High performance glazing

Below is a link to article about the slim line vacuum glazing that is now commercially available and some people who have period properties may find this an usefull option (although the price and fact that is shipped from Japan (!) at present doesn't make it fully add up). I think we are a few years ahead before this will become really feasible.

http://www.building.co.uk/story.asp?storycode=3139081

Originally submitted by lukasz on Tue, 04/05/2010 - 10:41am.

Last update on Tue, 04/05/2010 - 10:22pm.

tags:

#1

Submitted by Jack on Tue, 04/05/2010 - 10:56am.

Dear Lucasz,

Many thanks for the info on vacuum glazing. Very interesting and very timely - I'm researching glazing options for our own refurb today.

We're aiming for high performance windows which look as much as possible like single glazed sash. The vacuum glazing is an interesting option. however, like you said, it probably doesn't quite add up yet. The vacuum glazing has an overall thickness of 6mm and a U-value of 1.4 W/m2k, costs a lot and has a protection cap in the corner. The glazing we were looking at has a total thickness of 11mm and a U-value of 1.6 (3-4-4 using Krypton gas, low-e glass and warm spacer). Our current plan is to commission a local wooden window construction company to build draught-proofed sash windows using this 11mm double glazing unit. But I'm a bit hesitant because the frames of a wooden sash will conduct heat rather well and won't be wonderfully airtight. The window company is keen for us to use the thinnest possible glazing unit for aesthetic reasons but they can accommodate 22mm thick DGUs. If we go to 22mm thick then we can get slightly higher performance for the same money.

I'll probably add an entry to my 10:10 diary on the Peckham Power website about glazing soon.

Thanks,

Jack

#2

Submitted by Clyde on Tue, 04/05/2010 - 12:57pm.

Jack et al.

I had come across the idea of vacuum glazing before but didn't know it was commercially available yet. The problem is always that of counter-acting atmospheric pressure, in this case by casting in tiny 'stipples' which act as spacers. Also the lower the U value obtained by the actual glass, the more important it is to ensure the frame is airtight and properly thermally broken. Jack seems aware of this in his quest for high performance sash windows. Who do you have in mind to do your prototype and how much will it cost?

All high-performance glazing comes at a price. When completed, you all must come round and see the glazed wall we constructed as part of our new rear extension. The total area is about 16 square metres with glazing which is 6:16:12, with argon filled cavity, low E glazing and of frameless construction. This gives it a U value of 1.1, (probably about 1.3 overall) The cost works out at about £800 per sq.metre! One should beware of extrapolating this figure for smaller unites however.

regards

Clyde

#3

Submitted by Jack on Tue, 04/05/2010 - 1:31pm.

Many thanks for the info.

The joinery we're talking to is a company called Draught Busters Ltd (!), SE23. They came highly recommended on East Dulwich Forum. The salesman is pleasant enough and has been quite accommodating. We've seen their work on a house across the street and they do make gorgeous windows for reasonably competitive prices.

When they first came along they were offering windows with a u-value of 2.0. So I asked if I could supply them with higher performance glazing units to their specs that they'd fit into a frame. I provided them with my research notes and they made some calls. They came back and said they could do a u-value of 1.6 for the same price (using a double glazing unit 11mm thick). They're a bit uncomfortable going much wider than 11mm thick for aesthetic reasons which troubles me because if we go to 24mm thick then we can get down to 1.1 (for £70 per m2 for toughened glass from UA Glass, Norwich) and I'm currently trying to get a price for a triple glazed unit from Carey Glass in Ireland which gets us down to a u-value of 0.7 (the performance required by Passivhaus) with a thickness of 28mm. A fellow on Green Building Forum made his own sliding sash window frames using 34mm thick triple glazed units and he didn't have to make the frames any wider than single glazed sash because he used the glass itself as the structural element in the sashes and used white warm-spacers. If we can import triple glazed units for a reasonable sum of money they I'll approach our local joiner to see if they can use the triple glazed units structurally. I'm also looking into getting complete sash windows off the shelf from Carey Glass andEnviroNomix/Vrogum

All interesting stuff. Although it takes a bloody age to research. It really shouldn't be this hard to get high performance windows.

Thanks for all the info.

Thanks,

Jack

#4

Submitted by Clyde on Tue, 04/05/2010 - 2:28pm.

Double glazing is clearly an issue that needs revisiting. If Jack can spare another session, perhaps he can bring me up to speed in more detail.

#5

Submitted by Jack on Tue, 04/05/2010 - 2:40pm.

As you say, Double Glazing is remarkably challenging. I just had a lovely conversation with a guy from Swedish Timber Products (based in York!) who do high performance windows (but not sliding sash, unfortunately) and we had a long chat about the challenges of refurb. Very happy to have another chat. Perhaps over a pint?

#6

Submitted by lukasz on Wed, 05/05/2010 - 8:42am.

Jack

For improving further on thermal performance with slim line glazing you may just add thermally insulated internal blinds (if there are no aesthetic reasons against). There are many companies doing these. They commonly have some insulation and aluminium foil inside and are really effective in keeping the heat inside at night - apparently 30% improvement.

For airtightness improvements you usually create double rebate/seal (in casement windows) - may be worth discussing with joinery maker if it is possible for a sash.

Lukasz

#7

Submitted by lukasz on Sun, 06/06/2010 - 12:25pm.

Below is my shortlist of triple glazing available in the UK.

1. Triple glazed performance contemporary style windows (sorted low/high price order - prices are supply only, excl VAT and very indicative - exact price of windows will vary considerably depending on size, whether is openable or fixed, finish etc):

Rationell - good value timber (window U values as low as 1.0) or timber/alu (window U values as low as 0.8) - approx £350/m2
http://www.rationel.co.uk/rationel-uk/data.nsf/webDocuments/CE538483C17D264EC12574E1004317BB?OpenDocument

Protec 7 - timber/fibre glass composite high performance windows with low U-values - triple glazed with U values as low as 0.7 - approx £350/m2 - SADLY I JUST FOUND OUT THEY DO NOT SUPPLY TO DOMESTIC MARKET - COMMERCIAL ORDERS OVER 50m2 OF GLAZING ONLY
http://www.protecwindows.com/en/pro_tec_7/Product%20information.aspx

INTERNORM - timber/alu in many style options. Do passivehaus certified windows (but add 15% to the cost) U values as low as 0.7. Price approx £600/m2.

http://www.internorm.co.uk/

They also do triple glazed UPVC windows which must be better value for money but I would not recommend this route unless there is no alternative.

ENERsign - timber/fibreglass passive haus certified with U value <0.7. Sleek design and minimum sight line from the outside. My overall winner at the moment but not cheap - approx £600/m2.
http://www.enersign.com/en/home/

Skyframe - sliding triple glazed windows bonded to slim fibreglass profiles for frameless experience. Decent U-values in triple glazed category. Preffered choice of bauhaus lovers with deep pockets - over £1k/m2!

2. Triple glazed performance rooflights/skylights:

Fakro FTT U5 Thermo - triple glazed with U value of approx 0.95 (which beats velux equivalent by approx 0.05)
http://www.fakro.co.uk/htmle/220.php

Glazing Vision Skylights - flat roof skylights available in triple glazed version. More expensive than the above.
http://www.glazing-vision.co.uk/fixed-flushglaze-rooflight.html

More types/info can be found here - http://www.greenspec.co.uk/html/products/list413.html

I am planning soon (subject to getting my planning approval) investigating DIY budget option for a triple glazed fixed windows in fibre glass frames.

2. Triple glazed sealed units:

Reflex Glass - triple glazed sealed units with warm edge spacer manufacturer. By buying direct you will save yourself some cash. Centre pane U-value as low as 0.6. Approx £135/m2. 20 years warranty for unit seal!

#8

Submitted by Jack on Mon, 07/06/2010 - 9:29am.

That's really, really useful - many thanks Lukasz

#9

Submitted by Chris Dixon (not verified) on Wed, 13/10/2010 - 2:57pm.

Hi,

Saving the best until last - it is the window FRAMES that are the key to low U value windows, because they are invariably the weakest part of a window when it comes to thermal efficiency. Glass units themselves can be down to 0.6 but the frames in aluminium or PVC will lower the performance of the window to 1.5 or 1.6.

GRP composite-material frames (same material that the Boeing 787 is made from!! Really!) like Pultec Windows can provide 0.6 U values on the total window!

...and they cost less, simply because the manufacturing process is lower cost. Genuinely 'more, for less'. Worth checking out!

Post new comment

Your name:

E-mail:

The content of this field is kept private and will not be shown publicly.

Homepage:

Comment: *

Insert Flickr images: [flickr-photo:id=230452326,size=s] or [flickr-photoset:id=72157594262419167,size=m].
Web page addresses and e-mail addresses turn into links automatically.
Link to content with [[some text]], where "some text" is the title of existing content or the title of a new piece of content to create. You can also link text to a different title by using [[link to this title|show this text]]. Link to outside URLs with [[http://www.example.com|some text]], or even [[http://www.example.com]].
Allowed HTML tags: <a> <p> <span> <div> <h1> <h2> <h3> <h4> <h5> <h6> <img> <map> <area> <hr> <br> <br /> <ul> <ol> <li> <dl> <dt> <dd> <table> <tr> <td> <em> <b> <u> <i> <strong> <font> <del> <ins> <sub> <sup> <quote> <blockquote> <pre> <address> <code> <cite> <embed> <object> <param> <strike> <caption>
Each email address will be obfuscated in a human readble fashion or (if JavaScript is enabled) replaced with a spamproof clickable link.

More information about formatting options

CAPTCHA

This question is for testing whether you are a human visitor and to prevent automated spam submissions. If you were logged in then you won't have to do this tedious task.

What code is in the image?: *

Enter the characters shown in the image.

High performance glazing

#1

#2

#3

#4

#5

#6

#7

#8

#9

Post new comment

Menu

Active forum topics

User login