Homeowners in New Zealand often invest in Heat Recovery Ventilator (HRV) systems, expecting them to improve indoor comfort throughout the year. While HRV systems are excellent for maintaining air quality and reducing moisture buildup, many homeowners are disappointed when their HRV doesn’t cool their homes in summer.
The truth is that HRVs are not air conditioners. They are designed for ventilation and heat recovery, meaning they regulate airflow, remove (some) stale air, and help transfer attic heat in winter—but they don’t provide active cooling.
In this guide, we’ll explain how HRV systems work, break down common problems, mistakes, and solutions, and help you optimise your home’s ventilation for summer comfort.
How Does an HRV System Work?
An HRV system is a mechanical ventilation system that helps reduce moisture levels inside the home by forcing air from the attic down into the rooms below and pushing the stale air inside the home out through gaps in windows, walls and doors. The system can be programmed to bring this air in only when it reaches a certain temperature, so that In winter it brings in the warm air from your attic, but this works only on sunny winter days and not when it is overcast or raining..
Key Components of a standard HRV System
Fans – A fan (more than one if the home is large) sucks air from your attic and pushes it into rooms below.
Ductwork & Vents – These distribute fresh air throughout the house and remove stale air from wet areas like kitchens and bathrooms.
Filter – Since the air is coming from your attic, a filter is needed to remove dust and other potential contaminants before entering your home
Wall Controller – Sets the temperature range your air is introduced into the home at.
How It Works in Different Seasons
In Winter: The HRV pushes the warm air inside your attic, down into the rooms below, introducing warm air (on sunny days only) as well as helping to push out stale, damp air to reduce the likelihood of mould forming..
In Summer: Some HRV systems can be equipped with a summer bypass feature which sucks air from outside (usually on the shaded side of the house) instead of from an overheated attic.
Key Takeaway: An HRV reduces excess humidity and CO2 levels, but does not actively cool your home.
Common Problems and Mistakes with HRV Systems in Summer
1. Expecting an HRV to Act Like an Air Conditioner
Many homeowners mistakenly believe that HRV systems provide cooling, similar to an air conditioner. However, HRVs are not designed to lower temperatures. Instead, they improve air circulation and remove excess humidity, which can make a space feel fresher but not necessarily cooler.
Solution:
If you need active cooling, consider complementary cooling solutions such as:
Adding a summer bypass feature (usually sold separately or as an upgrade or add-on to a standard HRV system)
Ceiling or pedestal fans to improve air movement
TIP: try reversing the direction of your ceiling fan so that it is not pushing down the hot air that has risen up and is trapped against the ceiling
Passive cooling techniques like shading and cross-ventilation (open windows on opposite sides of the house to allow the prevailing wind to blow air from one window through the house and exit through the other).
2. Incorrect Installation
How an HRV system is installed can significantly impact its effectiveness. If your system’s ducting is the wrong size or not properly installed, airflow can be significantly reduced, impacting the system’s efficiency .
Solution:
Have an experienced HVAC professional climb up into your attic and review your installation
3. Lack of Insulation or Poor Home Ventilation
HRV systems work best when paired with proper insulation and passive cooling techniques. If your home is too airtight and lacks sufficient insulation, summer heat can easily penetrate, making it difficult to maintain comfortable indoor conditions.
Solution:
Upgrade insulation in your walls and ceilings and consider. installing insulation directly under the roof to reduce heat transfer.
Use internal and external shading solutions such as curtains, blinds, awnings, pergolas or trees to block excessive sunlight.
Open windows strategically on opposite sides of the house in the evening when temperatures drop to promote natural cooling via passive airflow.
4. HRV Not Being Properly Maintained
Over time, HRV filters can become clogged with dust, dirt, and debris, reducing airflow and efficiency. When airflow is obstructed, your HRV may struggle to ventilate properly, making your home feel stuffy and hotter.
Solution:
Clean or replace filters at least every 12 to 24 months.
Schedule annual maintenance checks with a professional to ensure the system is operating efficiently.
Check ducts and vents regularly to identify loose connections and airflow restrictions.
5. Incorrect settings on the wall controller
HRVs typically have different temperature and mode settings that need to be adjusted depending on the season. Having temperature settings too high brings more warm air into your home, making it feel hotter.
Solution:
Adjust HRV settings seasonally:
In winter, HRVs should run at higher speeds to introduce heat.
In summer, use lower speeds to maintain fresh airflow with the timer set to avoid pulling in excess heat.
Check if your HRV has a summer bypass mode, which can help bring air from outside, not the hot attic.
6. Using HRV During Peak Heat Hours
Running an HRV system at the hottest part of the day (11 AM - 4 PM) can lead to warmer indoor temperatures, as it may draw in hot air from outside.
Solution:
Run the HRV system early in the morning and later in the evening when the outside air is cooler.
If your HRV has timed controls, schedule ventilation for cooler parts of the day.
7. Not Having an Alternative Cooling System
HRVs are great for air circulation and humidity control in winter, but are not a substitute for air conditioning. If your home tends to overheat in summer, you will need to install air conditioning.
Solution:
Install a high wall or ducted air conditioning system for effective summer cooling.
Consider ceiling or portable fans to improve air circulation.
Close curtains to block out direct sunlight. Invest in roof insulation or other passive cooling solutions such as reflective roofing paint, heat-resistant window films, and improved home insulation.
Best Practices for Using Your HRV in Summer
To make the most out of your HRV system while keeping your home comfortable in summer, follow these best practices:
Adjust the HRV settings for summer use (lower speed, bypass mode if available).
Run the HRV only during cooler hours of the day.
Regularly clean and replace filters to maintain airflow efficiency.
Ensure proper home insulation to prevent excessive heat buildup.
Pair your HRV with other cooling methods, such as air conditioning, fans, heat pumps, or external shading.
By following these simple strategies, you can improve your home’s ventilation and comfort levels while avoiding unnecessary heat buildup.
Avoid common HRV mistakes now!
If your HRV isn’t keeping your home cool in summer, it’s important to understand that it’s not designed to function as an air conditioner. However, when used correctly and paired with the right cooling strategies, an HRV can contribute to a fresher and more comfortable home environment.
If you’re struggling with ventilation or home cooling, our team at OneAir is here to help. Book a consultation today, and let us optimise your HRV and home cooling system!