The photo shows the big bay window on the north-east side of the house. The total span of the bay is about 5.5 metres. The height of the glazing is 1.5 metres.

The existing double glazing was fitted in 2002 approx. The closest room is used as a bedroom. the furthest room is a guest bedroom = storage.

Current challenges :-
These bay windows are badly affected by condensation during the winter. Fully closing the blinds and curtains makes it worse.
During the summer I have to keep the blinds and curtains closed to minimise the solar gain. ( Up until around
midday in mid-summer ).
I used to like the open feel of this huge bay window, however since the new neighbours have arrived, with their "more active" lifestyle I would be quite happy to close down the panoramic aspect.

Possible responses :-
- Do nothing : sell up and move on
OR
- Replace the existing window units with triple-glazed units
OR
- Replan the glazed areas and infill the rest with highly insulated walls. ? How to estimate an acceptable amount of light i.e. How big/small the new windows ?

Additional :-
Either side of the bay windows the corners are cold corners. The internal wall surfaces are prone to ( mild ) mould growth.

Any thoughts or guidance would be appreciated.

Posted By: malakoffeeI used to like the open feel of this huge bay window, however since the new neighbours have arrived, with their "more active" lifestyle I would be quite happy to close down the panoramic aspect.

Possible responses :-
- Do nothing : sell up and move on
OR
- Replace the existing window units with triple-glazed units
OR
- Replan the glazed areas and infill the rest with highly insulated walls. ? How to estimate an acceptable amount of light i.e. How big/small the new windows ?

Additional :-
Either side of the bay windows the corners are cold corners. The internal wall surfaces are prone to ( mild ) mould growth.

Any thoughts or guidance would be appreciated.

Have the new neighbours caused you to think about moving house other than for the reasons mentioned. If not it's quite drastic to move house for the sake of altering the windows.
Are the walls insulated, if not, is that causing the mould or are the curtains preventing ventilation and is that causing mould to form.
I don't think triple glazing is going to help at all.
If your 'active' neighbours are on your left and can see into the room through the corner of the bay you could replace the angled area of glazing with insulated wall which wouldn't greatly decrease the amount of light entering the rooms.

Posted By: malakoffeeIf I could find a plot I would love to build a super-insulated eco-home

wouldn't we all !

however, for the vast majority, the art of music is in eco-renovation...

gg

A few thoughts, that may/may not be helpful...

Re. altering the glazed exterior, is the bay an original? It looks like it might have been increased in area at some point (esp. as wall internal room divider wall depth captured in window mullion).

If it has been altered, are there any other same/similar houses locally, that still show the original design? Perhaps you could take it back to the original if that's the case (visually) but employ current insulation/construction techniques to reduce the heat loss??

I have a bay window type and just about to do the same thing - I have strapped out all of the walls and about to insulate with PIR slabs 125mm thick. I will tape all the seams together to provide a vapour control layer (ensure you rub the tape down) but, for belt and braces, I will apply an air tightness membrane and then I will plasterboard over the entire area. That will all be plastered to further enhance the air tightness. You could maybe look at running a dehumidifier (I am) to draw out some of the moisture prior to insulating as you don't want to be locking any moisture in there (interstitial condensation). Incidentally, my rooms are down to bare brick wall. So, when I install my new very low u value triple glazing, I will be sealing them in with air tightness membranes and tapes.

Not your area, I think but may be helpful:

https://www.newforestnpa.gov.uk/planning/frequently-asked-questions/guide-types-alterations/

Yes, you can get windows with excellent frame insulation - PH or better standard - but they do cost more money!

Your window area does look to be high, especially with a NE aspect.

Update :

Increased Privacy :
6 metres of yew hedge now planted alongside the boundary with neighbour - although it will take a couple of years before it grows up above the height of the garden wall. . . . patience . .

Experimenting with the overlarge bay window :
I'm experimenting to get some idea of the benefit of replacing the double glazing with triple G.
I have fixed, with magnetic tape, large acrylic sheets across a couple of the large panes.

There is still extensive condensation on the room-side of the acrylic sheets. The volume of condensation is significantly reduced.

If I had I spent a good deal of money buying 3G, then seen the condensation issue still outstanding I would have been very disappointed.


I speculate that high relative humidity in the house : 80% @ 13 degC is most probably due to the damp penetrating the oversite (rough) concrete ( no DPM ). From the subfloor the water vapour proceeds through the insulation jammed between the floor joists : 40mm of PIR + rockwool loft insulation. Finally, round or through the chipboard sheets into the living space.

Notice that there is no vapour control/block layer in the floor sandwich. Do I need one ?

Alternatively, dare I block the airvents and fill the subfloor space with expanded polystyrene beads . . . . . bearing in mind that the oversite concrete shows some dark damp patches after heavy rain ?

Posted By: djh
Another way of looking at it might be to say that the high humidity is due to a combination of too little ventilation and perhaps too little heating. 80% is not a good humidity to have inside your home. It can result in all kinds of problems that can eventually affect your health.

+1

Target humidity levels are 50% ±10%

Posted By: GreenPaddyI think 80%RH @13oC is approx 50% at 21oC. See what transpires when the house is closer to 20oC for a while, and occupied (I'm assuming it's unoccupied at 13oC).

This house is full-time occupied by one eco-mentalist. . . . me !
Thanks, that is a useful comparative RH figure and certainly corresponds to the complete disappearance of condensation as soon as the internal temperature rises a couple of degrees in the spring.
? Why don't I turn up the temperature ? -> Are we not facing a severe climate emergency ? Is it not encumbent on every individual to do what they can to cut their fossil fuel CO2 emissions ?

13degreesC is no hardship to me. I'm comfortable in my long-john & pullovers. Fully fit & healthy . . . . . and deeply suspicious of Minimum House Temperature recommended by bodies such as NHS, etc.

? How did we ever survive the winter, for tens of thousands of years before central heating ?

Posted By: GreenPaddyAs to potentially being disappointed with triple glazing, because you got condensation on secondary glazing, not sure that's a logical extrapolation.

. . . . but I think it does give an indication that 3G alone may not solve the condensation problem.

I would prefer to keep the winter internal temperature of the house low but to lower the Relative Humidity.
Better sealing between underfloor and living space is a proposed improvement.

Malakoffee, great that you're making efforts to minimise your impact on the planet. Something occurs to me, and this is just something to ponder...by keeping the house at a cooler air temperature, the surfaces inside the house will be at an even lower temp, things like wall junctions, lintels, timber parts of the structure, and of course glazing.

There will often be times when moisture is able to condense on these cold surfaces, whether that moisture is liberated by yourself/cooking/bathing/etc, or moisture from outside as our weather jumps from 0oC to 15oC day by day, and warmer humid air comes in from outside and finds those cold surfaces.

Those "surfaces" may be not necessarily on the visible surface (like a window, or skirting), but may be inside the house structure.

So where am I going with this?? Well, just to raise the possibility that by reducing your carbon footprint a little by reducing heating, you "might" possibly, inadvertently be causing a deterioration of the building fabric, which would of course have a much bigger carbon footprint impact.

Just putting it out there for your consideration

13C does seem too cold as recent posters advise and increasing is likely beneficial. Reducing water vapour added to air and increasing ventilation rate are other things to consider.

If you increase temperature by 5C then it air holds about 35% more air from 0 to 30 C range.
It is quite a dramatic increase. Or for each 10C rise the air holds about double the water.

Cooking, breathing, laundry and life generate moisture and the air mops it up till it is full and then it drops out on cold surfaces some visible and some not. If air is cold then with same amount of water in the air it is closer to condensation point (100 % RH)

Increase ventilation on cold days when air is dry and cold and sweeps away all the moisture in the house air

If it is raining (100% RH) 13C inside and out, all you can do to get RH down inside the house is heat it up and warm up all the cold stuff that the water can condense on.

Posted By: malakoffeeI have to burn more fossil fuel

Well no, it can be renewably generated electricity if you'd rather.

I sympathise with your wish to make do with a low room temp. Re de-humidifiers, I'm told that you would need the dessicant sort to work well at 13C. They cost a bit more and maybe use a bit more power but you would get that back as a heat input, plus I presume heat from the phase change from vapour to liquid of the water collected.

Incidentally, aircon units aka heat pumps come with a dehumidifying setting, but in my experience only work at temperatures above 16C.

Posted By: bxman" the DPCs are level or sightly higher (!) than the internal floor level."
How could any house have been built like that ? . . . . if that is not the problem . . . I think you have to find out why the R.H is so high

DPC is AT internal floor level on three sides & higher on one side . . . with a discontinuity at the two points of change !
I don't think that it's a major problem . . .but probably doesn't help in the overall situation.

The larger problem :-
This house was built too low w.r.t. ground levels + it sits in a slight dip in the local topography.
During heavy/prolonged rain the water table can rise to the surface.

When I bought the place the oversite concrete was 20cms below the outside ground level on three sides.
I observed large dark patches of damp on the oversite corresponding to heaviest periods of rain ( in 2012 - if you remember that year ). No water penetration though.

First major works (2012) : french drains down to foundation level on the three sides : periscope vents all round to vent the underfloor - where none existed before ! : very large new soakaway : insulation between rafters.

This has all made a previously damp wreck very habitable.

However, the fundementals are perhaps a bits inadequate for my extremophile living requirements.

Posted By: bxmanIn the areas where you get the condensation is the temperature stable over the 24 hours ?
Are those areas at a lower temperature due to a thermal bridge ?

Pretty stable - North-East side of the house. The corners beyond each side of the bay are cold corners. Condensation observed on the underfloor inner-leaf brickwork.

Posted By: bxmanWhat type of heating are you using ?

Gas CH + occasional woodburner on colder evenings

Posted By: bxmanHow do you dry your laundry ?

Outside only !
Kitchen & bathroom have powerful inline fans - which are used diligently.
Microwave oven & breadmaker in garage to keep those steam-generators away from the house.

Nothing wrong with 13 deg most of my house is there or below during winter.
Just so long as you have minimal air movement .

my R.H. is nearly always between 40 & 60

80 is absurd.


have a look at

https://www.youtube.com/watch?v=TIDb-pdOnXM



Do you have a water meter?

if so turn everything off and check the meter stops dead.

" the oversite concrete shows some dark damp patches after heavy rain "

Is that area within the house itself ?

"The existing wall cavities are filled with some sort of paper-fluff "

and how damp is that ?

Get some out and if it is not bone dry think about having it removed .