Double/Triple glazing

[Nemo]

It's freezing cold and snowing and there was a knock on the door around lunch time - a double glazing/window salesman would you believe?

We have hardwood windows with double glazing and he was trying to get us interested in energy efficient windows (triple glazing possibly). He said that it would save us money. Told him politely that I wasn't interested and off he went. Quite a nice guy.

Just interested (not going to do it) but are these energy saving panes any good. Is there some standard set for them or can anyone just stick a label on the window and call it energy efficient?. Would they save much money given the costs involved?

[bungeejumper]

When I lived in Berlin, even my grotty mansarde flat had triple glazing, and so did everybody else's. The block had been built in the 1890s.

But then, Berlin is very nearly in Poland, and they get bad winters out there. (It hit minus 20C when I was there, and it stayed that way for two weeks.) The chances are that you don't.

Will triple glazing be better than your double glazing? Yes, but you'll be into the territory of diminishing returns. It's like asking whether 15 inches of loft insulation is better than 10? Yes it is, but the first 10 are doing all the really heavy lifting.

Another difference is that, in the good old days, where the air gap between the separate glass panes panes was 5cm, you could just double up by adding another glazing shutter so as to make it 10cm. But any modern DG system with sealed glass units will presumably need to be completely ripped out and replaced with TG.

Diminishing returns indeed.

BJ

[9873210]

If you're interested in saving money, you should probably look at adding window treatments before changing windows. There's only so much you can do with glass. Properly fitted and used cellular shades or shutters can cut heat lose through the window to a quarter for the 60% (or more) of the time you don't want to look through the window.

Automatic roller shutters with house automation are the apex, but you can do a lot with manual cellular shades or proper drapes. Just make sure they are designed by a thermodynamicist before they go to the interior decorator.

[Nemo]

If you're interested in saving money, you should probably look at adding window treatments before changing windows.

Not too bothered about changing things but I just wondered.

Our hardwood windows were all custom made by a joiner on site some years ago. Two of them are twelve feet across! They are also all leaded.

I've been looking on-line. Apparently the standard width of double glazed units is 28mm while triple glazing is 36mm. I'm not too sure how easy they would be to modify.

I suspect that the cost of changing over would run into a few thousand pounds given the work involved - and then there's also the conservatory round the back which the salesman never saw!

[jaizan]

Apparently it's a legal requirement to include trickle vents in double glazing now.
If people leave those open, I suspect they're going to have higher heat loss when switching from old to new double glazing units.

So on the one hand we have airtightness rules for new housing, then they have mandatory air leaks in windows.

I would argue that trickle vents ought to be illegal on new windows, with people encouraged to have ventilation systems with heat exchangers.
[I was going to replace my bathroom extractor with a heat exchanger, until I discovered I needed building regs approval for this]


My house has some awful Everest aluminium double glazed units. Although they have a thermal break in the frames, it's not that good and the spacers between the glass are aluminium with no thermal break. Truly awful for performance. But the damn things are still in good condition.

I would like to think of an upgrade, but there are a few hurdles, e.g.:
1 How do I get indicative prices without having to deal with pushy salesmen ?
2 The windows are supposed to be argon filled to achieve the energy efficiency requirement. How would I know that they have actually filled them with argon ?

[BullDog]

Apparently it's a legal requirement to include trickle vents in double glazing now.
If people leave those open, I suspect they're going to have higher heat loss when switching from old to new double glazing units.

So on the one hand we have airtightness rules for new housing, then they have mandatory air leaks in windows.

I would argue that trickle vents ought to be illegal on new windows, with people encouraged to have ventilation systems with heat exchangers.
[I was going to replace my bathroom extractor with a heat exchanger, until I discovered I needed building regs approval for this]

My house has some awful Everest aluminium double glazed units. Although they have a thermal break in the frames, it's not that good and the spacers between the glass are aluminium with no thermal break. Truly awful for performance. But the damn things are still in good condition.

I would like to think of an upgrade, but there are a few hurdles, e.g.:
1 How do I get indicative prices without having to deal with pushy salesmen ?
2 The windows are supposed to be argon filled to achieve the energy efficiency requirement. How would I know that they have actually filled them with argon ?

I share your thoughts completely. I have uPVC windows and today I wouldn't buy them. The windows are fine but it seems the quality of the opening and closing latches is universally dire. Problem is that the latching always fails when the window is shut. And because of the secure multi point latching it renders the entire window assembly as scrap. The windows cannot be opened to repair the latches without destroying the window. So, a simple failed latch pretty much means a complete new window. Unfortunately I have fitted the entire house with uPVC double glazing. As far as I can determine, this is a problem common to all makes of uPVC windows.

What would I do today?

I would look at windows by a company called Velfac. They are fited to a relative's property and the quality is light years ahead of typical double glazing. Take a look. They won't be as cheap as uPVC in the short term but they'll likely last 50 years at least with minimal care and maintenance. And, importantly, they can be repaired. Hope that helps.

[bungeejumper]

[I was going to replace my bathroom extractor with a heat exchanger, until I discovered I needed building regs approval for this]

Happy to be wrong, but I'd doubt that you'd need building regs approval just to install a heat exchanger in a domestic property. (Although it wouldn't surprise me if they were required on newbuilds or major modifications, in which case you'd be into building regs territory already.)

Heat exchanging extractors are really no more complex than the standard type, except that most of them are designed to run constantly. (Relax, in idle mode they draw just a few watts of power, and they're all but silent until they get old.) And they're quite a lot bigger than the standard type! And a blooming sight more expensive!

We've just installed both heat-exchanging and standard extractors into a commercial property. We were doing a fairly major renovation which already involved full building regs approval for new walls, etc, and yes, the inspector did glance at them - but that's not quite the same thing as needing an entire building regs process just to fit an extractor into an existing location in a domestic dwelling. Surely that would be serious regulatory overkill, since there are no additional elf and safety risks whatsoever?

Forget all of the aforegoing if you were going for the full Passivhaus specification! In which case you could hardly avoid building regs anyway. Oh well, it gives the building regs inspectors something else to do. As if they weren't overworked enough already.

BJ

[9873210]

Never mind the building regs. Properly installing an air to air heat exchange for ventilation is not so simple.

You don't want the inlet and outlet near each other. If the inlet and outlets are at opposite ends of the building it ventilates the entire building. At the very least you want these in different rooms. This means ductwork, which is a pain to install in typical brick buildings. High efficiency systems mean large ductwork, which is even more of a pain.

The whole house needs to be considered as a system. A lot of things you should do on new construction make no sense as retrofits unless it's a gut job and total rebuild.

This shows up in windows that are not designed to be opened. If you have mechanical systems designed to control the interior opening the windows is usually counterproductive. It lets in a big slug of heat, or cold, or humidity, or dryness that make the mechanicals work harder. The reason some latches break easily is they are mostly for show and not expected to be used daily.

[csearle]

I recently wired up a house where each room had an in and out vent of a MVHR piped to it. The nozzles were, by design, presented at the same place in each room.

On another note my son moved into a brand new rental flat with some kind of ventilation system in the form of a unit. It was at the height of summer and the flat was severely overheating, He asked me what to do. The operating instructions just said, "If the spaces get too hot then open windows." Only thing was none of the windows were designed to be opened. It is a total dog's dinner out there. C.

[BullDog]

I recently wired up a house where each room had an in and out vent of a MVHR piped to it. The nozzles were, by design, presented at the same place in each room.

On another note my son moved into a brand new rental flat with some kind of ventilation system in the form of a unit. It was at the height of summer and the flat was severely overheating, He asked me what to do. The operating instructions just said, "If the spaces get too hot then open windows." Only thing was none of the windows were designed to be opened. It is a total dog's dinner out there. C.

The overheating in summer problem is likely because the cheapskate building developers specify the lowest spec, cheapest MVHR unit possible. For a little bit more money, they incorporate a heat recovery bypass to use in summer so that the heat recovery isn't in use in hot weather. A relative of mine in one of these new super insulated sealed living boxes (sorry, apartment) had this same overheating in summer issue. When I looked into it, the developer saved a grand total of £20 by buying a MVHR unit with no bypass. An absolutely appalling cheese paring decision.

[bungeejumper]

The overheating in summer problem is likely because the cheapskate building developers specify the lowest spec, cheapest MVHR unit possible. For a little bit more money, they incorporate a heat recovery bypass to use in summer so that the heat recovery isn't in use in hot weather.

Yes, a heat recovery bypass is basically just a plastic flap (or louvre) that closes off the incoming warmed air. It's hardly rocket science. There are no excuses for not having it as a summertime option.

We're getting somewhat O/T here, since the OP was about double or triple glazing. But FWIW, the individual units for single rooms are a different kettle of fish from the whole-building ducted systems that 9873210 was talking about.

We did look into those during our refurb, but as 9873210 says, they're just too horrible for retrofitting into an existing home. Two lots of six inch square steel ducting, running right throughout the building, would have made the place look like a flipping factory. The fans are much meatier, and somewhat noisier (as the installers very honestly warned us). But what we hadn't realised was that those ducts can also carry the sound of conversations throughout the building, even if you fit attenuators. (Which are blocky, large and pretty unsightly.) We went for the individual heat recovery units and saved ourselves twelve thousand quid. No regrets yet.

BJ

[stewamax]

Heavy lined curtains? Pretty good at keeping a room cool on a hot day as well.
You can take them with you when you move, and they don't mist up...

[ten0rman]

FWIW we have recently changed our Everest double glazing (white painted aluminium and perfectly ok, but the hardwood frame was rotting nicely, the front of house windows were 50 years old and used allen screws to lock the windows) with Everest upvc triple glazed units with trickle vents.

Upvc because at my age, I can't be doing with maintenance. Trickle vents because I thought they might be of use. And in any case, with, if I'm lucky, only a few years life left I really couldn't care less - if that makes sense.

So far we have had one window lock fail - replaced under warranty and which involved removal of two of the three triple glazed units. Otherwise ok. And the trickle vents? Not at all sure about them!

Ok it cost a lot - £22K, but as the saying goes, I can't take it with me, and it's £22K less for the government thieves to tax.

Cheers,

ten0rman