UKC

Our house had cheap double glazing put in very badly just before we bought it. The sealant strips all around each window grows black mould each winter as a result of condensation on these cold spots. Is there anything I can do to stop this without taking the windows out? Is there, perhaps, some kind of insulating sealant I can buy to put an extra layer of sealant around each window without taking them apart? Cheers, Sam

In reply to Sam Beaton:

If you are prepared to take the plaster off on the inside, expanding foam will do the trick.

Squirt it in, leave, cut off the excess and make good, although it will probably always be a cold spot in reality.

Steve D

In reply to SteveD:

Steve is rite, id suggest also making sure the window is sealed correctly on the outside. Window reveals, (in fact all around windows and doors) are notorious for cold spots. Very often causing black mould, when ventilation isn't adequate enough.

In reply to xplorer:

Is it obvious if windows are not sealed properly on the outside (sorry for the dumb question but I don't know much about DIY!)?

In reply to Sam Beaton:

Is it sealant between the frame and the wall (mastic or plastic trim) or the frame and the glass (rubber trim) that grows mould?

Whichever it is the only way you'll realistically stop it condensing and getting mouldy is by reducing the humidity, either locally by increasing ventilation with trickle vents, or in the room as a whole (fan, dehumidifier, remove drying rack...). Or by wasting heat keeping your windows warm all night. Regular bleaching will help suppress the mould.

If the frames are cold you could perhaps remove and sacrifice one to work out where to drill to inject PU foam into the remaining in-situ units but it really won't be worth the effort.

Most of the heatloss from my crappy old double glazing is from tired compressed seals and non-adjustable locking mechanisms (cheap cheap... also crap). At least the drafty seals mostly prevent condensation. Every cloud has a silver lining

jk

In reply to Sam Beaton:


Yeah, there'll be gaps around them either where the silicone sealer has pulled away from the brick or was never applied.

jk

In reply to Sam Beaton:

If you put your hand around the frames on the windows and doors, inside the house, can you feel the wind/air coming through?

In reply to Sam Beaton:

I had a similar problem when some cowboy installed my windows at my last house without sealing them into the walls properly, so I just got draughts round the frames. I have a picture of some climbing rope tied around the frame on one window! Unfortunately, the company had gone out of business, but the install was insured with a 3rd party company, who did the remedial work.

Check if the installers insured the work - should be transferred to the new owner, i.e. you. Might still be valid and you could claim?

The guy that came to fix them took off the outside trim strips, applied a lot of assorted sealants and re-glued the strips.

In reply to Sam Beaton:

There are no draughts, just cold spots where I can feel dampness from condensation when it's really cold outside.

Can one retro-fit trickle vents? Is it worth adding another layer of sealant inside (in summer, when bone dry, and when I've got rid of all the mould)?

I will also have a look at the trim strips outside when the weather is better and think about whether it is worth taking them off and seeing what is behind them.

In reply to Sam Beaton:

You will probably find that behind the trims will be hollow. If they are use some expanding foam, if there is lots of space you could possibly try actual insulation, don't pack it in though as it will loose its insulating properties.

Your best bet would probably be a few tins of expanding foam.

In reply to Sam Beaton:

Expanding foam has very good insulative properties so if you can get at the gap around the windows from either side it would solve your problem. Its usually used when windows are installed anyway (if done properly).
I'd recommend the low expansion type though http://www.toolstation.com/shop/Adhesives+Sealants/Expanding+Foam/Exact+Gap...
Normal expanding foam really does expand and not straight away so you can be lulled into thinking you need more. This stuff still expands but nowhere near as much. Either of them stick to anything though and can only be scraped off when dry so be careful and cover everything, its a pig to get off.

In reply to Sam Beaton:

Thanks LastBoyScout, pec and xplorer. One final question - what do I fix the trims back in place with?

In reply to Sam Beaton:


Assuming these are uPVC, normally silicone sealant but if you need to paint over whatever you seal the edges of them with I'd use acrylic sealant as you can't paint over silicone (and its more messy than acrylic).

In reply to pec:

yes, they're uPVC, silicone sealant it is, many thanks

In reply to Sam Beaton:

Sounds like there are no cavity closers around the windows, your house is well over 10 years old right?
Fitters aren't paid to insulate/close the cavity with expanding foam or anything else before fitting the window.
Those who say that the fitters "should" have used expanding foam obviously don't know why some fitters use it. Some use it to fix the window instead of using screw fixings through the frame(Bodge job), others use it to fill gaps around the edges before the window is silicone sealed(where the surveyor doesn't know how to use a tape measure)It stops the silicone dropping into the cavity.
There is no quick fix to your problem other than removing the windows and closing the cavity then re-fitting.
You asked about retrofitting a trickle vent, yes you can, but this would go to the top of the glass itself rather than into the frame, this would mean having a new unit made for the window.
Do not, under any circumstances try to fill any hollows in the window frame itself, be it behind the glazing beads or anywhere else, they are made like this for a purpose, that it to help drain any water ingress!

Fitting cavity closers sounds like more work than I want! Wouldn't removing the trim, filling any obvious holes with expanding foam (avoiding filling hollows in the frame itself) be loads easier and quicker and almost as effective?


I've only ever seen trickle vents in frames, not in the glass.....??

In reply to Sam Beaton:

You would need the correct type of cavity closer otherwise you risk bridging the cavity which in all likelihood would cause a whole host of damp problems.
The vent I'm talking about slots over the top of the unit and the bead is replaced so simple to fit it's unreal. Go direct to a glass factory rather than to a window shop/manufacturer who will let you pay through the nose for the materials you need.

In reply to mwr72:

Hmmmmm. This is beginning to sound more trouble than it's worth given that I don't really know what I'm doing. Thanks all anyway.

In reply to Sam Beaton:

another option would be secondary glazing

In reply to Sam Beaton:

Give the foam a go on one of the windows, what have you got to lose ?

It seems a bit bonkers that expensive and substantial heat retaining glazing units are often fitted with big gaps around them which are then just hidden with some trim.

In reply to Jim Hamilton:


I could end up bridging the cavity and causing worse damp problems according to the advice above

In reply to Sam Beaton:

Yes you could. I have the experience having fitted hundreds of windows in my time, both commercial and domestic.

In reply to Jim Hamilton:


It's not the worst job done on this house before we bought it. After our first winter here one bedroom seemed colder than the rest. We called the company who'd guaranteed the cavity wall insulation only five years previously and they agreed to come and drill a couple of holes and have a look. They found NONE in that corner of the house so we asked them to drill a few more holes elsewhere just to check. Turned out there was next to no cavity wall insulation anywhere so they topped it up everywhere for free under the guarantee.