Attic condensation - Droplets on the felt

ando

Hi,

I have a 20 year old house with 20 year old insulation in the attic. There is a condensation issue up there which I'm trying to deal with. I'm not sure if the old insulation has had its day and is letting warm air into the attic and causing it to condense?? Anyway, I'm trying to source these vents to add additional ventilation in the attic. I bought 10 of them years ago and they really helped. I'm not getting far though as everywhere does not have them in stock. If anyone knows where to buy, please let me know: https://www.amazon.co.uk/dp/B00M97O5YY/ref=aod_recs_desktop_prsubs_1

About 10 days ago there were droplets on the attic felt and I seen some of the wooden joists were wet (where they touch the felt). Warm air must be getting into the attic I thought, or ventilation is not occurring up there. I resolved the droplets issue with an en-suite extractor fan fix. I believe warm air was leaking into the attic from the ensuite, but that's resolved now with some insulated duct piping from the fan to the attic vent. It seems to be working and the attic now seems much dryer, there are no droplets on the felt anymore however the wooden joists are still wet where they touch the felt still. I'm hoping its just taking time to dry properly and the main cause of the issue is now resolved.. but I cant relax knowing the wooden joists up there are still wet. Is there any point looking into replacing the old insulation with new? Would that achieve anything for the amount of time & money invested?

10-10-20

What type of insulation is installed? I presume it's wool rolls?

If so then this is an open-type of insulation meaning that vapour may pass through the insulation and not become trapped at the interface of the wool and the underlying plasterboard. Replacing the insulation would not help in this matter.

To what extent are the droplets on the felt? All over or only on the North facing side, or only in pockets on a particular side? If you lift some of the existing insulation, is the plasterboard on the ceiling foil-backed?

It might just need more time to dry out, Sunday was a wet day and a lot of moisture came into my attic over the duration of the rain and the RH went up from 60% RH at 9 degrees to about 72% at 9 degrees. That also caused condensation in mine when the temperatures dropped overnight.

C. Eastwood

https://www.boards.ie/discussion/2058276461/attic-condensation-droplets-on-the-felt

Do not replace the insulation.

If the Condensation on the felt is now eliminated, it means the ventilation of the attic void is adequate.

With the is ventilation - the moisture in the rafters will dry out. The rafters cannot get attacked by Wet Rot or Dry Rot.

It is unbelievable the amount of houses where some Plonker exhausted the moisture, with a fan, from a Bathroom/ Shower Room up in to the Attic void. Human Stupidly knows no bounds.

Dolce99

Hi, I have the exact same problem - house 25 years old, wooly-type of insulation on attic floor since house was built (never added to). Attic felt is coveted in droplets of water and dripping onto floor of attic, wetting boxes of Christmas decorations and very near-miss with kids Xmas toys. I'm wondering if we need more ventilation rather than insulation but no clue how to do this. .

Really don't know what to do and am looking for any advice please, thanks

10-10-20

https://www.boards.ie/discussion/comment/120041380#Comment_120041380

Loads of advice here:

https://www.google.com/search?q=site%3Aboards.ie+on+felt+condensation

Furze99

Surely there should be a vapour barrier of some sort between the ceiling and the insulation? I know when installing our, I fitted insulation in between the joists etc and then stapled up plastic sheeting underneath, then installed the ceiling.

10-10-20

https://www.boards.ie/discussion/comment/120042997#Comment_120042997

Yes, there would be in newer builds since about 20 years ago. There is a vapour control foil commonly included in plasterboards (foil-backed) but the plastic sheeting (VCL) is also applied to seal between the joints, etc, but it's not easy to retro-fit except where there is a deep refurb going on.

Dolce99

I really don't know re insulation barrier . . .what would it look like??

10-10-20

https://www.boards.ie/discussion/comment/120044178#Comment_120044178

Like this if you view it from the attic.

https://www.goodwins.ie/products/Foilback-Plasterboard-12.5mm-2.438-x-1.2Mtr.html

But nonetheless, do have a read of the other links provided above as the typical treatment of attic condensation is well documented on this forum.

loyatemu

I've had the same issue recently, went up to get the Xmas decorations and there was a lot of drips on the boxes and on the felt. This was during the cold snap. I don't think enough moisture would make its way into the attic through the ceilings below to cause this amount of condensation.

We do have vents in the soffits, I can see the light from them when I stand in the attic so they're not blocked, and I can see the felt rippling when it's windy so I think the ventilation is OK (though I have noticed one of our neighbours has installed ridge vents).

I suspect the main cause is our bathroom fans which are ducted out to the eaves, and the moist air is probably being blown back into the attic and then condensing on the felt if it's cold enough. I'm going to put a couple of these into the roof and attach the fans to them, if I can find a roofer willing to callout for a small job.

C. Eastwood

https://www.boards.ie/discussion/2058276461/attic-condensation-droplets-on-the-felt

I would not be worried about a Vapour Barrier (VP) ( which must always be on the warm side of the insulation).

If the lack of a VP was a problem then it would result in Interstitial Condensation- within the Insulation.

Your problem is Surface Condensation on the felt

Your insulation is perfect - it is reducing the heat loss from the living rooms, and therefore it is very cold in the Attic Void. This is the function of the Thermal Insulation.

Adding more insulation will allow less heat loss to escape in to the attic void, which will reduce your heating costs of the house. This will make the attic void colder and cause more Surface Condensation.

You need to find the cause of the moisture in the attic void which is causing the surface condensation on the underside of the felt.

There are 2 reasons for this surface condensation.

Readon 1

1. Moisture from the dwelling escaping in to the attic
2. This could be caused by extractor fans exhaustion steam/ moisture from Bathrooms or Kitchen in to the attic void. ( Yes some Plonkers do this).
3. Moisture escaping from the dwelling in to the attic void through holes in the ceiling of the Hot Press, and through gaps in the Attic Access door and through small holes in the ceilings where the wires of the ceiling lights pass through the ceiling slab.
4. You must seal all of these gaps. I would use Mastic to fill these gaps.
5. Fit Draught Excluder strips on the Attic Access Door.

Reason 2ack of Ventilation in the Attic Void

Surface Condensation on the underside of the felt is generally caused by a lack of Through Ventilation of the Attic Void - vents in the Soffit at the front of the house and also at the rear of the house. Therefore to solve the problem to prevent the surface Condensation of the felt- you need to fit plenty of Soffit vents - back and front.

If you do not know how to do this- let me know.

MildThing84

I had this problem pre xmas. Seems to be fairly common issue! Panicked immediately and feared the worst until i saw others in a similar predicament. The entire attic felt was covered in droplets and naturally enough started to fall onto the in place insulation, xmas decorations, kids xmas toys and my football programme stash!

Had it inspected recently by recommended family friend (insulation co) and it's a new insulation (adequate) and 4 new roof vents needed. Not ideal but to improve energy efficiency etc, going to go for it. Also get a decent grant from SEAI to take the sting away.

C. Eastwood

https://www.boards.ie/discussion/comment/120087561#Comment_120087561

Your family friend did not give you correct unbiased advice.

You received biased advice from a Salesperson who only wishes to take money from you.

Here is free, unbiased, professional advice from a stranger.

Ignore what your friend advised.

Your Attis has a lack of Through Ventilation.

The fact that there is condensation forming on the underside of the felt, indicates that the Attic Void is cold, which means that your Ceiling Insulation is functioning correctly.

You need to provide Through Ventilation to you attic void.

Here is a Diagram from Technical Guidance Document F of the Building Regulations.

If you comply with this it will eliminate the surface condensation in the Attic Void.

A96A1255-411C-4737-8D05-B6AA129777B9.jpeg

From this diagram you can see the ventilation area required at both sides of the roof is an area - the length of the roof x 10 mm.

Say you roof is 12 m long.

For each side:- 12,000 mm x 10 mm = 120,000 mm2.

Assume each PVC round vent gives 2,500 mm2

120,000 mm2 divided x 2,500 mm2 = 48 circular vents at each side.

A Carpenter Joiner could fit vents in the soffit for you.

A soffit and fascia fitter could fit soffit vents for you.

You could fit any types of recommend vents available, but the following 2 photos show PVC Circular vents, which are simply to fit.

FC971E73-1743-4B42-A51C-B7D636E5EAEA.jpeg

E98789BF-DF14-4FE8-BABE-0D34D4D1D516.jpeg

finnyob

We have the same problem as OP and subsequent poster described here. Condensation is always worst during the real cold snaps. The reasons are obvious in our case, no ventilation, poorly laid insulation and bathroom venting into attic space unbeknownst to us.

Seems when original owners got PVC fascia and soffit installed the lads just covered over the original boards and didn't cut out any vents, even though the soffit has vent grilles. There is no vent of any other kind elsewhere in the attic so airflow in the attic is minimal.

We had the attic floor insulated with ~300mm of fibreglass rolls when we moved in, but the installers did a half assed job of it, and layed insulation over anything that happened to be in their way. So there are plenty of air gaps under the rollout insulation where there was junk left behind by previous owners. Also we did a job on the house last year, so lads in and out of the attic piled insulation out of the way to work, and it didn't get put back right.

Only last week I also discovered that at the same time our builder put a new duct for the vent from the bathroom through the ceiling and ran the duct out to the eaves... then he stopped and didn't bother his ass cutting out a vent in the soffit/eaves for the lovely warm moist air to escape. Side note, I also discovered that the cold water storage tank overflow pipe was left sitting out on the eaves as well. Top marks for laziness there.

My plan now is to do

1. Cut 70mm holes for similar push in vents as C.Eastwood has linked above (approx 1 per section between rafters on each eaves - 24 in total)
2. Also cut a hole for the shower vent
3. Get eaves vent trays along the lines of these: https://klober.co.uk/storage/variant_images/Image1-Loft-Vent-Tray-KP965000.jpg to sit right out into eaves to maintain the airgap between insulation and roof to allow airflow through soffit vents.
4. lift all the floor insulation, clear up any debris/junk, fill the various holes in plasterboard and re-instate insulation ensuring it is pushed right out to the vent trays
5. Cover and insulate around and over the water storage tanks
6. Finally I have to figure out something about the trapdoor to provide a better airtight seal, and layer of insulation to reduce heat loss from the landing.
7. Also considering coring and installing 2 vents on the gable wall
8. Also considering lap vents to maintain a gap between overlapping layers of felt, though the felt is old and quite brittle so this may be pointless.

Wondering if guys here have any other comments on or recommendations in addition to the above?

Dr_Colossus

wow some levels of incompetence, laziness and indifference displayed there from multiple different installers and so called professionals. Goes to show if you want anything done correctly you have to do it yourself.

Good looking plan above and in relation to point 6 depending on what sort of access you have with a loft ladder, stira etc an insulated hatch cover (something like the below) could work well. If just a straightforward hatch with no attached ladder or other obstacles then it's much easier insulate with some PIR board.

https://www.irishinsulationdirect.com/attic-stairway-insulation-cover.html

Let us know if you get easy and reasonably priced vent trays as in point 3. I looked for these a couple of years ago and were difficult to source and very expensive. Good thread here on that matter which might be of interest:

https://www.boards.ie/discussion/2058032282/attic-ventilation-baffles

10-10-20

https://www.boards.ie/discussion/comment/120115295#Comment_120115295

They have these in Goodwins:

https://klober.co.uk/roof-ventilation/eaves-roof-ventilation/p/roll-out-rafter-tray

I have a roll myself, but they aren't in place yet. Seems flimsy enough and I don't know that it won't fold closed under compression from the insulation.

C. Eastwood

https://www.boards.ie/discussion/comment/120115135#Comment_120115135

What a Plonker of an Electrician to pump Steam from the Bath/ Shower in to the Attic Void. It’s not unbelievable as I seen it in many houses. It must be exhausted to the external air.

Soffit and Fascia Experts - PVC Vents going nowhere. A bunch of Langers. I have also seen this on many houses.

The builder was another Plonker not to exhaust the bathroom vent duct out through the soffit to the external atmosphere.

The Construction Industry is full of totally incompetent morans.

finnyob

My advice on the following as you have listed above:-

1. Yes
2. Get the Bathroom steam out of the attic void immediately.
3. No. Waste of time and money. Push insulation down approximately 40 mm from felt at eaves to allow through ventilation flow from one side of the attic to the other side.
4. Yes. Fill with mastic - all holes around wires of ceiling lights, holes around pipes in ceiling of Hot Press and all pipes passing through the ceiling. Seal around attic access door.
5. See sketch- below. Insulate around and above the water tank with rigid insulation. No insulation under the tank.
6. Yes. And stick 100 mm high density insulation on top of the trapdoor with mastic.
7. No. Not necessary.
8. No. Not necessary.

1BEFA5B1-84B7-46BE-8997-C43A429231E5.jpeg

Dr_Colossus

I looked at those roll out rafter trays some time back but they're very light gauge and designed to be installed as part of the roof build. I decided against them but they could work stapled to to the inside of the rafters where you have them taught enough that any insulation pushed out against them will only go way half to the felt.

finnyob

https://www.boards.ie/discussion/comment/120117333#Comment_120117333

Good shout @C. Eastwood, thanks very much. I suppose just on the eaves vent trays, I'll probably still go with them as they would guarantee that the insulation can't block up airflow. Our attic is very awkward, 25deg slope so access to eaves is difficult for a tall chap like me. The Klober ones I have seen are 20quid per pack of 10 from a supplier in Ballymount, so I think it's worth it for the 60 quid I'd spend.

C. Eastwood

https://www.boards.ie/discussion/comment/120119301#Comment_120119301

Thanks finnyob

Regards

C.