secondary glazing for reduction of condensation ?

[88V8]

Mmm, condensation. No problem in our previous 1920s house where the RH was 30/40% and we had gfch. Not even a problem on northerly single glazing.
Then we moved.
Our C17 cottage is inherently damp. No dpc nor dpm.

Our single glazing often runs with water, the Karcher window vac is well used. Worse to the north.
We do have some conservation dg in wood frames, air gap quarter inch. It mists a little.
Also have some secondary glazing, successful to the south, less so to the west and not at all to the north as it mists internally.

13C is too cold. Cold air cannot hold much water vapour, so it readily condenses. We heat to a baseline of 60F/16C with storage rads.

Humidity, we measure in every room. 40/60% RH is considered a 'comfortable' range. In autumn, we will be near 70%, but by this time of year, with two woodburners going in the evening, it has pulled down to about 50% which is as low as it will get. Healthy draughts around windows and doors ensure good inwards ventilation, and I keep the woodburner dampers open when not in use so there is always some air going out.
Extractors in kitchen and bathroom.

We run two dehumidifiers full-time in winter and overnight in summer. Ebac 2650 condenser models. They pull the rh down about 10 points.

So.... what to do... north windows will always be prone to condensation. Heating units beneath the windows will help, even if its only those tube heaters one uses in the greenhouse. Keep the temp at 60F or better. The room needs some ventilation, preferably an open fireplace.
You will never get payback on the cost of triple dg, but it would help with the condensation.
Put an Ebac in there and just let it run on auto. They are cheap to buy, here you are, £220.
https://ebac.uk.com/product/2650e-dehumidifier/
Ours each suck about half a gallon a day; lime-free water, good for the car's cooling system, and pot plants.

V8

[malakoffee]

Thanks all - much to consider in a real-world system.

The cheapo, LCD hygrometers ( I bought a pair ) are proving that "you get what you pay for".
Side-by-side the relative humidity % readings vary between 10% - 6% between them.

Neither of them have dipped below 70% in the two rooms on the north-east side ( unless the woodburner gets going ).

In a way I think I already have some dehumidifiers . . . . i.e. the panes of the windows themselves !!! Running cost £0

I think I might try to prototype triple glazing by adding 4mm acrylic sheets to the most condensation prone window panes.

[kempiejon]

Calcium Chloride, a handful inside the end of an old pair of tights suspended in a plastic bowl to catch the water was excellent at drying out a slow leak I found in the cupboard under the stairs and I have subsequently used it to pull condensation out of the boot of my car after using it transport wet carpets and cardboard to the dump. I got a about 2 pints out the cupboard in a couple of days and under half a pint from the boot in a week.

https://www.amazon.co.uk/Moisture-Absor ... lp_pl_dp_8

[UncleEbenezer]

Someone said that maintaining the internal temperature at 13C is not good for the fabric of the house but it would not be good for many people either. I am surprised that the OP needs a guest bedroom.

I would think that the internal temperature has a great deal to do with the high level of humidity. I must say I never have any and nor do I open my bathroom window very much but I do have a good extractor fan when using the shower. The internal temperature in my house is usually at least 21C. It is now 3.15 pm on a rather cold Sunday afternoon so I will now go and light my logburner.

Dod

My house is currently at 13 degrees. On a cold day it can get colder than that. It only gets warmer when the weather does, or if I have guests who need it. The window in my bedroom and french window in the living room are both north-facing.

No condensation problem whatsoever. Not even (to my surprise) in the two bathrooms, both of which are internal with no windows: one has a shower cubicle, the other a whirlpool bath.

I did have a problem in the kitchen due to defective plumbing. That was back in the autumn: plumber came in Oct/Nov to fix it.

I do have (and recommend) a dehumidifier. I bought it for my previous house, where I felt the damp to the extent that it wasn't doing my health any good (despite the fact that I moved there in early May, so it was much warmer), then discovered how great the dehumidifier was for drying clothes as well as discouraging whatever growth had been bothering my breathing. I've just got a new one since the old one died, and am using it to blitz the kitchen for any remains of autumn, particularly in the floor.

I also recently bought a cheapo hygrometer. I'm not convinced of its accuracy, but it tells me the RH is around 70% - which is OK - reduced to 60% (nice) by the dehumidifier, and at one point to a very dry 51%, which had me constantly needing another glass of water. In my bedroom with the window open it's currently a comfy enough 67%.