Hello all, just looking to see if anybody has any advice on reducing thermal bridges where steel columns are taken below ground level to foundation.

We are building a new passivhaus and are trying to design a robust detail to reduce local thermal bridging for two columns. The main wall structure is a 215mm AAC block with 280mm EWI / Render. The floor is a 150mm slab on 300mm XPS. For the columns, our current design is to use a thermal break (farrat) where the column meets the foundation. Because this is all below ground, we will encase the column in c.100mm concrete to form a plinth, and the plinth will be painted with liquid dpc as with the other area of the wall. We are then planning to wrap the plinth in 100mm insulation up to the same level as the floor insulation to provide thermal continuity. See attached drawing.

This feels like an ok solution. An alternative we are considering is to again use a thermal break but move the insulation in so that it wraps the steel with the plinth then around that. Again, with DPM etc around the plinth.

In both cases, we will then RIW damp-proof products and apoxy mastic / similar around the column at the top of the plinth.

Does anybody have any experience with either or the above suggested methods? Or, can anybody recommended other ways to reduce thermal bridging for columns below ground level?

We obviously need a solution that can take the structural loads, but also needs to be robust to stop corrosion and condensation. Any tips / solutions that have worked would be greatly appreciated.

Best regards,

D

That would be fantastic. Thank you very much.

* The higher of the two columns has an unfactored loading of 91Kn (131kn Factored).
* The second column has 21.6Km and 31Kn unfactored and factored respectively.
* The Tie Angle has no compressive loading (this is tension only).

The foundations are existing, so we are looking for a solution that we can add to the foundations. And, obviously we need to ensure good corrosion prevention of the solution whilst designing out the cold bride. Any thing you are able to provide would be greatly appreciated.

Regards,

Dean

Should this be linked to http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=15113&page=1#Item_15 ?

But both about column bases which don't bridge the insulation

There's no shortage of space. Why would you use aerogel?

Thank you for comments so far.

There are similarities between this and the other post suggested by fostertom, but as also stated there are differences as this is a steel dropping to trench foundations the other is timber to concrete pads.

I think the main question is should we keep the insulation outside of the plinth (as shown) or bring internally to wrap the column up to the blue blocks (which are a continuous layer of Marmox Thermoblock)?