María Eugenia Velásquez
Windows are very important elements in the design of a house. In addition to the aesthetic component, they serve the function of illuminating spaces, allowing views to the outside and ventilation.
In a passive house, windows also play a crucial role in the energy efficiency and thermal comfort of the house. However, as the weakest point of the thermal envelope, they require special attention.
In this article I tell you what is so special about Passivhaus windows and the importance of installing them correctly. I also answer the eternal question of whether or not you can open the windows in a passive house, and I leave you with a very important final recommendation. Let's get started!
Passivhaus windows are high-performance windows with double or triple glazing and their chambers (the space between the panes) contain a noble gas, usually argon, which is denser than air and improves insulation.
The carpentry of these windows is also designed for maximum airtightness and energy efficiency. PVC or wood is often used, which are materials with lower thermal transmittance, and the frames are thinner than that of an ordinary window. This is because the thermal performance of the glass surface is better than that of the frame, so a higher proportion of glass allows for greater solar energy gain.
In addition to being thinner, Passivhaus window frames have at least 5 air chambers, as does the window sash.
(Parenthesis: If you are like me, who are not window experts, here's a little tip for you. The frame is the structure that is fixed to the wall, the sash is the movable structure, hinged or sliding, that contains the glass 😉)
It is important to mention that the Passivhaus standard is adapted to the climate where the house is going to be built, so the characteristics of the windows to be used in a house built in the Swiss Alps are not the same as those of a house built in Barcelona.
In this article you can read more about how the Passivhaus standard is adapted to the Mediterranean climate.
On the one hand, there is the location. In a passive house the location of the windows needs to be carefully planned. For most climates, it is recommended that windows face south, as this orientation allows solar radiation to penetrate the interior of the house in winter, and to take advantage of draughts in summer.
On the other hand, a good window that is badly fitted will be of little use, so the installation process is also crucial. In a passive house, windows are installed on top of the insulation layer of the wall and then the frame is covered with insulation material (special foams and tapes). This is intended to ensure that the window is an integral part of the thermal envelope and that no thermal bridges occur at the window-wall connection.
If you want to know more about thermal bridges, have a look at this article on thermal bridges vs. Passivhaus
Of course you do! Although it is very likely that in a passive house you will not feel the need to do so.
Let's see, if we are purists, the Passivhaus standard does not recommend opening the windows, mainly because this means letting the cold (or heat) into your home, and therefore returning to the desired indoor temperature will mean an energy cost. That said, it is understandable that on a spring or summer day you might feel like opening the windows in your house, and of course you can, but you should be aware of the extra energy cost.
Now, if your intention is to open the windows to ventilate the house, you should know that in a passive house this is not necessary. Passive houses have a mechanical ventilation system that is constantly moving air in and out, so your house is always ventilated.
I must admit that the Passivhaus Institute itself has already shown more flexibility to the possibility of opening windows, in fact, it is a practice that they recommend as a passive strategy for cooling spaces in hot climates or during the summer. Night cooling consists of taking advantage of the slightly lower temperatures at night to ventilate the home, so it is during this time of day that it is suggested to open the windows.
Watch this video where Jordi tells you more about opening or not opening windows in a passive house.
A very important final recommendation is that you don't forget sunscreens for your windows.
As I said before, the most recommended location for windows is south-facing, to capture as much solar radiation as possible. This is fine in winter, but in summer it can be a problem if you don't plan for solar protection, whether it is a cantilever, awning, awning or louvres. Well-planned vegetation can also be very useful as sun protection.
To conclude, we can say that Passivhaus windows are windows that are designed to insulate the home as well as possible. From the glass, to the frame, to the way they are installed, everything is carefully planned to ensure high airtightness, and this translates into greater energy efficiency, which is the ultimate purpose of the Passivhaus standard.
Thinking of building a passive house? Schedule a video call with us and let's start shaping your project.
Source: "Active for more comfort: Passive House", International Passive House Association.
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