I had to go up into the roofspace yesterday, and found a considerable amount of condensation on the roof lining and on some objects up there.
The house is 10 years old with cavity wall insulation fitted, the roof space is fibre glass insulated and the house is centrally heated from a gas boiler.
What should I do to cure this? I can't do it myself as I'm 72 years of age, and ladder work is out of the question.
Peter
The answer is venting, either a vent ridge system or vent tiles.
You might find that the insulation has been fitted badly and is blocking ventilation from the soffits. This would have been contrary to building regulations in force 10 years ago. The problem could possibly be reduced by change of habits eg not drying clothes indoors, cooking with saucepan lids on and a cooker hood and ventilation of bathrooms immediately after baths/showers.
Bob
We do have a cooker hood, along with a bathroom/toilet extractor fan. And as for drying clothes indoors, that's not one of our habits. I guess I'll need to get up into the roofspace and see if the insulation is blocking ventilation to the soffits. I can see from outside of the house that there are no vents in the soffits.
Peter
I also noticed water running down the roof lining. To my great surprise, a very well qualified person advised me that it was normal in cold weather and not to worry about it.
Chris R
From memory, The BRs require the equivalent of 25mm gap along the soffits. this can be either a slot or spaced ventilators but to stop the problem of creepy crawlies getting in as well, roof tile manufacturers make a ventilation tray that is fitted in one of the lower few rows of tiles and that has the same effect. Either your roof has something like that or was a non compliant build.
Bob
That=92s what the underlay is there for, a vapour barrier. It should carry the condensation that as turned to a liquid to the eave, but with out a =93over fascia felt support tray , all it will do is collect at the eave and rot the underlay. Most roofs suffer from condensation in the type of weather we are experiencing at the present time. No matter how much insulation you have, there will most likely get condensation. As I stated before the answer is to vent the roof. Venting either at the eave above the insulation height with a few vent tiles or with a dry vent ridge system
I agree with the venting. Condensation is the result of the air in the attic being warmer than the outside air I think, so you certainly need to make sure that the upstairs ceilings have 300mm of insulation quilting above them and with no air gaps. Check also that you haven't got any central heating vents up there which would introduce warm moist air. Don't forget to check that the loft hatch seals well and is insulated. As someone said the weather is unusually cold so it's almost inevitable that your roof space will be a few degrees higher.
For soffits with a large void above (a loft over a flat ceiling), 10mm is the minimum. Vaulted ceilings require 25mm to eaves/soffits & 5mm at high level.
Roofs with most breathable membranes do not require ventilation provided they are constructed properly, i.e., with the felt draped between rafters or counterbattens over, a mimimum 10-25mm gap between the membrane and insulation, and vapour barrier on the warm side of the insulation.
To the OP; some condensation is to be expected in very cold weather. If it's still there when the outside temperature has risen above
5degrees for a few days, then it needs further investigation.
Many thanks for all of the replies. They were very instructive, and as a later poster suggested, I'll wait and see what the condensation is like when the temperature is above five degrees centigrade.
Peter
That is correct re manufacturers' claims and building regulations approval (in England), but I always advise providing 50mm air space under the membrane of new extensions to allow ventilation from the eaves to help combat condensation.
If the condensation is still around when the temperature rises then you might need to provide extra ventilation eg vents is the gables, if you have them.
I tacked a polythene VCL under my loft rafters followed by 4mm exterior ply. The void between the rafters is joined at the ridge so I should be getting airflow from eaves to eaves to. My loft is used for storage which is why I used the 4m ply under the rafters.
A somewhat belated and long winded response, but based on recent personal experience. Agree with all other suggestions, but I'd guess a house of the vintage described probably doesn't have vapour barrier plasterboard ceilings. This didn't matter with the 100mm of insulation that was probably installed when built, because sufficient heat was lost to keep the roof space warm enough to avoid condensation, but if the roof now has current standard circa 300mm insulation, then even with clear soffit ventilators, ridge ventilation, there's a good chance you'll get condensation from vapour migration through the standard plasterboard the builders used for ceilings. I had this in my similar vintage house despite bathroom vents and cooker hoods etc.
Given the recent cold spell condensation might just be a temporary issue, so you might want to wait, but personally I'd rather fix the problem properly than hope it goes away. I've seen condensation bad enough to cause mildew on everything in the loft, and dripping down which is a hazard for the electrics, and I wasn't prepared to let that continue.
If you've looked at the other ideas, you've still got condensation, and the roof is in good condition, then I suspect you probably need a vapour barrier sealant on the ceilings. Not many primer sealers come with guidance on their vapour barrier properties, so I had to contact the various tech support lines. Zinsser tech support were excellent, ICI's was useless (didn't even understand the problem). Zinsser B-I-N primer or Zinsser Coverstain Primer Sealer are stated by their maker to work in this application, have a very good reputation, although they are expensive and relatively difficult to find. I opted to use Gyproc Drywall Sealer, which I could get easily from B&Q (£45 for 10 litres). Gyproc guarantee vapour sealing on bare or skimmed plasterboard, although I used it on previously painted surfaces, and it has done the trick in my house.
Priority areas are bathrooms and shower rooms, but ideally you'd do the entire upstairs ceilings. And not only do you need two coats of primer/sealer, but the surface finish will need repainting with a proper topcoat - the off white colour of the primer/sealer might be acceptable, but you'll never get a decent finish with it.
So, suggested course of action, assuming the roof is in good order in all other respects:
1) Check soffit ventilators are clear of insulation (can you see daylight coming through them?). Also insulation must not push up to the roof at the edges, otherwise air circulation is impeded even if the soffit ventilators are clear. This can be done inside the roof space, but requires a degree of agility. 2) Clean the soffit ventilation grilles. Over time these fur-up with organic debris and this restricts the airflow. It's a tedious job to do this, and if they are zinc expanded metal they are very fragile when a few years old. Probably a ladder job, I'm afraid. 3) Check the loft hatch - must have a good seal round it - use something like the brown or white EDPM self adhesive sealer rather than open cell foam or the like. 4) Check that if you've got a central heating header tank in the loft this is covered, otherwise this could be a significant contributor to the condensation. 5) Apply primer/sealer on all upstairs ceilings. Not a difficult job, but it'll cost you about £50 for the sealer, and about the same again for a new top coat. Do check that you don't have vapour barrier chipboard before stating this - if you've made any holes in it and found a foil layer, that's the vapour barrier, alternatively lift some insulation in the loft until you can find some maker's labelling. 6) If you've still got the problem, then you're probably looking at building work to install additional ventilation, although on a house of the age you describe I'd have thought the designed ventilation would work fine if unobstructed and you've addressed the various sources of moisture.Regards
Led (now the happy owner of a dry and bloody well insulated loft, having had to do each of these steps apart from number 6)
Thanks for that - I shall get some of the Gyproc and put it on.
So far I haven't found any condensation with insulation and boarding, but I open the windows when having a shower and the loft is almost an outside space - soffit vents and the sarking has several holes in it, so the wind does just blow through.
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