However, it is quite typical that changes in ventilation functionality after window renovation are overlooked during window renovation. In this article, we will discuss what should be taken into account when planning a window renovation or if a window renovation has already been carried out.

---

Which to do first: window renovation or ventilation renovation

If a window renovation is planned, one should generally also plan simultaneously Ventilation performance. The gravity ventilation in old houses has traditionally worked with air coming in through slightly loose windows and between window frames and walls. The air entered the house through natural forces such as wind or the chimney draft from a fireplace hormone phenomenon due to its effect, so even small improvements in airtightness in windows or frame attachment might completely stop fresh air from entering the building. 

New windows are nowadays mainly made of aluminum or some other material than wood, and the windows are considerably more airtight than old windows have been. In addition, window frames are usually sealed into old house window openings with very airtight sealants. This is a big change for the building's ventilation, as old windows have traditionally been sealed with porous natural materials that easily allow air to pass through. 
​
For these reasons, the building's ventilation functionality should be re-planned before starting the window renovation. And only when the functionality of the ventilation has been confirmed can the window renovation begin.

How does gravity-based ventilation change after a window renovation?

Gravity-fed ventilation This process is based on the effects of natural forces, which is why wider windows have played a major role in the effectiveness of ventilation. After window renovation, inadequate ventilation is usually observed, both by gravity and in old houses with mechanical ventilation. The most common changes have been

• A shortage of oxygen, which has made it necessary to ventilate continuously
• Odors from cooking don't go away very quickly
• Moisture builds up on the windows
• Window Gusset Valves The coming weather will be felt as a draft
• Air has begun to seep into the interior through the floor edges and wall corners, which have become cold, and indoor air quality is deteriorating without anyone noticing.
• VOC levels, In other words, volatile gases are no longer effectively vented from the building
• In areas with radon, radon levels have risen higher than they were before the renovation

Is it worth installing window vents in new windows?

​Window dealers and some renovation designers sometimes try to install window gap vents in windows. However, it has been found in practice that standard window gap vents alone are not sufficient after a window renovation. While a window gap vent does improve ventilation to some extent, when comparing its surface area to that of the gaps in old windows, the change is for the worse by more than half. 

A quick calculation shows that the window in the picture has seams 660 cm long and an estimated surface area of 132 cm², while the window trickle ventilator has a surface area of 40-72 cm² (40-60 cm). For comparison, a hole the size of a bank card has a surface area of 47 cm². Both gaps are, of course, filled with porous and filtering material, which is why the air does not actually exchange through such a large surface area. In conclusion, even if window trickle ventilators were installed in every window, it is highly likely that the ventilation would decrease by as much as half compared to before. In reality, window trickle ventilators are not usually installed in every window. For example, ventilators are omitted from bathrooms, showers, and kitchens to avoid spreading dirty air throughout the house.

The answer to the question ”Is it worth improving the natural ventilation in an old house by installing window vents in the new windows?” is that you should always seek advice before starting a window renovation project from a ventilation expert and Proposal for Improving Ventilation in the building before starting renovations. The biggest known problem with window gap vents is cold, drafty incoming air, which affects a great many Finns during the winter. The freezing air comes in even more forcefully, creating a sensation of drafts. 

Even if window vents were installed above the radiators, this does not change the fact that the cold outside air must be heated inside the house at the very latest. For this reason, it would be wisest to request a quote for room-specific ventilation units that recover heat and improve ventilation before beginning window renovations, which ensure that the air coming inside is always warm and that heating energy isn’t wasted unnecessarily. This way, you can ensure that the family always has enough fresh air and that indoor air quality issues don’t catch you off guard.