Thursday, September 27, 2007

Warm at last!

Completed conservatory
Mission accomplished: The Mur Crusto passive solar gain project is largely complete and we’re reaping the benefits immediately. We should have done it years ago. There’s more to do, of course, but now if you want, you can see all the best pictures of the construction from beginning to end. Click here to take you to my photo album where you can choose either to see all the captioned pictures as a slideshow in sequence, or move around the album of thumbnails to click any you're interested to see full-size.

Wonderful to be warm! The most obvious immediate benefit is that the core of the house, previously like a cold store even in summer, is now permanently warm. The temperature outside last night dropped to 3 degrees Celsius but we were perfectly warm in our living room, needing no additional heating. Remarkably, even late in the evening, the conservatory still felt quite warm. So we really are reaping our passive solar gains.

Battle against the weather: This summer has been lousy. A lot of it was dry but cold, but there have been long periods of 'unsettled' weather; Met Office parlance for rain and wind. Whilst there was no glazing, the concreted floor (see photos) repeatedly flooded and had to be pumped out. I developed a sort of 'cut and run' strategy for working, keeping all my tools in a wheelbarrow and coming out when the rain stopped. I'd work until the next rain and then trundle everything away into shelter. This is no way to work but I had no choice. Latterly, we did have a few weeks of dry weather which was perfectly timed for me to get on with glazing the roof and then the windows. Glazing the roof was what one might term 'a non-trivial operation'. (It said in the assembly instructions something like, "Now glaze the roof"!) Doing the lead flashings before that was also quite difficult, lead being heavy and difficult to fit in the continuous slot I'd cut in the wall of the house. But the roof glazing took the biscuit for difficulty: the glass units are heavy and locating them tricky. The seals for waterproofing are fiddly and messy (silicone all over the place). But I managed in about 2 weeks of struggling.

Last minute: The last pieces of glazing went in the east gable end a matter of 2 hours before the rain started again, just in time to stop the loss of warm air from inside the structure. From that time on, it's been a different world inside. Lots of light, warm space and the wonderful feeling of warmth flowing into the old, formerly cold, stone building -- all for free and without burning any fuel. There are a few small leaks which I have to sort out when the rain stops but otherwise, it's really great. Everyone should do this if they can. It really makes a difference!

The next stage: To gain the full advantage of this structure, I have to complete various things. One is the floor which I shall insulate. Another is the internal wall plastering and painting with a tinted paint ('sandstone' is the name of the tint). White houses are a serious mistake; very pretty but cold. It's just like the (vanishing) Arctic sea ice. Being white, both reflect almost all heat away. A dark wall or ice-free sea surface absorb most of the solar radiation and so heat up: good for warm housing; bad for warming oceans and accelerating ice melt. It's the albedo effect and it applies to houses just as it does to the Arctic Ocean. Ideally, I'd paint the internal wall black to absorb as much heat as possible and act as a massive heat store. But one has to compromise. A black house is not acceptable! So it's going to be that sandstone tint. Even so mild a colour makes a difference too. On a sunny day, place your hand on the white paint and it's cold. Place it on the sandstone paint and it's nice and warm.

Controlling the warmth: I also need to investigate simple control systems to duct heat actively into the house, using a fan, but only whilst there is heat to duct. In other words, I need to devise a simple system which switches on whilst it's hot in the conservatory and off when it's not. It would ideally recirculate the cooler air from the house into the conservatory for re-heating. What I don't want to do is dump heat into the atmosphere if it's needed in the house. If you, reader, have any ideas about how best to do this, please leave a comment below this post. I'm sure there are systems available so I don't have to re-invent the wheel.

Details of the building: For those interested, the U-value of the low-e double glazed units is 1.3 (Planitherm). The conservatory was manufactured by Portland Direct, the DIY branch of Amdega, all made from treated and painted softwood from (they claim) sustainably managed Scandinavian forests. This large structure cost around £10,000 delivered, with telephone back-up support available and very good. It's guaranteed for 15 years. The other bits and pieces (like blocks, cement, lead and so on) have probably cost another £1500 or so.

Then there's the small matter of my labour. I started excavations in January and completed the glazing in mid-September. I have probably spent one third of my available time working on this during that period, saving 4 weeks away in Scotland. Val has helped when needed, particularly with laying concrete and holding things in position and I have employed Simon, a carpenter friend and one of our organic veg customers, for 4 days in total. That's about it. Hard work, definitely a 'non-trivial operation' but rewarding. Most reasonably fit (I'm aged 60) and reasonably competent people could do similar. Building is, in part, a question of thinking things through slowly and carefully before doing them and using ingenuity where possible to save time and trouble. So... go for it!