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Post by andy king on Nov 4, 2008 16:32:19 GMT
I think the energy saving is only part of it. If you also factor in noise reduction and the minimised condensation (I don't miss ice on the inside of the window on a winters morning any more!  ) then it starts to become more desirable for those reasons as well as heat retention. One thing that might be worth checking on a 4/6/4 unit is the guarantee. I know a few years back (around this area anyway) the manufacturers wouldn't put the usual 10 year guarantee on those units. 4/8/4 and over was fine. Not quite sure why though. Andy |
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Post by jake on Nov 4, 2008 16:34:14 GMT
Answer to Spud elsewhere. Can we keep this thread factual and not fill it up with b*ll*cks, please?
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Post by mrgrimsdale on Nov 4, 2008 16:41:26 GMT
DG calcs. The only calc which really counts is the cost benefit. It is often surprisingly low or even negative. DG is not a high priority if energy saving is the issue. I think that is right if the issue is whether to rip out old windows to install new DG units, but if you are installing new windows anyway, the incremental cost of putting in a sealed unit rather than single pane (very unscientifically) just has to be a much better return than you are suggesting. Show us your sources, and maybe we can deal with it? Last time, you evaded this one. Easy peasy - do a heat loss calculation for a project of your choice comparing savings against cost of DG. I did it for my two previous houses and DG wasn't worth the candle - by a very large margin. The rule of thumb is that 10% of heat is lost through windows, DG halves this, saving 5% of the typical heating bill. A much bigger figure this winter, but still not a huge sum for the average house, and peanuts compared to savings through insulation and draft proofing. The percentage rises of course, for a highly insulated house, but it's a fraction of a smaller heating bill, with the same result cheers Jacob |
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spud
New Member
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Post by spud on Nov 4, 2008 16:53:17 GMT
I did my best to stop it filling up with 'b*ll*cks'! I admit I put Gore's cropped photo in, that he used to terrorize you, but I regret it from the bottom of my heart.
I'm out of here, the naivete scares the crap out of me!
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Post by jake on Nov 4, 2008 17:09:13 GMT
OK, I was being lazy and looking for the data and assumptions for the other items on the list. Let's do it on payback.
Let's take the glazing I'm about to put in - all replacements needed anyway (previous doors and non-original knackered aluminium sliders and windows non-original crittal beyond redemption/repair). So only the incremental cost of the glazing counts - single-glazed frames would have been the same cost/u-value (maybe a bit higher because thinner but I'll ignore that)
Total glazed area = 5.27m2.
U-value of single glazing = 5.4
Let's take the kypton fill at 1.4
Difference x glazed area = 36 watts/hour/ deg C temp differential.
Assume heating on for seven months of the year (Oct/Nov to April/May), take an average differential of dunno - guesswork for simplicity - 10 deg C (20 inside, 10 outside)?
36 Watts x 24 hours x 210 days x 10 c = 1800kW at about 4p per kW = £72.
Payback is about 5 years. Not bad at all as far as such things go - better than insulating walls (except with cavity insulation which is reckoned to be 2-4 years). About as good as topping up of loft insulation if you've got 50-100mm up there already.
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Post by mrgrimsdale on Nov 4, 2008 17:50:44 GMT
Sounds reasonable - I seem to remember figures of £50 ish when I last did the same calculation. If you include your labour costs, 1 weeks work? then your payback time extends somewhat! In fact you will very likely be replacing faulty units sooner, and will get no pay back at all. QED  When you get to total window replacement say 3 to 8 £K then it's madness. cheers Jacob |
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Post by jake on Nov 4, 2008 17:56:32 GMT
Where is there any extra labour (on my assumption that new windows etc are needed anyway)?
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Post by mrgrimsdale on Nov 4, 2008 18:01:19 GMT
What, your "£130 on top of the £277 for 16 argon fill units (6 of them laminated outside/toughened inside)" includes fitting? Sounds like a good deal.
cheers
Jacob
PS oops no ignore that. They need replacing anyway. But why?
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Post by jake on Nov 4, 2008 18:05:57 GMT
You don't fit single panes? Don't they fall out?
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Post by jake on Nov 4, 2008 18:12:13 GMT
Because some cretin took out the original door many years ago and put in hideous aluminium sliding doors - the tracks/wheels of which are knackered, and they are so horrible they have to go on aesthetic grounds alone. Some cretin (probably an earlier cretin, maybe the same cretin when younger) ripped out the original timber bay window and replaced it with some tasty Crittals which had rusted though at the hinges (and which also always look nice on Viccy).
Good enough?
The point holds for new build as well, or anywhere where the existing is beyond redemption/repair.
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Post by jfc on Nov 4, 2008 18:57:35 GMT
Plus the fact that if you are replacing a whole window you have to put in double glazing as it is the LAW .
I had a very irate phone call a few years ago from a customer saying that the only thing stopping the sale of his house was the window i had made him because it didnt comply with regs . I had to stop him in full flow of Mr Angry to tell him it was fitted before the date the law came into force and if he shows the surveyor my invoice all will be ok . That made me decide that if people dont want to comply with the regs i do supply only and if they want me to fit the glass it complies with regs . People dont think "ops my mistake " when they try and sell a house they look right back at the person that did the job .
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Post by mrgrimsdale on Nov 4, 2008 19:31:40 GMT
Because some cretin took out the original door many years ago and put in hideous aluminium sliding doors - the tracks/wheels of which are knackered, and they are so horrible they have to go on aesthetic grounds alone. Some cretin (probably an earlier cretin, maybe the same cretin when younger) ripped out the original timber bay window and replaced it with some tasty Crittals which had rusted though at the hinges (and which also always look nice on Viccy). Good enough? The point holds for new build as well, or anywhere where the existing is beyond redemption/repair. Hmm I'll have to look more closely at the figures. I reckon on a saving of £50 to £100 on fuel for a whole house DGd, not just a door and a window. cheers Jacob |
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Post by jake on Nov 5, 2008 11:46:32 GMT
Oooopps. I got the spreadsheet wrong and added the double glazed energy loss instead of subtracting it. 21 Watts/hour/deg c rather than 36, so on my guesstimates, the saving is £40, and the payback shoots up to a pretty poor ten years. From the data here www.metoffice.gov.uk/climate/uk/2006/winter/averages1.html it looks like the UK autumn/winter/spring average temp is more like 8C than 10C, though, which pops it back up to £50 a year and an 8 year payback. The argon rather than krypton fill saves £43 year for a 6.5 year payback. Rate of return on capital is 14% for krypton fill and 19% on argon fill, assuming a 15 year lifespan and 3% fuel price inflation, and still 8% and 15% with a 10 year lifespan. Pretty good RoRs, compared to investing the money. |
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) then it starts to become more desirable for those reasons as well as heat retention.
