Triple vs quad glazing?

[anonymous]

I've looked this up and it seems that quad glazing has lower U values than triple glazing 

 

Why then, do suppliers typically only sell triple glazing as something that's PassivHaus certified? Why not use quad glazing assuming costs were similar? 

[jack]

18 minutes ago, anonymous said:

Why then, do suppliers typically only sell triple glazing as something that's PassivHaus certified? Why not use quad glazing assuming costs were similar? 

 

I'm not sure it's reasonable to assume costs will be similar. As well as the cost of an extra pane of glass (+spacer, plus gas assuming it's argon or krypton filled), the glazing unit will be about a third heavier (and triple glazed units are already quite heavy). You also need to account for yet more thickness, which potentially means deeper frames (and again, triple glazed frames are already pretty deep and heavy).

 

Quad glazing is generally only sold into countries with climates that make it worthwhile. Even in the colder parts of the UK, the benefits of quad glazing are probably marginal. Certainly if you live in the more temperate parts of the UK, the additional cost is unlikely to make it worth the extra cost, weight, and bulk of adding a further pane.

[Kelvin]

It’s like razors. 
 

Costs won’t be similar. Probably requires a re-design of the frame. Weight problem making large windows more challenging to make and fit. Are they really needed in much of the country? In Scotland there possibly could be a justification but the market size is probably too small. 

[PeterW]

You also lose light every time you add a pane of glass so it needs to be considered especially if you factor in any solar gain in your modelling 

[JohnMo]

Cost versus diminished returns.  It usually the frame that kills the whole window U value not the triple glazed glass.

 

Passivhaus specs are based on comfort, and inside glass temperature compared to room temp at a given temperature outside. I have triple glazed and it's 2 degrees outside sat right next to a huge glass window, do not feel the cold outside, window is not making me feel cold, ( sucking the heat from me) a single glazed would and a double glazed may also but to a much lesser extent.

[Radian]

1 minute ago, JohnMo said:

window is not making me feel cold, ( sucking the heat from me) a single glazed would and a double glazed may also but to a much lesser extent.

It's a fascinating phenomenon to me - that you can feel the effect of radiating your body heat to a cold surface. Sitting in a room with large glazing units at a comfortable (stable) air temperature, it can start to feel colder as the sun goes down just because of increased radiative cooling. Ears and forearms seem particularly sensitive to this effect.

 

Daft Q: How do you measure the temperature of your glass? Is it with an IR thermometer?

[mike2016]

Suppliers will always do it for less if it meets the specification / performance values. Advances in spacers, coatings and glass have help keep triple glazed as the best balance of cost/performance. Some double glazed units aren't half bad in some cases too (modern ones). I'm getting a few Velux windows and they are quad glazed but all my others are all triple glazed to meet the PHPP U value requirements. Even finding some triple glazed with low U values can be harder where the area / ratio of frame to glazing is large (1m x 0.275m for example has a U value of .99 and .5m x .1m has .8 from one particular supplier). There are several performance metrics Ug, g, Uw, Uf all measured in the passive house specs to give an overall value. Very detailed!! 

[anonymous]

24 minutes ago, Kelvin said:

It’s like razors. 
 

Costs won’t be similar. Probably requires a re-design of the frame. Weight problem making large windows more challenging to make and fit. Are they really needed in much of the country? In Scotland there possibly could be a justification but the market size is probably too small. 

Thanks. I live in greater Manchester, so when I update my Windows I'll go for triple glazing instead of quad glazing 

[anonymous]

13 minutes ago, PeterW said:

You also lose light every time you add a pane of glass so it needs to be considered especially if you factor in any solar gain in your modelling 

I'm factoring absolutely zero solar gain, largely because the house already exists, so it's just about upgrading to retain heat inside 

[Russdl]

@anonymous it may be worth looking in to vacuum double glazing, apparently can be as good as triple glazing. Thinner, lighter, no idea of price comparisons though. 

 

[JohnMo]

5 hours ago, Radian said:

Daft Q: How do you measure the temperature of your glass? Is it with an IR thermometer?

You can do by calculation, that is the easiest way.  Got the calculation somewhere on my PC, but on my phone now.  Down to about -3, double glazed (1.2 U value) actually meet the comfort criteria set by passivhaus because the inert pane, stay above a given temperature.  Did all the calcs as part of the house design process, but then went triple glazed anyway.

 

5 hours ago, mike2016 said:

to meet the PHPP U value requirements.

Our roof lights are Passivhaus institute approved and certified.  U value is 0.93

 

https://database.passivehouse.com/en/components/details/skylight/roof-maker-ltd-fixed-flat-1153sk03