Steel beam thermal bridging problem

[GasManDan]

Evening all, 

I’m looking for some help and advice regarding insulating a steel goalpost structure in order to try to stop thermal bridging and bad moisture problems internally. 
We have just had the internals plastered and the plan originally was to clad the external steels with oak but have had to put that on hold temporarily due mostly to cost. 
my plan B is now to insulate the external steel as best as possible then possibly clad with aluminium. 
it’s the first winter we have had doors and windows in but the moisture on the steels internally is real bad. I’ve purchased some 10mm cold bridge strips from proctor group to cover steels internally and then was maybe thinking again to clad with aluminium as don’t think plasterboard would last with the amount of moisture.

has anyone else been in this situation and can offer any further advice? 
thanks in advance for your help 

[Andehh]

Thin layers of 25mm PIR carefully and rightly packed around every bit of it outside, expanding foam on any nooks, then tape over the top for good measure, then aluminium sheet over the top of it!

 

That's what I did, ours were I beams so I got lots in the middle of it difficult for the I protrusion but then most of it was behind external blocks with insulation which helped.

 

Try it out over a days work, and see what difference it makes.

 

That looks like quite a large damp patch for condensation? Sure its not water ingress from driving rain around windows?

[Conor]

We stuck on 50mm PIR then alu flashing over. Out posts were only 80mm tho and set back so minor surface area. Build out the insualtion, foam and gaps, tape up, until the right depth just to be covered by the flashing. 

[GasManDan]

That’s great thanks and appreciate your responses. 
 

has either of you looked into a closed cell spray foam in place of the PIR? Just thinking if the spray insulation is directly bonded to steel then maybe insulation values would be better?

[JohnMo]

Your windows seem to installed within the steel instead of in front or behind the steel. So you have a cold bridge that bypasses the window.

 

So you have a cold source outside in the winter and at any time external conditions are colder than indoors, plus the steel will never be warmer than the ground it's attached too. So will always be colder than either inside or outside or both.

 

So you need equal insulation inside and outside of the house and it really needs to overlap the window frame to prevent a short circuit.

 

You need a minimum of 10mm aerogel or 15mm PIR, ideally more covering the steel internally and externally. You need to tape the whole lot to make it airtight to stop condensation forming.

 

Spray foam isn't you friend here, a couple of sheets of PIR and aluminium tape are.

 

If you haven't done the above where it's been plastered, that will need to be stripped back and redone correctly.

[GasManDan]

1 hour ago, JohnMo said:

Your windows seem to installed within the steel instead of in front or behind the steel. So you have a cold bridge that bypasses the window.

 

So you have a cold source outside in the winter and at any time external conditions are colder than indoors, plus the steel will never be warmer than the ground it's attached too. So will always be colder than either inside or outside or both.

 

So you need equal insulation inside and outside of the house and it really needs to overlap the window frame to prevent a short circuit.

 

You need a minimum of 10mm aerogel or 15mm PIR, ideally more covering the steel internally and externally. You need to tape the whole lot to make it airtight to stop condensation forming.

 

Spray foam isn't you friend here, a couple of sheets of PIR and aluminium tape are.

 

If you haven't done the above where it's been plastered, that will need to be stripped back and redone correctly.

 Thanks for your reply @JohnMo; yes you are correct with regards to the fixing of the doors and windows. I went back to our architect with this question and it is an issue that seems to be overlooked by everyone including myself but then on the flip side felt that by fastening a heavy door direct to the steel was a more secure option. 
Im now thinking to wrap some 10mm aerogel cold bridge strips and seal to all external steel faces and then also fit PIR over the top of this and then seal and clad? Is there such thing as over insulating in this situation? 
internally I am more restricted space wise as we only have 40mm from the steel face to the window unit so here I am installing the 10mm aerogel and then was going to clad over the top of this?