A new building was recently described in a newspaper where the air exchange is regulated through window rebate ventilation.
Is this a reasonable alternative to a controlled ventilation system, and does it help prevent mold?
How exactly does it work?
Is this a reasonable alternative to a controlled ventilation system, and does it help prevent mold?
How exactly does it work?
Window rebate ventilators are small air vents that can be installed in new and existing windows. They provide a minimum air exchange that helps remove some moisture from living spaces. However, their effectiveness is debated in practice. We explain why this is the case and provide information on their functionality, areas of use, and costs.
Window rebate ventilators are small air vents
Window rebate ventilators (abbreviated as WRVs) are small valves that can be easily installed in the frames of windows. They are nearly invisible and create a controlled air leakage in the building envelope. Their name comes from their installation location: the ventilators are positioned in the so-called window rebate between the frame and sash. When cold air flows in from outside, it enters through the window frame and warms up as its temperature rises. To limit the air exchange rate, window rebate ventilators are equipped with a pressure-compensating mechanism known as a wind pressure safeguard. These small vents operate purely mechanically and do not consume electricity. They ensure a minimum air exchange but allow much less air inside compared to other ventilation systems. Professionals can now install window rebate ventilators in new and old windows made of uPVC, wood, or wood-aluminum.
Air exchange rate depends on many factors
For window rebate ventilators to allow air to flow through, there must be a pressure difference between the windward and leeward sides of a building. This happens when wind presses against one side of the building, creating a lower pressure on the opposite side that pulls air out of the house. In calm conditions or when all windows face the same direction, very little air flows through these small vents. As a result, used and humid air remains inside, increasing relative humidity and potentially leading to mold growth in the home.
Regular airing is still necessary with window rebate ventilators
It is important to understand that these small vents circulate only a limited amount of air through a house or apartment. The air exchange is just enough to handle moisture produced independently of occupants. However, when people are at home, they release much more moisture through their skin, cooking, or bathing. To safely remove this excess moisture, occupants still need to regularly open windows for short periods to allow for adequate ventilation, even with window rebate ventilators installed.
Applications and limitations of window rebate ventilators
New or energy-renovated buildings are usually very airtight. Outside air no longer penetrates naturally, allowing moisture or pollutant levels to build up over time. While this affects comfort, very humid air can also lead to mold problems. Window rebate ventilators help to partially prevent this by ensuring a continuous minimum air exchange independent of occupants. Typical applications include:
They are usually unsuitable for use in decentralized exhaust ventilation systems. Such systems extract air from the building using a fan and allow fresh air to enter through specialized outdoor air inlet elements (OAIs). The capacity of the small window rebate ventilators is typically insufficient for this purpose.
Window rebate ventilators are small air vents
Window rebate ventilators (abbreviated as WRVs) are small valves that can be easily installed in the frames of windows. They are nearly invisible and create a controlled air leakage in the building envelope. Their name comes from their installation location: the ventilators are positioned in the so-called window rebate between the frame and sash. When cold air flows in from outside, it enters through the window frame and warms up as its temperature rises. To limit the air exchange rate, window rebate ventilators are equipped with a pressure-compensating mechanism known as a wind pressure safeguard. These small vents operate purely mechanically and do not consume electricity. They ensure a minimum air exchange but allow much less air inside compared to other ventilation systems. Professionals can now install window rebate ventilators in new and old windows made of uPVC, wood, or wood-aluminum.
Air exchange rate depends on many factors
For window rebate ventilators to allow air to flow through, there must be a pressure difference between the windward and leeward sides of a building. This happens when wind presses against one side of the building, creating a lower pressure on the opposite side that pulls air out of the house. In calm conditions or when all windows face the same direction, very little air flows through these small vents. As a result, used and humid air remains inside, increasing relative humidity and potentially leading to mold growth in the home.
Regular airing is still necessary with window rebate ventilators
It is important to understand that these small vents circulate only a limited amount of air through a house or apartment. The air exchange is just enough to handle moisture produced independently of occupants. However, when people are at home, they release much more moisture through their skin, cooking, or bathing. To safely remove this excess moisture, occupants still need to regularly open windows for short periods to allow for adequate ventilation, even with window rebate ventilators installed.
Applications and limitations of window rebate ventilators
New or energy-renovated buildings are usually very airtight. Outside air no longer penetrates naturally, allowing moisture or pollutant levels to build up over time. While this affects comfort, very humid air can also lead to mold problems. Window rebate ventilators help to partially prevent this by ensuring a continuous minimum air exchange independent of occupants. Typical applications include:
- retrofit solutions in existing mold problems (root cause of mold must be identified first)
- moisture protection ventilation in new and old buildings (as cross-ventilation or shaft ventilation)
- secure minimal ventilation solution resistant to break-ins
- combustion air supply for appliances dependent on room air
They are usually unsuitable for use in decentralized exhaust ventilation systems. Such systems extract air from the building using a fan and allow fresh air to enter through specialized outdoor air inlet elements (OAIs). The capacity of the small window rebate ventilators is typically insufficient for this purpose.
We also have trickle vents in the window frames. There is no draft. With an air-to-water heat pump, we have an energy consumption of 2500 kWh for 220 sqm (2,368 sq ft). Just slightly above KfW55 standard.
Don’t let anyone convince you that it only works with one method. It’s neither an energy disaster nor a non-breathable plastic bag you suffocate in.
Make it dependent on your ventilation habits. If you like to ventilate regularly, then you don’t need a mechanical ventilation system with heat recovery.
Don’t let anyone convince you that it only works with one method. It’s neither an energy disaster nor a non-breathable plastic bag you suffocate in.
Make it dependent on your ventilation habits. If you like to ventilate regularly, then you don’t need a mechanical ventilation system with heat recovery.
bauenmk202015 Sep 2019 09:05We will also have window frame vents plus exhaust fans in the bathrooms and utility room.
Building solid without insulation.
One house builder strongly recommended such a system to us. Our current builder, on the other hand, considered it unnecessary—provided proper ventilation is ensured, of course.
Building solid without insulation.
One house builder strongly recommended such a system to us. Our current builder, on the other hand, considered it unnecessary—provided proper ventilation is ensured, of course.
R
RotorMotor15 Sep 2019 11:57Nordlys schrieb:
Two years in the house. Zero mold. Good air quality, with an exhaust fan in the bathroom and trickle vents around the windows. We always keep one or two windows open, both summer and winter.Always keep windows open? ops:
What are your heating costs then, or do you prefer it rather cool?
Similar topics