(as would a normal much cheaper blind)

Much cheaper? What are you basing your base price on? And I doubt you either get the same level of insulation nor the other benefits that shutters will give you.

That appears to show that you’ve taken a 1.8 u value window, put it in a cavity with a blind and come up with a lower u-value. The read out doesn’t really mean much to me as it doesn’t show any of the properties of the window. It appears to be comparing a window unit with a window built into a highly insulated wall?

Yup. Good aren’t they. 😀

Base price of circa £200sqm for a Pelini interstital venitian blind, versus something from Homebase 🙂

Average u value for a window built into an insulated wall is always going to be better than a window calculated on it’s own, but you haven’t really improved the u value of the window, just included something in one calculation that you haven’t in the other.

Base price of circa Base price of circa £200sqm for a Pelini interstital venitian blind, versus something from Homebase

£200sqm? That’s mighty expensive and mighty sexy too, but still, mighty expensive. I assume the Homebase ones you’re talking about you’re bog standard venetian blinds, no? Because I’ve never seen insulated shutters on their shelves, the externally mounted ones that make burglars think twice.
EDIT: Don’t seem to be able to find technical specs on the Pelini. 🙁

You buy 1 you get 1 free ..

Don,

Here you goPelini Website

and yes I was referring to a bog standard Homebase blind.

Still no technical info, I’m afraid.
They look like the blinds I mentioned earlier where the guy had a Grand Designs glass fronted house which for some reason got too hot when the sun shone.
They look quite sexy and seem quite appropriate on those glass fronted homes, what I don’t see is what they offer over Homebase style blinds, except a bit of style. Will they reduce heat loss or just reduce solar gain? Will they reduce solar heat gain by much, I mean they are behind a pane of glass afterall? but I guess the gap is minimal, so not really an issue.
They don’t look like they’ll block that much light out either, a personal beef of mine. I hate getting up at sunrise and I think you get a higher quality siesta when the room is practically blacked out.
£200 per m² seems an awful lot just for style.
The other main problem I see is one of security, night time ventilation means that the window will have to be open and inviting to our less honest cousins. But again, I assume, the market that pays that sort of money will have their own security team at the house anyway. 😆

I think you mean Brise Soleil. It will reduce solar glare and allow solar gain during the winter months when the sun is low. I can quote the BRE for the calculation / ratio tables but don’t go there its boring.

The 0.81 calculation is incorrect. It needs to be the reciprocal of 1 so 1/0.81 = 1.2 U value.

Solar and blinds = yes you can include it within the calculation. Never allowed for a blind or curtain on a U value calculation. That would be cheating.

Mention Grand Designs and I thought Brise Soleil

I have that type of internal DGU blind on my extension. At £1800 + VAT money well spent.

The 0.81 calculation is incorrect. It needs to be the reciprocal of 1 so 1/0.81 = 1.2 U value.

So the other calculation is wrong too and the 2G window is 1/1.8 = ??
I don’t think so and not far off if you work with the k and r values, but feel free to take it up with the guys who tested it.

That would be cheating.

Why would it be cheating if it’s a part of the fabric of a building? You could argue that the u-value is only valid when the blinds are down, in the same way that the u-value of a window is only valid when it is closed. 😉
I think logically the blind is very difficult to argue against on the practicalities. You use them when you need them, you don’t use them when you don’t need them. it’s an extra layer of insulation and will reduce solar gain. They allow night time ventilation while keeping the property more secure with the windows open. They offer an extra layer of defence against buglaries and are hidden away when you don’t. A range of colours mean that a smart architect can use them to enhance the look of a building, and some of the €million + homes I’ve seen them on, the architects have done a bloddy good job. nd when we have starting prices in the region of less than £100 delivered, they’re not as expensive as you’ve been led to believe either. 😉

I think you mean Brise Soleil

Who means Brise Soleil? What and where?

Outside surface resistance – – 0.040
WINDOW 20.0 – 0.385
Inside surface resistance – – 0.130

Add together 0.04 / 0.385 / 0.130 = 0.555

1 / 0.555 = 1.8 U value.

Pointless argument on the second one. The thermal properites on a internal blind are so low it not worth adding to the overall calculation. A curtain sits out from the window and therefore cold air will bypass around the sides so how do you measure the gain. However both can be used to counter solar gain and figures / correction factors were previously available. (It’s all done via building modelling these days)

I paid £1800 + VAT for my blinds in 2010.7m2 so around the £300m2 mark.

I think logically the blind is very difficult to argue against on the practicalities.

Quite right. Now how do you get over people not liking them and them not being the vernacular architecture in the UK?

the u-value of a window is only valid when it is closed.

Hence the pragmatic / balanced approach I have to employ every day within the construction industry

Pointless argument on the second one.

That’s quite a strong staement to make when you haven’t had access to the product or the testing procedure.

The thermal properites on a internal blind are so low it not worth adding to the overall calculation.

And this confirms that you are talking about something entirely different.

I paid £1800 + VAT for my blinds in 2010.7m2 so around the £300m2 mark.

I’m very happy for you, and I really hope that they work for you, but please don’t make judgements on the blinds I have without being party to all the information I don’t recall gicing you any samples, again, feel free to contact the guys who tested the blinds to get their opinions. You appear to have made a couple of schoolboy errors, actually more than a couple. 😀
£300 + VAT, I hope they’re seriously sexy. They should, at least, be very, very sexy at that kind of price.

Post the information and I will review.

The calcuation is wrong but if the THERMAL blinds offer up to a 0.4 increase in thermal resistance then they need to be reviewed for their day to day practicality.

Post the information and I will review.

What info do you need?

Sufficent information to make a review and a technical report or test data for thermal preformance in accordance with BR 443 – 2006.

If you want the u-value of the shutters, the slats are 5,87W/m²K and the boxes are 1,5W/m²K as an example.
Woo hoo a free BRE test.
What’s your licencing number/accreditation number? It will be good to have some officially recognised and impartial testing done.

Unfortunately not I’m a senior technican, contract adminstrator, lead consultant, technical adviser, design team leader and best friend to most architects :-).

The industry has been caught out before hence the BR 443 “ground rules”.