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Double or triple glazing on south facing walls?


eandg

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We are thinking double in the sliding/bi-fold doors in the living areas to allow for solar gain and triple in bedrooms to make them a bit cosier. But then would this leave the rooms around the big expanses of glass feel a wee bit cold? 

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3 minutes ago, eandg said:

We are thinking double in the sliding/bi-fold doors in the living areas to allow for solar gain and triple in bedrooms to make them a bit cosier. But then would this leave the rooms around the big expanses of glass feel a wee bit cold? 

 

Do you need the solar gain, or will it be likely to contribute to over-heating?

 

With a good level of insulation and airtightness most of the heat loss in a house is from the glazing, and solar gain is a very mixed blessing.  I cursed the amount of heat that came in through our glazing, and dearly wish that I'd specified glass that kept much more of it out, as that would have saved on having to have reflective film installed on the outside of the glass to try to cut down the spring and autumn over-heating.

 

The amount of solar gain we had during the heating season in winter, before we installed the reflective film, was negligible in practice, and we don't notice any difference at all, even though we've now blocked something like 80% of it.

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I really think it depends on location, we were told on here that with a large south facing conservatory we would cook in the summer and we have large bifolds into lounge and dining/kitchen but so far it’s been acceptable with large openable windows and doors, some locations are sun traps ( @JSHarris ) we are more open and usually wind washed.

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12 minutes ago, JSHarris said:

 

Do you need the solar gain, or will it be likely to contribute to over-heating?

 

With a good level of insulation and airtightness most of the heat loss in a house is from the glazing, and solar gain is a very mixed blessing.  I cursed the amount of heat that came in through our glazing, and dearly wish that I'd specified glass that kept much more of it out, as that would have saved on having to have reflective film installed on the outside of the glass to try to cut down the spring and autumn over-heating.

 

The amount of solar gain we had during the heating season in winter, before we installed the reflective film, was negligible in practice, and we don't notice any difference at all, even though we've now blocked something like 80% of it.

Planning on - costs depending - having a 1m overhang (in the form of a balcony from the first floor) over the ground floor. And in Glasgow which isn't necessarily the warmest place most of the year. But we will have - again costs depending - a passive slab and very efficient walls/roof. So a bit of a mixed bag. 

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Our experience has been that a large roof overhang is OK in summer, but summer isn't the problem.  The really BIG problem we have is in Spring and Autumn, when the weather is relatively mild and the sun is low in the sky, so penetrates deeply into the house.

 

We are in a sheltered spot, and the lack of wind where we are definitely contributes to our overheating problems, but I'm still kicking myself, 6 years on, for having been obsessed with heating, when the reality has been that heating is a complete irrelevance, the main problem we have is cooling.  We start actively cooling the house in March, and will carry on using active cooling through to at least October, so cooling is far and away our biggest energy consumer, accepting that most of that energy comes from our PV system.

 

FWIW, SAP showed that we had about a 5% overheating risk, which is massively in error.  We don't like the bedroom to be warmer than about 21 deg C, or the living rooms to be above about 22 deg C, yet even today, when it's been cloudy here, we're sitting with the air cooling running flat out since about  7am, (it's still running) and the bedroom's at 21.5 deg C and the living room is about 22.5 deg C.  We've had the cooling systems running every day for the past month or so.

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50 minutes ago, Onoff said:

@JSHarris, what would the payback be if you were to retrofit Sageglass?

 

TBH, in purely financial terms it would never pay for itself, as most of our cooling energy comes from the PV system.  The problem we have now is that, having paid for the 3G, and then paid another big wedge for the reflective film, we've already splashed a lot of cash on the glazing.  That would be wasted if we decided to retrofit Sageglass. 

 

However, it's not all about whether something pays for itself, there's a certain value in having glazing that provides greater comfort.

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19 minutes ago, K78 said:

 

The glass. Windows are 2.2m x 4m upstairs. 

Not single panels though ..?

 

Even at 950x2150 a triple glazed panel would only be 63kg. So the total window is only going to be 300kg or so. 

 

Double will only save 21kg per panel. 

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1 hour ago, PeterW said:

Not single panels though ..?

 

Even at 950x2150 a triple glazed panel would only be 63kg. So the total window is only going to be 300kg or so. 

 

Double will only save 21kg per panel. 

 

The website I used for a quote refused triple glazing at that size. 

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I think an important aspect is to plan for resilience if it turns out to be worse than we expect; there seem (anecdotally) to be far too many occasions when post-facto adjustments are needed. Personally I am not keen on those funny ladder-frame wooden or ally briese soleil at nearly roof level.

 

I am not clear exactly how I would do that yet, as a mix of 'fabric' and 'system' measures. And I do not think that an identified toolkit exists yet, nor exactly how to use ihe different tools.. 

 

Perhaps we need a list.

 

Ferdinand

 

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With the benefit of hindsight, pretty much the only changes I'd make to our house would be related to over-heating.  I dearly wish that I'd not been so focussed on heating during the design stage, as heating is a complete non-issue.  A single fan heater would keep the whole house warm in mid-winter.  I should have spent far more effort in designing out solar gain, without any doubt whatsoever.    Getting heat out of a house that's already overheated is much harder than stopping that heat from getting in in the first place. 

 

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8 minutes ago, Onoff said:

Are people fitting just plain tinted film or photochromic transitional film?

 

https://www.windowfilmdepot.com/product/coolvu-transitional/

 

I didn't see this available here when I was looking around.  It looks as if it might be a good option, although the 3M film we have on the East windows is pretty clear, yet still blocks about 80% or more of the solar gain.  The film we have on the outside of the front gable could do with being less dark, though, and this film would have been a good option if I'd seen it at the time.  There's a definite grey tint to the light coming in through our front glazing, that makes it seem as if it's a cloudy even on a bright day, and this photochromic film may well reduce that effect a bit.

 

The key thing will be making sure that it's compatible with high performance 3G glazing, as we initially struggled a bit to get our window supplier to agree that it was OK to fit external film (internal film is a definite no-no).

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18 minutes ago, Onoff said:

Are people fitting just plain tinted film or photochromic transitional film?

Ours isn't photochromatic nor I think plain tinted. I was told that in order to have the film, it must not have a mirror finish and must be not be noticeable. We went for Clearview Vista 80X because it was the closest to meeting those criteria. It is very effective, but expensive, and if the photochromatic film was more expensive I couldn't be tempted.

Clearview Vista 80X

Total solar energy rejected - 45%

(55% on double glazing)

Visible Light Transmission - 77%

Visible Light Reflection - 8%

Ultraviolet Transmission <0.1%

Glare Reduction - 12%

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I had only one option due to laminated 3g windows.  My supplier was excellent they went to a huge amount of effort to ensure they go the right film for us....other suppliers just said use anything but (high) risk is yours or dont use film at all...the guys I used went the extra mile or 10 for me.

 

It is a film made by Solarguard who are part of St Gobain.  It was the specialist dept at St Gobain that advised our supplier.  As I understand it St Gobain provide the glass for Internorm.

 

Luckily the one and only film for us also came in an extra wide roll so no joins (would not have had film if there had to be joins, no join is invisible)

 

This is my spec sheet from manufacturers.....this film is for laminated glass, if you have toughened then it will be different film but this is the sort of thing suppliers should send you with the sample of film.  

Sentinel-Plus-SX-Silver-50-Sample-Page-0314SSX50OSW.INT_.pdf

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