Months of Site Exposure to Elements - Building Fabric + Insulation

[marmalade]

Without going in to too much detail onto why this happened, for one reason or another, the site has been left exposed to the elements since August.

We’ve build up to the first floor level, however sadly, it's not been covered via tarps/a tin roof

Subfloor, internal blocks, timber joists and insulation (Knauff Dritherm 32 Cavity Slabs) has all been exposed to the rain 
The steels show signs of light rust

A few images attached

What I’m trying to understand is
1) The risks and remedial actions required

Which of these are minor, which may cause major issues e.g. Water absorption into the building fabric causing mould in the future

 

2) What remedial actions are needed?

Protect the site - We’ve agreed to split the costs to call in a scaffolder to install the tinroof which should complete next week.
Replace the insulation - Me and the builder have agreed to replace the insulation (although I’m being told we only need to replace the top segments)
Dry out the site – Not really sure if demudifiers will do the job/how this is possible without waiting for months?

 

3) What should a good cavity wall and well insulated home look like
It’s a brick and block structure.
There is an airgap left at the DPC level although this currently looks to have a lot of debris with in.
Cavity is fully filled with insulation (32 Knauf Cavity Slab Insulation and 150mm Celotex to be used for the ground floor). Steel wall ties.
I see differing advice about leaving an air gap/not leaving an air gap.

[Oz07]

Nothing disastrous to me there. At least your floor deck isn't on. The insulation would surely dry out in time? Stopping the insulation at that dpc level is poor but nothing to do with being exposed to elements. Ideally you want it to overlap the level of pir insulation in floor so say going 225mm below dpc. Id consider having this area of missing insulation blown in with a machine as I think it would effect your real life performance. Any reason for traditional timber joists? It looks a smart job just not common on new build. Was there a big saving vs posi or I joists?

[Oz07]

I don't think moisture from weather during building brings mould later. Isn't mould more to do with humidity and ventilation once finished. 

[Redbeard]

Dehumidifiers will do the job if the 'box' (the house) is closed. If it's not you will be trying to dehumidify the world (and that will take a long time!). If my guess re floor level is right and that residual cavity at the bottom of Pic 1  remains open you will have a sizeable thermal bridge all around the perimeter of the house at floor level. I find it hard to imagine the intention was to leave the lower cavity open, so what was the original plan for it? @Oz07 is right, I think, that injected bonded graphite EPS beads are your only option now (and the right option, compared with Rockwool which may absorb moisture, below DPC). I have had difficulty getting EPS blowers to engage with partial jobs or 'non-standard' installations, so I hope you have better luck in your area. For such a relatively small area, but one which it is essential to 'treat' with insulation, I think whatever you have to pay is worth it. I don't have any contacts in the SE, I am afraid.

 

I am sorry you have had a difficult time of it.

[Russell griffiths]

Looking at your other post

 

have you actually had this built or have you bought an unfinished project ?

look at the financial aspect here you might be better re doing some of the work to make moving forward easier and you will end up with a better overall product, instead of coming back in a year asking why your new house is cold. 

[saveasteading]

As above. It will dry. 

Steel stops rusting when it is dry.

Timber. Will dry. Just check fir severe warping.

Insulation. Cavity stuff should dry out.

 

Once you get a roof on you'll be surprised how quickly it all dries. Lots of airflow is much more efficient than machines.