Why are windows important in a positive house

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Why are windows important in a positive house

Why are windows important in a positive house?

Two reasons window are important in a positive house.

The basics of windows in a positive house


May you don’t know us yet, let’s have a quick introduction: we are ERA architects.
Actually, I am Esther Rovira, architect and passive house designer in Barcelona, Catalonia and Andorra for either passive houses, efficient houses and positive houses.
In this post ‘Aerothermal with underfloor heating or fan coils?’, You will find our professional recommendation.
I hope it helps you!
Let’s go!

The 5th must of a positive house is to avoid thermal bridges.
May you’ve skipped the first four, feel free to check our post: ‘6 musts for a positive house’


Why are windows important in a positive house?

Windows in a passive house are very important for two reasons.
First, they are part of  the thermal enclosure of your positive house.
Second (and also very important), they capture the sun’s heat in winter but also repel the extra heat in summer. This is done thanks to special glazing.


1) Window as thermal enclosure

As you may already know, all parts of your house thermal enclosure needs to be: insulated, free of thermal bridges and airtight.
Then, those windows as part of your thermal enclosure MUST also comply those three standards in all its parts.
This means frames but also glazing need to comply with all the three must-haves.
Since this is too much information to digest for a blog post, I’ll break it down into two other posts:


2) Special glazing taking the best of Sun’s energy

Before we dig into glazing, let’s do a brief description of how the Sun’s energy works.
The Sun has different types of energy called the solar spectrum.
It consists of: UV light, visible light and infrared light.
Some of these energies are beneficial, some aren’t and need to be regulated depending on your house location.

So, the glazing does three things with the Sun’s energy: transmit, absorb and reflect.
Depending on the climate of your location, the glass needs to be designed to have the perfect balance between these transmissions and reflections so it captures enough sun’s energy in winter while repels enough heat in summer.

Let me explain it in another way.
Windows glasses capture the sun’s heat. This is good in winter, but terrible in summer if you live in a warm or temperate climate. Then how to deal with this?
This is done with a solar protection layer applied on the glass when it’s being manufactured (coating).

However this solar protection layer also has an effect during winter (not allowing all sun’s heat to go inside). 
Then the architect needs to take the passive simulator requirements, in order to design the glazing in a perfect balance to deliver enough sun heat during winter and enough sun protection during summer. 


What you need to know:

Now, let’s forget all those technicalities.
The only thing you need to retain is that your architect needs to design the glass combination that matches the passive simulator.

I cannot give you a list of values that work in Spain in each type of climate.
The reason is that every house design is unique with different surfaces, volume, square meters of windows, oriented differently, with different surrounding shadings. And all in different climate conditions.
So you really need to ask your architect to give you that value.
And she needs to do it by using the combination of the passive house simulator and the glass design simulator before paying the builder the glasses.



Our professional recommendation:
If your house is to be build in Spain, you need to know this.
Architecture universities in Spain don’t teach how to design glazing (at least not in 2022). So you need to consider an architect that also has a Passive House designer degree.
This is not a trick to hire us. You may not hire us, but PLEASE, hire an architect with a passive house designer degree.

You may also be interested in:
Our post about the fourth must-have of a positive house: airtightness and ventilation


Hope this is helpful!

Best of luck on this adventure.
See you on the next post,



Founder of ERA architects
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By |2023-02-07T20:10:25+01:00June 7th, 2022|Passive House Architect Barcelona|0 Comments

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