Why Do They Appear?
At Ateliers Thomquin, a general contractor for interior renovation and exterior renovation in Brussels, and an expert in renovation projects in Uccle and Beersel, we often receive questions from our clients about the appearance of mold and mildew in certain rooms, particularly after window replacements or other energy improvements, or before starting a full-scale renovation.
We draw their attention to a crucial point: replacing windows or undertaking renovations without considering the impact on ventilation and insulation can lead to humidity problems.
In this blog post, Ateliers Thomquin guides you through the best solutions to prevent mold and ensure a healthy indoor climate, while optimizing your home’s energy performance in compliance with current PEB (Energy Performance of Buildings) standards.
Indoor temperature, detail insulation, and ventilation: the magic trio to prevent mold
In many older buildings, mold often appears due to poor insulation, inadequate ventilation, and improper temperature control. To prevent these issues, it is essential to work on three key elements: indoor temperature, thermal insulation of building details, and ventilation. This trio, applied by Ateliers Thomquin in its renovation projects, is essential to maintain a healthy and durable indoor environment.
1. Indoor Temperature: Maintain a Proper Level
Maintaining a sufficient indoor temperature is crucial to prevent condensation on cold surfaces, particularly around windows and thermal bridges. Keeping the temperature above 15°C limits the risk of stagnant moisture on walls and window frames. Below this threshold, indoor air cools on contact with surfaces, increasing relative humidity and creating a favorable environment for mold.
2. Insulation of Construction Details: Avoid Thermal Bridges
Insulating construction details, especially junctions between walls and windows, around lintels, and in door and window frames, is essential to maintain surface temperatures close to ambient air. A poorly insulated detail becomes a thermal bridge, an area where heat escapes easily. This heat loss lowers surface temperatures, encourages condensation, and eventually leads to mold growth.
Ateliers Thomquin, as a general contractor specializing in renovation, advises and assists you in improving the insulation of these sensitive areas during your renovation projects. By measuring a detail’s temperature factor, we can assess the thermal quality of the insulation: the higher the factor, the closer the surface temperature is to the indoor air, reducing condensation risks.
3. Ventilation: Regulate Indoor Humidity, Especially in Bedrooms, and Comply with PEB Standards
Effective ventilation is essential to evacuate humidity produced daily by occupants (kitchen, bathroom, etc.). In bedrooms, this is especially important, as a person releases several hundred milliliters of water as vapor during the night. Without proper ventilation, this moisture can accumulate and cause condensation on cold surfaces, especially in winter when windows often remain closed.
To maintain an optimal humidity level, Ateliers Thomquin recommends airing out bedrooms every morning. In well-insulated modern buildings, we suggest installing Renson Invisivent ventilation grilles alongside new windows for continuous and discreet airflow. These grilles allow constant air intake without drafts, even when windows are closed, and comply with current PEB standards.
Compliance with PEB Standards in Dry and Wet Rooms
PEB regulations require separate ventilation systems for dry and wet rooms in a house or apartment renovated by Ateliers Thomquin:
• Dry rooms (bedrooms, living room): Passive air inlets like Renson Invisivent grilles are needed to ensure a constant flow of fresh air. Placed at the top of windows, these grilles allow natural airflow without drafts and maintain appropriate humidity levels.
• Wet rooms (kitchen, bathroom, WC): These require forced air extractors to remove humidity and odors. Typically, they are connected to a controlled mechanical ventilation (CMV) system that activates when the room is in use, ensuring effective removal of stale air.
Kitchen Hood Consideration: Avoid Conflict with the Extractor
The kitchen hood choice is crucial. A hood venting to the outside can conflict with the forced air extraction system, disrupting the home’s ventilation balance. Ateliers Thomquin recommends installing a charcoal filter hood that recirculates air by filtering it before returning it to the room. This maintains balance with the extractor and ensures indoor air quality.
Choosing Between Single-Flow and Double-Flow Ventilation: Obligations and Preferences
During a renovation project, Ateliers Thomquin examines with each client the most suitable ventilation system — single-flow or double-flow — based on PEB requirements and the client’s preferences:
• Single-flow ventilation: A simpler and more affordable system, using air inlets in dry rooms and extractors in wet rooms. It
