Heat recovery ventilation systems (MVHR) are a fantastic way to keep your home comfortable, fresh, and energy-efficient—something that’s particularly important for homeowners these days.
However, like any home system, MVHR units require proper installation and maintenance to function as intended. An issue some users face especially in colder months formation of condensation inside the ducts, which can drip into rooms and damage ceilings.
If you’ve encountered this problem—or want to ensure you don’t—this guide is here to help. We’ll explain why condensation happens, how it can be prevented, and what steps to take if it’s already causing problems. With the right knowledge, you can ensure your MVHR system works efficiently without compromising the comfort or integrity of your home.
Why Does Condensation Form in MVHR Ducts?
Condensation occurs when warm, moist air meets a cooler surface, causing the moisture in the air to turn into water droplets. In an MVHR system, this typically happens in the ductwork where temperature differences are most pronounced, especially during the colder months.
Some of the common reasons for condensation include:
1. Inadequate Duct Insulation
If the ducts carrying warm air aren’t properly insulated, the heat can escape, cooling the air as it travels through the system. This makes it more likely for condensation to form when the warm air meets the colder surfaces of the duct walls.
2. Improper Installation
Poorly installed ductwork can create low points or dips where moisture collects, increasing the risk of leaks and damage. Additionally, incorrect gradients in the ducts can disrupt airflow and exacerbate condensation.
3. Blocked or Dirty Filters
Dirty filters restrict airflow, which can cause air to cool down as it travels through the system. Reduced airflow also leads to an imbalance in pressure, which can further contribute to condensation build-up.
4. Excess Indoor Humidity
Homes with high levels of indoor humidity—often due to activities like cooking, showering, or drying clothes indoors—can overwhelm the MVHR system, leading to increased moisture levels in the ductwork.
5. Cold Weather Conditions
During winter, the temperature difference between the warm indoor air and the cold outdoor environment is more significant. This increases the likelihood of condensation forming within the system, especially if preventative measures aren’t in place.
How to Prevent Condensation in MVHR Ductwork
The good news is that condensation issues in MVHR systems are entirely preventable with the right measures. Here’s what you can do:
1. Ensure Proper Duct Insulation
- Use Insulated Ducting: All ducts running through unheated spaces, such as lofts or crawl spaces, should be insulated with high-quality material designed to prevent heat loss and condensation.
- Seal Joints: Ensure that all ductwork joints are sealed tightly to prevent cold air from entering and causing temperature drops within the ducts.
2. Check and Maintain the Condensate Drain
- Regular Cleaning: Inspect and clean the condensate drain regularly to ensure it’s free of debris and functioning correctly. A clogged drain can lead to water pooling and leaks.
- Correct Installation: Verify that the condensate drain is installed with the proper slope to allow water to flow freely to the drainage point.
3. Balance the System
- Professional Commissioning: Have your MVHR system balanced by a qualified technician. This involves adjusting the airflow rates to ensure the system operates efficiently and effectively.
- Monitor Humidity Levels: Use a hygrometer to monitor indoor humidity levels and keep them within the recommended range of 40–60%. This helps reduce the moisture load on your ventilation system.
4. Invest in a Quality MVHR Unit
- Advanced Features: Look for units with features like automatic humidity control and high-efficiency heat exchangers, which can help manage condensation more effectively.
- Trusted Brands: Choose a reputable brand such as Zehnder with a track record of quality and reliability to minimise the risk of issues.
5. Schedule Regular Maintenance
- Annual Servicing: Have your MVHR system serviced annually by a professional to ensure all components, including ducts and drains, are clean and in good working order.
- Filter Replacement: Replace filters as recommended by the manufacturer to maintain airflow and system efficiency.
Keep Your Heat Recovery System in Top Condition
While condensation in MVHR systems can be a frustrating problem, it’s entirely preventable with the right precautions and maintenance. By ensuring proper insulation, maintaining the condensate drain, balancing your system, and monitoring indoor humidity, you can enjoy the benefits of fresh, energy-efficient ventilation without the worry of water damage or mould.
If you’re installing a new MVHR system or need assistance with an existing one, always work with experienced professionals to ensure it’s set up correctly. A little effort upfront can save you from costly repairs and help maintain a comfortable, healthy home environment for years to come.
Need expert advice or service for your MVHR system? Contact us today to keep your home fresh, efficient, and worry-free.