20 Jan 2015

Security Tips for Selfbuilders

The average private dwelling currently suffers an attempted break-in every 12 years and over half of these attempts are successful. Of course, it all depends on where you live. Some quiet locations still exist where no one locks their front doors, whilst there are some inner city areas which seem to get burgled regularly.
Wherever you live and whatever the future holds, burglary is not a problem that is likely to go away and anyone considering building a new house would be foolish not to consider the matter very carefully. 

The burglar
As you might suspect, the typical burglar is a young male but you might be surprised to learn that he is not part of a well-organised gang but usually a lone wolf whose break-in is often done on the spur-of-the-moment, when he sees the opportunity arise. There is really no reason to adopt a fatalistic attitude because, although it’s entirely true that if someone really wants to get into a house they can, most of the time they won’t bother if you go to the trouble of making life difficult for them. 
Our young burglar’s main concern is not to get caught in the act and to this end he values being able to get in, and out, quickly and preferably unseen. Another surprising statistic thrown up is that as many as 40% of burglaries take place while the home is occupied. You’d think this would be amazingly risky for our burglar but it only takes a few seconds to come in through an open door and walk out again with something and you may not even realise that you’ve been burgled. If you are worried about this sort of thing happening, get a dog.
With regard to new housebuilding, current thinking focuses on the following areas:
• Site layout
• Preventing access to the rear of the house
• Decent locks fitted to ground floor windows and doors
• Burglar alarms where risk is high
• Security lighting.

Site layout
Although this area has more relevance to estates than to single dwellings, it’s worth mentioning what they are on about. Dark corners and unlit alleyways should be avoided and houses should be sited where their neighbours can see who is coming and going. There is often little the individual housebuilder can do about this, though it is possible that consideration can be given to the issue when there are two or more houses to be sited near each other.
One obvious point that the professionals have tended to overlook is to locate the most widely used room in the house – usually the kitchen – at the front, so that the occupants can see who is coming and going out on the street. However, this arrangement remains an extremely unpopular layout in this country; we still prefer our kitchens to be by the back door.

Restricting access 
The rear of the house is the preferred area of entry for burglars. This is largely because the back of the house is almost always more private and is often screened from neighbours. A burglary often starts with a casual casing of the front of the house; if it looks as though there is no one at home, the second stage will be to go round the back and take a closer look. Only when they’re convinced the coast is clear will the break-in proceed. If access to the back of the house is impeded, then the would-be burglar may abort the job at this early stage in the hope of there being easier pickings further up the road. 
A 2 m fence and a stout gate – even without a bolt – will provide a considerable measure of defence against unwanted prowling. A tip from my 2010 Milton Keynes benchmark house is to use a 2 m fence but to have the top 300 mm made up of a see-through trellis which is just as difficult to get over but allows you to see who is walking along behind it. Back gardens can be protected, to a lesser extent, by walling or hedging them in. Plan in any obstructions that will at least slow down the progress of a potential burglar. However, bear in mind that a fully enclosed garden, once breached, makes an ideal spot for our burglar to force an unseen rear entry so if your garden is going to be enclosed for security reasons, you need to do it well.
Robust locks 
It is an NHBC standard to have five-lever locks on all external doors and to have window locks as well. The relevant standard here for door locks is BS 3621: you may even get a small discount from your insurers if your locks meet this standard. At least one exit – usually the front door – must be protected by a night latch (Yale-type locks), which can be opened from the inside without a key; this is to aid escape in case of fire. The idea is to lock the door on the night latch when the house is occupied and to use the five-lever mortise lock when the house is empty. Window locks used to be fitted as standard on volume joinery, but a change to the fire regs in 2002, calling for all first floor windows to be openable internally, has thrown this all into a state of confusion. Ideally, you want downstairs windows to be key-lockable and upstairs windows to be openable easily without having to find a key, but the chances of your joinery supplier getting all right are not high! 

French and patio doors
It is marginally easier to force a door inwards than to prise it out but it is likely to be rather noisy. Most front doors open inwards. However, note that double-doors (French doors) are particularly easy to force in or prise outwards; most French doors open outwards and if you fit them be sure to fit decent sliding bolts to the top and bottom of both doors. For extra security, make these lockable bolts. Sliding patio doors are generally a much more secure (and draughtproof) alternative (though not half as elegant); however, many break-ins have occurred where the patio door frame has been levered out of its seating, having only ever been held in by six short screws or, sometimes, nothing more than mastic sealant.
The current building regulations will ensure that you have to fit double-glazed sealed units, and the safety standards on glazing insist that safety glass is fitted to all doors, windows next to doors and all glazing less than 800 mm above the internal floor level. Safety glass is expensive, costing nearly twice as much as ordinary float glass. It comes in two varieties, toughened or laminated, and they perform slightly differently. 
Toughened is harder to break but when it breaks it collapses into small nodules, whereas laminated glass has a sheet of plastic sandwiched between two layers of ordinary glass; this makes it harder to break through (from the burglar’s point of view) and is therefore slightly more secure. The police are big fans of laminated glass, and suggest that it should be fitted wherever there is glass next to an accessible lock, but as this includes virtually every ground floor opening window it would be an expensive option.

New security standards
Factory-glazed windows are available which meet a new British security standard, BS 7950, also known as Secured by Design. Rather than just testing the individual locks or the glass, BS 7950 tests the whole window assembly in situ. Typically such a window will have laminated glass on the external face and shootbolt espagnolette locking mechanisms. To get windows to this standard, they really need to have been factory glazed but this doesn’t mean they have to be plastic – most of the big timber joinery manufacturers now produce BS 7950 windows. 

Burglar alarms
There is a huge variety of different alarm systems out there and it’s not easy deciding what to fit. It is usually cheaper to install a wired system, which is particularly well suited to new housing as the wiring can be concealed during first-fix stage. Installation quotes for a four-bedroom house are likely to vary from £500 for a basic system based on a mixture of internal infrared detectors and contact points to over £1,000 for external vibration detectors which are triggered by interference with doors and windows. Should you not want to go to the expense of installing an alarm, as an alternative, the wiring can be first-fixed in a day for between £100 and £200, so that the intruder detectors can be fitted at a later date without disruption to the decorations. Burglar alarms are eligible for zero-rating of VAT when building a new home. 
Fixing a burglar alarm should not be beyond the capabilities of a competent DIYer and there are a number of systems designed for just this. DIY alarms usually consist of a control panel, the detectors and an external siren. The wired systems are the most reliable and are probably best suited to new builds. However, wireless alarms have their advocates and are easily fitted as an afterthought. The standard wireless systems still need mains connections for both the control panel and the siren but the latest generation work entirely on radio signalling: the siren and the control panels are solar powered and you activate the alarm by using a remote control.  
More features tend to add to the cost but it is still possible to get a well-featured wireless system for under £200. Zones are the areas covered by individual detectors and most burglar alarms allow you to arm or disarm any of your zones individually. This is useful if you have pets or if you want only the downstairs armed when you are upstairs at night. Better systems have a capability of checking that all component parts are working – a feature sometimes referred to as a 24 hour zone.

The detectors on which burglar alarms are based come in a number of guises. The two commonest are the passive infrared (PIR) detector, which is triggered by movement across its path, and the door or window-opening detector that is set off when a magnetic contact is broken. You can also get detectors based on pressure pads – typically these would be under a doormat and would be triggered when someone unexpected treads on it. You can give great thought to just which detector to put where and still get it all wrong. 
Many a break-in now occurs via an upstairs window: the thieves never go downstairs because they reckon it will be alarmed, so they just ransack the bedrooms before leaving the same way they came in. So maybe it pays to have lots of detection zones but possibly only if you are very confident in your ability to operate the system.
If you’ve never lived with a burglar alarm, you might be forgiven for thinking that they are the last word in home security. However, the consequences of fitting an alarm can be fairly tortuous for the householder and their neighbours. All systems are set to make a loud noise for a few minutes; false alarms will make you very unpopular and false alarms do happen, so a burglar alarm is not without its problems. A recent police estimate reckoned that no less than nine out of ten ringing alarms are actually false alarms and the police now have a policy, in effect in most areas from 2006, of withdrawing their response after more than three false alarms. 

Monitored alarms
If you have a very remote site or are not entirely happy about a 105-decibel alarm ringing when a mouse crosses the floor, the next step up the security ladder is to get a monitored alarm. These link your house via the phone lines either to the local police or to a security firm. If you want the police to monitor your alarm, then the system must be installed by a company approved by one of two bodies; NACOSS (National Approval Council of Security Systems) or SSAIB (Security Systems and Alarm Inspection Board). Needless to say NACOSS or SSAIB approved systems cost rather more than unapproved ones. Or as one wag put it to me, it’s daylight robbery what these guys get away with. Monitored systems also carry an annual charge which is likely to be in excess of £150; they are only available if two key holders besides the occupants live close by and are prepared to be called out in the middle of the night. 

Movement sensors
Alarm systems don’t have to just concern themselves with making loud noises or sending messages off to police stations. You can also rig up detector beams running across the front and the back of your house which set off a buzzer inside when they are crossed. They vary in sophistication from simple passive infrared beams like the ones used to trip lights, to multi-height beams running between two concealed posts which aim to be cat and fox proof. The well designed systems will give you fairly reliable intruder alerts: a poor system, tripping out every time a bird flies by, will just make you paranoid. 

Car parking
Both integral and detached garages can be included in whole house intruder alarm systems, but this tends to be very inconvenient; the car has to be left outside whilst the alarm is deactivated (usually inside the house). It rather defeats the purpose of these remote control devices for garage doors. 

Other measures
Door chains (from £3) and viewers (from £4) are becoming more common, and are recommended by the police. Surely the most cheeky is the fake ‘Protected by Burglar Alarm’ bell casing which you screw on to your outside wall. Available at around £8 from DIY sheds.

Security lighting
Passive Infrared (PIR) detectors, similar to the ones used on internal movement sensors in burglar alarms, are also used on external lighting. These can be very useful around dark entrances although the halogen bulbs (sometimes 500W) can be so bright that you dazzle passers-by and tend to make them think you live in a high-security prison.  There are some very cheap versions on the market (at around £10-£15) which are best avoided; at around £30 you start to get ones where it is possible to change the bulb. Better forms of external lighting exist that can be wired to PIR switches, as well as manual override switches, which give pleasant external illumination as well as some form of security .
There are also a number of products that can be used to give the effect of occupation when the house is empty. For around £20, you can buy a gizmo which fits in between a lightbulb and its lamp holder that acts as a light-sensitive switch, useful for simulating occupation when you are away. 

Shutter protection
To fit security roll-down shutters to every opening on a detached house would cost over £6,000 so no way is this a cheap and cheerful option. Indeed it looks pretty severe as well, but if you are away a lot and have particular reason to fear intruders, then shutters are very secure. They don’t work well with outward opening windows (think about it) and are best designed around either sliding sash style or tilt and turn windows. On the Continent, shutter protection is often taken as a given, but then on the Continent windows only ever seem to open inwards. Strange to reflect how different something as basic as a window can be.


Home safes are available from £150 for a wall fitting one and from £200 for one bolted to the floor. Placing a safe in an existing house can be awkward but in a new house it’s a doddle – if you’ve planned ahead for it.

30 Dec 2014

What it takes to buy a city centre building plot

I've been busy. I've bought a derelict warehouse on a backstreet in Cambridge and am making plans to knock it down and build a house there.

It all came about very suddenly. The site was put on the market at the end of October and, as it was said to be "the last brownfield site in Romsey Town", it attracted enormous interest. There are lots of people in Cambridge who would love the chance to build a house in the city and, in this day and age, any potential city building plot attracts a Grand Designs premium. Conventional notions of what it is worth and whether it stacks up financially go out the window in the stampede to buy into a dream.

Offers poured in during the ten days the site remained on the market and the agent decided to take it to sealed bids. What was unusual was that the vendor didn't want to sell to the highest bidder necessarily but wanted the buyer to build a single family home (rather than student flats) and also wanted the house to be an eco-house. This rather threw me. Although I've been involved in various green building projects over the past thirty-five years, I actually bridle at the term eco-house because to my mind it's indefinable. It's like natural food or organic shampoo: it's a cuddly, friendly sort of term but in the great scheme of things it's also utterly meaningless. A house is basically either a good house or a bad house and I don't think sticking a grass roof on a bad house makes it a good house.

But now was not the time to get bogged down in semantics. So I checked it with my partner, who was game for the adventure, then I checked the various savings accounts and utility company index-linked bonds into which I had parked the proceeds of the sale of my last house four years ago, and knowing I had the wherewithal to make a cash bid, I put in an offer, together with a brief CV and a word about my interest in Passivhaus and the like.

But I didn't win the bid. Mine wasn't the highest bid, but the one that won was lower than mine. Someone had obviously lit the vendor's boat rather better than me. Maybe my mixed feelings about eco-homes had shown through. Anyway, I put it behind me, wrote it off to experience and decided to look again for a city building project.

But then six weeks later, the agent rings me and asks if I'm still interested. Apparently the winning bid had hit problems and was unable to complete in the timescale the vendor was wanting, and so I was back in with a chance. But there was a very demanding condition. I had to complete in a week. There was to be no exchange of contracts, just a straightforward completion in one fell swoop.

I'd never heard of such a thing. Surely the property industry was incapable of working to such tight deadlines? The only good news was that the searches and all the preparation work had been completed and I could buy these from the solicitors. But I had to find a new solicitor and that wasn't straightforward — everybody wants to complete before Christmas and the Cambridge property market is very hot this year. After an afternoon on the phone, I tracked someone down who actually relished the challenge of completing in a week. And the deal was on.

The reality is that city centre building plots are so few and far between that you have to take on inadvisable risk in order to secure them. No planning permission in place. Not even time to talk to planners or anything sensible like that. Just buy a derelict warehouse and see what you can make of it. Only cash buyers need apply as no bank would lend on such a project without planning permission in place. And if the vendor says you have one week, then you have one week.

If I took the trouble to actually read the Housebuilder's Bible instead of simply writing it, I might just have cottoned onto the fact that I've been extremely reckless here. But somehow I suspect that it's not actually that big a risk because the community would very much like to see this site redeveloped and I think the political wind is blowing our way. It helps that the previous week, it was announced that small sites would in future be exempt from S106 planning contributions. That was a potential hidden tax that could have had a crippling effect on the budget.

My hope is to build a delightful house which may or may not qualify with the soubriquet eco-house (I don't mind either way) and also to have some fun doing it. Let's see how it all works out.....

27 Nov 2014

On Sea Level Rise

On Tuesday night this week, I had the pleasure of listening to Prof David Vaughn talking about the work of the British Antarctic Survey where he has worked almost all his adult life. Vaughn is Professor Ice Sheet and he spends his time exploring the goings on in Antarctica, Greenland and the 200,000 plus glaciers that pepper the world's mountain ranges. It's a fascinating area of science and one that's obviously key to our understanding of where our climate and our sea levels are heading.

At this point, I would expect a number of people to rise angrily from their perches and accuse me of listening to a pinko greenie engaged in a conspiracy to pull the wool over our eyes by manipulating the data to suggest we are all doomed. "British Antarctic Survey? British Alarmist Society, more like." I have no doubt that UKIP will be planning to slash their £44m annual budget under their charming "Axe all green subsidies" policy.

May I suggest that, before they do, they spend an hour listening to David Vaughn talk. He dresses very conservatively, he talks very quietly, he is polite almost to a fault. In fact, he comes on like an accountant, which perhaps is what he is actually is, albeit one with some very sophisticated measuring kit. He just weighs ice and measures sea levels. He looks for trends and patterns and he peers into the future to try and work out where things are headed, but he steers clear of making suggestions about what we should or shouldn't be doing — "that's for economists and politicians to decide".

What was interesting to me is the huge strides that have been made in our knowledge in the past few years, between the IPCC reports AR4 in 2007 and AR5 in 2013. We now have two satellites (the Grace mission) which are measuring gravitational variations caused by changes in mass at surface level. If the mass of an ice cap is changing, Grace will pick it up. Clever stuff.

And the mass of ice sheets is changing. As you might expect, it's decreasing, although the picture isn't  uniform nor necessarily easy to interpret. Thus far, the changes are fairly moderate and are occurring at the margins, but what scientists fear is that there might be a sudden catastrophic event. One area on the Antarctic coast is of particular concern because there the ice sheet rests on bedrock which is far below sea level and there is a possibility that relatively small changes in sea temperature could cause it to all slide into the sea. How big an area? The size of Cornwall? Belgium? Norway? No one knows, but Vaughn probably has a better handle on it than anybody else. If we can afford MI5 and MI6, then I think we can afford the BAS.

Back at the height of the last ice age when ice sheets covered much of the northern hemisphere, the global sea level was 120m lower than it is today. The Mediterranean was not there and there was a land bridge between Britain and France. The temperature was approximately 7°C colder than it is today.

Still locked up in the Greenland Ice sheet is another potential 7m of sea level rise and in Antarctica it's 60m, so if we were to head for a 4°C increase in global temperatures, which is within the bounds of possibility (though far from certain), then we could anticipate a much higher sea level, though it might take 500 years to play out.

What is known today is that global sea level is currently rising at 3.2mm per annum. It the last century, it averaged around 2mm and in the 19th century, they think it was around 0.8mm. There is no hiatus in sea level change — the rise is pretty much constant. 3.2mm may not sound like much, but that still equates to 300mm by 2100. In fact best estimates are rather more than this at present but it's a field open to a lot of doubt and speculation. (Sea level is affected by a number of factors beside ice sheet melt.) It's probable that the relatively small amount of climate warming that we've already seen has locked in sea levels rises of several meters, but the timescale on which it will all happen is contentious.

The questions are can we manage this? Can we arrest it? And over what timescales are we talking? Should we be planning now to mitigate sea level rises which won't be fully played out till maybe the 25th century? What exactly are our planning horizons? This isn't the stuff of blind panic: it's good old risk assessment played out over a very long timescale. It does however ask some very uncomfortable questions about whether our actions now are making things better or worse for our distant descendants and what exactly we are hoping to achieve on Planet Earth.

In the shorter term, what is likely to happen is that storm surge events like the one that accompanied Hurricane Sandy are going to get worse and more frequent, but we already know that our coastal cities (New Orleans) and infrastructure (Fukushima) are at much greater peril than we care to think about. Sea level rise simply changes the odds and, if you like, makes coastal protection more expensive. Right-wing commentators who claim that it's simply too expensive to stop burning fossil fuels should bear this in mind. The longer we keep bingeing, the bigger the hangover.

21 Nov 2014

Lighting the future

I visited LuxLive on Wednesday to see where the lighting industry is headed. As you might expect, it can be summed up in 3 letters — LED. They were everywhere and there was very little of anything else. For someone used to writing about construction, where the pace of change is lugubrious, it's quite exciting to see an industry undergoing a rapid transformation. For most players in this space, it is a question of how to add value to a product which is both dropping in price and increasing in quality all the time. It's not enough to just sell LEDs: the future market is just too unpredictable.

And many so-called experts turned out to be almost as clueless as me. I was told on good authority that dope growers have no use for LEDs because they can't do ultra-violet light. A quick Google afterwards revealed dozens of really cheap UV LEDs. In fact, we may be about to be entering a world where growing all manner of plants at home becomes a whole lot easier and more productive.

For the past ten years or so, much of the emphasis in the lighting industry has been on increasing energy efficiency both by squeezing more performance out of the lamps themselves and by adding better control gear and better design. The arrival of cheap and very efficient LEDs has already made much of this work look pointless. Cree, the NASDAQ-quoted LED powerhouse, have now produced an LED that delivers 300 lumens per watt, which is about eight times more efficient than the best compact fluorescent, and although it's not yet in commercial production, it seems just a matter of time before the bar is raised again. In five years time, maybe 1,000 lumens per watt will be possible. By then lighting will have become so cheap to run, that it will be nearly-free. An old-fashioned 60-watt bulb could be replaced by an LED running on less than half a watt. A whole house could be lit by as little as 10 watts at a cost of maybe £5 per annum.

Not that LEDs are without their issues. The light itself is produced from a very focussed source which means there is a glare issue. Lots of work is going into shielding and diffusing this glare and making it more acceptable in every application. Backwards compatibility with existing light circuits is not always guaranteed and there are issues with dimmers not working with LEDs though, again, technology seems now to be producing LEDs that will work with existing dimmers.

One of the neatest and simplest ideas I saw was at the Megaman stand where they had adapted a dimmer so that the colour appearance of the lamp got warmer as the light level was decreased. I'm not sure this is commercially available yet, but it seemed like a very simple way of addressing the issue of the colour appearance of the lamps which exercises some people quite a lot.

The future of cabled switching also seems to be in question. Lots of stands had wireless switch plates for lighting and Megaman were also displaying a wireless home automation system which allowed you to control the heating system as well, all from your smartphone. If this is really advantageous remains to be seen — I think most people will still want a physical switch or thermostat as well, if only because smartphones get misplaced or run out of battery or break down. Wireless switching really comes into its own when you want to pre-program your lighting or heating or switch it remotely, but how many people actually want that function? We will see.

In the meantime, the wireless switchers are not being helped by a protocol turf war rumbling away in the background. Wi-fi v Bluetooth v ZigBee v Z-wave. It's all very well have Z-wave enabled kit, but how do you know the world won't have gone fully wi-fi by 2025? You could end up being Betamaxed, although, to be fair, you won't exactly run short of content, so it may not be quite so critical as all the existing protocols will be supported for decades, even if they stop being used for new applications. Nevertheless, it doesn't help matters that it isn't clear which home wireless system will prevail.

14 Nov 2014

Eco Bollocks Award No 9: Clear Heater Units

Recently, I've become aware of some striking claims being made for electric radiant heating. Like a new way of heating homes has been discovered that is way more efficient than anything else that we have come across before. I think not.

The practice of using radiant heating is not new and it seems to work very well in many places. But claims that is somehow magically more efficient than other forms of heating  is, in my opinion, pure baloney.

Take a look at this website. Clear Heater Systems have a neat looking wall panel radiator which they claim will save you a pot of money. They claim that you can save up to 65% against gas heating on a three-bed semi, and up to 90% on electric heating on the same house. Impressed? Let's investigate.

Their claims are apparently backed-up by a piece of academic research by a chap from Leeds University which, at first glance, looks very compelling. It concludes: Overall, the results that we have produced show the Logicor Clear Heating System in a good light. They certainly do. 

However, if you read the report carefully, you can see that it's not quite all that it appears to be in its conclusion. The report is based on an analysis of the energy used in 53 properties in the north of England which have been fitted with the Clear Heater units. The results are, however, not being compared with properties heated by other methods, but with an estimated heat loss for each of these 53 properties, based on their own calculations using standard U-values. What this tells you is not how efficient Clear Heater units are but how inaccurate U-value calculations can be if used inappropriately. They are a useful tool for working out maximum heat loads, but not for predicting annual heating bills.

The methodology is even made explicit within the report. Buried away on page 4, under the heading Statistical Analysis, the author states that the study is not a measure of savings against competing heating systems but rather a measure of performance against theoretical heat losses. With the emphasis on the word theoretical

You'd have to be a bit of a Sherlock Holmes to figure out that the apples here are not being compared with other apples, but with a load of dodgy oranges. And it's on this basis that they claim that you can save pots of money against gas heating. Which is frankly incredible because the Clear Heater Units are electric radiators, albeit with a very thin carbon ceramic heating element sandwiched between two sheets of toughened glass. Much as they would have liked to, Logicor haven't managed to change the laws of physics and, for just hinting that they might have, they get a House 2.0 Eco Bollcocks award.

24 Oct 2014

Whither Passivhaus?

Last week I attended the 4th Annual Conference of the UK Passivhaus Trust. On many levels, it's all been a super success with the number of UK projects burgeoning towards the 250 mark and expected to get to 1,000 sometime in 2015. Interest is growing far and wide beyond the little core of activists who launched the trust back in 2010.

But of course it's still very small fry when set against the total amount of building going on and there were voices to be heard saying that maybe, just maybe, Passivhaus isn't quite the way forward we thought and hoped it would be. It sets out to be an exacting target and therefore an expensive one to meet. Whilst for new builds it looks eminently achievable and economically justifiable, in the retrofit market Passivhaus has the feel of being overkill. The structural changes you have to undertake in order to get an existing house to EnerPhit, the reduced retrofit standard, are so great that you begin to wonder whether it is really be worth the bother. Only a very keen energy wonk is ever likely to undertake an EnerPhit conversion: fuel prices would have to be an order of magnitude greater than they are now to make economic sense. Even the environmental sense is questionable.

There were lots of very interesting presentations. Caroline Martin of WARM caught my attention with her analysis of post-completion testing of a number of Passivhaus homes in the West country. The usual spread of outcomes was on display — there always seems to be a joker in the pack who leaves all their windows open throughout the winter and shows up as a total energy hog, and Caroline's sample didn't disappoint in this respect.

But there were also a handful of homes where the heating hadn't been put on at all during the winter. "Was it a particularly mild winter in Exeter?" she asked herself. Weather stats showed that it hadn't been — it was very average. So these homes hadn't just met the fabled Passivhaus space heating standard of 15kWh/m2/annum, they had scored zero kWh/m2/annum. This set me wondering whether they hadn't been over engineered. The design idea is not to eliminate heating costs altogether, merely to reduce them to a very low number and presumably the cost of getting the score down below this is deemed to be money wasted.

In general, the Passivhaus standard is responsive to weather data, thus making it easier and cheaper to build in warmer climates, certainly as regards the amount of insulation to be built in. Conversely, it is much harder to build in colder climes and this has led to a revolt in North America where many low energy enthusiast feel that the standard is just a little too German and that different climates would be better served by variations on the standard. Their specific beef is that when you get into the far north of the US and Canada, the wall insulation becomes unrealistically (and pointlessly) thick. They argue that it would be far cheaper and more cost effective to generate a little electricity on site than to build to an arbitrary standard which is optimised for central Europe.

Now Passivahusers have long desisted from offsetting their heating standard with renewable energy. "No green bling, let's keep it simple" went the oft repeated refrain. But now it appears that the Passivhaus Institute in Darmstadt is about to jump aboard the green bling bandwagon and start offering alternative Passivhaus standards which incorporate on-site energy generation. Watch out for Passivhaus Plus and Passivhaus Premium. Old die hards will have to make do with Passivhaus Classic.

It seems that politics is at work here. I couldn't quite get to the bottom of it, but the EU is pointing us towards a new target, the Nearly Zero Carbon Building, and it will be requiring that these have some form of onsite electricity generation. In this light, if Passivhaus is to stay relevant it has to bring PV into the equation. It also has to take into account not just the primary energy used (a lesser known target of the Passivhaus standard) but the carbon intensity of that primary energy.  Hence the new versions of the standard referring to carbon intensity of energy used.

But in doing this, the Passivhaus standard starts to resemble other standards (like the Code for Sustainable Homes) which no one much loved. I fear they may be a small backlash amongst British and Irish enthusiasts who set their stall out on the simplicity and robustness of the original standard. But a full scale American-style tea party revolt? I don't think so. You might not guess it from our newsprint, but I think we are just a little too European for that.