Window insulation

[Joeboy]

There was, once upon a time a DG factory in Wales who supplied a huge amount of DG to the trade. U might have to hunt a bit and pay a little more for a circular DG unit. All is possible via the net. Exciting!

[spread-tee]

Or get a small pack of silica gel and conceal it within the gap between the DG unit and you leaded light, if you seal it well it could last for years.
If it were mine I would fit the DG unit in the frame and then secondary glaze inside with your fancy light.

Desp

[AE-NMidlands]

I would not disturb the original window but build a very simple square frame into the opening to take a secondary glazing sheet of glass. It's what I did with the upper window after I double-glazed the back door.
Fit the glass at a time of low absolute humidity (extreme cold) and leave it so that you can get the glass out if necessary. I left my nail heads proud, but you could use small brass screws instead. Amazingly it has turned out that there is only - very occasionally - a small patch of mist on the (inaccessable) inside of the new window pane, which usually disappears fairly quickly.

A

[Bugtownboy]

Thanks AE - that’s reassuring. It’s the least disruptive option. I’ll probably include some silica gel as a bit of peace of mind too.

[GarethC]

Hi guys,

Thanks so much for the interest in my product. I'll give you some background and I'll try not to make it too advertorial. If I cross any boundaries, let me know and I'll edit appropriately.

I'm -completely- open to all feedback, including negative, but in the case of the latter, only if it's very strident, would you mind private messaging it to me instead of airing it publicly? I'll take it on board, and in fact am grateful for it. I'm just starting out, so it's a critical time for me (and I'm rushed off my feet all the time).

My product is very simple. It's a made to measure acrylic pane which fits inside existing square or rectangular window frames (so long as 11mm or more protrudes at a right angle to the glass on the room facing side). The pane has a PVC or (for larger panes, where more stiffness is required) aluminium spacer frame, which provides rigidity while ensuring a minimum cavity width of 9mm (it can be greater if you don't push it all the way against the glass, but you get 90% of the max reduction in U-value at 9mm, and this maximises the likelihood that window furniture won't get in the way of installation).

It's held in place by an EPDM sponge surround. This holds the pane in place and provides a reasonably air and moisture tight seal. At the same time, this fixing method allows the pane to be removed easily. The sponge surround also allows for a degree of measurement error, or for the windows to be warped. It's pretty easy to install, is completely removable and doesn't damage the existing building fabric in any way (so is proving particularly popular with period and listed properties).

As you guys probably know, most of the benefit of double glazing (in terms of U-value reduction) derives simply from forming a cavity of trapped air. Inert gasses and low emissivity coatings improve things, but not by a massive amount.

Basically I developed it because I wasn't happy with existing options for my own period sash windows. I wanted a way to upgrade single glazed windows which was easier, cheaper and (I think at least) better than existing options. Especially I want to help people avoid skipping historic building materials.

I'll leave it there for now. My website is www.geckoglazing.co.uk. I put it there because it's the easiest way to provide more info. Still a work in progress, so as I say, feedback welcome. If having website here is inappropriate, let me know and I'll take down.

Thanks!

P.S. in addition to silica gel packets, by the way, you can get 'pads' which are less visually obtrusive. I'm thinking of including with my product. Will find a link if I get a minute.

[AE-NMidlands]

One thing that secondary glazing on just the glass does not address is the cold air infiltration around the sashes. Apart from losing the very thin old glass I am glad to have got the better seal (and hence also sound reduction) which our new uPVC sash windows have given us. When we used to do secondary glazing with polythene sheet and double-sided tape each winter we stuck it to the frames to prevent the draughts.

Going back to the top of this discussion, about how the room feels warmer when (as soon as?) you can't see the actual window glass, don't forget the effect of radiant temperature. It doesn't affect heat loss from the room but it definitely influences your comfort...
The inner face of the glass will be quite cold relative to the room air temp, even if it is double glazed. As soon as you hang a curtain or blind in front of it you will isolate the window and the fabric will be pretty well at room air temperature instead. Admittedly the wedge-shaped windows are a relatively small part of the whole room, but a cold window surface is the reverse of a wbs or gas fire radiating warmth, although of course the temp diff is nothing like as great.
A

[John_S]

Hi guys,

Thanks so much for the interest in my product. I'll give you some background and I'll try not to make it too advertorial. If I cross any boundaries, let me know and I'll edit appropriately.

I'm -completely- open to all feedback, including negative, but in the case of the latter, only if it's very strident, would you mind private messaging it to me instead of airing it publicly? I'll take it on board, and in fact am grateful for it. I'm just starting out, so it's a critical time for me (and I'm rushed off my feet all the time).

Hi

I like your idea. I did something similar with one of my windows 22 years ago when I moved into my house. I replaced all the old crittal metal single glazed windows with good quality uPVC (still going fine) except for one which was a wood framed non-opening window on the stair case landing. Less choice then of alternative products.

For that window I cut an acrylic sheet to size and put it into the frame recess and held it in with unobtrusive panel pins. It was a temporary solution that has lasted 22 years. It has been taken down once or twice for cleaning behind it, but that is all.

Regarding your website, I suggest that you include your name on the about page. Yes, it is on the how to install video, but should be on the about page as well.

How thick an acrylic sheet do you use? Does it vary with pane size?

John

[GarethC]

Imagine forgetting to put my name on the About Us page... Thanks for the heads up. Amended.

Thanks for the feedback, sincerely appreciated. Wouldn't surprise me if many have done something similar before on a DIY basis - such a simple concept, isn't it? It was one of those 'why can't I buy this already?' products, which I just couldn't find, so set my mind to developing. I use 2mm acrylic for all pane sizes. Doing so allows me to minimise wastage.

As I'm sure you know, the sheet thickness doesn't make much difference to the U-value. 2mm seems to provide the best balance in other ways. 1mm isn't rigid enough for anything other than quite small panes (the pressure on the sponge surround isn't sufficient and the whole pane bows in a slightly unsightly manner). 3mm is too heavy. With 2mm, even quite large panes are quite lightweight. Biggest I've made are 1.66m x 0.66m. That's useful, because I don't want vertically sliding windows to become too heavy to open (or anyone to be able to injure themselves with one).

I take AE's point that this solution does nothing for draughts, but I think those are best sorted separately. I do like the simple draught-proofing tape I sell on my website. I need to improve my draught-proofing guidance a bit though. When I've installed both Gecko panes and draught-proofing tape, I tend to get great feedback on the 'transformation' in warmth, especially around old bay windows. I shouldn't admit this publicly, but I sometimes suspect that the draught-proofing has the greater impact!

[Stan]

I don’t think that you’ve mentioned the thermal conductivities of the companions.

House glass 0.8W/m degree K
Acrylic glass 0.17

[nowty]

I don’t think that you’ve mentioned the thermal conductivities of the companions.

House glass 0.8W/m degree K
Acrylic glass 0.17

And thermal conductivity of air is only about 0.024 so if you can trap a volume of air the thickness of the material makes little difference. You do get some additional losses due air currents circulating though, rising up the warm side and descending down the cold side.

I read a lot about it near 20 years ago when I installed secondary glazing to my standard double glazing in the flat I used to live in. My motivation back then was to reduce noise as I lived near a very busy road. I used triple core acoustic glass (glass/plastic/glass like in the side windows of a TM3 car) with an 80mm air gap between the existing glazing and the secondary glazing for maximum sound insulation, to a similar spec airports use.