new attic conversion water build up

inabina

hi all
just got my attic converted and the builder placed thermoboards between rafters and Low E foil over the rafters. 4 weeks ago, after the plastering was completed, serious amount of condensation was running off the themoboard...I can see the evidence in the storage area where i place my hand between the low e and thermoboard. the felt is also wet.


4 weeks later the level of condensation is the same, no change.

is this normal given the water from the plastering and the time of year or am i lacking ventilation? there is air running between the low e and thermoboard, i can feel it.

BryanF

inabina wrote: »

hi all
just got my attic converted and the builder placed thermoboards between rafters and Low E foil over the rafters. 4 weeks ago, after the plastering was completed, serious amount of condensation was running off the themoboard...I can see the evidence in the storage area where i place my hand between the low e and thermoboard. the felt is also wet.


4 weeks later the level of condensation is the same, no change.

is this normal given the water from the plastering and the time of year or am i lacking ventilation? there is air running between the low e and thermoboard, i can feel it.

Poor specification and lack of ventilation. 1. Did you have drawings and
2. was there a cert of building reg compliance &
3. what has the builder offered to do to fix?

A fella called fish

How deep are the rafters and how deep is the insulation board?

Are there any ventilation gaps in the eaves?

omr1976

Hi,

I am having the same issue, attic just converted, plaster just done.
Rafters are 100mm and insulation 75mm

inabina

The builder did place a lot of the glass wool insulation into the eaves and I argued that this could be a factor and he said there was enough coming through the tiles and he had not actually blocked the flow. I asked him to remove all the insulation from the eaves and he has now done it. I hope we will see dramatic improvement within the next 2 weeks.

Ush1

There should be a 50mm gap between the insulation and the roofing felt if the roof felt is not breathable.

There should be air inlets at the eaves which should flow up and I think normally the roof tiles along the ridge are ventilated to let the air out.

omr1976

Ush1 wrote: »

There should be a 50mm gap between the insulation and the roofing felt if the roof felt is not breathable.

There should be air inlets at the eaves which should flow up and I think normally the roof tiles along the ridge are ventilated to let the air out.

Thank you for your input. Can you see a solution for my setup? the felt is not breathable, and the gap is just 25mm?

sydthebeat

Ush1 wrote: »

There should be a 50mm gap between the insulation and the roofing felt if the roof felt is not breathable.

There should be air inlets at the eaves which should flow up and I think normally the roof tiles along the ridge are ventilated to let the air out.

regardless if the felt is breathable or not, there should still be 50mm ventilation gap.

Water cannot penetrate through breathable felt, only vapour can.
the moisture laden air will condense on the inner face of the felt.

omr1976

sydthebeat wrote: »

regardless if the felt is breathable or not, there should still be 50mm ventilation gap.

Water cannot penetrate through breathable felt, only vapour can.
the moisture laden air will condense on the inner face of the felt.

would ventilated ridge tile help at all? or this need to be redone with 50mm gap?

omr1976

I should have mentioned, our water tank is in the crawling area, right underneath where condensation appears? any link? moisture coming from the tank?

sydthebeat

omr1976 wrote: »

would ventilated ridge tile help at all? or this need to be redone with 50mm gap?

you need cross ventilation from one side to the other.

ridge vents help but are not a replacement. you need ventilation at the eaves.

what you could do is to get 50mm dia wavin pipes and cut to lengths to suit and push down into the eaves, probably 2-3 per each gap between rafters.

there is a specific product called an eaves ventilator which does this.

omr1976

sydthebeat wrote: »

you need cross ventilation from one side to the other.

ridge vents help but are not a replacement. you need ventilation at the eaves.

what you could do is to get 50mm dia wavin pipes and cut to lengths to suit and push down into the eaves, probably 2-3 per each gap between rafters.

there is a specific product called an eaves ventilator which does this.

Thanks for your help, I am going to investigate this.
Would you push down the wavin pipe from the ridge to the eave or from the side stud wall down to the eaves?