanded and maintained a database of whole building envelope leakage measurements of U.S. commercial and institutional buildings.

The Engineer Research and Development Center, Construction Engineering Research Laboratory (ERDC-CERL) recently developed design/construction strategies that improve the energy efficiency, reduce the potential for mould, and improve indoor air quality in newly constructed buildings and buildings undergoing major renovations. ERDC-CERL performed building envelope leakage tests on Army facilities to test their general integrity and the effect of increased airtightness on building energy consumption.

This paper presents results from whole building air leakage tests used to document the leakage reduction due to envelope sealing and assess the accuracy of contractor's estimates of the impact of their sealing. The measurements also compare the differences in envelope leakage reductions determined from depressurization versus pressurization tests and determine mechanical system leakage.