Window film for extra insulation

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

alex robinson

Established Member
Joined
12 Jan 2022
Messages
379
Reaction score
194
Location
Reading
Now the cold weather is approaching, does anybody have any experience of using window film to improve insulation. We have (pretty old) double glazing and the north facing side of the house is always cold and gets terrible condensation. Would one of those add on window films help reduce condensation by keeping it a bit warmer?

I see there are both films that stick directly to the glass, and those that stick to the frames. I assume the ones that stick to the frames conserve more heat, but won't the gap between fill with condensation?

Thanks!

Alex
 
You are meant to seal any internal glazing layer to the frame - seal to the inside and vent to the outside is a worthy principle to avoid misting. But yes if your dg windows are themselves sealed & weatherstripped and you apply an extra internal layer, there's no guarantee that condensation won't occur in the new trapped layer of air. But since the room air will no longer have direct access (if the new secondary g is sealed as mentioned) it should be less than before. It's a fudge and you take a chance.

It's possible that what you're proposing won't have a huge effect. It's an experiment, ok? A slim gap (between old & new) is better than a wide gap that allows wholesale convection circulation within the gap. Maybe the whole wall is cold, though? Which opens a larger can of worms.
 
the surface of the glass is getting below the dew point

the main problem is curtains keeping the window reveal void from getting any room heat.

sometimes the only way to stop terrible condensation is to have a tube heater sat on the windowboard and put on over night -you could try one and see


the only real solution is triple glazing which does mean the inner pane temperature is significantly warmer
 
Many, many years ago, I lived in student accommodation where each 10-foot square room had a floor-to-ceiling window nearly 4 feet wide. Heated only by electricity. Marginally less well insulated than a tent!

I fixed transparent plastic shrink film (can’t remember where I got it), stapled to the timber frame then shrunk tight with a hairdryer. Put a bag of silica gel in each cavity.

Pretty ugly, I’ll grant, but it made a huge difference - I could heat my room!
 
Thanks for that. Sounds as if it might be worth an experiment, but not to get hopes up too much? Seems worth giving any passive option that might work a go before increasing the heating in that room, or putting a window on trickle and letting all the warmth out!
 
the surface of the glass is getting below the dew point

the main problem is curtains keeping the window reveal void from getting any room heat.

sometimes the only way to stop terrible condensation is to have a tube heater sat on the windowboard and put on over night -you could try one and see


the only real solution is triple glazing which does mean the inner pane temperature is significantly warmer
But strangely with triple glazing you can get condensation on the outside, just like on a car
 
But strangely with triple glazing you can get condensation on the outside, just like on a car
yes, in fact that is common on double glazing nowadays - low emissivity coatings and warm edge spacer bars mean external pane stays cold enough for condensation on cold mornings.

When I was making windows I used to get clients being concerned about it
 
I used this years ago in a house with steel crittal window frames and single glazing - it did make a small difference.

The old house we live in now has single glazed windows as well, in the bathroom I have attached twin wall poly to the outside of the windows - this has made a massive difference and is OK, for now, as having obscure glass is fine for this room.

In the long term we will make thermal shutters which will be closed overnight and all the time in bedrooms we are not using, this enables us to keep the nice old wobbly glass but have very efficient windows.

The other thing I have taken a lot of time over is sealing all the windows with good draught excluders - even the smallest draught significantly cools a room on a cold day. When we first arrived we were getting a gale blowing in through the front door and lounge window. 🥶
 
When I worked in that industry, I was always coming across people who were complaining about cold rooms and internal condensation.

The best way to reduce condensation is to increase ventilation. However, most people then complain that it makes the room colder and increases their heating bill.

The thing is, seal a room and heat it and it generally increases humidity and thermal currents: Hot air will be drawn to a cold point in the room (often a window) and the moisture in the air will condense on the glass and cause condensation. It will also draw cold air into a warm space and make it feel draughty.

Low E glass typically has an insulative coating on surface three of a double-glazing unit and this tends to increase the surface temperature of the inside pane. The result is that the window is no longer the coldest surface in the room and the moisture in the air then condenses somewhere else - often a cold wall. This is less noticeable because the surface area of the wall is greater than that of the window - but it still happens.

Filling the glazing void with a denser gas improves the insulative properties of the glazing unit. Argon is a typical example. At one time glazing salesmen sold units on the gap between the panes - 20mm being typical. The last time I looked, the optimum gap for air was considered to be 16mm. With something like an argon fill, a like for like or better performance could be achieved with a 12mm gap. Generally, in replacing glazing units in existing frames you are stuck with the existing stack height - it being very difficult to retrofit thicker beads (in uPVC at least) to compensate for thinner and more efficient units.

Triple glazing, fine in theory and I've had it. I wouldn't have it again, here's why: every double-glazing unit has a working lifetime. Largely a function of sunlight, over time, the seals between the units break down. Once there is an avenue for air to travel from outside the unit to between the panes the glazing unit starts to act like a bellows. Moist air can travel across the gap and the moisture can condense inside. Over time, this leads to misting between the panes. With double glazing you have one set of seals. With triple glazing you have two (so twice the risk). Also with triple glazing, you have a 50% heavier unit, and many installers do a poor job of installing heavy units. If each pane in the glazing unit isn't properly supported when it is packed into place a pane can slip and this causes the seal to prematurely fail. Our previous house was terrible for this - all, luckily replaced under warranty and watched by me during replacement!

In the case of the original poster, firstly, make sure the room is properly ventilated. If the units still condense, then consider replacing them with Low emissivity glass (Low-E). It can be a relatively cheap thing to do and plenty of companies can do it for you. Don't bother to insulate the frames - most have some form of honeycombing which does a passable insulation job and, anyway, the surface area of the frame is small compared to the glass.
 
The ventilation aspect always seems very frustrating. Surely there must be a better way of managing things than just venting warm air outside? I feel it ought to be more efficient circulating air within the house and using a dehumidifier.

I am sure replacing the windows would be a better option, and in a few years we will probably do that. Unfortunately it isn't an option for now, hence the interest in a slightly ugly bodge!
 
My daughter owns a house she rents out and the tenants have just moved out after 6 years, there was signs of mild condensation throughout the house mainly around the upvc double glazed windows caused by (we think) the tenant drying clothes over radiators but not ventilating the house.
When they moved out we used the opportunity to update things, new bathroom, full redecoration etc. we also fitted a PIV unit on the landing How to Install Positive Input Ventilation Unit
Time will tell if it helps but I have 2 friends that have them fitted in their homes and they were both impressed with the results.
 
Now the cold weather is approaching, does anybody have any experience of using window film to improve insulation. We have (pretty old) double glazing and the north facing side of the house is always cold and gets terrible condensation. Would one of those add on window films help reduce condensation by keeping it a bit warmer?

I see there are both films that stick directly to the glass, and those that stick to the frames. I assume the ones that stick to the frames conserve more heat, but won't the gap between fill with condensation?

Thanks!

Alex
I fitted them to my single glazed workshop and it made quite a big difference. Cost about a fiver. Double sided tape fitted to the frame; apply sheet; warm gently with hairdryer to remove wrinkles.
When I redo it (next year probs) I'll take more effort to clean the frame well before applying the tape, and ensuring the film is VERY well stuck to the tape prior to its blow dry.
 
A dehumidifier makes a world of difference. Years ago, we bought one to dry out our new home as it was deliberately flooded by the son of the previous owner (the house was repossessed). After a week we noticed how much warmer the house felt, AND it turned out to be cheaper to get it warmed up.
HTH someone.
 
Back
Top