Stephan Lang of Daikin explains how ‘whole-building approaches’ to heating, ventilation and air conditioning in new build homes can balance energy efficiency and the vital need to improve indoor air quality.
New build homes must be built in compliance with a vast array of requirements, and in recent times a key focus has been on both the environmental impact and the energy efficiency of these homes.
In December 2021, Building Regulations were announced, for example, and will apply from June 2022, stating CO2 emissions from new build homes must be reduced by 31% compared to current standards.
Due to the increased airtightness needed to meet these requirements, indoor air quality (IAQ) could be adversely impacted if the house is not designed and built correctly.
WHY IAQ IS IMPORTANT
Air pollution has long been considered a major health issue. The World Health Organisation (WHO) has often voiced this concern, and has proclaimed air pollution from both indoor and outdoor sources as the single most significant environmental risk to global health, contributing toward the deaths of over seven million people each year.
When coupled with the statistic that people spend an estimated 90% of their time indoors, the importance of ensuring IAQ is closely monitored is clear.
A wide range of factors contributes to IAQ from various sources, both inside and outside the home – everything from industrial practices to road traffic generates air pollutants, including carbon monoxide (CO), nitrogen dioxide (NO2) and particulate matter. These types of pollutants, and natural allergens like pollen, can easily infiltrate homes through natural or mechanical ventilation or through the building’s fabric. There are plenty of indoor contributors to air pollution too, such as mould, dust, Volatile Organic Compounds (VOCs) emitted from the floor and wall coverings, along with furniture and appliances.
The physical ill effects from air pollutants are well documented, but there is also rapidly mounting evidence for the impact on mental health, with conditions like bipolar disorder and depression being linked back to poor air quality. Additionally, it shows detrimental links to children’s ability to learn and concentrate.
The design focus for HVAC systems in new build homes is usually centred around the efficiency of the system and the energy use associated with it. For most clients this is a key requirement, and it also contributes the highest rewarding factors in BREEAM assessments.
However, HVAC systems that maintain high indoor air quality are also rewarded under the same assessments by controlling humidity, temperature, the management of pollutants, and ensuring a good supply of fresh air. As such, the correct choice of HVAC systems can satisfy both energy efficiency and IAQ requirements.
A significant issue for energy efficiency is the amount of heat wastage through ventilation systems, particularly those that exchange indoor air for fresh outdoor air. However, building effective heat recovery into the system can significantly reduce the effects of this issue and contribute further to the overall energy efficiency of the system and home. Units with this heat retention ability will utilise heat from certain areas of the home and use this air to heat another area. Some units can even use this heated air to help generate hot water for the home.
When grading heat recovery systems, manufacturers usually state Seasonal Energy Efficiency Rating (SEER) figures of 3 and 4; however, it isn’t unrealistic for this score to almost double when recovered energy is utilised through the HVAC system. A good option here is to use Centralised Heat Recovery Ventilation (CHRV) systems.
A crucial consideration for designing an HVAC system is the location of the ventilation intakes and exhaust outlets situated on the home’s exterior. The placement of these intakes is vital, and they should always be situated as far away as possible from sources of air pollution such as road traffic or exhaust flues from the home.
The filtration system is another vital aspect of effective ventilation in the home. HVAC units are fitted with filters primarily to keep the systems dust and debris free to allow for optimal energy efficiency. However, opting for indoor units that feature automatic cleaning filters will ensure that the IAQ is positively affected, along with the energy-saving aspects.
By taking a whole-building approach to HVAC in new build homes, and considering the above, such systems can easily protect indoor air quality, while maintaining energy efficiency, in tandem.
Stephan Lang is product specialist at Daikin