Improving air-tightness in dwellings, following concerns about energy consumption, is a major consideration for the building industry. Domestic housing uses a very large percentage of the UK’s total energy consumption. Continuous efforts to minimise energy use through improved insulation techniques, suggests that if reduced air loss is not matched with properly controlled ventilation, the health of the occupants will suffer.
Controlling indoor air quality without compromising comfort and energy-efficiency is one of the prime challenges facing the HVAC industry. The best way to avoid toxin build-up and humidity is to provide plenty of ventilation. But how can one ventilate a building without letting costly heated or cooled air out of the window?
It’s frightening to know just how much we rely on indoor air for survival, consuming an average of 20 to 30 kilograms of air per day (almost 25,000 litres). Most of us spend an estimated 90 percent of our time indoors. Strange then, that we still pay more attention to the outdoor air we breathe and do little to improve our primary source. Reason enough to make indoor air quality a top priority. Fifty years ago, allergies were relatively uncommon, but today almost everyone has either had allergies themselves, or know other allergic individuals in their immediate environment, one of the many signs that the air we breathe needs serious review.
Focus must lie not only on understanding the best modus operandi for air quality control and energy saving, but making the installation of air handling and heat recovery systems simple and straightforward as there are still so many poorly ventilated buildings. There is certainly more knowledge about indoor air pollution, but not enough change is taking place.
Poor air quality in offices, schools, day care centres, etc. often means poorer work performance and ventilation experts have many issues to address. For maximum performance and energy-efficiency, air hygiene systems require high performance heat exchangers that can recover an estimated 90 percent of the winter warmth that would otherwise be wasted by conventional extract ventilation. This is key in reducing power consumption. The last decade saw a 5.5 percent increase in energy use in the UK. Domestic use alone has rocketed by nine percent in the 21st century.
Factors affecting our air quality include problem areas such as air velocity, humidity, temperature and air pollution. The ideal ventilation solution is a system that brings fresh air indoors. The system should be adapted to the building, taking into consideration its construction, population, nature of occupants (school children, retirement people, office workers), external building environment and climatic conditions. A good system is appropriate, reliable and conserves resources. Appropriate means that it should adhere to all unit and building requirements and should correctly fit the installation. Reliable means that the system is long lasting and easy to maintain. Resource-conservation means cost-effectiveness.
A technically correct ventilation plant enables a greater airflow to be maintained without increasing energy consumption. There are, traditionally, three technical systems used for indoor ventilation, which are natural drafts, fan-controlled exhaust systems and balanced ventilation systems that include supply as well as exhaust air fans. The balanced option can be improved by a heat recovery system.
When an investment is made today, people tend to take the longterm view, unlike several years ago when they took the simplest and cheapest option for immediate reward. Thanks to this modern reasoning, we see investments in life cycle costs (LCC). Heating and ventilating a building plays a large part of the overall running and maintenance costs. To lower overheads, ventilation should be high performance and energy-efficient. To achieve this, the system requires heat recovery and demand control. LCC is low because of drastically reduced energy bills and overall effectiveness and
comfort.
Smaller apartments, where air is tighter and more restricted, have rotating heat exchangers, which automatically alternate between normal operation with heat recovery and summer operation without. In summer mode, the unit will restore chilled indoor air, which acts as a cooler. Smaller dwellings, where air quality is often poor and sound travels quickly, should employ systems with quiet operation. With standard ventilation, air circulates through static, open vents or is expelled by fans, such as those used in bathrooms, kitchens and attics. When air escapes, the energy that was used to heat or cool is wasted. Units designed for larger apartments usually have counter flow heat exchangers. These units, designed for wall fixing, are ideal because they are compact which makes positioning easy. An efficient controls system ensures uncomplicated airflow
management and individually adjustable fans guarantee balanced ventilation. When air quality controllers offer more functions and options, the control panels should be easy to understand and administer. Installers should be able to simply insert the unit without fuss.
In larger dwellings where air is less tight, pollutants get trapped and build up, particularly in today's super-insulated buildings. When pollutants accumulate, some concentrations can considerably exceed levels of outdoor pollution. Sufficient evidence exists to conclude that indoor air represents a major portion of the public's exposure to air pollution, reinforcing the need for air handling and heat recovery systems. Heat recovery’s fundamental operation is to push out stale air, pull in fresh air, and with little or no mixing of the two air streams, transfer the heat or chill from the outgoing air to the incoming supply. The fresh air arrives pre-heated or pre-cooled. When being installed in larger applications, the units require more power and a slightly longer installation process. Low-ventilation individual rooms such as bathrooms, laundry rooms, artist studios and darkrooms require low-power systems. Larger units provide fresh air for all rooms. These often require routing ductwork to areas where air is stale, particularly bathrooms, laundry rooms and kitchens. Though whole-house systems are installed primarily in new houses, they can be retrofitted into homes with good access for ductwork, particularly those with unfinished basements. To simplify installation, some systems can take advantage of existing ductwork by piping into the return-air system.
Heat recovery for larger applications is designed for installation in the utility room or similar. These ventilation systems should offer users a choice of airflow and larger systems should be flexible for varying installation styles. The checklist for a good ventilation system should include a good indoor climate. This means paying attention to lack of draft, low noise level, appropriate temperatures and superior air quality.
Other items on the checklist are low energy use, simple operation, easy maintenance, simple adjustments, good flexibility, low LCC and easy, simple-to-understand instructions for operation. Understanding the significance of clean indoor air quality and adhering to the new ventilation and building air tightness regulations is a primary focus for air management manufacturers.
With increasing knowledge and greater awareness of the various sources of health problems and allergies, the building services industry needs to look at air handling and heat recovery afresh. Specifying ventilation should become a more stringent process, insisting on high performance, energy-efficient and effective systems for superior indoor air quality. After all, can we really ever put a price on our health and wellbeing?
