This might be worth reading before you add extra insulation to your loft.

SuzieSue

http://www.telegraph.co.uk/finance/property/advice/11333991/Why-is-there-condensation-in-my-loft.html

escapee

Thanks for the post Suziesue

Sadly this is what we're now experiencing since we had cavity wall insulation and extra loft insulation installed several years ago. Prior to the install the house was fine but after the install, moisture was dripping off the felt in the loft - I've just about remedied this by moving the insulation away from the eaves, this has helped tremendously.

The main problem now is cavity wall insulation, external bricks are showing lots of problems with 'efflorescence' which is where the salt seeps through the bricks and throughout the period of late September to late March, ALL upstairs windows are completely saturated with condensation on the inside and I have to squeegie them every morning, removing approximately a quarter of a pint of water from each window. I've noticed this year some windows are showing signs of mould caused by excess condensation - I battle this with bleach water which helps for a week or so until it begins to reform.

We NEVER had any problem with the house prior to the installation of cavity wall/extra loft insulation and it seems we will continue to experience this for the remainder of the time we live here (house was built 1940s and we moved in mid 70s). I am just hoping it doesn't get worse with age.

I would now warn anyone considering cavity wall insulation to read the online stories of endless problems and seriously weigh up the facts before deciding whether to have this or not.

jeallen01

I have a 1920's terraced house with solid walls, and about 100mm rock wool above the ceiling, and later added solid insulation (60mm Cellotex with foil on either side, between the eves joists - but left about 1200mm uninsulated at the lower, ceiling, edge all around the roof, although I did fill the gap with rock wool which stops the draughts but still allows air to circulate through it.

When I had a a GDF assessment last November, the assessor said that I had done exactly the right thing because to completely seal the sloping part is the "right" way to cause condensation in the roof void - and I have never had that since I insulated the eves.

NB: the slated area is not felted and so there is enough air coming past the slates to ensure that the roof space is properly ventilated, but not enough to ruin the insulating effect - and the house is a LOT warmer than before I did the insulation in the eves


PS: My attic roof space is now relatively warm and as dry as the proverbial bone (always has been), and so I think one of the best things to do, although not covered by the insulation grants, is to put the insulation between the woodwork that supports the slated area - rather than immediately above the bedroom ceilings, or else in addition to the latter - but DO leave an airspace ("building regs appear to specify a min of 50mm) between it and the felting.

Also, before fitting that insulation, consider having one or more small vented areas put into the top and bottom of the slated areas so as to allow air to flow through that space and ventilate it. (I did not need that because my slates are fitted onto wooden boarding, and there is no felting - and that used to result in horrendous drafts, and a lot of dust (!) in the attic)

jhs14

escapee wrote: »

Thanks for the post Suziesue

Sadly this is what we're now experiencing since we had cavity wall insulation and extra loft insulation installed several years ago. Prior to the install the house was fine but after the install, moisture was dripping off the felt in the loft - I've just about remedied this by moving the insulation away from the eaves, this has helped tremendously.

So the problem was lack of ventillation, not the insulation per se.

ALL upstairs windows are completely saturated with condensation on the inside and I have to squeegie them every morning, removing approximately a quarter of a pint of water from each window. I've noticed this year some windows are showing signs of mould caused by excess condensation - I battle this with bleach water which helps for a week or so until it begins to reform.

Again, that's hardly the fault of the wall insulation. Because the walls are well insukated, the condensation is concentrated on the windows rather than spread out across the walls as well. It's because the windows aren't insulated enough - are they double glazed?

jeallen01

I might also add that my house is a weird shape - a end-of-terrace with FOUR outside walls of roughly similar length (so the floor plan is pentagonal!) and it was very cold, and did suffer condensation on many walls until I dry-lined it in the late 70's - and also blocked up all the fixed wall air vents that let gales blast through the house.


Since doing that, and double-glazing all the windows, we have never had much of a problem with condensation, except very occasionally, on cold mornings, in the bathroom when someone has had a hot bath, or in the kitchen when some steamy cooking has been done - in fact, with the gas c/h running, the problem can sometimes be that the air is TOO dry - so the insulation is not the cause of the issues here.


Another example: for a few years in the late 80's I also had a small 1960's brick-built end-of-terrace house in Bristol as I was working there for a time (a long story!) and that was very cold the first winter and regularly had condensation on the inside of the exterior walls. However, after I had rock wool cavity wall insulation installed, the house almost instantly became much warmer and dryer (and that was over a very cold Xmas period when the work was done). That also had about 200mm of loft insulation and secondary double-glazed windows - and never suffered from condensation after all that work was done.


By comparison, my mother's very old Cotswold stone cottage in Oxfordshire was a "damp magnet", and the wooden window frames literally rotted out from the inside due to condensation on the window panes - much less of an issue after the wooden windows were replaced by d/g UPVC!


So the problem is not insulation as such but how you approach the whole subject of adequately insulating, ventilating and heating a property, taking into account the structural design - and making sure that the windows are very well double glazed. If you don't do the latter, then the air in the house itself will get warmer because less heat escapes through the walls but will adsorb more moisture than before, which, of course, is then released when the air strikes the remaining interior cold surfaces, which are generally the windows, and cools again!


BTW: and in that respect, IMHO, secondary glazing is less effective than sealed glazing units because the warm moist air inevitably gets past the secondary panels and contacts the exterior glass and cools - and the condensation thus occurs on those.

esmerelda98

Government and industry advice implies both loft and cavity wall insulation are 'no-brainers'. The fact they carry risks is rarely mentioned. No-one discusses what you do if the cavity insulation gets wet as it might with a leaking gutter or drain and what the costs are. And claiming on CIGA seems nigh on impossible.

I have single glazing and had a localised damp wall problem which I couldn't figure out. Did the assessor care that my very old house might not be suitable? No. When we later opened one of the walls we discovered a load of debris his survey hadn't picked up - hardly a rarity and not a ringing endorsement of the survey process.

It seems that in the push for better insulated homes some are 'sacrificed', in that most people will have warmer homes but some will suffer significant problems which they weren't warned could happen and often-times no-one in the industry will admit are real.

jeallen01

esmerelda98 wrote: »

I have single glazing and had a localised damp wall problem which I couldn't figure out. Did the assessor care that my very old house might not be suitable? No. When we later opened one of the walls we discovered a load of debris his survey hadn't picked up - hardly a rarity and not a ringing endorsement of the survey process.

It seems that in the push for better insulated homes some are 'sacrificed', in that most people will have warmer homes but some will suffer significant problems which they weren't warned could happen and often-times no-one in the industry will admit are real.

OTOH, my assessor was recommended by the guy at the company that is likely to do the external solid wall insulation that I hope to get via the GDF on two walls, and he was very good indeed - spent a lot more time on the survey than I had anticipated and made some very useful comments.
I live in W. London, so if anyone needs his contact details then please PM me.

Gloomendoom

jeallen01 wrote: »

By comparison, my mother's very old Cotswold stone cottage in Oxfordshire was a "damp magnet", and the wooden window frames literally rotted out from the inside due to condensation on the window panes - much less of an issue after the wooden windows were replaced by d/g UPVC!

Our house is hundreds of years old with thick stone walls and single glazed timber or metal windows. The loft insulation is 12" thick.

Condensation in the house isn't a problem. There is a humidity meter in the loft that I can monitor from downstairs and, while humidity levels are usually higher than I would expect, I've not noticed any evidence of actual condensation.

jeallen01

Gloomendoom wrote: »

Our house is hundreds of years old with thick stone walls and single glazed timber or metal windows. The loft insulation is 12" thick.

Condensation in the house isn't a problem. There is a humidity meter in the loft that I can monitor from downstairs and, while humidity levels are usually higher than I would expect, I've not noticed any evidence of actual condensation.

Thick old stone walls can be very good for insulation because of the sheer mass of poorly conducting material in them.


However, they can also be very poor for damp issues if the underlying ground tends to be damp for a large portion of the year - that was the case with my mother's cottage - unless an impervious damp-proofing solution has been injected into them (and that does not always guarantee total success). This is especially true where a lime-based mortar has been used, and/or the centre part of the wall is just fairly loose rubble piled in between the outer layer of harder stone, because those types of materials are porous and hygroscopic.


There is also the related issue that, unless the floors are very solid and with a damp-proof membrane properly installed, the dampness can come right up through them (as it did in the cottage).


Either way, a lot of moisture can get into the living areas (I know, I battled with it in that cottage for nearly 30 years because we did not have enough money to get it dealt professionally!)


So, if the house is on well-drained sub-soils then you may well be OK, but, if not, then you may well have "problems".


PS: It was for those very reasons that I checked VERY carefully for signs of damp when I bought my current house - but I completely missed the fact that the walls were of the solid, and not the cavity, type :-(

r2015

Because the walls are well insulated, the condensation is concentrated on the windows rather than spread out across the walls as well.

That is what I have found as well, the cistern also has more condensation on it after a bath or shower.

I ended up fitting an extractor fan in my bathroom.

escapee

jhs14 wrote: »

So the problem was lack of ventillation, not the insulation per se.

But why don't the companies who fit this know the procedure, I remember the young lad sent to do ours and recall him saying he hated the job, especially in the summer months. I think companies are latching on to this for quick profit and not considering the customer and any future problems.

jhs14 wrote: »

Again, that's hardly the fault of the wall insulation. Because the walls are well insukated, the condensation is concentrated on the windows rather than spread out across the walls as well. It's because the windows aren't insulated enough - are they double glazed?

Our windows are double glazed yes, I can't speculate as to why we get condensation now and didn't beforehand. All I know is that the house feels colder (as though cool air is now trapped internally) and if I knew then what I know now, I wouldn't have had it done. I advised my next door neighbour of this when he was approached about three years back, he ignored my advice and now complains of the same issues (house feeling cooler and damp). The neighbours living across from me have moisture dripping down the internal walls in the winter time, they've had professionals out to investigate and feel the problem is something to do with the insulation in the loft but haven't yet determined a remedy.

All houses were perfectly fine prior to the Government initiative to make homes more 'efficient'.