Typical estimations are that EE is between 90,000 - 100,000 KWh. From memory embodied energy is typically <10% of the cumulative energy use of a building. Therefore a 50% cut in EE is a reduction of 5% of the total energy consumed by a building (i.e. EE + energy-in-use.) A reduction of 50% in energy-in-use equates to a reduction of 45% of the total energy consumed by a building. As a consequence of the above reducing energy-in-use is of greater import at this time. (In a Passive House EE rises to 40-50% of cumulative energy demand.)

So reusing the existing building has limited advantage especially if retaining the building compromises energy performance. If lime mortar has been used in the existing building you could always demolish the building with some care and re-use the masonry and salvage any timber that it re-usable.

Mark

P.S. Check out the Whole House Book, Harris and Borer for more discussion of EE.

Posted By: biffvernonNevertheless, it may have it's part to play in the cultural landscape of our historic heritage.

The original posts says its of no architectural merit so I would say demolish it and build an exemplary low energy building and set a good example.
Whats more you can reclaim the VAT on a new build.

Hi Leo, If the focus is on energy conservation, then it is likely that a superinsulated airtight new build will easilly negate the embodied energy of the new materials that you use.

Compare this to keeping the old building, having less 'new' materials, but ultimately more energy 'in use' as you cannot realistically achieve the same insulation and airtightness standards as the new build.

Unless of course you can integrate carbon-free renewables which make energy conservation beyond achieving internal comfort conditions irrelevant. Probably not cost effective though.

Another way of looking at this problem is to ask what is the payback period on a new house, as against a major renovation? Either route you choose is going to involve using lots of new building materials, although the new house will presumably use a lot more.

The options would probably look like this:
1 Do Nothing. EE 0 tons C02, annual CO2 emissions 10 tonnes
2 Renovate. EE 15 tonnes, annual CO2 emissions 5 tonnes (payback 3 years)
3 Rebuild. EE 40 tonnes, annual CO2 emissions 2 tonnes (payback on 1= 5 years, on 2 = 9 years)

blockquote>Posted By: biffvernon And to say, as Mike does, that you cannot realistically achieve the same insulation and air-tightness standards in an old building as in a new build, suggests a lack of inventiveness and determination.

Biff, why the insult suggesting a lack of inventiveness and determination? Insults and ridicule seem to be a favoured argument of yours lately. Not very inventive is it?

I am surprised that you take exception to my comment regarding air tightness as I have the impression from some of your previous posts that you are not in favour of airtight buildings at all. Perhaps you just wanted to provoke a response with your latest post? Or perhaps you just like to advocate improvements under any circumstances, and not new build?

Anyway, there are probably buildings where it is possible to upgrade to superinsulation and airtight standards, but in the main, I do not believe that it is practical to attempt this.

Why?

Around 70% of the existing stock was built without any insulation requirements. As such these buildings deal with other performance characteristics [such as moisture resistance] differently to buildings designed to accommodate insulation. Many such buildings are also very leaky having suspended [sub ventilated] floors, open flues and ventilated eaves/soffits.

To try and upgrade these buidings to SUPERINSULATION specification akin to that possible in new build is often very unwise, as the effects of doing so on the existing fabric can be detrimental in other ways. Examples include fully filling cavities on severely exposed sites; internally insulating stone walls with wooden lintels [while also ignoring the thermal bridging of internal walls and floors].

To try and give these buildings high levels of air tightness while maintaining the integrity of insulation is also very difficult indeed, and there are often many different technical problems which need to be overcome. A common example: How do you stop the infiltration effects of a howling gale under a sub-ventilated timber floor, while mitigating the effects of convective losses on the insulation between the joists? How do you eliminate the thermal bridging of the joists in this scenario?

Of course there are solutions to most technical difficulties, the question is how much work do you have to do, and at what cost? In many cases [such as Leo's I suspect] a new build is the prudent option.

Why can you claim the VAT back when you build a new house? Anyone understand the logic here? I don't.

Posted By: biffvernonNo insult intended at all - except to those who would destroy our historic townscapes because they can't be bothered to work out how to improve an old house or because they don't like paying VAT. Advocate improvements under any circumstances, and not new build? Not me guv, didn't I say, "I have never said that buildings from the 40's, 50's and 60's should never be demolished. Far from it!"

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You a very quick to judge or should I say misjudge. You have picked the wrong person to insult. Many buildings have merit and can be upgraded. I have recently converted and restored a Grade 2 listed building to well in excess of bldg regs levels of insulation and I am now converting an old pumping station into offices, this time with a u value of half that required by the bldg regs. Clearly it is preferable to reuse a building, I would never build on a greenfield site, but each situation needs to be judged on its merits without the presumption that we should not change our cultural landscape and historic heritage.

Both these buildings had merit and were upgraded but there are a great many that do not have merit and are fundamentally badly designed and badly built. These building represent an opportunity to build exemplary buildings that look good and perform.

There is nothing unsustainable about reclaiming vat its a purely financial transaction it does not use any resources. And if reclaiming VAT means the client can spend more on improving the energy performance of the building then so what.

Oh and I build tight too - so lets wait for the next set of insults for daring to have a different opinion to Mr Biff Vernon

I wonder if people read what I wrote or read what they think I wrote

What's wrong with designing buildings to last 1200 years, with components that are repairable and replaceable? Surely that should be at the heart of the Green Building Ethic.

Demolition should be seen as a failure of building or planning.

I inherited my grandfather's scythe. I replaced the blade and later I replaced the handle but it is still fit for purpose.

Posted By: Mark Brinkley When VAT was introduced in 1984, ...

Er, VAT was introduced in the UK quite a long time before 1984. 1st April 1973, in fact.

Posted By: biffvernonAnd to say, as Mike does, that you cannot realistically achieve the same insulation and air-tightness standards in an old building as in a new build, suggests a lack of inventiveness and determination.

I totally agree. We can't afford the mistaken assumption that top-notch energy performance can't be achieved in uprated old buildings, including precious Listed Buildings. True, much ingenuity in design/specification and much care in construction is required - each building requiring a unique solution. And true, it may cost more and won't be @ zero VAT, but the benefits tend to be great. A horrid 30s to 80s house can be totally transformed e.g. by putting a skin of strawbales round it, extending the eaves, altering the window layout and probably extending, say putting a sunny atrium on its south face. Never mind cavity insulation - that's completely obsolete - fill the cavity with weak mix and get 13" of thermal mass inside superb bridge-free external insulation.

Bit of both! Did I say demolish cavity walled estates? certainly the blobndob has to go but the shell might be upgraded as suggested above, except for lack of space to thicken walls outward. Perhaps the useless tiny gaps between estate houses could infilled with useful floorspace. The ones that I suspect are really hopeless are the stud-framed brick skinned ones. The point is that whatever puny insulation, windows etc a typical house of today has, it's best almost ignored or ripped out in an upgrading to the level that's reqd - certainly don't pay a penny at housebuying time, on account of the energy half-measures that the seller's proudly pointing out.

Part of the answer to improving build quality is for more (or even most) people to self build like in the rest of Europe. If you are building a home and an asset for yourself, even just as a client, then you care about it and put some effort into getting it right. More than you can say for the average developer who is primarily interested in selling quickly for maximum profit. The only person with a genuine vested interest in the ongoing performance of a building is the occupant, so more families and companies commissioning buildings for their own use must be a good thing.

Or to carry out post construction testing using a thermographic camera and also an airtightness test.