warm edge

Windows with Muntin/Georgian Bars – better than thought

March 31st, 2016. Glazing bars (Muntin or Georgian Bars, “Sprossen”) are an indispensible instrument to design the appearance of buildings. But not only aluminum spacers in the edge bond of insulating glass elements are thermally-wise disadvantageous. Bars between the panes of a multiple glazing create thermal discontinuities, that have to be taken into consideration when determining the Uw-value of windows.

In my new webinar “Sprossen” for the BF (German Federal Flat Glass Association) on Wednesday, April 13th, 2016, I will explain why such glazing bars occur on windows at all, which types of bars are possible with multiple plane insulating glass and how Muntin/Georgian windows can be determined thermally-wise in a fairer manner compared to the high surcharges from the product standard for windows, EN 14351-1. (The webinar will be in German language).

Online-signup to the BF-Webinars is possible here.


Lukewarm edge? Does not exist!

February 5th, 2016. Just to clarify again: “warm edge” refers to insulating glass edge bond with a thermally improved spacer. There is a clear definition of “thermally improved”. It can be found in the relevant international standard for the thermal transmission coefficient of windows, ISO 10077 part 1, as well as in the standard ISO 12631 for the thermal performance of curtain walling. Both standards contain each a chart with linear thermal transmission coefficients Ψ (Psi-values) for spacers made of aluminium and steel and a second chard with lower values for spacers with thermally improved performance. In cases of coubt, the definition helps to decide which chart is the right to use.

According to this definition, spacers made from steel are definitely NOT thermally improved. “Warm edge” does begin with stainless steel spacers. Stainless steel has a considerably lower thermal conductivity compared to aluminium or steel – it’s not for nothing, that the handles of steel cooking pots are often made from stainless steel.

Therefore, it is definitely not ok to praise steel spacers as somehow thermally improved. And by the way: Just the colour black alone does not provide sufficient evidence for a good thermal quality. Lukewarm edge – something like that just does not exist.


BF Technical Webinars Spring/Summer 2016

January 17th, 2016. The webinars offered by the BF in spring/summer will take up and continue the themes that were offered during the last semester (All webinars will be held in German language).

My contribution this time will be the following four webinars:

Wednesday, 20.1.2016 – Abstandhalter / Warme Kante – Teil 2 (Spacers / Warm edge – part 2)
Thursday, 3.3.2016 – Glasbruch – Teil II (Glass breakage – part 2)
Wednesday, 13.4.2016 – Sprossen (Glazing bars)
Thursday, 2.6.2016 – Kondensation bei Isolierglas (Condensation on insulating glass)

The full program including possibility for registration can be found [here] on the BF websites.

On 17. January 2016|By |Dates|0 Comments

What helps against the heat of the summer?

August 7th, 2015. It is common knowledge that a thermos bottle keeps cooled matter cold and heated things hot. Nowadays, refridgerators are extremely insulated and everyone knows that otherwise, they would be bad power guzzlers. Have you ever fancied the idea to keep your fridge door ajar? Certainly not.

An air-conditioned building is nothing else than a huge refridgerator. But what can be observed during these hot summer days? Air conditioning is set to arctic temperatures and doors/windows are left wide open. Cooling energy is wasted, and the costs for its generation often exceed the heating costs of winter times. You may wonder, what this has got to do with ‘warm edge’. Now, of course, the thermal insulation of the building envelope matters for this question.

Despite the incredible heat of the summer, it should be comfortably cool inside a building. It is necessary to prevent the heat from getting into the building. Once it is inside, it requires a lot of effort and costs to get it out again.

It is always the heat that moves – provided there is a temperature gradient, no matter in which direction. For a heated building, a) transmission heat losses, i.e. direct heat transfer through the building envelope (walls, roof, windows, etc.) and b) ventilation heat losses through joints, leaky or in extreme cases open windows and doors have to be considered. As a matter of principle, the same mechanisms are working for air-conditioned buildings, only in opposite direction. On top are the effects of solar radiation through the glazing.

Meanwhile, it is well known that in winter, it is much more comfortable to live in a building with excellent thermal insulation. But not everybody realizes that the heat does not care if it moves from roomside to outdoors or from outdoors to the roomside.

Compared to a poorly insulated one, in a highly-insulated building it takes much longer for the summer heat to transfer to the inside – provided doors and windows are kept close, to prevent the hot air from getting in. (Over the long term, of course, this requires a controlled ventilation with heat recovery). The lower temperatures of the night are used for cooling the building down, and as soon as the outer temperature comes close again to the roomside temperature in the morning, all windows are closed and if possible shaded. Then, even during these days of extreme summer heat, you can stay inside a highly insulated building at comfortable 24 °C (75 °F), and this for outer temperatures of 32 °C (90 °F) and more.

What do you actually need for a highly insulated building? Highly insulated walls, highly insulated and air-tight windows with triple glazing – of course with warm edge for the glazing edge bond – plus exterior shading, to keep the unwanted solar radiation outside. (Don’t forget an energy-efficient controlled ventilation system!). Without the thermally improved spacers, i.e. with conventional aluminum spacers in the edge bond, the windows would have loopholes all around their glass edges, quickly conducting the heat to the inside.

Therefore: Investing right means making investments in saved energy, with improved thermal insulation of buildings. This is easy on your budget and protects the climate.

Heat, that is not allowed to penetrate into a building, does not require a costly air condition to transport it out again. It’s so simple.

Warm edge – Profile bars of the future

May 28th, 2015. There are different approaches to thermally improved glass edge bond: hollow profile bars (“rods”) made from materials with low thermal conductivity, flexible foam spacers on coils or thermoplastic material from drums. You can find an overview of the presently offered “rods” in my latest article in issue 5/2015 of GLASWELT here, including a glimpse at the future of warm edge (Article is in German language).

BF Technical Webinars: Autumn/Winter Semester 2015

May 3rd, 2015. The new BF-Webinar program (in German language) is available now – restructured, cleared and more organized. The basic courses are offered autumn/winter 2015, the courses of spring/summer 2016 will be based on them. You can find a description of the full webinar program in the new BF-Webinar-Flyer here (sorry, only available in German language).

My contribution to the autumn/winter program this year are two webinars:
Wednesday, October 14th, 2015, 10:00 “Abstandhalter / Warme Kante – Teil 1” (spacers / warm edge part 1)
Monday, December 7th, 2015, 10:00 “Glasbruch – Teil 1” (glass breakage part 1)

Registration for interested parties is quick and easy through the BF websites here. The fee per webinar and participating company is 95 EUR.

Dates for the autumn/spring webinars in 2016 are not yet fixed, but I will offer the following topics:
Abstandhalter / Warme Kante – Teil 2 (spacers / warm edge part 2)
Glasbruch – Teil 2 (glass breakage part 2)
Sprossen (new) (muntin/georgian bars)
Kondensation bei Isolierglas (new) (Condensation on insulating glass)

As soon as the dates are available, I will announce them on this page.

Extended scope for application of BF data sheets ‘Psi values for windows’

April 3rd, 2015. The data sheets ‘Psi-values for windows” of the Working Group Warm Edge of the BF Bundesverband Flachglas (German Federal Flat Glass Association), containing representative Psi-values for windows for thermally improved spacers are suitable for a simplified verification of Uw-values of windows. However, it is not allowed to use them for each and every window, especially not for facades. The application is only possible according to the ift guideline WA-08.

For wooden-, wood-aluminium- or PVC-windows for example, the representative Psi-values can only be applied for frame-U-values Uf greater than or equal to 1,0 W/m²K, and for aluminium-windows as far as greater than or equal to Uf ≥ 1,3 W/m²K. A minimum depth of glass insertion into the frame profile of 13 mm is required as well as the fact, that the real frame profiles must be comparable with the representative frame sections shown on the data sheets. The data sheets must not be used for windows with unprotected glass edge.

Driven by steadily increasing demand on thermal insulation of building envelopes, window systems are thermally-wise continuously improved. After all, they play a key-role in energy-efficient building. This is only possible if the thermal transmission coefficients not only of the glazing, but of the frame profiles as well are optimized, i.e. reach lower values. The level of thermal insulation of the frame profiles should not differ too much from the excellent U-values of modern triple insulating glass, to avoid problems like condensation to move from the glass surface to frame or reveal. The number of systems with Uf-values below 1,0 W/m²K is growing.

To open the use of the data sheets for those highly insulating frame systems as well, the Working Group Warm Edge run another project. ift Rosenheim made an analysis, under which conditions the application of the existing data sheets could be allowed for better = lower frame-U-values as well. Result is an extension of the scope of application according to this chart:

The chart shows the relevant requirements on Uf-values for window frame profiles for the application of representative Psi-values. Highly insulating frames must have a depth of glass insertion of minimum 18 mm.

Source: BF Bulletin 004 – Guide to ‘Warm Edge’ for windows

The updated ift guideline WA-08/3 is available since February 2015. It can be ordered from the ift Rosenheim online-shop, as pdf-file for download or as a printed copy (here).

Moreover, the ift guideline specifies requirements on the thermal transmission coefficient of the glazing, Ug and on the pane thicknesses. For panes thicker than 4 mm, surcharges have to be applied on the representative Psi-values.

Explanations can be found in detail in the ift guideline, and also in the updated version of the BF Bulletin 004, Guide to ‘Warm Edge’ for windows, published by the Bundesverband Flachglas (download here)

Warm Edge – Where is the journey heading?

December 27th, 2014. Without doubt, an excellent thermal insulation is one of the most efficient measures to reduce energy consumption of buildings. As a consequence, windows and facades, key components of building envelopes, have to provide even better (lower) U-values. My latest article published in issue 12/2014 of German glass magazine GLASWELT here discusses the consequences for the development of warm edge systems (article is in German language).


Glasstec 2014 – News about “warm edge”?

December 9th, 2014. In a contribution to the column “Pro & Contra” of the October issue of the German magazine GFF-Magazins [here], I anticipated no quantum leaps regarding warm edge technology, shown on Glasstec 2014 in Duesseldorf. During my visit of this spectacular event, I could verify my point of view – no revolutionary new material or machine technology were exhibited, but I found an increase in options for existing solutions, and that both regarding material and machines for processing. You can find details in my latest article in GFF-Magazin, issue 12/2014 [here], (I apologize that it is all in German language.)

Please note

December 9th, 2014. The office of the Consultant for warm edge and glass has been moved from Herrenberg to Boeblingen, closer to the captital of the German federal state Baden-Wuerttemberg. Please note the new contact data at the bottom of these pages.

As soon as everything is unpacked, you will find here again regular contributions to the subject of thermally improved insulating glass spacers, glass and other related topics.