One shouldn't complain about "free" but I don't trust the head honcho Dr Craig - appears liable to be selective of data to suit his own ends.


Here for example he chooses odd numbers seemingly just to produce a "shock" answer to drive publicity for his database:

http://www.inspiredefficiency.co.uk/wp-content/uploads/2013/10/Building-magazine-article-6-9-13.pdf

http://www.circularecology.com/1/post/2014/01/double-glazing-or-triple-glazing-all-pane-and-no-gain.html


-Why compare "acoustic" 3G with "energy saving" 2G?

With argon fill the optimum gap between panes is ~20 mm. 4-20-4 2G units have a U-value of 1.5 W/m^2k centre-pane (hard coat) or 1.2 (soft coat)

"Acoustic" 3G is where you stuff 3 panes into a 2G mm thick frame; typically 4-12-4-12-4. This is what all the folks that advertise on TV try to sell you, because it fits their cheap and nasty frames.

"Energy saving" 3G units are 4-16-4-16-4 and 0.8 W/m^2k centre pane (hard coat) or 0.6 (soft coat).

Disbelieve this? Ask the Pilkington website, rather than relying on the numbers presented by window retailers with vested commercial interests in extracting maximum life from their existing tooling before upgrading to manufacture the deeper profile 3G frames - as the author of this analysis has done.

Whole window with a relatively cheap 70 mm profile PVC frame you'll get 2G 1.4 W/m^2k or 3G 0.9 W/m^2k (both soft coat). The extra pane of glass in a 70 mm PVC frame adds <£10/m^2 and choosing this is economically a no-brainer unless your retailer is a shark or doesn't own a production line that's 70 mm profile capable. (most of the advertise on TV types)

They need to re-run the numbers with 1.4 vs 0.9 U-values.


-Internal temperature is lower with 3G units and they've not taken this into account in their analysis

A 2G unit is "cold" in winter. You get "cold" air sheeting down the window and into the room: this draught means that for a given comfort level your average room temperature needs to be higher. 3G units elimiate this and allow a lower average internal temperature for a given comfort level. This is why they're specced in passivhaus - they reduce fabric losses elsewhere, not just at the windows.

Most unqualified people make the same mistake when evaluating the 2G vs 3G decision.

They need to re-run the numbers with say a 0.25C or greater reduction in internal temperature, depending on window size relative to room size.


-Lifecycle cost isn't just embodied energy + energy savings.

Embodied energy is irrelevant where the materials are subsequently recycled, such as with the aluminium frames.


He has ignored all requests for showing his working via twitter and email. The bloke has to earn a living, but given that he won't show even the most basic working, and chooses unreasonable comparisons to generate headlines, can you trust the rest of the data?

I'm amazed and disappointed. I have to agree with Marko's assessment of the window comparison; it seems a very amateurish effort. I've been aware that the detail in ICE varies a bit depending on how much some vested interest has spent on providing data in an appropriate form, but hadn't spotted anything as crazy as the window example. But is there anything better than ICE for such assessments?

Posted By: jamesingramI presume you've seen
Dutch study http://t.co/0q4YEA7CXT

Sadly that site seems to be written by a script kiddie and just shows as 404 for me.

Note that version 2 was published in 2011. There's nothing new here.

Entry of 12 Dec 2013 in http://markbrinkley.blogspot.co.uk

Ah I see how you did that - good.

When efforts to reduce embodied energy transform into a priority to increase sequestered unoxidised carbon, it gets interesting, and it then makes less sense to try to weigh against reduced energy-in-use - it becomes a 'different animal'!