What’s a thermal bridge?

What’s a thermal bridge?

What’s a thermal bridge?

That strange combination of words defines the connecting spots where your house is not insulated.
If it’s not insulated, it means there is a bridge to the outside temperature through that material’s thermal transmittance. (Remember the U value?. If not just check chapter Thermal behaviour of materials).
This is usually well understood by checking the cut view drawing of your positive house.

 

Thermal bridge (right image)

So, consider a middle slab connection with the façade.
If we taka a look at the image on the right we’ll see that the insulation is only inside, then a piece of concrete is left without insulation.
This piece of concrete is a bridge to the outside world and climate. Since concrete has a very high thermic transmittance, this piece of shown concrete will highly conduct the temperature on both sides. Then, if it’s winter, the cold will break into your house through that piece of concrete not covered. And also the heat inside will go away through that spot. 

 

No thermal bridge (left image)

Your positive house must avoid thermal bridges.
Being fully insulated by a continuous layer of proper thickness insulation is the best way to prevent thermal bridges.

Let me tell you something that happened to me:
A desperate possible client called us with a project from another architect supposed to be designed as a sustainable home.
They already had the Town Hall permits and were ready to start building.
Then when their architect sends them the final plans. For the very first time, the clients sees the side cut view of their ‘supposed-to-be-sustainable’ home. To their surprise, there was very little insulation and the connections were not solved properly, then in every connection there was a massive concrete thermal bridge.
That client had to switch architects to redo the full construction project to make it sustainable (for real). They hired us, so we re-designed the construction system by redrawing the section view, redefining materials, calculating values with the passive simulator and solving all connections. The house resulted to be a certified passive house plus at the end!
The clients were happy with their new healthy home at the end. However, they had to spend more money and time due to this change of architects.

 

 

Our professional recommendation:
Ask your architect to show the construction section cut of your positive house to check if there are any cuts on the insulation layer.
If there are, ask him to calculate the thermal bridge that this means to your loss of heat inside your home.
Or even better, avoid all these questions and just hire an architect that is also a passive house designer.
It doesn’t have to be us, but PLEASE for the sake of your future mental health, hire a passive house architect.

You may also be interested in:
Probably you’ve heard of thermal bridges before when talking about windows.
Let’s dig into windows now that you’re warmed up: ‘Windows in positive houses’

 

 

Hope this post is helpful!

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

 

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