Internorm: Order with solar glass, or apply external film later?

[tanneja]

Thanks all for the feedback.  My other half is against shutters, and I don't think external shutters or fabric would fly in the neighbourhood, we are seen as radical but opting for a grey roof tile.  We also seek super low maintenance, external shutters probably have a fair bit of that to keep them in good condition?  

 

It is possible I don't have a future solar gain overheating issue.  If it is very similar costs to apply an aftermarket film later vs. the option of adding solar glass now (around £10/m2) and has good durability to the elements (+10/20yrs without deterioration), then waiting and seeing is obviously the way forward.  I have the impression films were more expensive than that.

[osmononame]

For anyone who has applied external film later how did you manage with larger sliders? Our sliders are 2.4 high by about 4 wide and so thats a lot of glass to apply film to later if required? I'm thinking of the height and joins in the tape being difficult to line up? Might be over thinking it but I'm about to make decision on it and would hate to regret it later. Our sliders will be facing east!

[Mr Punter]

13 hours ago, osmononame said:

For anyone who has applied external film later how did you manage with larger sliders? Our sliders are 2.4 high by about 4 wide and so thats a lot of glass to apply film to later if required? I'm thinking of the height and joins in the tape being difficult to line up? Might be over thinking it but I'm about to make decision on it and would hate to regret it later. Our sliders will be facing east!

 

The quality films like 3M Prestige are very expensive and require specialist fitting and edge sealing.  £80 per m2 as a budget cost.

[tanneja]

For what it is worth, I have tried with a few internorm suppliers to get quotes for Sage Glass, without success.  And Sage Glass say the fabricator must go to them for their product, so seems too many barriers to get access to pricing let alone a finished product.

 

Plan is to have solar glass upstairs in the east and south elevations (no west facing windows), while leaving the downstairs as regular windows, will plan plants and tress to partially shade the downstairs.  I don't know who to pay to see if we will have an overheating problem, so seems like the best solution rather than aftermarket films.

 

Will also provision for some through wall A/C in (hopefully) strategic places should we need to install for active cooling.

[Mr Punter]

That sounds a good approach.

 

Be very conservative with the amount of glazing on upper floors if they contain bedrooms.  Go for just adequate daylighting.

 

There are a few firms and software packages that can do an overheating risk assessment - they do a basic one with you design SAP assessment.  PHPP has a spreadsheet approach and I understand it models the building throughout the year.

[Dan F]

Quote

 I don't know who to pay to see if we will have an overheating problem, so seems like the best solution rather than aftermarket films.

 

There are a number of consultants that will model house in PHPP for you, if you don't want to do it yourself.  Where about are you based? We saw doing this modelling as an investment, as we felt it was best to get the overhangs, window sizes and type of glass right upfront.  If you use solar glass but don't need it, for example, then your heating costs will be higher and the house may not be as bright internally.

 

 

[Mr Punter]

11 minutes ago, Dan F said:

 

There are a number of consultants that will model house in PHPP for you, if you don't want to do it yourself.  Where about are you based? We saw doing this modelling as an investment, as we felt it was best to get the overhangs, window sizes and type of glass right upfront.  If you use solar glass but don't need it, for example, then your heating costs will be higher and the house may not be as bright internally.

 

Could you give any indication of the costs for this, given that the OP is only interested in solar overheating?

[NSS]

4 hours ago, tanneja said:

And Sage Glass say the fabricator must go to them for their product...

 

Really? That wasn't the case when we purchased, and I know of another poster who's had pricing more recently. Who have you spoken to? If you would like me to I can put you in touch with the guy we dealt with.

[Dan F]

2 hours ago, Mr Punter said:

 

Could you give any indication of the costs for this, given that the OP is only interested in solar overheating?

 

We paid around 750+vat for initial model which analysed a couple of variables.

[Russdl]

Apologies, I've not read the whole post in depth but if you apply the external film to combat the summer thermal gain won't you kill off the winter thermal gain that you want? I definitely recommend 'modelling' it but tread carefully with PHPP experts, I've met a few and they most definitely were not expert and potentially very expensive. I bought a copy of PHPP, struggled through that and think I got it right... Whilst we are still far from finished, the house/windows seem to be performing as predicted.

 

We have external roller blinds, hidden when not required, and easy to see through from inside out when they're down (I've already walked into them twice because I forgot they were down) but almost opaque from outside to in when they're down.

Edited August 21, 2020 by Russdl

[Adam2]

@Russdl would you mind providing some info and pics on what you installed. I'm thinking through blinds vs brisse soleil

[Russdl]

I'll take some pic's tomorrow and post them (if I remember, nudge me if I forget!)

 

We used these (designed as fly screens for the US market, turns out they keep the hot sun out as well.)

[Adam2]

They look great. Any price info, if you wouldn't mind sharing would be handy by pm. 

[tanneja]

@NSS can you send me the contact via PM as i may already be in contact with them via the quote process. Thanks very much!

 

@Russdl that is intersting, i couldn't easily find an external model on the link, if you have any pictures i would be interested as perhaps we can integrate these into the planned EWI 

 

As @Mr Punter says, i feel less concerned about losing out on winter solar gain, with heat rising I expect that bedrooms should rarely require much heating.  Just to say this is a retrofit project of a 1930s semi where we are having new poured floor, new roof, EWI and triple glazing, so while will be well insulated, not a passive house by any stretch of the imagination. I expect to have to pay for heating in the future, keeping our combi boiler for now as only a couple of years old, from before we considered this project.

Edited August 22, 2020 by tanneja

[Russdl]

@Adam2 @tanneja Here’s a couple of quick vids of the blinds. 

 

We made a space for the blinds by recessing the timber frame above the window heads and then standing the cladding off the face of the timber frame by 100mm, that gave us the void we needed to instal the blinds and hide them in the cladding (they are fully accessible for maintenance - but it’s not a 5 min job!)

 

Of course they are not particularly cheap, our worked out to circa £850/linear meter. The width/drop doesn’t affect the cost much, it’s the motor that costs and they all have the same one. 

 

 

[Adam2]

Great thanks for that. Will contact them and see how it goes price wise as looking at 6.2 wide x 2.8 high

[Dan F]

On 23/08/2020 at 10:25, Russdl said:

@Adam2 @tanneja Here’s a couple of quick vids of the blinds. 

 

They look very simialir to the Roma textible screens.  We never considered these and instead when with the venetian blinds but they look like a very good option, especially if you can get them independant quite easily and you aren't limited to specific window supplier who resell Roma.

 

[tanneja]

In case it is useful to anyone in future, know that today I will go ahead and order Internorm with the SKN176II grade glass upstairs on east and south elevantions, and keep to regular triple glazing downstairs.  While the screens look nice, they are relatively expensive, the SKN176II on the upstairs is relatively cheaper with no maintenance / operation required, the risk being a dull day seeming a little more gloomy when you wake up first thing in the morning, and loss of some amount of useful solar gain on a sunny winter day.

 

The numbers from @Dan F showing that SKN176II only has 1% less light transmittance than normal 3g has me less worried about the potential gloominess, not that I have a feel for 1% light transmittance feels like in real life:

 

Typical Triple Glazing:                         71% Light Transmittance, 0.5 g-value
SKN 176 II Coating Triple Glazed:     70% Light Transmittance, 0.37 g-value

[Dan F]

7 hours ago, tanneja said:

The numbers from @Dan F showing that SKN176II only has 1% less light transmittance than normal 3g has me less worried about the potential gloominess, not that I have a feel for 1% light transmittance feels like in real life:

 

Typical Triple Glazing:                         71% Light Transmittance, 0.5 g-value
SKN 176 II Coating Triple Glazed:     70% Light Transmittance, 0.37 g-value

 

I'm not sure where I got those numbers from now. I assume you doubled checked them with supplier?  The datasheets all talk about 70% but unclear if that is double or triple-glazed.

 

If in doubt you can use https://calumenlive.com/ to run the calcluation, but exact numbers will depend on glass thickness, cavity thickness and other low-e coatings etc.  When I posted the previous numbers calumen live was down so couldn't run the numbers, tried running just now and seems LT may be around 64%, still only -10% LT, for -30% reduction in solar gain though..

 

[tanneja]

I'll use the link to check thanks, however I have also seen situational photos and feel comfortable there isnt large percievable reduction in sunlight

[tanneja]

@Dan F thank you for the link, as best as I can see, the comparative numbers are:

 

 

Standard Internorm Triple Glazing:   71% Light Transmittance, 0.5 g-value
SKN 176 II Coating Triple Glazed:     62% Light Transmittance, 0.34 g-value

 

Has anyone got a feel for how impactful this would be when looking out of the window throughout the year light levels?

[Nick Laslett]

On 30/08/2020 at 21:50, tanneja said:

@Dan F thank you for the link, as best as I can see, the comparative numbers are:

 

 

Standard Internorm Triple Glazing:   71% Light Transmittance, 0.5 g-value
SKN 176 II Coating Triple Glazed:     62% Light Transmittance, 0.34 g-value

 

Has anyone got a feel for how impactful this would be when looking out of the window throughout the year light levels?

@tanneja Hello, how did you get on with your windows? We are looking at Pilkington Suncool 70/35 triple glaze which have LT 60% and 0.35 g-value. 

[osmononame]

For what its worth I ended up with SKN176 coating on my rear elevation and unless side by side you couldnt really tell that it was solar glass.

[tonyshouse]

External shading is best and west facing windows generally cause biggest problems with overheating 

[Conor]

We asked this question and the guy said don't even think about it as the cost will be way out of our budget. The units have arrived with the standard glazing as requested, and have a fair bit of shading on the inside and reflective on the outside, have noticeably darkened the rooms. Wouldn't want any more than this.