Holes in underlay of new build

robp

Hi,

I noticed two large holes in a roof underlay of a new BER A2 house. There is a heat recovery system which has a duct connecting to slates through a similar hole. So I presume the unused holes may be due to its installation. Are these holes a significant concern for insulation or dampness?


A picture is visible here: https://www.dropbox.com/s/m6tcggi6q51pfr1/20180125_165303.jpg?dl=0

BryanF

Builder should repair holes but if it were me I’d buy a roll of contega tape and do it myself.

B-D-P--

Yea as Brian said,

You'd be far far quicker getting a roll of A/T Tape and sealing it than chasing a builder.

That hole would have significant impact on heating.

Now its not doing any harm as it is, only letting heat out the house through a unnecessary hole. Hence I'd seal it, Dont go using duct tape or anything similar, get airtight tape from building merchant.

kieran.

It appears that the felt/underlay is within the cold attic space so you should have no issues with air tightness here as the space is probably designed to be ventilated anyway.

Dampness the may be a issue if the water was to get behind your tile/slates gorilla tape or similar would be sufficient here probably no need to go to the expense of AT Tape.

robp

The attic is a cold attic. Behind the hole I can feel the cold slates so there is no other layer. It is interesting to hear it would be a dampness issue and possible an insulation issue too. Despite being a brand new BER A2, the house is hard to heat above 19°C and we are very keen to understand the cause.

BryanF

robp wrote: »

The attic is a cold attic. Behind the hole I can feel the cold slates so there is no other layer. It is interesting to hear it would be a dampness issue and possible an insulation issue too. Despite being a brand new BER A2, the house is hard to heat above 19°C and we are very keen to understand the cause.

No insulation issue here

kieran.

What's your heat source and output method. I'm guessing a2w hp with rads?

MicktheMan

robp wrote: »

The attic is a cold attic. Behind the hole I can feel the cold slates so there is no other layer. It is interesting to hear it would be a dampness issue and possible an insulation issue too. Despite being a brand new BER A2, the house is hard to heat above 19°C and we are very keen to understand the cause.

While these holes should be repaired as described above, they have no effect on the house being hard to heat. The most direct way to definitively find the issue(s) is to have the house tested for heat loss with a heat loss survey.

Calahonda52

robp wrote: »

The attic is a cold attic. Behind the hole I can feel the cold slates so there is no other layer. It is interesting to hear it would be a dampness issue and possible an insulation issue too. Despite being a brand new BER A2, the house is hard to heat above 19°C and we are very keen to understand the cause.

The purpose of the felt, when it was the black bitumen was, inter alia to

1. stop driving rain coming in under the slates and dropping on on the ceiling
2. stop condensation on slates dropping down on the ceiling
3. reducing the wind passing through the roof space.

So not an insulation issue.

The roof felt you have is, I suspect, breathable, to let moisture vapour pas through it but not to let rain/condensation/wind in

I would use A/T tape as the high summer temps will cook the other suggestions here, in addition, the inside of the membrane may be fluffy and hard to tape.

In passing, where is the MHVR unit located and where is the other intake/exhaust pipe fitted?

BryanF

Calahonda52
What other suggestions? Everyone has suggested AT tape?

mickdw

I think someone suggested gorilla tape.
I would do the old fashioned repair. Slit above opening and insert square of felt in correct direction to keep any running moisture out. Could tape inner flap and cut also.

robp

[font=Times New Roman","serif]I don't have the exact specs here but the house has a Joule 300l water cylinder, gas and solar thermal.[/font]
[font=Times New Roman","serif] [/font][font=Times New Roman","serif]I’d love an airtightness test, however with the house being so new and the builders still onsite in another part of the new estate I would have like to get the builders to sort this out. One other thing I wonder is if the attic temperature is so low, presumably attic doors must be air tight and insulated. The attic door is very heavy but it is not insulated and probably not totally airtight. [/font]

robp

The purpose of the felt, when it was the black bitumen was, inter alia to stop driving rain coming in under the slates and dropping on on the ceilingstop condensation on slates dropping down on the ceilingreducing the wind passing through the roof space.

So not an insulation issue.

The roof felt you have is, I suspect, breathable, to let moisture vapour pas through it but not to let rain/condensation/wind in

I would use A/T tape as the high summer temps will cook the other suggestions here, in addition, the inside of the membrane may be fluffy and hard to tape.

In passing, where is the MHVR unit located and where is the other intake/exhaust pipe fitted?

In the pic in the dropbox, one of the Vent-Axia MHVR pipes is located in the top left, going through the slates. It is all insulated so I can't tell if it is a exhaust or intake pipe.

Calahonda52

robp wrote: »

In the pic in the dropbox, one of the Vent-Axia MHVR pipes is located in the top left, going through the slates. It is all insulated so I can't tell if it is a exhaust or intake pipe.

Normally exhaust is not insulated but sometimes is to make it easier to do both.
Where is the MHRV box located

robp

Calahonda52 wrote: »

robp wrote: »

In the pic in the dropbox, one of the Vent-Axia MHVR pipes is located in the top left, going through the slates. It is all insulated so I can't tell if it is a exhaust or intake pipe.

Normally exhaust is not insulated but sometimes is to make it easier to do both.
Where is the MHRV box located

Roughly two metres away on the attic floor.