Ventilation of Plastic Windows

Ventilation and Plastic – A Deadly Combination!

In most residential buildings, the ventilation system is set up in the cheapest, simplest, and most primitive way: natural exhaust from the kitchen or bathroom and fresh air intake through gaps in door and window frames. This system works successfully in apartments with standard (traditional) window frames and doors: the standard of 30 m³ per person per hour is easily met.

Now let’s see how it works after installing nearly airtight windows with excellent geometry and seals. Air intake almost disappears, disrupting the indoor microclimate: humidity increases, rooms become stuffy, and discomfort is felt.

Moreover, due to insufficient fresh air intake, a reverse airflow effect may occur in the ventilation shaft: air may flow not outdoors, but back into the apartment. The only advantage? Full awareness of your neighbors’ meals from below, and sometimes even above.

The problem also has a psychological aspect. When installing plastic windows, marketed as draft-free, customers experiencing stuffiness and fogged-up glass often complain. The usual response? Keep the sashes slightly open. Naturally, this causes buyer dissatisfaction: purchasing perfect windows leads to the same old problems.

Comfortable Ventilation and Plastic Windows: Can They Coexist?

Short answer: yes! But to make it work, you must consider fresh air intake already at the window selection stage. Possible options or combinations include:

• Sash with a stop-grip (hinge stop).
• Window with a trickle vent.
• Window with self-ventilation.
• A ventilation valve.

A stop-grip installed on the opening sash allows tilting or fully opening it in stages. This inexpensive and convenient device helps avoid the common issues: too little ventilation in the cracked mode, and too much airflow when fully open. The stop-grip fixes the sash at several intermediate positions.

The traditional and familiar trickle vent provides exactly the ventilation mode we’re used to with plastic windows. Air enters the upper part of the room, mixes there with warm or cool indoor air, and gradually spreads throughout the space. This prevents drafts.

However, the trickle vent has drawbacks: it complicates the window design, increases cost, and slightly reduces light transmission.

A self-ventilating plastic window with a breathable profile uses a special profile with small holes in the lower external and upper internal parts. Air passes through a special chamber, warms up, and enters the upper part of the room.

This principle works satisfactorily, but with limitations: on higher floors, installing such (more expensive and wider) profiles makes little sense due to insufficient airflow. Also, summer heat may disrupt the convection process.

All the above disadvantages are avoided by intake ventilation valves, at least according to manufacturers. Let’s examine them in detail.

Window Ventilation Valve

For effective performance, this device must combine several functions. Then, a proper indoor microclimate will be established not only near the window but throughout the entire room. The valve’s class is determined by several key parameters.

• Installation method. Two options exist: replacing the glazing unit with a smaller one and installing the valve in the resulting space. Disadvantages: cost and reduced light intake. The second method—installing the valve in the upper transom of one sash—is more preferable. The process takes only 30 minutes.
• Manual or automatic control. We don’t consider non-controlled valves—regulation is essential. The choice between manual and automatic (based on humidity or temperature) depends on comfort, not just price (manual is cheaper). Manual control allows ventilating only needed rooms, saving heat. Automatic control enables setting an exact thermal-humidity regime (TWR). However, a combined device is also an option.
• Sound insulation and compliance with air exchange standards. Modern standard windows reduce noise by 30–35 dB, so the ventilation valve should have similar performance. The standard for air intake and exhaust (30 m³ per person per hour) has already been mentioned—valves must meet it.
• Winter operation. Whether condensation and subsequent frost will form on a specific valve cannot be predicted in advance. Too many interdependent factors: indoor and outdoor air parameters, airflow patterns at the installation site, casing material, etc. However, some risks can be avoided in advance:

• The valve casing must be well insulated, especially on the indoor side.
• If metal is used as the casing material, a plastic thermal break must be installed between inner and outer parts.

On cost: a plastic window ventilation valve is a fairly complex device and cannot be cheap. Therefore, a price range of 1,500–2,000 rubles is quite reasonable.

Final note: everything described here will only work effectively if the exhaust system is well-functioning. If not, no combination will help.