condenstation on upvc windows

[stayclean]

hi ask by a customer to have a look at a problem she was having with condenstation on all her windows inside the property.
the windows were fitted 7 years ago using internal beaded upvc with 28mm sealed k glass units fitted
all windows have been trimmed around inside and silicone on the outside,
windows have been badly measured there around 12mm gap between brickwork and upvc frame hence a lot of silicone.
also all internal window sills are all loose .
i did notice the house was warm house
any ideas

 

[JohnD]

condensation on the inside glass you mean?

I bet she drapes wet washing around the house and over the radiators

If she refuses to stop, no-one can help her.

 

[Richard C]

As JohnD; most likely cause is poor ventillation, inadequate or no extract fans in kitchen/bathroom/utilities & drying washing inside the house.

An internal water leak or damp will also cause high ambient humidity levels.

 

[Alastairreid]

And no trickle vents

 

[stevethejoiner]

Your post seems to imply that you think the window installation may be the cause of condensation. This will not be the case unless as previously mentioned trickle vents have not been installed in the PVCu window heads. This is now a building regulation requirement with replacement windows unless the property has whole house mechanical ventilation, such as a heat recovery unit.
One of the objectives of replacement windows is to seal up all the draughts, and properties that have never suffered with condensation before, all of a sudden start to get damp as there is no air circulation.
You should investigate the source of the moisture.
Ask questions like;
Have they only suffered with condensation since the windows were originally fitted? if the answer is yes, you may have found the cause, THEY MUST VENTILATE. If it is no and the condensation is a recent problem have they started using propane or butane heaters?
Have they changed their heating regime? Warm air will hold more moisture than cold air so having heating timed to come on only for a few hours during the early am and again in the evening, allows the house to warm up and hold onto the humidity. Then when they go to bed, the house cools and the air dumps its moisture onto the coldest surfaces.
If you think that may be the case, suggest having the heating on for longer periods but at a lower temperature setting and have a small amount of air changes by having a some small fanlights ajar.
That sounds crazy, but its healthy for the occupants as well as the fabric of the dwelling.

Steve.

 

[JohnD]

I don't think he's going to answer.

 

[Richard C]

This is now a building regulation requirement with replacement windows unless the property has whole house mechanical ventilation, such as a heat recovery unit.

I don’t disagree with the rest of your post but that’s news to me! I know many B Regs. were updated in Oct 2010 but, for my benefit, can you enlighten me with links please?

 

[stevethejoiner]

This is now a building regulation requirement with replacement windows unless the property has whole house mechanical ventilation, such as a heat recovery unit.

I don’t disagree with the rest of your post but that’s news to me! I know many B Regs. were updated in Oct 2010 but, for my benefit, can you enlighten me with links please?

I will do that asap.
We are building such a house at the moment. Totally air tight. No tile or window vents. Heat recovery unit in the loft, all wet rooms ventilate to the unit, moisture is removed and piped by 6mm drip pipe to eaves, cold fresh air is brought in from outside to recovery unit and mixed with the now warm dry air from wet rooms, and ducted to lounge and bedrooms etc.
Even the tumble dryer outlet will be run to the heat recovery unit.

 

[Richard C]

I will do that asap. We are building such a house at the moment. Totally air tight. No tile or window vents. Heat recovery unit in the loft, all wet rooms ventilate to the unit, moisture is removed and piped by 6mm drip pipe to eaves, cold fresh air is brought in from outside to recovery unit and mixed with the now warm dry air from wet rooms, and ducted to lounge and bedrooms etc. Even the tumble dryer outlet will be run to the heat recovery unit.

Erm I think that's possibly for a new build ; different rules apply to replacement windows in an existing residental building but I’ll await your response with genuine interest.

 

[stevethejoiner]

I am not a building control officer but I do not think it is only relevant to a new build, although installing ventilation duct etc in a new build is easy whereas a retrospective installation is almost impossible, that's why trickle vents are used on replacement windows.
I was not implying that you can just install some type of heat recovery in the loft without ducting in my 1st reply, I was simply saying that trickle vents are the only option to ventilation. In fact you could replace windows without trickle vents but then if you could not install a heat recovery system you would have to install some kind of ventaxia ventilation in every room.

I have looked into the regs and cannot find the words "if you install heat recovery unit you do not require trickle vents"
But,
Right back to the 2000 Approved document F page 5, it states: Means of Ventilation: The Requirement: There shall be adequate means of ventilation provided for people in the building.
On page 11 of F1 Section O, General Guidance it defines types of ventilation and in section 0.10 it says "Types of Ventilation "buildings are ventilated through a combination of infiltration and purpose-provided ventilation.
It defines them as:
Infiltration is the uncontrollable air exchange between inside and outside of the building by a wide range of air leakage paths in the structure.
And says:
Purpose-provided ventilation is the controllable air exchange from inside to outside of a building by means of a range of natural and/or mechanical devices.

The later 2006 and 2010 documents simply clarify and confirm ducting sizes etc.

So as I see it when we replace old draughty windows with air tight replacements we have to install a Purpose-Provided ventilation system and that can be in many forms. One being trickle vent the other heat recovery. But we don't both or you would be defeating the object of the heat recovery idea.

 

[Richard C]

Replacement windows in existing dwellings do not require trickle vents & never have. They are a good idea but are only compulsory in new builds, which includes extensions, or if they were fitted previously. The B Regs update in 2010 didn’t change this as far as I can see & the only requirement for replacement windows in existing dwellings is that you don’t make the situation any worse than it was before.

http://www.planningportal.gov.uk/uploads/br/BR_PDF_ADF_2010.pdf

Check out section 7 for existing dwellings, page 38 & clauses 7.3 - 7.6 in particular.

Interestingly you do not require fire escape windows either; similarly only that you don’t make the situation/provision for escape any worse than it was before but, again, it would be wise to make provision.