ductwork

Calcium Silicate fire protection boards can be used to construct fireproof ductwork for smoke extraction and/or HVAC services. In this paper, the airtightness of the duct system is evaluated. 

Ventilation Information Paper no40 "Ductwork airtightness - A review", aims to complement Ventilation Information Paper VIP 01 “Airtightness of ventilation ducts”. It provides a literature review of the work performed since 2003 in the field of ductwork airtightness. Its objectives are to provide information on:

Building airtightness requirements are becoming more and more common in Europe (Leprince, Carrié, & Kapsalaki, 2017). However, airtight buildings require an efficient ventilation system to ensure good indoor air quality. In France, the inspection of ventilation system (Jobert, 2012) has revealed many noncompliance. They are mainly due to bad conception, poor implementation, and lack of maintenance. This often leads to reduced ventilation flowrates and poor indoor air quality. Leaky ductwork is one of the reasons for this noncompliance.

Noise remains a major concern for building occupants, both in their home and workplace. Ventilation system is one of the noise sources in buildings. Usually, the main issue is the resulting noise level in the room. It is generated by the fan and the ductwork components, travels inside ducts, and is then radiated into the room by air diffusers, air inlets, and air outlets. But ducts also go through other indoor spaces. Airborne noise will pass through the duct wall and radiate in the surrounding space. This can be an issue for occupants. 

Aeroseal technology utilizes air laden with fine aerosol particles (2-20 μm) to pressurize a duct system, resulting in deposition of those particles at the leaks within that duct system. By reducing leakages of duct systems by 90% in average Aeroseal sealing technology allows reducing leakages to a standard better as air tightness class D or ATC 1 for a complete system. Aeroseal technology can be applied in new constructions as well as in existing systems to improve energy efficiency, cleanliness of ventilation systems, IAQ and comfort.

Against the background of increased global demands for energy efficiency, property owners should raise the standards of ductwork systems for ventilation, heating and air conditioning. This would not only save energy, but also mean lower installation costs, shorter assembly times and better air quality thanks to less leakage. The importance of energy-efficient buildings will increase in the future, not only due to rising electricity prices, but also due to increased environmental awareness.

The air tightness of ventilation ductwork was measured in two recently built low-energy houses and in two conventionally built houses in the summer of 2013. The ducts and components were metal in three houses and plastic in one house. The air tightness of the ductwork had been checked by an installation survey after construction. The measured leakage airflows corresponded to air tightness class A or lower, therefore did not satisfy the minimum requirement set for class B regarding the air tightness of ventilation ductwork.

Reduction of energy consumption and green house gas emissions of buildings is a great challenge in Europe. In this context French energy performance regulation, RT2012, requires an improvement of the buildings' airtightness. In airtight buildings, ventilation must be perfectly controlled to ensure good indoor air quality.  However, many failures are observed when ventilation systems are inspected (Jobert, 2012). They are mainly due to bad conception, poor implementation and lack of maintenance.

Most existing non-residential buildings have Constant Air Volume (CAV) ventilation leading to over-ventilation in periods with low or no occupancy. Demand controlled ventilation (DCV) can considerably reduce the ventilation airflow rate and energy use for fans, heating and cooling compared to constant air volume (CAV) ventilation. There is a potentially enormous upcoming marked for converting from CAV to efficient DCV in existing commercial buildings.

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.