Condensation inside my house due to cavity wall insulation??

[Virgil]

Weve lived in this house for a few years and never had any problem with condensation. We had cavity wall insulation put in last autumn and the house was much warmer over the winter. But now the weather has warmed up the house is freezing and today we've come home to wet floors which we think is condensation. Could this be because of the cavity wall insulation?

PigletJohn

sorry vivandtom I don't understand your point.

It's not complex but I can't be buggered.

Right I have arrived home and today I left all the upstairs windows open. This did nothing to improve the security of my home but has made a massive difference to the temperature of the house and there is no condensation in any room apart from the garage. The garage is attached to the house and was also insulated (has a room above it). It is cold in there. The door was left ajar for fifteen minutes there's condensation all over the floor. So it IS the suddenly influx of hot air into an insulated and therefore cold room right?

Certainly sounds like it to me, particularly if the floor was dry straight after the door was opened and then went damp as you looked at it.
If so its nothing to worry about, it'll sort itself out as the slab warms up.

Vivaandtom, I understand your point. It is KS2/KS3 science. If I leave water in a sink/mop bucket in a cold house, less water vapour will be created than if I leave the same water in a warmer (insulated house). That water vapour will then form condensation.

Op, the question then has to be where has all the water in the garage come from to create so much condensation?

If you live in an exposed location or it has rained a lot where you live over the past year, I would suggest it is penetrating damp which is now turning into water vapour due to the hot weather heating the damp in your walls.

Cavity wall insulation is water resistant; it is not water proof.

I particularly noticed that "the house is absolutely freezing compared to outside and the wooden parquet floor in the hallway was covered in condensation"

When you walk into a house that has had a bad water leak, it is strikingly cold (due to some of the water evaporating) and also damp (due to the high humidity caused by the leak).

Since water vapour is lighter than air, under normal circumstances it rises through the house until it either escapes through ventilation, or condenses on a cold surface, typically a window (in cold weather) or a ceiling. Condensation occurs when the amount of water vapour being released into the air increases the humidity so that when it reaches a cold surface it is oversaturated. This is rarely severe in a UK home unless ventilation is poor or the moisture load is excesssive.

It is very difficult to cause condensation to occur on the floor of an occupied house, since the floor will usually be close to room temperature, and, if concrete, is not exposed to the outside air. I was interested to know if the house had been unoccupied for a long period allowing the fabric to cool down, but the empty period was "Only from about seven thirty in the morning until about five in the evening but it was literally like walking into a freezer."

Water from the incoming mains is usually quite cold, and will chill the slab in the event of a leak.

I will watch with interest to see what the cause turns out to be.

Good luck!

Thanks VashtiBunyan - that's exactly my point - but made much better than I did :)

I know nothing about condensation, causes thereof and science etc but......a friend had her house inspected for installation of free cavity wall insulation by British Gas, last Summer/Autumn when many companies seemed to be offering this (part of a Government Innitiative I believe) and she was advised by the chap who came to see her that she should not have this insulation installed as "it may cause more problems than it solves" - something to do with the construction of her house (approx 15 - 20 years old).
Interestingly, a few weeks later she answered her door to a guy who was installing free insulation in the area (and several of her neighbours were having it done) and was happy to sign her up there and then to have hers done.
Needless to say, she declined.

I wonder if it was a timber-framed house?

Yes cavity wall insulation or more specifically poor installation of, can cause damp and I will not have it for this reason.

www.which.co.uk/energy/saving-money/guides/how-to-buy-wall-insulation/cavity-wall-insulation-damp-problems/

yes, as your "Which" link says "It's very rare that cavity wall insulation causes damp, but it's worth checking whether your home's at risk."

If you Google - does cavity wall insulation cause or exacerbate condensation and / or damp - you will get as many people saying yes it does as you will find saying no it doesn't.

The problem is many of the people saying it doesn't cause problems are energy and installation companies who have a vested interest in getting you to put it in.

It's definitely not clear cut.
There is definitely no definitive yes or no answer and hearsay evidence from many householders would certainly indicate it can be a very serious issue.

Frankly, their views would count for more with me than those of installers, builders or tradespeople generally for whom it's an income generator.

Vivandtom - that is my viewpoint and I won't be having cavity wall insulation in my home.

The cavity insulation itself does not 'cause' damp. Injected insulation forms a closed cell foam (as I recall) that vapour cannot pass through. Hence moisture vapour that would previously have permeated out through the walls now cannot and shows up on the inside as 'damp'.

When the walls are insulated in this way the ventilation should be increased elsewhere to account for the decrease in permeability. This can be achieved by, for example, the addition of trickle vents to the windows.

The injected plastic foam has not ben used for many years. It's all fluffed up mineral wool or glassfibgre now. It is permeable.

Well, may be I'm wrong there then. But I'm highly unlikely to ever spec it for anyone, so not up to date.

Ok my first question stands. Can cavity wall insulation cause internal Damp problems? The insulation is the wool stuff. I have read that the water can enter through the external wall and be carried across the cavity since it is now stuffed with the wool. The wool gets wet and damp problems result.
Condensation problem not reoccurred by the way so did seem to be the hot moist air hitting the very cold air in the house.

Erm... What?