New build mould/ ventilation issues

Tillerman08

Hi all

We built a new house 2 years ago and we wanted to have sufficient insulation so we put insulated board on all the external walls.

We now have a problem where we have black dots coming through the walls. These black dots are the steel fixings used to put the insulted board on the walls and it looks like mould is growing on them. When you rub off...... They will only return after a couple of weeks.

We have been trying to get issue resolved but are struggling to find a root cause. Our builder says it's a ventilation problem after initially saying it was a product issue with the steel fixings.

We only have trickle vents in our habitable rooms and our architect insists that this is adequate ventilation? The rooms are quite large 15 x 15.

I have spoken to our builder who says he is now seeing this issue with another house he has built. They have repainted the walls with a sealant only for the dots to return after a couple of months.

Has anyone here every seen issues like this and how did you resolve it?

I would also like to get an independent expert to look at the ventilation etc and give their opinions- who should I be talking to??? I have been quoted €450 + vat for a report to be carried out but no intention of spending this money as I need either Engineer or builder to solve this problem for us but nobody is accepting responsibility.


Thanks for your help everyone

Metric Tensor

Just to point out that you want to have an independent expert review the situation but are unwilling to pay him/her €450 + VAT.

If you want someone independent you will have to engage and pay for them yourself and the amount quoted above is not unreasonable for same. Of course it's important to make sure the person is indeed an expert in this type of thing.

BryanF

tiler?
You in the trades?
Get out your chisel/drill, cut a hole in the concrete and inspect the cavity.
And take off a bit of insulated slab and inspect the inside face of wall.

Separately test RH in the room and
monitor wall temp internally.
Can you get a thermal imagining camera?
A borescope?

Edit : TILLer..

Tillerman08

BryanF wrote: »

tiler?
You in the trades?
Get out your chisel/drill, cut a hole in the concrete and inspect the cavity.
And take off a bit of insulated slab and inspect the inside face of wall.

Separately test RH in the room and
monitor wall temp internally.
Can you get a thermal imagining camera?
A borescope?

Edit : TILLer..

Not in the trade Bryan so I might do more damage by going anywhere near it- thanks for your help!

sydthebeat

Tillerman08 wrote: »

Hi all

We built a new house 2 years ago and we wanted to have sufficient insulation so we put insulated board on all the external walls.

We now have a problem where we have black dots coming through the walls. These black dots are the steel fixings used to put the insulted board on the walls and it looks like mould is growing on them. When you rub off...... They will only return after a couple of weeks.

first off this post should be stickied and shown to any poster who comes on and says "our builder suggests internal insulation on our new build"

no offence OP but its a bad specification on a new build.

You most likely have condensation occurring in that space between your insulated slabs and the inner leaf, and its condensing on the coldest part of the structure which is the mushroom fixing.

can you tell us what thickness of internal insulation you have, and what thickness and type of insulation you have in your cavity and if you have any cavity gap left... also, whats the external finish and whereabouts in the country the house is?

BryanF

Tillerman08 wrote: »

Not in the trade Bryan so I might do more damage by going anywhere near it- thanks for your help!

450 it is so

Make sure they are sufficiently 'chartered' to carry weight of you need to escalate maters with builder

MicktheMan

Tillerman08 wrote: »

Has anyone here every seen issues like this and how did you resolve it?

Yes, have investigated several cases like this. As others have said, this is not that unusual with your wall specification / materials used.

Gumbo

MicktheMan wrote: »

Yes, have investigated several cases like this. As others have said, this is not that unusual with your wall specification / materials used.

Is there any way to get around it at construction stage?

MicktheMan

kceire wrote: »

Is there any way to get around it at construction stage?

The clue might well be (partially) in the original post.
The first place I'd look would be the type of mech fixing.
The next is how exactly the cavity (assuming there is one) is insulated.

Alternatively ...

Don't internally insulate:)

Gumbo

MicktheMan wrote: »

The clue might well be (partially) in the original post.
The first place I'd look would be the type of mech fixing.
The next is how exactly the cavity (assuming there is one) is insulated.

Alternatively ...

Don't internally insulate:)

what about hollow block or solids on the flat and then internally insulated?
would the addition of a batten and then the insulation fixed to the batten help the situation?

MicktheMan

kceire wrote: »

1. what about hollow block or solids on the flat and then internally insulated?
2. would the addition of a batten and then the insulation fixed to the batten help the situation?

1. Issue here (other than interstitial condensation risk!) is that the mech fixing can create a very local thermal bridge. Using thermally broken mech fixings will deal with this. In the op it appears that steel fixings were used.
2. Generally yes, but then you have to deal with more lost internal space as well as creating an air circulation path at the back of the insulation which can easily put paid to good air tightness ambitions (if not thought through and executed properly). However, due to the wide use of dot n dab plus mechanically fixing of these boards, this air space is there already!

BryanF

kceire wrote: »

what about hollow block or solids on the flat and then internally insulated?
would the addition of a batten and then the insulation fixed to the batten help the situation?

Read the 'breaking the mould' series