How To Fix HVACs DIY

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So – how to fix problems caused by improper planning of the air duct and ventilation system. These problems can come to you from the old owners, can be, made by your own hands – we will try to find an answer and solutions to the questions that arose. Of course for all the arisen “if” to give answers will not work, but nevertheless we will try.

To begin with let’s talk about how in general how to improve natural ventilation?

In houses with natural ventilation, even if the system was installed without errors, the air exchange is often unsatisfactory.

This happens if:

  • The weather conditions are unfavorable (particularly in summer, when the outside air temperature is higher than the indoor temperature);
  • The air pollution in the ventilated rooms increases intensively, e.g. in the kitchen – during cooking, in the bathroom – during bathing or showering (humidity increases);
  • The cross-sectional area of the exhaust duct is too small.
  • A simple and effective way to increase ventilation performance in these situations is to install electric exhaust fans. They are mounted at the inlet of the duct or in the ductwork. If there is no ventilation duct in the room, you can install a special fan in a window or in the outside wall. In the wall, it should be placed at least 3 m away from the nearest window (horizontally). If there is another floor above this room, the distance to the upper floor window should be at least 2 meters. Especially if the exhaust air is heavily contaminated, for example from an extractor hood above a stove. Exhaust fan should be installed;

How to fix the most common mistakes:

Problem: Lack of a ventilation duct in a room without windows

The humidity in the room increases. This leads to the development of mould and mildew.

Solution: This room has to have a separate ventilation duct in order to remove 15 m of air and the unwanted moisture from the room within one hour.

Problem: Hole in the outside wall instead of connecting to a ventilation duct

Air can come in from outside instead of leaving the room through the hole. It will be very cold in the winter.

Solution: A small axial fan, preferably controlled by a humidity sensor, can be installed in the opening. To meet regulatory requirements, a separate ventilation duct would have to be built that diverts 30 m3 of air per hour.

Problem: no gaps or ventilation openings in the interior doors

Internal doors must allow free air movement between rooms, even if the doors are closed. If there are no gaps, the air cannot pass from less polluted rooms to more polluted rooms (kitchen, bathroom, toilet). From there, contaminated air can be ducted to the outside.


Solution: Cut a slot or openings in the door and install special grilles or decorative sleeves in the door. The total area of the openings in the doors between the rooms must be 80 cm2 and in the doors leading to the kitchen or bathroom 200 cm2.

Problem: No ventilation duct in a room separated by more than two doors

On the way to the ventilation grille, a double door creates a very significant obstacle for the air.

Solution: In such a room, a separate ventilation duct has to be built that diverts 30 m of air per hour


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