Why a Correctly Configured MVHR System Should Aim for Slight Positive Pressure in Your Home
One often overlooked advantage of a well-designed MVHR (Mechanical Ventilation with Heat Recovery) system is its ability to maintain a very slight positive pressure in the home. This setup is subtle yet effective, gently pushing indoor air outwards instead of allowing unfiltered outdoor air to be pulled in. Here’s why that matters, especially in older properties like Victorian homes, where issues like damp and drafts are often more pronounced.
How Positive Pressure Protects Your Home
The aim of positive pressure is to prevent negative pressure inside the house, which would otherwise cause the building to “draw in” outside air through any available gaps, cracks, or openings in the building envelope. When a house has negative pressure, it essentially acts like a vacuum, which can pull in cold, damp, or polluted air from the outside. This unwanted air bypasses your MVHR’s filtering and heat recovery processes, entering without being cleaned or warmed.
By maintaining a slight positive pressure, an MVHR system gently prevents this effect. Instead, it promotes the outward movement of air, ensuring that the only air coming into your home is filtered, warmed, and controlled through the ventilation system. The result is a more comfortable indoor environment, free from sudden cold drafts or unexpected sources of moisture.
Benefits for Older Homes
In older properties, where airtightness is often lower than in newer builds, positive pressure can play a key role in managing indoor air quality. Historic homes are more susceptible to drafts, moisture ingress, and pollutant infiltration, all of which contribute to issues like damp and mould. A slight positive pressure helps limit this intrusion, supporting the building envelope in maintaining a healthier indoor climate. Over time, this can help reduce damp spots, improve air quality, and minimise the conditions that allow mould to flourish.
Positive Pressure vs. Negative Pressure: A Lasting Solution
While it might seem minor, avoiding negative pressure is crucial to maintaining a balanced indoor environment. It’s a practical example of how MVHR systems do more than just recover heat—they actively create a healthier, more comfortable home by regulating airflow. For properties looking to prevent moisture ingress, pollutants, and drafts, a correctly configured MVHR with slight positive pressure can be a long-term investment that extends the life of both the building and the comfort of those living within it.