Mechanical Ventilation with Heat Recovery Facesheet

Mechanical Ventilation with Heat Recovery (MVHR) systems maintain excellent indoor air quality while also conserving energy. These systems extract stale air from your home and replace it with filtered, fresh air from outside, all while recovering heat from the outgoing air to warm the incoming air.

The demand for well-insulated buildings has increased significantly in recent years. However, if a house is well insulated but not adequately ventilated, it may result in poor indoor air quality. Poor indoor air quality in a building can lead to condensation, dampness, mould, unpleasant odors, the accumulation of toxic gases, and potential health issues such as asthma, an MVHR system will combat these issues providing a constant supply of fresh air and significantly reducing heating costs.

When designing an MVHR system for your home, several factors must be considered to ensure optimal performance. These include the layout of the property, the positioning of vents and ducts, and the specific climate conditions of your area. Proper planning and design will help maximize the efficiency and benefits of the MVHR system.

Regular maintenance is also crucial to keep the system functioning efficiently, which includes cleaning or replacing filters and checking the unit for any signs of wear or damage.

Mechanical Ventilation with Heat Recovery (MVHR)

Description, Design, and Installation

Mechanical Ventilation with Heat Recovery (MVHR) is a system designed to improve indoor air quality and energy efficiency in buildings. It works by extracting stale air from wet rooms, such as kitchens and bathrooms, and replacing it with fresh, filtered air from outside. The unique feature of MVHR is its ability to recover heat from the extracted air and transfer it to the incoming fresh air, minimizing energy loss.

An MVHR system typically consists of:

• Heat exchanger unit: This is the core component where heat recovery takes place.
• Supply and extract fans: These fans ensure the continuous movement of air into and out of the building.
• Filters: These remove dust, pollen, and other particles from the incoming air.
• Ductwork: This network of ducts distributes fresh air to living spaces and extracts stale air from wet rooms.

Designing an MVHR System

Designing an effective MVHR system requires careful planning and consideration of several factors to ensure optimal performance and efficiency.

1. Assessing the Building

Begin by evaluating the building’s size, layout, and existing ventilation. Determine the number of rooms that require ventilation and the air volume needed to maintain good indoor air quality. Consider the building’s insulation and airtightness, as these will impact the MVHR system’s efficiency.

2. Selecting the Heat Exchanger Unit

Choose a heat exchanger unit that matches the building’s ventilation needs. Look for units with high thermal efficiency (typically above 90%) and low power consumption. Ensure the unit complies with local building regulations and standards.

3. Planning the Ductwork Layout

Design a ductwork layout that minimizes pressure drop and noise while ensuring efficient air distribution. Use rigid ducts where possible for better airflow and fewer air leaks. Plan the placement of supply and extract vents to provide balanced ventilation throughout the building. Avoid long duct runs and sharp bends to maintain system efficiency.

4. Integrating Controls and Sensors

Incorporate controls and sensors to optimise the MVHR system’s operation. These may include:

• Humidity sensors: To adjust ventilation rates based on indoor humidity levels.
• CO2 sensors: To adjust ventilation rates based on indoor CO2 levels.
• Timers and programmable controllers: To schedule ventilation based on occupancy patterns.

Installing an MVHR System

Proper installation is crucial to ensure the MVHR system operates efficiently and effectively.

1. Positioning the Heat Exchanger Unit

Install the heat exchanger unit in a central location, such as a utility room or loft space, to minimize duct lengths and maintain easy access for maintenance. Ensure the unit is securely mounted and has adequate clearance for ventilation and service access.

2. Installing Ductwork

Install the ductwork according to the planned layout, ensuring all connections are airtight and well-insulated to prevent heat loss. Use appropriate fittings and supports to secure the ducts and minimize vibrations. Seal all joints with duct tape or mastic to prevent air leakage.

3. Connecting Supply and Extract Vents

Install the supply and extract vents in their designated locations, ensuring they are securely fixed and properly aligned with the ductwork. Use adjustable vents to balance the airflow and maintain consistent ventilation throughout the building.

4. Integrating Controls and Sensors

Install the controls and sensors, following the manufacturer’s instructions. Ensure they are correctly wired and positioned to accurately monitor indoor air quality and adjust the MVHR system’s operation.

5. Commissioning and Testing

Once the installation is complete, commission the MVHR system to ensure it operates correctly. This involves:

• Balancing the airflow: Adjusting the supply and extract vents to achieve balanced ventilation.
• Testing the system: Checking for air leaks, noise levels, and overall performance.
• Providing user instructions: Educating the building occupants on how to operate and maintain the MVHR system.

Conclusion

Mechanical Ventilation with Heat Recovery (MVHR) systems play a vital role in enhancing indoor air quality and energy efficiency in buildings. By carefully designing and installing an MVHR system, you can ensure optimal performance and long-term benefits for occupants. Whether it’s a residential or commercial building, MVHR is an investment in comfort, health, and sustainability.