16 Aug 2011

Cash for Sprawl

I last wrote about the Green Belt on June 2nd, before the Draft National Planning Policy Framework (NPPF) had been published. I identified it then as a very Tory problem because the Tories in the government want it loosened, whilst the Tories in the shire counties want it maintained - strengthened even.

The NPPF appeared at the end of July, and most of the mainstream press coverage since then has been expressing the widespread fear that the countryside is about to be concreted over and that we are all about to be engulfed in urban sprawl. The usual suspects are behind this, notably the CPRE and The National Trust, and big names such as Griff Rhys Jones and Simon Jenkins have been persuaded to write eloquent pieces in the Times and the Guardian. They are trying to whip up a fear, a hysteria, along the lines of campaign to save our forests which resulted in a Government U turn earlier this year. They want to "turn back the tide" of development which the NPPF vaguely hints at.

In fact the NPPF is a wonderfully vague document. You'd think in managing to trim planning guidance down from 1,000 pages to 50-odd, it would now read like a concise cinema listing or a menu, but most of theses pages are taken up with aspirational statements and rather woolly policy indicators, so it's quite hard to figure out what the NPPF is actually on about.

The thing that these objectors object to is this tell-tale phrase (oft repeated, it must be said) that there should be a presumption in favour of sustainable development. Jenkins, in particular, tore into the S word, accusing the government of using it as a smokescreen to push through any development, but as far as I can work out, there is little if any guidance in the NPPF on what is meant by sustainable development. My guess is that, in the spirit of localism, the definition will be left to individual councils to work out.

But it remains an important adjective because presumably if there is no national definition of sustainable, then each council can more or less tinker with the definition to encourage or discourage development. What NPPF doesn't offer is clarity: I can see years of ugly planning battles ahead with expensive QCs discussing whether or not Development X is sustainable. "Not in Berkshire, m'lud."

Jenkins's assumption that it is a weightless word, a shim-sham put there to dress any development as good development, is probably a little off the mark.

The next point to consider is the status of the Green Belt. It appears to hold two separate meanings. The first is the technical one, the one planners recognise, of land specifically delineated as Green Belt (or as an Area of Outstanding Natural Beauty), which in fact is a surprisingly small amount of the countryside. The second is the idea that all open countryside is green belt, which is the perception that most of the public has. In fact most of the UK is designated in planning terms as farmland and for the past 50-odd years you haven't been able to build on it. Not because it's green belt, but because the planning system has chosen to restrict building to existing settlements.

Now what's at risk, if presumption in favour of sustainable development becomes the norm, is the status of this non-green belt farmland. This explains how supporters of the NPPF can say that Green Belts (and AONB) remain as protected as they ever have been, whilst those railed against the changes claim that the countryside is about to be concreted over.

But NPPF doesn't say anything as simple as this. It doesn't state that concepts such as village envelopes should be shredded or that all non-green belt farmland is now up for grabs. Rather it frames the whole issue around the proposals being judged to be suitably sustainable and leaves the locals to figure out what to do.

Which brings us onto the thorny issue of Cash for Sprawl, which is slowly simmering away in the background. This is the libertarian concept that current planning restrictions have a monetary value which is expressed in the difference between the cost of non-developable farmland (peanuts) and land with building permission (squillions). An individual may own a piece of land but, the way things stand, the right to develop it is something vested in the surrounding community. The argument goes that, as the ability to turn a field into a building plot (and thus perhaps £10,000 into £1million) rests with the neighbours, it is the neighbours who should benefit - especially as it's the neighbours who will be inconvenienced by a) the building work) b) the loss of a nice view and c) maybe lower house prices as a result. If you like, it's compensation money. Or, as I have seen in succinctly summarised by anti-campaigners, Cash for Sprawl.

Needless to say, there is nothing about any of this in NPPF. The concept of planning gain is nothing new - in fact our social housing budget has been based on little more for decades. But up until now, there has been a very clear distinction between community gain (i.e. more playgrounds, cycle paths, new schools, etc) and individual gain (via rate rebates or even cash payments). The thought of crossing this dividing line makes many people very uncomfortable because it's beginning to feel less like big society stuff and more like greed or bribery. So to date this sort of debate has been going on away from the glare of mainstream media, and hasn't really entered the public realm.

But that too may be changing, if this week's Sunday Times is anything to go by. It carries two pieces on the planning debate. The first, by Jenni Russell, Throwing the Countryside to the Developer Wolves, is a call to arms to all national Trust/CPRE types, very much in the Simon Jenkins mould. But two pages further on, in a Think Tank piece, an article by Neil O'Brien of the Policy Exchange is entitled Get Paid to loosen the Green Belt. Unfortunately, the articles are paywalled so I can't provide a link. But if you've followed this piece so far, you will have a pretty good idea of what is in them. O'Brien's killer paragraph goes thus:

A better solution would be to let communities keep more of the planning gain and concentrate the money on those nearby who are most affected by development. Cash should go directly to households, rather than just councils or neighbourhoods. A big cheque in the post might prove some consolation for having development nearby.

No one has got as far as outlining a mechanism by which this might happen. Who would decide who would be eligible, and how much each household might receive? You don't have to think about this very long and to see that you might be opening a can of worms here, setting neighbour against neighbour in a pro-development gold rush. But if it "worked", suddenly every village in England might be falling over themselves to climb aboard this particular bandwagon - precisely what the CPRE fear. NPPF is no help here. It's simply left to local councils to decide how to handle it, and to decide what is or what isn't sustainable.

And this is perhaps the nub of the problem. NPPF doesn't really make it clear how much power the local councils will have in future. Are they still going to remain the sole arbiters of where development can or cannot take place? Or are developers (be they individuals, groups or professionals) going to be able to bring forward their own schemes on any bit of farmland that takes their fancy, in return for some form of "community cashback." You can't really have both. Either the planning system remains top-down, council led, or it becomes bottom-up, developer pushed, with the role of the council reduced to protecting specific areas, and arbitrating on whether the proposals are sustainable or not.

10 Aug 2011

Confusion over roofing underlays

Back in the 1980s when I was working as a general builder, if we had a re-roofing job we always used a product called Zylex, a bitumen roofing felt produced by Ruberoid. It was heavy, came in 16m rolls and above all it was cheap. I can remember the first time I ever saw Tyvek which was said to be the future. Tyvek was that magic thing, a vapour permeable underlay (VPU), which would allow roofs to ventilate and do away with all the complex little fiddles we had to do to stop condensation. It sounded so cool.

Fast forward to now and Zylex has all but vanished. There are now dozens of manufacturers produced VPUs and it's what everyone now uses. VPUs used to be much more expensive but there isn't a great deal of difference in price now (they seem to cost between £1.50 and £2/m2). But what is interesting is that, according to reports coming from the NHBC, they don't seem to work any better than Zylex. The recent hard winters have led to a spate of condensation claims, as water forms on the underside of the VPUs, and then drips down through the ceilings of the new homes below. The NHBC deems that eaves-to-eaves ventilation is inadequate and that we should use eaves-to-ridge ventilation, which introduces some sort of stack effect, in order to remove the moist air form these cold lofts.

If you want to avoid having to install ridge vents, then there is another option and that is to go for an air permeable underlay (APU). A what? Well an APU promises to do what VPUs promised back in the 1980s and didn't really manage. Just like Goretex jackets don't actually stop you sweating. It's a similar idea, a woven fabric underlay, but it allows air to permeate through the fabric which basically requires bigger holes than ones that just admit vapour. The best known (only?) APU on the market at the moment is Klober's Permo Air (£93 for 50m2, so not that much more than the others).

Two thoughts occur. Will we be coming back in twenty years time saying that APUs don't work either and that we are still getting dripping condensation in lofts. We seem to have come a long way in developing superior roof underlays and got precisely nowhere. And secondly, can an APU be used as an air barrier in airtight construction systems? Or is it, by its very nature, leaky?

Good piece of further reading here on the Monier site.

8 Aug 2011

Unintended consequences No 12: PV for water heating

One of the more bizarre aspects of the Feed-in-Tariff is that electricity producing photovoltaics are being used to power immersion heaters for hot water tanks. The "correct" technology for this task is the solar thermal panel, as these are much more efficient in converting sunlight into hot water. They are cheaper to install and they do it directly - or more directly than PV will ever do.

• 1m2 of solar thermal panel will produce around 500kWh of hot water per annum. Installation cost around £1500.

• 1m2 of solar PV will produce around 100kWh of electricity per annum. Installation cost around £700.

• Put another way, hot water powered by solar thermal is around half the price of hot water powered by PV.

Yet such is the distorting effect of the feed-in-tarrifs that people are now thinking of using PV for domestic hot water heating because they can't think of anything else to do with the surplus electricity produced on sunny days. Around 90% of the tariff is available just for producing electricity, and its easy to end up with a system that is oversized for purpose when the weather is right. On hot sunny days, you just don't need much in the way of electricity, so heating a hot water tank makes sense. And if you install more than 15m2 of PV on your roof, then you should be producing enough power to heat your domestic hot water, at least on a par with 3m2 of solar thermal.

So perversely, the way the feed-in-tariff is set up, one of the losers is set to be the solar thermal industry.

It makes senseBut only in terms of the strange Alice-in-Wonderland economics of feed-in-tariffs

4 Aug 2011

How do you assess a product like Oxyvent?

Here's an interesting press release that just landed on my desk. It's for a new plumbing product called Oxyvent. It's a box that you add onto your radiator or underfloor heating system that helps it run better, and it promises huge savings in fuel burned.

According to the PR lady, Paul Worswick, director of Oxyvent, is "very keen that Oxyvent isn't seen as some magic box of tricks as the physics behind the product is straight forward when explained." There's lots of information about on the website and a YouTube video sequence showing Paul himself with a Pimlico Plumber who is busy installing Oxyvent in someone's house. There's an FAQ and there is a brief summary of some tests carried out by Dr Tony Robinson, a lecturer at Trinity College, Dublin (the kit hails from Ireland). And there are some ringing endorsements from satisfied customers.

But what there isn't is any simple to understand explanation of what makes Oxyvent so special. It seems to turbo charge the flow rates of water through the radiators, which enables them to run cooler, but to my mind that doesn't equate to making them more energy efficient. Some where in this system there must be a trade off - an extra pump or two, another heat exchanger, something unexplained.

I'm quite prepared to accept the claims at face value, but only if there is a coherent explanation of how it all works. As it stands, the publicity poses more questions than it answers. Installing one of these is going to set you back the best part of a grand: that's an awful lot of money for something being sold on trust.

So I looked up Tony Robinson, the Dublin academic who has been testing Oxyvent. He was easy to track down so I emailed him. He got back to me in a couple of hours and what he wrote was very illuminating.

The simple answer is that under the conditions that we tested in my lab the Oxyvent system did something useful; and there is no questioning this because our experiments were well thought out, they were accurate and we are experts in this field.

We observed two things: (i) when the radiators were balanced (to give approximately 11°C temperature drop at around 75°C boiler setting) the radiators we tested showed major non-uniform distribution in temperature, i.e. very large cold regions, due to the low water flow rates, and (ii) there were large fluctuations in the radiator temperatures and power outputs due to the boiler switching on and off which caused the inlet water temperature to cycle hot and cold.

He went on. For this scenario the Oxyvent system made a difference by smoothing out the fluctuations in the main inlet water temperature and thus the power output of the radiators. It basically added thermal inertia to the system so that the radiators did not react to the switching of the boiler. Now, the water flow rate can be increased i.e. unbalancing the radiators, without large excursions in the power output, so that for a given water set point temperature the radiator power output is nearly constant with time. The knock-on effect is that with the higher flow rate the temperature distribution of the radiator is much more uniform (we used thermal imaging to show this) so that, for a given inlet temperature, the unbalanced radiator would output more power since it would be, on average, hotter. Thus, the even temperature over the radiator provides more heat (for a given water temperature) and the Oxyvent tank ensuring that there are no severe cycling of this heat combine nicely, in the sense that the boiler water temperature can be reduced, which reduces fuel consumption, whilst still outputting adequate heat that is not pulsing over time.

One might ask then why use the Oxyvent tank for this; why not just reduce the water temperature (thus saving on fuel) and turn up the flow rate (thus improving the heat spreading on the radiators and thus the power output)? The answer is that for this case, the water inlet temperature is still cycling due to the on-off nature of the boiler so that the radiators may well reach the same peak power output but will also drop to a very low one, so that on average over time the power output is much lower than the case with the Oxyvent tank which provides a much more constant inlet water temperature to the radiators, even though the boiler is cycling.

Are you any the wiser? I'm not sure I am. It makes it look like it does something, but what exactly is still hard to tell. Other experts I know had reservations, but perhaps the best comment I got was from Michael Holmes of Homebuilding & Renovating magazine. He wrote I suspect that this product is a large heat exchanger/store, so the boiler flow and return go direct from this box, which acts as a thermal flywheel. Any benefit in terms of energy saving is likely to come from increasing the amount of time the boiler is in condensing mode, and by setting the boiler to a lower output temperature so it gradually heats up this thermal store. It is not clear whether it offers direct DHW too.

I suspect there are ways to achieve the same using controls. A boiler with a modulating burner that has a second low temp output for UFH etc. might achieve the same results without the expense. A thermal store cylinder can also work as a thermal flywheel, and provide DHW on demand.

So there you have it. A product that does something but we are not really sure what. It doesn't come with any 3rd party accreditation, like a BBA certificate, so we are left with lots of customer feedback and the observations of a Dublin academic. My hunch is that there are some installations where Oxyvent may make a huge difference, but others where it may do very little. And I realise that's not very helpful either.

2 Aug 2011

Cantor on Air Source Heat Pumps

John Cantor has a deserved reputation as a knowledgeable and independent commentator on all things heat pump. And here he has distilled much of what he knows on the vexed issue of air-source heat pumps. Anyone thinking of installing such a beast would do well to read through John's thoughts beforehand.

He looks at why so many people end up being disappointed by their heat pumps, and what they might have done to ensure that the installation had worked better for them. He analyses the Energy Savings Trust survey last year which showed generally poor results for ASHPs, and undertakes some comparisons with Germany and Switzerland where heat pumps are more widely used and apparently give better results. And he looks at the implications of the widespread adoption of heat pumps to UK energy policy - can the Grid cope?

All in all, a really useful contribution to the debate, and a very practical guide as well.