Attic Condensation after Re-Roofing

g0g · 29-11-2020 3:06pm #1

I see a few threads about attic condensation but none identical to mine. Getting a lot of moisture under the attic insulation since we got a job done earlier this year. It's making some boxes go softer and getting me worried. Summary as follows:

House is probably late 70s
Lots of cracked tiles and ancient felt when we moved in a few years ago so we decided to do a job earlier this year
As part of renovation work (previously) we moved the water tank to the shed, so that's not part of the equation
Checked with smoke pellets that the bathroom extractor fans (2) don't appear to be venting into attic
Roofing company re-layed the tiles (early 2020) and replaced any broken ones
As part of the job they put in a brand new breathable felt membrane
They also added insulation under the membrane

They put vents in along both sides of the house which they said should keep air moving around. A few weeks after completion I noticed the volume of moisture still up there so they also put 3 vent tiles in the roof on each side of house. I questioned how that could work if the moisture is blocked inside by insulation and felt. They said not a problem as felt is breathable membrane and it should get past the insulation as that is layered through the attic.

I see suggestions online of drilling bigger holes in gable front and back of house. Does that typically make a big difference? I have a good bit of stuff up there but not blocking the path to the side vents for sure.

Calahonda52 · 29-11-2020 6:00pm

can you post a picture or 2 of the inside of the roof, especially the roof tile vents?

mickdw · 29-11-2020 6:03pm

Do you have attic rooms?

g0g · 29-11-2020 6:08pm

mickdw wrote: »

Do you have attic rooms?

Nope. Two storey detached house and the roof is too shallow to ever convert attic.

mickdw · 29-11-2020 6:09pm

So it is insulated on the ceiling then or insulated along the roof slope

g0g · 29-11-2020 6:14pm

Calahonda52 wrote: »

can you post a picture or 2 of the inside of the step, especially the roof tile vents?

Excuse my ignorance but what part is the step? If that's the "bottom" of the roof then maybe the attached helps which illustrates how it was looks sometimes.
20200215_144550.jpg
Granted this pic makes it look like the insulation is all bunched up at the edge and blocking the side vents but it's not really like that throughout, and if I go up in the dark and shine torch from outside house under the vents I can see the light from attic.
As for the tile vents, I can't see them from inside. I think I took a pic of the outside at some point will try to dig it up.

g0g · 29-11-2020 6:23pm

mickdw wrote: »

So it is insulated on the ceiling then or insulated along the roof slope

When the house was renovated when we moved in I remember insulation boards being used for the ceiling and a new attic access was put in. At that stage we decided to leave the roof untouched and it had ancient brittle felt plus some cracked tiles, hence revisiting that part a few years later. So now I guess both the upstairs has insulation in the roof plus the attic now has its layer of insulation too. The attic layer is that stuff that looks like thin bubble-wrap with "tinfoil" on the outside - not a big fancy material with fam etc or anything.

greasepalm · 29-11-2020 6:25pm

Is that something like tin foil with moisture on it?

g0g · 29-11-2020 6:29pm

greasepalm wrote: »

Is that something like tin foil with moisture on it?

That's the extra bit of insulation the roofers put in "below" the felt membrane material to keep some heat in or whatever I guess.
The roofing company are still in business but I've seen some questionable reviews online, so I'm trying to assess if it's a disaster job or what. Perhaps without that insulation layer I would be rid of the moisture and simply have a colder attic? But if I thought a simple vent both ends of the attic would make everything go away then that sounds like an easier solution?

g0g · 29-11-2020 6:30pm

I would guess it's this sort of stuff

mickdw · 29-11-2020 6:36pm

Thats a crazy detail.

Blowheads · 29-11-2020 6:41pm

Tiles, breathable membrane, non breathable insulation layer underneath, could be your problem, tapping the air.
I'd imagine you need more vents to circulate the air and allow moisture to escape.
We have 3 vents on each side of roof pitch and several in the soffit.
The attic shouldn't really be warm, the insulation should be between attic & 1st floor.
Could be tricky enough to rectify but I'd start making a few more air vents. In the interim get a few of those moisture collection (unibond?) And depending how bad it is and how long until a fix maybe a dehumidifier

Calahonda52 · 29-11-2020 7:27pm

g0g wrote: »

Excuse my ignorance but what part is the step? If that's the "bottom" of the roof then maybe the attached helps which illustrates how it was looks sometimes.
20200215_144550.jpg
Granted this pic makes it look like the insulation is all bunched up at the edge and blocking the side vents but it's not really like that throughout, and if I go up in the dark and shine torch from outside house under the vents I can see the light from attic.
As for the tile vents, I can't see them from inside. I think I took a pic of the outside at some point will try to dig it up.

my bad with the auto correct typo, have corrected it to read roof.
So the roof vents an NFG as they dont penetrate the breathable membrane which is also NFG because of the expensive bubble wrap.
Its unreal

I would be boring a 6 " hole in each gable, up at the apex, and cover with insect mesh

Blowheads · 29-11-2020 8:00pm

Calahonda52 wrote: »

my bad with the auto correct typo, have corrected it to read roof.
So the roof vents an NFG as they dont penetrate the breathable membrane which is also NFG because of the expensive bubble wrap.
Its unreal

I would be boring a 6 " hole in each gable, up at the apex, and cover with insect mesh

I would open the roof vents also, the breathable membrane, while it prevents moisture and allows air it doesn't really allow air to circulate as it's still a barrier if you know what I mean. I suppose many roofers use this now and a call to one of them should answer this definitively if the roof vents should be a "hole" with insect cover

Pasteur. · 29-11-2020 9:23pm

Blowheads wrote: »

I would open the file vents also, the breathable membrane, while it prevents moisture and allows air it doesn't really allow air to circulate as it's still a barrier if you know what I mean. I suppose many roofers use this now and a call to one of them should answer this definitively if the roof vents should be a "hole" with insect cover

The roof vents surely penetrate the membrane?

Bullocks · 29-11-2020 9:32pm

Are the tile vents coming through the membrane ?
I'd be popping 2 wall vents through each gable if possible and I think another layer of loft roll over the ceiling joists would help keep in more heat and avoid condensation

Pasteur. · 29-11-2020 9:36pm

Bullocks wrote: »

Are the tile vents coming through the membrane ?
I'd be popping 2 wall vents through each gable if possible and I think another layer of loft roll over the ceiling joists would help keep in more heat and avoid condensation

If they added vents both ends and roof vents surely that's enough if they're open

Sort out the breathable membrane on the roof

g0g · 30-11-2020 12:19am

Thank you all, really appreciate all those replies! Think I'll pick up a dehumidifier in the short term (I believe they're good for drying clothes indoors too - so can use for other purposes in future) while I find someone to install vents front and rear.

There were a couple of suggestions about opening the access to the vent tiles. I presume the suggestion isn't to cut through both the insulation and the membrane? Isn't the membrane meant to be the backup for any water that gets past the tiles in bad weather if it blows in etc? I guess I could try remove a chunk of the insulation behind each vent tile, but would have to somehow figure out where each (6) of them are from the inside.

Hadn't thought of adding more insulation on the floor of the attic, although most of the attic is now floored plus if I put extra insulation right to the edge it might obstruct air flow from the soffit vents?

Calahonda52 · 30-11-2020 8:39am

The reason the roof vents were not done properly is that it is harder to do the flashing around them, correctly.
IMO, leave them as they are because the result could be more water in the form of rain

The membrane has two functions, the one you mentioned, which can be achieved by much cheaper materials.
The second one and the one you pay the money for is to allow moist air from the attic space pass through it as moisture vapour, not as moisture.
Thats what the breathability piece is about, it works best when roof is counter battened.

The glorified bubble wrap has 100% negated the breathability aspect, you now have a 100% impermeable, non breathable layer.

The other " much improved"

suggestion is drill the holes on the gable and fit the north face one with a trickle fan, wired through a humidity sensor placed in the middle of the roof, mid way between both gables

Biker1 · 30-11-2020 9:29am

The issue seems to be that warm moist air is getting into your attic and condensing on the bubble wrap.
Either add sufficient insulation at ceiling level or remove the useless bubble wrap and the current ventilation should be ok.

Lumen · 30-11-2020 10:29am

Biker1 wrote: »

The issue seems to be that warm moist air is getting into your attic and condensing on the bubble wrap.
Either add sufficient insulation at ceiling level or remove the useless bubble wrap and the current ventilation should be ok.

It's not a ceiling insulation problem, it's a ceiling airtightness problem.

The vapour barrier is in the wrong place. It should be on the warm side of the boundary of the heated envelope, i.e. the ceiling of the topmost habitable floor.

It seems like a half-arsed attempt has been made to extend the heated envelope to include the attic, but without the right combination of insulation, ventilation and membranes to make that work.

This issue would not have occured if the following sensible steps had been taken:

1. Making the ceilings and attic hatch air tight.
2. Having working ventilation of the attic space itself
3. Using a breathable membrane on the warm side of the rafter insulation.
4. Using sufficient well-detailed rafter insulation to avoid condensation on that surface.

Alternatively just (1) and (2), and then you'd have a conventional cold attic for storage.

The fact that this job was done by "professionals" for money is really shameful.

listermint · 30-11-2020 10:40am

This looks seventeen shades of wrong. In fact it would have been better much much much better had they forgone their supposed insulation and just left with just installing the breathable felt and slates/tiles .

There is no airflow beneath the tiles and membrane I'd imagine. Also the insulation they chose just provides a handy condensation Barrier due to where it's fitted and it's aluminium surface. This is ****e.

Should ideally look like attached please excuse my quick sketch

My immediate reaction to this is tear the bubble foil out asap.

mickdw · 30-11-2020 10:44am

Lumen wrote: »

It's not a ceiling insulation problem, it's a ceiling airtightness problem.

The vapour barrier is in the wrong place. It should be on the warm side of the boundary of the heated envelope, i.e. the ceiling of the topmost habitable floor.

It seems like a half-arsed attempt has been made to extend the heated envelope to include the attic, but without the right combination of insulation, ventilation and membranes to make that work.

This issue would not have occured if the following sensible steps had been taken:

1. Making the ceilings and attic hatch air tight.
2. Having working ventilation of the attic space itself
3. Using a breathable membrane on the warm side of the rafter insulation.
4. Using sufficient well-detailed rafter insulation to avoid condensation on that surface.

Alternatively just (1) and (2), and then you'd have a conventional cold attic for storage.

The fact that this job was done by "professionals" for money is really shameful.

Yep. No understanding at all of even the basics of insulated v non insulated area.

g0g · 30-11-2020 7:07pm

Calahonda52 wrote: »

The reason the roof vents were not done properly is that it is harder to do the flashing around them, correctly.
IMO, leave them as they are because the result could be more water in the form of rain

The membrane has two functions, the one you mentioned, which can be achieved by much cheaper materials.
The second one and the one you pay the money for is to allow moist air from the attic space pass through it as moisture vapour, not as moisture.
Thats what the breathability piece is about, it works best when roof is counter battened.

The glorified bubble wrap has 100% negated the breathability aspect, you now have a 100% impermeable, non breathable layer.

The other " much improved" suggestion is drill the holes on the gable and fit the north face one with a trickle fan, wired through a humidity sensor placed in the middle of the roof, mid way between both gables

Thanks for the suggestions. Do you think gable vents could compensate enough without the need to remove the useless insulation?

Biker1 wrote: »

The issue seems to be that warm moist air is getting into your attic and condensing on the bubble wrap.
Either add sufficient insulation at ceiling level or remove the useless bubble wrap and the current ventilation should be ok.

I'm amazed how much is somehow getting up there when I saw myself how thick the insulation sections looked upstairs in the house plus you have the attic floor insulation on top of that too. A neighbour on one side has the vent/exhaust from their heating system in a passage between the houses around the height of a door - any chance this could be a cause and some of it come in via soffit vents or is that mad talk?

Lumen wrote: »

It's not a ceiling insulation problem, it's a ceiling airtightness problem.

The vapour barrier is in the wrong place. It should be on the warm side of the boundary of the heated envelope, i.e. the ceiling of the topmost habitable floor.

It seems like a half-arsed attempt has been made to extend the heated envelope to include the attic, but without the right combination of insulation, ventilation and membranes to make that work.

This issue would not have occured if the following sensible steps had been taken:

1. Making the ceilings and attic hatch air tight.
2. Having working ventilation of the attic space itself
3. Using a breathable membrane on the warm side of the rafter insulation.
4. Using sufficient well-detailed rafter insulation to avoid condensation on that surface.

Alternatively just (1) and (2), and then you'd have a conventional cold attic for storage.

The fact that this job was done by "professionals" for money is really shameful.

Yeah, like I said, I read some less favourable reviews about the company after the job, which is frustrating when they appear on page one of Google searches. To be fair they came back a couple of times for example with the vent tiles, but I'd prefer resolve this elsewhere now.

listermint wrote: »

This looks seventeen shades of wrong. In fact it would have been better much much much better had they forgone their supposed insulation and just left with just installing the breathable felt and slates/tiles .

There is no airflow beneath the tiles and membrane I'd imagine. Also the insulation they chose just provides a handy condensation Barrier due to where it's fitted and it's aluminium surface. This is ****e.

Should ideally look like attached please excuse my quick sketch

My immediate reaction to this is tear the bubble foil out asap.

I'm on the verge of removing bubblewrap but for the fact that I can't undo that. Will also have to be very careful cutting it out that I don't hack away any of the felt too!

mickdw wrote: »

Yep. No understanding at all of even the basics of insulated v non insulated area.

Yep, sadly.

listermint · 30-11-2020 7:44pm

g0g wrote: »

Thanks for the suggestions. Do you think gable vents could compensate enough without the need to remove the useless insulation?

I'm amazed how much is somehow getting up there when I saw myself how thick the insulation sections looked upstairs in the house plus you have the attic floor insulation on top of that too. A neighbour on one side has the vent/exhaust from their heating system in a passage between the houses around the height of a door - any chance this could be a cause and some of it come in via soffit vents or is that mad talk?

Yeah, like I said, I read some less favourable reviews about the company after the job, which is frustrating when they appear on page one of Google searches. To be fair they came back a couple of times for example with the vent tiles, but I'd prefer resolve this elsewhere now.

I'm on the verge of removing bubblewrap but for the fact that I can't undo that. Will also have to be very careful cutting it out that I don't hack away any of the felt too!

Yep, sadly.

Cheapest solution right now with most reward is pull out the bubble wrap. As you say careful does it , you can leave the bits behind the rafters obviously. Should be easily done with a scissors for protection of the roof membrane rather than a Stanley blade which is unwieldy.

The Continental Op · 30-11-2020 7:58pm

Is there any ventilation in the attic? I wonder if the attic floor insulation was pulled back at the eves and eve trays installed there would be any improvement - might also require some vents in the sofits. Perhaps eve trays and the removal of the strip of insulation nearest the ridge would be enough to get enough air flow?

That does seem to be a lot of condenstation? Now it shouldn't have anywhere like that to build up but I do wonder if there is an excess for any other reason like a shower vented into that space.

greasepalm · 30-11-2020 8:03pm

Without going mad and pulling it all out what about cutting a few squares out to improve circulation and see how it goes from there as air can flow through the membrane then.

The Continental Op · 30-11-2020 8:18pm

greasepalm wrote: »

Without going mad and pulling it all out what about cutting a few squares out to improve circulation and see how it goes from there as air can flow through the membrane then.

Worth a try but I don't think a small area of membrane would be permiable enough?

greasepalm · 30-11-2020 8:29pm

I might suggest 3 cuts,left,right and top as if you wanted it could be retaped back up if needed.
With the vents open it might be enough to stir some air movement

MicktheMan · 30-11-2020 8:49pm

listermint wrote: »

Cheapest solution right now with most reward is pull out the bubble wrap. As you say careful does it can't leave the bits behind the rafters obviously. Should be easily done with a scissors for protection of the roof membrane rather than a Stanley blade which is unwieldy.

This ^^^ plus vents in gables should sort it.

listermint · 30-11-2020 9:37pm

greasepalm wrote: »

I might suggest 3 cuts,left,right and top as if you wanted it could be retaped back up if needed.
With the vents open it might be enough to stir some air movement

Definitely not. It won't ever need to be taped back up as it's simply not required. Badly installed and services no purpose where it is.

The bubble wraps a write off. It's actively causing a problem and will continue to do so if it's taped back up.

Attic Condensation after Re-Roofing

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