Which is warmer? Double glazed sash or secondary glass?

[duriandurian]

We moved into our forever/ long term home this Autumn. Four bed end of terrace, 1910ish vintage. Conservation area with window restrictions (don't think upvc permitted).
It is utterly freezing-the vendor installed new single glazed sashes. Given we intend to live here for a long time, what is our warmest and best option for Windows? Should we stump up for new wooden double glazed sash windows or should we stick glass sash Windows on the sills as secondary glazing? We are having the roof reinsulatwd. Ice on the inside of Windows atm and we don't want another freezing winter here if we can avoid! Thank you.

If they are vertical sliding sashes in a conservation area, it is very difficult or impractical to insert double glazed units. They will be too thick to fit the sash, and heavier so the counter weighting doesn't work. Secondary glazing will work better, and will also block sound and draughts.

If you have net or lace curtains, the secondary glazing will be pretty well invisible. Not everyone likes nets.

Our window guy (who doesn't do sashes himself) said that double glazed units have springs in rather than counter weights.
But that is cheering that secondary is not too obvious. Thank you.

oh yes, modern plastic ones have a spring spiral balance. So you could probably buy an uprated one to take the extra weight.

I was visalising the traditional wood frame with cords and weights at the sides.

mine have a spring and pulley system (almost unobtainable now).

I think good secondary glazing is better than ordinary double glazing and maintains the look of the house. Other solutions are internal shutters, blinds and thickly lined curtains. When its really cold keep the heating on all the time, but low ifvyou are out, as once these old houses get warm its easier to keep them warm - dont let it go cold during the day/night. Get an aga in the kitchen too 😄

So I thought secondary glazing was a make do, but it seems that it might actually be a sensible (and significantly cheaper) solution. Thank you! And yes trying to keep heating on at all times but have inherited four different nest thermostat zones all of which default to 9'c and which haven't yet learnt that we don't like to freeze!

I’d vouch for secondary.

My experience is slimline double glazing Is meh. Okish for heat, rubbish for sound proofing.

For good sound proofing/thermal benefits you need a 24/28mm glazing units for this you need to up the sash frame size from 130mm depth to 170mm depth this creates installation issues (expensive, braking out bricks replacing lintels)or visual compromises (having no cill, reduced glazing area)

Spiral balances are common in replacement windows. They need replacing before good old pulleys. Pulleys 100 years.... spiral balances 10 years.

Decent secondary glazing will set you back a fair wedge. DIY fit £300 a 1.5 x 1m window with slim unit with tilt and turn etc.
For supply and fit seems about £500/600. Seems a rip off to me unless you’ve got unusal shaped windows. It seems about 3 companies make the secondary glazing and frames so it’s aload of crap if they say their units are special.

Unless....

Some companies do frameless secondary glazing which looks amazing I’ve had a quote at £800 a window though ouch!

If you want to dip your toe you can get magnetic arlyic panels which will you about 50% of the result of good secondary with glass. Be a cheaper test for you.

@Squirreltamer - sorry to hijack, OP, but can you tell me the name of the company that does the frameless secondary glazing? About to go for this in our house and want it as discreet as possible!

Wasn’t sure if I could mention names on here but.
Specialist glazing projects Bristol do it using a clear seal around the perimeter and JBC do it in Scotland using a frame inside the reveal. Both use fixings more commonly used on shower screens. I think they look good.

I can’t vouch if it’s as good as the wood or aluminium systems but the same princples are there. Air gap, different mass of glass.

Or storm glazing use a mini frame which sits within the staff bead of the sashes. So is good on large windows for heat but without the larger airgap I can’t see it being as good for sound reduction.

Let us know how it goes. I’m about to replace my acrylic glazing for a proper system.

Either clearview or SPG Bristol (triple the price of clear view) cant decide if it’s worth it!

I've had Storm over and I'm tempted to go with them - hadn't heard of the Bristol company so going to google now, thanks! Very much after noise reduction above all else and they are big windows, which I've spent a small fortune on already (new double glazing and shutters).... good luck with yours!

Thank you! I don't need noise reduction- chose our house in part because it is on a very peaceful street but warmth is a priority. I will look up those companies now. Thank you for taking the time to post.

I see I'm going against the grain here - but if you can afford it - I would ALWAYS go for good quality double glazing over secondary glazing.
Not only does t look better, it's easier to clean and most importantly the majority of double glazed units are much better thermally than fitting secondary glazing. Given thermal performance is your priority, I would ensure you check this with any installer of either before proceeding.
We have replaced some of our single glazed sash and case windows with skim double glazed ones and I don't regret it. It's much warmer, and there is an acoustic difference too (secondary glazing is sometimes better acoustically but that is about the only benefit).

That should say 'slim', not skim!

We're not in a conservation area, house is a 60s Georgian style - our upstairs windows were wooden Georgian style sashes, with small panes, which were terribly time consuming or else expensive to re paint.

We replaced them with period-lookalikes in wood effect UPVC, with proper pane dividers - not those bars inside the glass - and period style brass fittings. Until you get very close up, you'd honestly think they were wood. IIRC the company (Bygone Windows I think) said they were approved for conservation areas.

We are very pleased with them. They have security catches so that they can be opened just a few inches, and can also turn inward for cleaning.
Downside is that they were considerably more expensive than ordinary UPVC.
A sister who has a genuine period house has recently had similar installed.

I have really old, 1980s aluminium sliding secondary glazing on our victorian sashes and they are the dogs bollocks for warmth and sound insulation. When the curtains are closed there is no heat differential between in front and behind the curtain. Downside is that they are visible if you look (though we bought the house with them installed so know no different - but its likely you would notice) and ladybirds and debris get caught inside and they are hard to clean out. We looked at getting ours replaced but the quotes were very expensive so we're sticking with what we have.

"ladybirds and debris"

this will be due to gaps round the old windowframes. There are ways of sealing them up.

it's possible to paint the secondary frames to help them blend into the window reveal, frame, or wall. I think this works better if they're all the same colour.

Old American houses have brilliant sash windows, with deep rebates, & slots on the inside for “storm windows” (= secondary glazing) in the winter & screen windows (for keeping insects out) in the summer.

Modern buildings have a similar set-up but they tend to slide horizontally instead of vertically.

But they do have far more extreme weather (& insects) than us so it needs to be very effective!

My ladybirds and debris between secondary glazing and sashes. I should hoover more!

Would paint work on the aluminium? I assume it would flake off.

Hmmm, I will Google for the upvc too. I was v keen on wood bur am keener not to have frost bite! I would seriously love if if we could get insect screens included as well- we appear to live in a v mosquito prone area and they are still coming in from outside even in this cold weather.

You can get some wonderful upvc sash or mock sash that are approved for conservation areas and almost indistinguishable from wood. Our front windows including a bay are black wood effect and look amazing, people tend to be surprised to find out they are upvc.