What is an airtight house?

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What is an airtight house?

What is an airtight house?

How to build an airtight house?

Who knows how to build an airtight 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 4th must-have of a positive house is to be Airtight and to have a Ventilation system.
May you’ve skipped the first three, feel free to check our post: ‘6 musts for a positive house’


What does airtight house mean?

An airtight house is a house with no air filtrations.
That means your house is sealed so you don’t lose the heat (nor cooling) that you’re producing inside.

I’m sure you’re familiar with the concept of waterproofing.
Then airtight is the concept of being airproofed (I’m not sure this word exist, I’m sure it helps you get the point).

Once the concept is clear there are two remaining points you need to understand.
On one hand, how does the passive simulator measure this?.
On the other hand, how to build an airtight house.


How does the simulator insert Airtightness value?

First, the passive simulator doesn’t calculate the airtightness value.
Instead it assumes the value of the final construction airtightness. So at the end of the construction of your house you’ll need to do a Blower Door Test (
more details and price in the post Blower Door Test). For now you just need to know that if your house doesn’t pass this final test, then, your house cannot be certified. So it’s not a neither a passive house nor a positive house.

OMG, right?
So after all the effort you’ve put into it, if the builder doesn’t build in the right way, then you’ll never be able to have the passive house quality stamp.
Yes, that’s right, if your builder doesn’t do it right, you’re screwed.


How to build an airtight house?

It’s very important to assure the construction of an airtight house.
This is done by hiring a dream team of people:

  • Architect who is also a proved Passive House designer.
    Responsible for the design of airtightness (the red pencil rule).
  • Quality surveyor who is also proved Passive House trade person
    Responsible of the correct delivery on site according to plans and materials to deliver airtightness (usually foams and tapes).
  • Builder that who is also proved Passive House trade person
    Responsible for the correct installation of each airtight tape and foam.

In that way, the three professionals work together for the same goal.
The architect designs the house plans, construction details, does the passive simulations and checks on site that everything is being built according to her passive house plan.
The quality surveyor checks on site that the construction details designed by the architect are executed as it’s supposed to, in order to secure airtightness (among other goals).
And of course, the builder, who knows how to build a passive house because he has studied for it, and hopefully, it’s not his first time.



So, let’s assume your dream team nails it and you have an Airtight house.
Then, what about the air inside? Wouldn’t you need to get the fresh air inside?
Yes you need fresh air inside.
That is the reason you need a ventilation system in your positive house.




Our professional recommendation:
Ask your passive house architect when was her last house certified.
Ask her if she certified with the same team that will build your positive house.
If the architect has recently certified within the same team: you are on the right track!

You may also be interested in:
Our post explaining the ventilation system of a positive house.



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 |2023-03-01T09:51:05+01:00September 7th, 2022|Passive House Architect Barcelona|0 Comments

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