Airtightness enhances a building’s energy efficiency by minimising the exchange of indoor and outdoor air through unintended gaps and cracks. By controlling air leakage, buildings can better maintain consistent indoor temperatures, reducing the energy required for heating and cooling. While airtightness is beneficial for energy conservation, it necessitates a reliable ventilation system to maintain indoor air quality, as stale air and moisture will still accumulate in a tightly sealed environment.
Less air leakage can enhance a ventilation systems effectiveness, as it allows for greater control over what air is moved, where it goes, and when that happens. Effective ventilation in an airtight building means inhabitants can breathe cleaner air and live warmer, healthier lives.
Good indoor air quality (IAQ) is crucial for the health and well-being of occupants. Poor IAQ can lead to various health issues, including respiratory problems, allergies, and headaches. It can also exacerbate conditions such as asthma and when combined with poor indoor environment quality (IEQ) reduce overall comfort. Key factors affecting IAQ and IEQ include the presence of pollutants, humidity levels, infiltration and ventilation rates.
Pollutants: Indoor air can contain pollutants such as volatile organic compounds (VOCs), particulate matter, and biological contaminants like mould and bacteria. These pollutants can originate from building materials, furnishings, household products, and activities like cooking and cleaning.
Humidity Levels: Maintaining appropriate humidity levels (between 40-60%) is vital for IAQ. High humidity can promote mould growth and dust mites, while low humidity can cause dryness and irritation of the skin, eyes, and respiratory tract.
Infiltration for Heat Loss: Humans are more conscious of temperature differences and air movement than they are temperature extremes. Natural infiltration sees air enter the building at unwanted temperatures, particularly in the winter season. We notice this infiltration as draughts and they can make a heated house feel colder than it is, adding insulation helps retain the warmth but draught stopping is critical to our overall comfort.
Infiltration for Heat Gain: Insulation and airtightness do not generate heat, but they can trap it which causes overheating. The primary contributors to overheating are solar gain, occupancy, and insufficient ventilation. Insulation and airtightness, when combined with adequate ventilation, reduce overheating by preventing external heat from entering the building uncontrolled.
Ventilation Rates: Proper ventilation helps dilute and remove indoor pollutants, regulate humidity and in some systems temperature, and ensure a supply of fresh air. Controlled ventilation allows us to reliably bring in higher quality air unlike infiltration that occurs uncontrolled in more “leaky” homes.
Airtightness and Ventilation Go Hand in Hand A house needs to breathe—but in a controlled, consistent way, not just when the windows are open. In an airtight Energytight™ home with proper mechanical ventilation, fresh air flows continuously without relying on the weather or sacrificing heat. This reduces condensation, musty smells, and the risk of hidden mould—creating a space that feels fresher, healthier, and more comfortable every day.
Airtightness and Ventilation Go Hand in Hand A house needs to breathe—but in a controlled, consistent way, not just when the windows are open. In an airtight Energytight™ home with proper mechanical ventilation, fresh air flows continuously without relying on the weather or sacrificing heat. This reduces condensation, musty smells, and the risk of hidden mould—creating a space that feels fresher, healthier, and more comfortable every day.
Proper ventilation can come in several forms from passive solutions to fully
controlled balanced solutions, the type of ventilation solution effects the overall efficiency of your home through varying levels of control.
Passive ventilation also known as trickle ventilation involves small, adjustable vents in the building envelope that allow a controlled amount of fresh air to enter. These vents provide continuous background ventilation through known penetrations without the need for mechanical systems.
The primary advantage of passive trickle ventilation is its simplicity and low cost. However, its effectiveness is limited in highly airtight buildings, as natural driving forces (such as wind and temperature differences) may not be sufficient to ensure adequate air exchange or a desirable temperature.
Continuous extraction ventilation systems use mechanical fans to continuously remove stale air from specific areas, such as bathrooms and kitchens, where moisture and odours are prevalent. Fresh air is drawn into the building through vents or gaps in the building envelope, replacing the extracted air. This method ensures a consistent flow of fresh air and can be particularly effective in maintaining indoor air quality.
However, in high performance homes extraction fans can be starved of
replacement air as they become unable to overcome the airtight seal of the
house. To address this, systems can be designed with make-up air pathways (in the form of passive vents) to ensure that fresh air can replenish the air being pulled out, thus improving effectiveness and consistency, however they still rely on the unmonitored source air for temperature and quality.
An MVHR system consists of two air streams passing through a heat exchanger, where heat is transferred from the outgoing air to the incoming air without mixing the two streams. This method ensures a continuous supply of fresh air as well as significantly reduces the energy required for heating or cooling the incoming air.
Because MVHR systems control both air streams they can autonomously respond to the needs of the home, further improving their efficiency while reliably delivering a higher indoor air quality. MVHR systems are particularly effective in
airtight buildings, where the reduced air leakage requires prescribed air pathways in both directions and sees a higher relative benefit of the enhanced efficiency of heat recovery.
Experience dramatic savings on home heating & cooling
Seal out mould, pollutants & allergens for a healthier indoor environment
Up to 40% reduction in outside noise from traffic & neighbours
Reduce conditions that lead to damp cavities, mould & timber rot
Feel warmer in the winter, cooler in the summer
Seal gaps & holes to create the first line of defense against insects & pests
Storm Harpham BE Hons
Market Manager – Home Ventilation | Simx Limited
“Compared to other upgrades, airsealing offers the biggest performance gain for the lowest cost.”
Chris Caiger, Aero
Looking to improve your home’s energy efficiency or build airtight from the start? Aero Ltd is New Zealand’s exclusive AeroBarrier provider. We partner with homeowners, builders, architects, and developers to deliver high-performance, Energytight™ homes that are healthier, more efficient, and built to last.
Enquire now to find an AeroBarrier installer near you.
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