Saturday, 24 November 2012

First Year Data Graphs: Feedback welcome

It's icy this morning - have a look at the beautiful ice patterns on the roof windows before I bombard you with a year's worth of graphs...

Pretty isn't it and it shows quite clearly that we are warmer inside than out and not leaking heat through the triple-glazing.

OK, never mind the aesthetics, here's the info:

This shows the amount of energy we've used and how much we've generated using the PV panels and solar thermal tubes. It covers the period from the early September when it first became possible to measure the tube output.

Between May and the middle of October the energy usage for two people working (more-or-less) full time in the house was running at  just about 18 kWh a day. When the house is empty (but still has fridges etc. and the MVHR running at its lowest setting) the average is 11 kWh.

The red spike shows all this changing in the second part of October when the house got cold. When the internal temperature dropped below 18°C we started using extra heating. Initially we were just switching on a couple of plug-in radiators we'd bought in the two downstairs rooms and that accounts for the rise in energy use at the end of October. The next spike shows us turning on the top-up house heating. The MVHR has a unit that provides top-up heat but if you look at red line you'll see just how much energy it uses when it's on. We are currently running this just in the mornings to heat the whole house and then using the radiators as before for the evenings.

This next graph shows the data for all the past year and illustrates the impact of having the house's top-up heating on. It may be that we have got some of the settings wrong on the MVHR control panel but at the moment the house's own heating cannot heat the ground floor above 18 degrees even when the top-up heating is burning up the kWh so I'd welcome any twitter feedback as to why this is.

In the chart here you'll see that there is a difference between energy usage now and a year ago. We'd hoped that there would be a difference in the amount we needed to heat the house after a year of occupancy but the house is as cold this winter as it was a year ago. The only difference in energy use now is that last year we were trying to maintain the temperature on the ground floor at 20 degrees so the thermostat was set to that and we were running the house heating for longer. This year, at the moment, we're only heating the rooms we're in and keeping the doors closed to all the rooms. This is saving energy but it doesn't tally with all those cosy images of a passivhaus; I find myself yearning for coal fires and feeling warm. On sunny days the house is OK whilst the sun shines through the big windows but this part of the country doesn't get many sunny days so such treats are rare.

Another thing I wouldn't mind feedback on is the impact of windy days on the house - we've had airtight test showing the house isn't leaky, indeed at one stage this was the least leaky house in England(!) but wind definitely has a measurable cooling effect. It's like it drags the warm air out through the vents before the MVHR  has had a chance to reclaim the full amount of heat - is that possible twitter? Does anyone else have experience of this?

This graph shows the profile of the year with the purple arc of the external temperatures and the year's worth of sunshine. You can see how the three floors had a different temperature for most of the year until the autumn equinox. Does this mean the house has now reached equilibrium you may ask? Nope, it just shows me shutting all the doors on any but the sunniest days in an attempt to stop the heat inside the rooms from shooting up to the top floor. This graph also shows quite clearly that in summer we struggle to cool the house and in the winter we have trouble getting it above 18 degrees on the ground floor.

The final graph shows the electricity generation from the PV and solar as a percentage of our usage, despite the best efforts of the English weather.

If anyone would like the spreadsheet with the breakdown of all the readings then tweet me - there are several sheets but we're happy to share them with anyone who's interested.

Sunday, 11 November 2012

Annual Review

We've now been in the house for a year so this seems as good as time as any to give the house and its technology a check-up, so let's start outside the front door and work up to the roof.

The Insulation

The external insulation is a winner (mind you, I don't know how it might compare with cavity wall insulation).  Although this year the cold weather has arrived a month earlier we didn't need to put in additional heating until the outside temperature fell to about 8°C at the end of October. It's hard to judge how soon we would have put heating on in a 'normal' house but I should think this was a good month later and in the spring we turned the heating off in early March. It therefore looks like we only need heating for five months of the year (maybe!). 

The Porch
The porch is great on sunny days in spring and autumn as it traps the sun. You can then open the internal door and let the warmth into the entrance hall which reduces the amount of extra heating you need. In winter, especially on a grey day, it gets freezing and you have to be really quick coming through the door so the cold doesn't get into the hall. In summer you have to have all the windows and external door wide open in an (often unsuccessful) attempt to cool it down. Leave any plants in the porch between June and August and they fry but the rest of the time they flourish and I have spectacular cyclamen in winter. Basically, the porch is a very expensive greenhouse.

Maybe it's me but the word passive doesn't quite tally with our experience of the heating, cooling and ventilating of this house. In the summer we were forever trying to cool it down and now the weather is cold we have tried endless permutations to get the internal temperature comfortable.

Of all the aspects of the house that we've found vexing this is is the pièce de résistance!

In the summer we eventually evolved a convoluted system of  excluding the sunshine during the day, messing round with the MVHR and opening the windows on the top floor to draw heat up through the house but it was really only the dismal weather that made things tolerable. In summer the average internal temperature was about 23°C but it could reach 26° if we weren't careful.
Now the house is struggling maintaining 19° but to achieve this we've had to develop a system of turning the fans to their lowest setting when the heating system that comes with the MVHR is off and onto their middle setting when it's on. The electric heating uses the most phenomenal amount of energy so at the moment we have it on for five hours in the morning and in the evenings we have plug in radiators to warm the room we're in.

We're also having to remember that whilst in summer you keep all the doors and windows open, in winter you have to keep everything closed - except when the sun is shining because then you need to open all the doors and blinds to let the whole house warm up..... If you watch Dr Who you'll be aware of the running joke that the TARDIS has a mind of its own. We haven't had to resort to hitting the heating controls with a hammer but we've felt tempted on occasions.
So, on the space theme, here's Saturn again representing the vents that blast air, at various speeds, into the rooms from the fans. I know the physics of all this but I do wonder why they are placed where they are in the rooms. The only room where you really feel the benefit of the system is the room where the desk is directly opposite the vent so I'm not sure why we don't have under-floor heating of some kind instead but maybe that's my inner classicist coming out. In the same way, in the summer, it was only sitting at the desk that you could feel the benefit of cool air coming in from the fans.

The corridors don't have vents at all so in winter, unless you keep the doors open, the corridors get very cold and in summer, as I've mentioned before, there seems to be no way (apart from opening the windows) of cooling the top floor so, in general, I remain baffled by the MVHR system (even with an English version of the manual).

Hot Water
I promised you a picture of the new 'improved' hot water cylinder back in September and here it is.

Looking back I see the spec for the water cylinder that preceded this one; as far as we can tell changing the cylinder hasn't made any difference to its efficiency.

The only difference we've noticed is that the display now works.
This means that we can now quantify how much energy the solar tubes produce, as the generation meter only records the PV generation. By the power of mathematics this has allowed us to calculate that over the year we pretty much generate 100% of the energy we use, even taking into account the poor summer and chilly autumn.
Chuck a few sunny autumn and winter days into the mix and we will be generating more than 100% of our energy over a year. The graphs will appear in a later post. 

Rainwater Harvester 
Oh dear.

Well, it's been drained and cleaned and had its pump replaced but the only time we've used it is when the local water board turned off the water supply for a day.

It works for the loos on the ground floor and it works on the middle floor but, alas, whilst the pump can pump the water from the harvester up into the house it can't pump it up to the top floor so it's only 50% effective.

Also, since the pump was replaced, everytime you flush a loo there is a curious rumbling sound like a distant pneumatic drill. Not that that is so much of a problem in the winter because you're having to keep all the doors closed (see above).

Really easy to clean and great cooling effect in summer but equally cool in winter so you need to wear sheepskin slippers to keep warm.

Drop something on it and it shatters neatly - there is no bounce at all so I'm glad there are no toddlers in the house.
In order to be more eco we have reduced water flow and this is another thing that drives me mad. It means that it take four minutes (believe me, I've timed it I was so incredulous) for the shower to run warm water if you're having the first shower of the day and four minutes to start hot water coming out of the tap when you wash up. Ironically it means you run the taps longer than you would just so you can get hot water, go figure.
External Blinds & Triple Glazing
The blinds play a vital role in keeping the house cool but in a perfect world we would have them on the east window on the first floor and the long windows on the west as both let heat in in summer. We also badly need external blinds on all the roof windows - including the ones on the north side of the house, especially at the western end as in summer the sun is high enough in the sky to shine directly in. The triple glazing is brilliant and there's no noticeable loss of heat through it so whether you sit next to the window or on the other side of the room the temperature feels the same.

PV Panels

28 panels and they generate enough energy to run a home and an office, including all our heating. Plus the house is occupied 24/7 and we're not hair-shirted greens we do have DAB radios (6 Music is the only thing that keeps me sane!), TV, laptops etc.

Does someone want to explain to me why we don't have a Green New Deal to put solar panels on all public buildings?

Sunday, 14 October 2012



One of the things that had to be done for this house to achieve Code 6 was to minimise its ecological impact both in terms of its construction and surrounding environment. 
Now, given that a year ago this is what the surrounding environment looked like, clearly the only way was up so every available moment I've had when it hasn't been raining (admittedly not much this year) I've been outside trying to do something to improve the biodiversity of the garden.

The first thing to do was plant the trees in the spring and thanks to the dismal rainy summer they have at least become pretty well established. One of my favourites is this crab apple which was dripping with fruit at the end of the summer. We used to have a wonderful crab apple next door that fed birds throughout the winter, including a flock of fieldfares one Christmastime and provided a glorious splash of colour in the winter sunshine. That tree was recently, unceremoniously, cut down so I'm pleased we have a small version in the new garden. The crab apple is a native tree and according to the excellent How to Make a Wildlife Garden by Chris Baines it supports around ninety species of insect; so apart from being beautiful it's useful too. Certainly our tree is providing food for local birds judging by the way they are helping themselves to the fruit.

Some features of the new garden are artifical aids for wildlife. We have this ridiculously-named hogitat for hedgehogs and actually saw our first hedgehog in the garden one evening, although I think it was just passing through. We also have a box for overwintering lacewings and, up in the trees, there are boxes for bats and birds.

The boxes have only been in place for the last month but we have at least one bat who visits so hopefully s/he will know she can roost in deluxe eco accomodation if required. For the plebs amongst the wildlife I also have log piles created from one of the trees that was felled during the house build.

Set into the insulation of the east wall we have two concrete swift boxes (you can see the holes above the narrow window at the top of the house). They didn't accomodate swifts this year but two blue tits raised a family there in the early summer.

In January each year I've taken part in the RSPB's annual bird survey but this year I couldn't because there were absolutely no birds visiting the wasteland that's pictured at the top of this page. I didn't find this very encouraging but by putting out food and digging and planting the garden I've now got a healthy population of birds. I was equally panicked in the summer when it was time to record butterflies for the Big Butterfly Count but that was due to the appalling weather and the number of butterflies in the garden increased dramatically during September.

As befits the resident of an eco house I've also been doing my bit for our apian friends and have had a succession of nectar-rich plants since the spring to keep them fed, so most visits to the garden have seen bees lazily roaming through the flowerbeds.

My other great contribution to encouraging wildlife has been planting and landscaping the pond. According to Chris Baines' book a pond is the sine qua non of a wildlife garden and I was much struck by his observation about how easily a pond manages to colonise itself. I haven't had to make any effort to bring creatures into the pond but it has taken the summer for them to arrive. Since the spring the pond has become home to at least one frog, a water boatman, a lot of midges, gorgeous electric blue damselflies (I don't care if they are 'common blue', it's still a fantastic colour) and a spectacular green and gold dragonfly. We also act as a watering hole for all the local birds and possibly a fox too.

So in a year we have gone from a muddy field with two trees and a climbing rose to a space rich in native trees, wild flowers and plenty of food and shelter. Next year I hope to be able to spend some time outside actually enjoying the space but we are still, very much, a work in progress!

Thursday, 13 September 2012

No, we're fine, honestly

Isn't this a nice and restful photograph? Soothing to the soul and all that? It's not the eco house that's for sure because that is neither soothing, restful, nor indeed inhabitable at the moment. This photo is close to where I'm hanging out at the moment because the eco house is having both snagging work done in (literally) every room and essential repairs done to spaces like the kitchen, office and all the loos. My better half is camping back on planet eco but I have weighed up the choice between staying sane or keeping a stiff upper lip and picked the former so courtesy of that nice Mr Branson I've fled to the uttermost east until it's all over.

Snagging work you expect when you've been in a new build after a while, but the other work has been hugely disruptive so here's a chance to experience a little schadenfreude to brighten your day, with the proviso (from my OH) that I must keep it objective, not subjective.

For some reason we have needed a new hot water cylinder because we had the wrong sort. When I get back west I will post a photo of the right sort of hot water cylinder and then we can marvel at the improvement. Replacing a hot water cylinder that's attached to solar thermal tubes is more of a palaver than it would be in a normal house: I was told it would take two days at most and so far it's taken four. I believe that the solar thermal had to be drained down before the cylinder was replaced and today it's due to be recommissioned by the firm that installed the solar in the first place. As I've said before, though, this blog is about the experience of the house so whatever the technicalities this meant no hot water from first thing on day one until late on day two. It also meant clearing one of only two storage spaces in the house as that is where the cylinder lives and as that cupboard is in the corner of the office that's meant the office has so far been out of action for four days (and counting).

Well, you can manage without hot water for a couple of days and if you can't answer emails or the phone it's not the end of the world when you work from home** but not having flushing loos is more of an issue. The rainwater harvester first became a problem back in November when we moved in and started using the loos so we just switched it to bypass the harvester tank and flushed the loos with mains water instead. On day two of this exercise the harvester was sorted and it was back to recycled water for the loos again. Yesterday (day three) it stopped working again and someone is coming back again today (day four). I may keep you posted on this but, alternatively, if it keeps failing and I need to go back to non-recycled water, I may just keep quiet to avoid more disruption to my life, who knows?

OK so despite the loos working intermittently, ditto hot water and not being able to reach the phones or computer without climbing over the contents of the only proper cupboard in the house things are still basically OK on planet eco are they? Alas no, let's now think about the kitchen where the worktop needs replacing and for that I blame myself entirely. There was the tiniest, most miniscule gap where the two sections of worktop joined and, like a fool, I mentioned this as water was getting in (because the join was within 15cm of the sink). The result was that the whole worktop needed replacing, but I wasn't to worry because that would take half a day at most. Sadly, confirming my view that we don't all live on the same planet (let alone the whole men-women-Venus-Mars thing) I hadn't realised we were talking about Plutonian, not Earth days (yes, I know it's been demoted but nothing else fits). Since day minus one the contents of all the kitchen units below the worktop have been stacked in a bedroom and for two days the cooker and kitchen have been out of action.

So, as I sit and watch the chickens outside the window and the house martins darting over the pond let's spare a thought for the eco house unable to provide water, loos or cooking facilities. Henceforth I will be very cautious about what I report and when asked how things are going I will simply take the advice a clergyperson gave me many years ago and reply, as Steven Tyler would say "fine".

PS: Many thanks to everyone who offered me an English version of the MVHR manual after my last post - it came in very handy even if I wasn't sure the Boolean logic it contained made sense!

** Sarcasm: Your body's natural defense against stupid. 

Friday, 13 July 2012

Some like it hot? Data up to the solstice

Last time I posted temperature data was in April and it covered the period from the winter solstice to the spring equinox (for an explanation of the solstices take a look at the BBC's website here). We've now got data for the next three months as the sun reached its highest point in the sky. Of course this has also coincided with pretty dismal weather here in the UK but we are getting a bit of a feel for the pros and cons of this particular house so first I'll give you the scientific data and then I'll give you the low-down on what that data feels like. 

Before I begin, I ought to say that I do love this house and largely enjoy its quirkiness, but as a recent school visitor said, houses are for living inso apologies in advance to any readers who won't be happy with what I say.

Here's the temperature data from the winter to summer solstice. We've changed the graph to show fortnightly averages to make it fit on one page:

As before the green bars show the amount of energy we've generated (so you can see how much heat we got from the sun that day) and the blue, orange and red lines show the floor temperatures but I've changed the external temperature record to a purple line so the graph is clearer. 

If you compare the peaks at the beginning of January, end of March and end of May you can clearly see how much stronger the sun is as we approach the solstice and each peak pushes the internal temperature of the house up to a new plateau. In the winter the internal temperature was running at an average of 18-19°C, by the time of the equinox in March it was 20-21°C and by the end of June this had become 22-23°C.

In the winter the house felt too cold and we assumed this was because it was drying out after the build so we were delighted when the weather warmed in the spring and we were able to switch off the heating boost but by the end of May I was tweeting that we were having problems with cooling the house and this has been a big issue now for a couple of months.

If you google "passivhaus overheating"  there are a number of sites that tell you that passive houses don't overheat and, technically, this house doesn't very often because the point at which overheating is defined seems to be when the internal temperature exceeds 25°C (that's 77°C in old money). But, whilst our internal averages have been in the low 20s Celsius we have had days when several days of sunshine or the combination of sunshine and high temperatures outside has caused the temperature on the top floor to rise to 25 and beyond. It may not technically be overheating but you try sleeping in 25° heat when you've been trained for donkey's years to keep your house thermostat on 21° to save the planet!

I jokingly posted on twitter that our house may be passive but we're having to be rather actively engaged with it and that's certainly been the case since it started warming up. We've obviously been keeping the blinds closed to exclude direct sunlight (and, irritatingly, block the views of my garden) but that wasn't enough. We've sought advice about how to cool it down but there's a lot of advice out there and what works in theory doesn't necessarily work in practice in this particular house and, in the process, we've discovered ancecdotally, about other passive houses experiencing similar problems. 

There have been elements of farce involved in reaching a modus vivendi with the house temperatures but at least the Jubilee and Olympics have bought me time by postponing summer. One suggestion was that we turn off the MVHR and open the windows to cool the house down. I tried that but we ended up with the 'wet' areas of the house (the bathrooms and utility room) reaching jungle levels of humidity so I battled through the lianas and leeches to the MVHR control panel and abandoned that idea. Another suggestion was to switch the MVHR to summer bypass mode. Sadly we didn't know what that meant so I wasted a day or so working it out and then trying to find out how to do it as the only manual we'd been given was all auf Deutsch. Well, you can't say you don't learn stuff in this house - not just physics and engineering but linguistics too. With a combination of German dictionaries, google and sheer bloody-mindedness, I managed to sort that but it only reduced the temperature by half a degree and I'm not even convinced that it was a key factor in that. So, at the moment, the only thing that is working is to open as many windows as we can on the top floor without the rain pouring in and keep the MVHR on the lowest possible summer bypass temperature. With all that going on the temperature on the top floor is now about 23°C and it's not as warm as I'd like downstairs so any sensible suggestions about how to vent the house further will be gratefully received.

This house only has external shading on the south facing windows and this, I think, is one of our key problems. We had to have rooflights on the top floors to counter planning objections and they only have internal blinds on the south-facing roof so some heat obviously gets into the top floor through this route. In addition, since May, the sun has been high enough in the sky to shine through the rooflights on the north side of the house and they have no shading at all. We are also finding that a lot of heat has been coming through the east and west windows since the equinox so probably those windows needed external shading too.

So, architects/engineers reading this, may I suggest some things to consider when planning a passivhaus?
  1. Please put external shades on all the windows
  2. Don't make a three-storey house unless you've got very efficient ventilation for the top storey
  3. Consider designing the house upside down - you want bedrooms to be cool and living rooms to be warm so perhaps bedrooms should be on the lowest floor and the living rooms at the top floor. Thus, ideally, you should be designing houses for south-facing slopes which are accessed from above not below!
  4. Give people manuals in their native tongue unless you feel that self-improvement is an integral part of living with your design
Next time I post I will write about the financial efficacy of the solar panels and probably be busting a few myths but I will wait and see what, if anything, we get in the way of our first FIT payment compared to the amount of electricity we've been generating.... I might be pleasantly surprised but don't hold your breath!

And because all the above may be received as criticism rather than the words of a critical friend let's finish with a pretty picture of the house because it may be a bit mad, but I am rather fond of it.

For copyright info on the image of Stonehenge see