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.

30 Sep 2014

On LED Lighting

Last week, I was in my local Medlock's looking for a replacement lamp for a downlighter. The one which had gone was about five years old and was a compact fluorescent — not a comfy fit in a GU10 lamp but it worked OK until it died. I showed the dead lamp to the man behind the counter and he said they did have a replacement but that it would be both cheaper and better to switch to an LED. "They are just about the only lamps we sell now" he said. "The halogen bulb has all but disappeared and the compact fluorescent seems to be going the same way."

Then on Sunday I am at the Homebuilding & Renovating show at Olympia in London and I visit a stand called SavingCO2 which sold nothing but LED lamps. LED GU10s for downlighters, LED bulbs for where we used to put tungsten bulbs, even LED tube lights. Just about any and every bulb and fitting you have ever come across is now available in an LED version at a wattage around half of that achieved by compact fluorescents, and close on a tenth of what we have been using with tungsten and halogen, and with a light quality that most people would readily prefer.

Now admittedly, these LEDs are still a lot more than a halogen lamp — TLC is selling these for less than £2 — but the promise is that these LED lamps will last longer and, if anything, give off a better light. What is more, an interesting article online on Optics.org states that LED prices are falling by about 9% a year, but speculates that quality may suffer in the race to the bottom. There is a danger that if the quality remains too high, then manufacturers will lose the replacement market.

There is also significant money to be saved here. If a typical house has 40 lights and each light runs for an average of 800hrs/annum (about 2.5hrs per day), then the house will consume
• 2,000 kWh/annum if everything was lit with tungsten bulbs (cost £250/annum)
• 1,000 kWh/annum if it's a mix of halogen, CF and tungsten (cost £125/annum)
• 250 kWh/annum if every light fitting was replaced by an LED (cost £30/annum)

And 40 LED bulbs would currently cost around £500, so there is a reasonable payback on offer.

It's interesting to compare LEDs with PV. PV installation costs have also fallen significantly during the past few years so that, today, PV is costing around £1,500/kW to install and each kW of PV produces about 800kWh/annum in the UK climate. That 800kWh/annum is similar to the amount of energy saved per annum by converting all your lamps to LEDs, for a third of the cost.

It's also interesting to note that the building regs have been left behind by the onward march of LED lighting. Currently, the lighting requirements for Part L in England are covered in a supplement called the Domestic Buildings Services Compliance Guide: 2013 edition. It is still batting on about having to have dedicated light fittings to stop recalcitrant consumers ditching their unpopular CF lamps and reverting to tungsten bulbs at the drop of a hat. The guide requests that 75% of the light fittings in  a new build should be  energy-efficient (defined as at least 40 lumens per circuit-watt). But with LEDs achieving over 100 lumens per circuit-watt, this definition is already looking out of date.

To its credit, there is a supplementary clause in the guidance which sates that light fittings whose supplied power is less than 5 circuit-watts are excluded from the overall count of total numbers of light fittings. As most of the halogen-replacing LED GU10 lamps are rated at 3 or 4 circuit-watts, this neatly side steps the issue and allows you to put in as many as you want. My guess is that then next version of this guide will probably do away with lighting guidance altogether, as by then LED lighting will have become ubiquitous in new installations.

The big question is will LED lamps really last the 40,000 hours or so the manufacturers claim? Or will the market take them down a route towards built-in obsolescence?

29 Aug 2014

On Scottish Independence

In a few days time, Scotland will vote on whether to remain part of the United Kingdom. As an Englishman, albeit with a Scottish father, I don't feel very strongly about it but I do find myself unhappy about the prospect of the UK being dismembered bit by bit. A country consisting of England, Wales and N Ireland seems pretty illogical and somehow threadbare. I'd much rather we did it properly and all split up into separate nations, than have this hotch-potch of territories that would exist post-independence.

But there is another more troubling question posed and that is "What is a nation anyway?" I never asked to be English or British, I was just born here and I have to accept my fate whether I like it or not. Even if I emigrate someplace else, I will remain English because I have spent most of my life here. But it's not something I chose. I didn't get a vote about it: it's not something you could realistically vote on.

But when Scotland casts its vote on September 18th, its people will have an almost existential choice to make, the nearest they will ever get to voting on identity.  What sort of country do they want to live in? Do they want to be primarily Scottish? Or British? Or even European (though this isn't a question being asked)? And what are these seemingly abstract concepts of statehood anyway?

I've no doubt Scotland would make it as an independent country — there's no reason why it couldn't — but would it be better or worse off? No one has any idea. And is it, in any event, even about being better off, at least in an economic sense? These concepts are so nebulous that I find them quite unsettling.

At the heart of the matter is the fact that the United Kingdom is and always has been a mini-empire. Unlike the USA (or even Europe, bless it), it has never been a collection of equals. Rather it's been one big bully (England pop 60m) and three little Celtic statelets (combined pop just 10m). England and in particular London has been imposing its will on the UK ever since the UK existed and in some ways it's a wonder that is has survived so long in the format it has now. The Irish forced their way out nearly a hundred years ago. Why has it taken the Scots so long to do the same? And why are the Welsh so mealy-mouthed about independence as well? I bet if Scotland goes, Wales will follow them within ten years. Where that would leave N Ireland? In a mess. But then it's been in a mess for a long time. The Protestants would have to eat humble pie and troop off to Dublin, hopefully not literally, for political representation. Ouch.

What's interesting is to hear David Cameron speaking up for the current union using classic Tory mercantilist rhetoric. The arguments he makes could equally well be used to keep the UK in the EU: easier trading, access to bigger markets, common currency (well we could have had it if we had wished for it). But whilst England doesn't like the thought of losing some of its muscle by waving goodbye to little Scotland, it's much less keen on sharing what it has with states like France and Germany who have similar power and status. I sense playground politics at work here: there is something quite primeval about it all.

I'm beginning to sound like a rabid pro-independence campaigner here, but the reality is rather different. The problem is that in a perfect world we would probably all be both independent and conjoined at a national and international level. But we are not in a perfect world and having independence votes like these unleashes the dark powers of nationalism and resentment. Just by asking the question, we are letting that nasty little genie out of the bag. Whatever the outcome, the political landscape has already moved just a little further away from tolerance and interdependence, towards narrow parochialism and mistrust. Not things we need in the 21st century.

And if Scotland votes for independence, doesn't it call into question the legitimacy of many other so-called nations? Will it herald a century of territorial Balkanisation around the world? Do we need it? Aren't there enough global problems without everyone using up energy trying to determine which country they want to live in? I fear it's a small step from genteel Edinburgh to violent Donetsk.

28 Aug 2014

Six Questions on Heat You Never Thought To Ask

Q1 What is heat?

Heat is a by-product of ‘work’ going on or, if you like, energy being spent. Heat is most commonly found where one substance is in the process of breaking down into its constituent parts. Our bodies (like our houses) leak heat and this leaked heat must be replaced, which we do by eating. Calories are just another measurement of energy. The colder it is outside our bodies and our houses, the more heat we leak and the more energy we have to take on board.

Q2 What is ‘Feeling warm?’

The rate at which we lose heat determines how hot or cold we feel. ‘Feeling cold’ is a signal that we are losing high and potentially dangerous amounts of heat; ‘feeling warm’ signals that all is OK.

Q3 What determines how warm we feel?

The insulating capability (U value) of our clothes (or duvets, or houses)
The temperature of the surrounding air
Wind speed (wind chill factor)
 Level of water vapour around
Whether our skin is wet or dry
How much heat is being ‘given off’ (radiated) by surrounding objects (including the sun).

When assessing heating systems, we use air temperature as the man indicator of background comfort but it is important to be aware that air temperature is just one of several factors at play. Anyone who has ever had a thermostatic control dial in their home will be well aware that what’s warm on a dry day can be 2° or 3°C too cold on a wet or a windy day.

Q4 How does Heat Move?
Heat transfers via three different methods: conduction, convection and radiation. Conduction is the passage of heat through a solid – the classic example is the poker placed in the open fire that soon gets too hot to hold. Convection is what happens to heat when it transfers into a gas (typically air) – it rises. Radiant heat is the glow you feel on your face when you are standing near a bonfire; the air temperature may be minus 10°C but you feel as warm as toast. We don’t often feel conducted heat but most heating systems deliver a mixture of the other two, convection and radiation.

Convected heat (or warm air) is characterised by being very responsive – i.e. you feel warm very quickly – but it can also be rather unpleasant, drying the throat and watering the eyes – think of the fan heaters in cars. In contrast, radiant heat you hardly notice. We experience it from things like underfloor heating systems, night storage radiators and Agas. Despite their name, radiators deliver a mix of all three forms of heat. The air convects through them, they are hot to touch (conduction) and you are aware of their warmth if you sit nearby (radiation). All heating systems deliver heat by all three methods but the mix varies according to the delivery system.

Q5 So what’s the perfect heating system?
I haven’t really been much help here, have I? You just need to understand that you must make a series of compromises and your aim is to make the least bad compromise.

Q6 Watts it all about?
Finally a word about how we measure power output, because I know people find it confusing, not least because there are different systems of measurement in operation. Here I try to plump for one, the watt (W), and its big brother the kilowatt (kW) which is 1,000 watts. These are measurements of power, rather than energy used. If you want to a measurement of energy used, you need to express it as so much power per hour, which we routinely call kilowatt hour or kWh.

Why the capital W in the middle of kWh? It's a strange convention to do with the watt being a unit attributed to James Watt, inventor of the steam engine. We seem to routinely refer to watts or kilowatts with a lower case w, but when it's written shorthand it becomes kWh.

To make it even more complex, there are other units used for energy measurements and one you frequently come across is the British Thermal Unit or BTU which, as you might guess is an imperial unit. The Americans still use it. What many people (myself included until recently) don't realise is that the BTU is a measurement of energy rather than power so its the equivalent of a kWh. If you want to know the power output of a boiler, you need to divide by hours. Thus:

1W = 3.41 BTU/h            1kW = 3,410 BTU/h

Let's finish with a table

1 litre
1 litre
1 litre
1 litre
1 kg

14 Aug 2014

Be wary of using Registered Contractors

A reader has alerted me to a thorny problem that crops up when manufacturers insist on you using their own list of registered contractors to install their products. It's a practice that has crept into the up-market housebuiding sector over the past few years and, contractually, there are pitfalls awaiting us here.

Why would a manufacture care about who uses their products? It's clearly to do with maintaining a reputation for quality. However good a product may be, if the people installing it are useless, the product's reputation will go down the plughole. Hence it's quite logical for a business that sells itself on quality to insist that you use contractors familiar with their systems and products. So far so good.

But what happens when a job with a registered contractor goes wrong? This has happened to my reader who has had a disastrous experience with an external rendering job on her selfbuild. She (and her architect) think that the responsibility for repairing the defective job lies with the manufacturer who was the one that insisted that she use one of its registered contractors. But the company in question disagrees and thinks that the fault lies with the contractor who, unsurprisingly, has now walked off the job and refuses to have anything to do with either the manufacturer or the selfbuilder.

The manufacturer has a contract in place which expressly shifts liability for errors and omissions onto the contractor. They say they cannot be held responsible for what happens on site: they are materials suppliers, not contractors, and their responsibility ends with the supply of goods.

But, if this really is the case, why do they insist on their end-users, their clients, having to work with their registered contractors? Why not let every Tom, Dick or Harry have a go? If the products are as good as they are cracked up to be, then there must be very few jobs which cause problems and it must make sense for the manufacturer to pay for the repairs, if only to keep their reputation sweet.

I don't want to name names at the moment because there is every chance that there will be a positive resolution to this particular case and I have no wish to cause any reputational damage to a well-regarded external render company.  But it's a contractual trap that we should all be aware of. Just because you choose from a list of registered contractors doesn't mean that the liability for mistakes transfers from the contractor to the supplier and, if relationships break down, don't expect the materials supplier to ride in to the rescue.

5 Aug 2014

How good does a Damp Proof Membrane have to be?

A reader asks how to detail a damp proof membrane (DPM) on a solid floor where there is a service penetration. The clever-dick answer is that you should avoid service penetrations through ground floor slabs but, in reality, that's rarely possible. The question is then do you go for the full gas-barrier treatment with proprietary fixtures and fittings like Top Hats, as shown on the Visqueen website, or do you do something more rudimentary with sticky tape and plastic bags? Or maybe even just cut a hole?

Interestingly the building regs guidance (Part C in England) is silent on the matter. Neither do the NHBC's technical standards have anything to say about it. They both indicate that a DPM must be installed and that overlapping sheets should be taped together, but the fiddly issues like corner details and service penetrations are ignored.

What should we make of this? That DPM's don't really matter very much? Or that they matter but that you don't have to go overboard on the detailing? They are not gas barriers and therefore there is no danger should they not work perfectly? I'd be interested to hear how others treat their DPMs.