House maker uses Matsumoto passive house design

Misawa home just nicked our house plan:
http://www.eco.misawa.co.jp/flagship/salesmodel/

Actually I don't think they stole it, it's just very similar. They're
obviously faced with the same challenges and objectives, and have
found the same solution. Great minds think alike!

Roof going round in circles

The foundation is racing ahead, but it's still not clear what is happening on the roof.  This needs to be decided so that the order can go to pre-cut the wood, and until that happens there will be no pillars, which will be needed to hold the roof up.

The South-facing roof is solar. Until recently solar roofs meant building a normal roof (compliant with the regulations for fireproofing and waterproofing) and then solar installers coming along and drilling holes in it to fit on their panels. Drilling holes is fair enough for retro-fits, but for new builds this seems foolish, especially if you're trying to get a highly insulated, airtight roof. Using a different construction does not meet their installation requirements and you lose their guarantee, and the panels themselves don't qualify as roofing. 

Last July one roof maker, Caname, who started out making roofs for temples, introduced a solar roof that meets the regulations for roofing, so there is no need for a double roof and, at least in terms of design, a more elegant solution is possible. Economically this should also make sense, but design simplicity does not always correlate with economics.

So, all we have to do it build up to the rafters, then Kaname will put their roof on top of it.  As long as they've got something they can put a waterproof sheet over, and into which they can screw the corrugated steel roofing which they mount the panels onto, everything will be fine.  The Kaname construction allows air flow under the panels, which is important to keep temperature down on the panels, which keeps efficiency up. Corrugated steel should work well for this, increasing the surface area and taking heat away by convection and conduction.

It's usually practice in Japanese building to have an air gap between the insulation layer and the external wall or roof.  As Kaname are putting corrugated steel on top, as well as providing air flow for the panels, this should also provide an air gap for the insulation. The reason for the air gap is in case humidity builds up and needs somewhere to go. Not everyone believes this is a good idea, and any gaps potentially can attract insects or even bats. The practice seems to have evolved to cover up for any problems with humidity, although, in theory at least, a well designed wall should not allow humidity to build up to turn to condensation. Also in theory, the gaps around the corrugated sheet should work both ways, but I've been battling both the roofer and the insulator (two different contracters) who seem keen to have things done their own way, and are looking at an assembly of parts rather than the whole, which was the main reason why Kaname seemed so appealing. 

However, there's also the west wall. In our wisdom http://minuszeroeco.blogspot.com/2010/04/west-wall.html, we decided that the house should not be square.  As the plot is not square, and non-square rooms do interesting things with space perception, this seems to be the correct decision long term, but when it comes to this issue, (and no doubt countless others that will emerge) it's causing problems. Kaname only make square roofs, so there is going to be a one metre overhand at the South west corner that needs to be supported somehow. 

One possibility is to get the rafters to stick out of the side of the house to support the overhand.  There are two problems here. In the original plan the rafters run up and down, north-south. Changing all of the rafters to run side to side, east-west seems to have been too difficult for the architect to adapt to without changing the whole structure. More seriously the rafters sticking out will lead to thermal losses and thermal bridge effects, sucking the heat out of the house. 

So we reached a plan to put the waterproof roofing sheet on top of the rafters (where the insulation layer ends) then put horizontal beams on top of that, which can stick out to the west and take the load of the overhanging corner. The panels need to be fitted with screws at horizontal intervals of 160mm and vertical intervals of 830 mm. Horizontal beams can cope with this, but if they are mounted horizontally, there are fears of beams twisting and the roof rolling off. The thinner the beams are, the less of a problem this is, but the beams need to all be the same thickness as the solar roof is flat, and they need to be thick enough to support the overhang. Extra beams can be added to the west to make this stronger. 

Another problem is that the solar roof installers need to add the roofing sheet, which would mean them making two trips, with some carpentry in between, rather than just coming and doing the whole job in one day. It's also not clear how they would feel about people making holes in the waterproof layer. 

The builder seemed much happier with vertical beams and some construction board mounted on top, although that will mean another air space and another layer of tyvec or some barrier sheet to stop any moisture that gets in there.  They pointed out that this would stop overheating in the summer, but we already have solar panels on the roof, and almost half a metre of insulation, so over-engineering is a much bigger concern to me than overheating!

So far all attempts to keep the design simple seem to be riddled with complications, and "simple" means very different things to different people!

Electrics and low-energy lighting

In terms of lighting, there are three factors to efficiency. First is the type of appliances used, second is the way that they are laid out, and third is the way they are used. In terms of appliances, LEDs and compact fluorescents are going to use less energy than incandescents and candles. If the light illuminates what needs illuminating to the degree it needs illuminating, then you will use less energy. Finally, if the lights are switched off when they are not being used, this could make a bigger difference than the first two points.

As well as the obvious energy efficiency benefits of low-energy lighting and energy-efficient electrical appliances, in a highly insulated, airtight house, they will mean a cooler summer. Energy efficiency is a measure of how much energy comes out in the form you want it, for example how much power is coming out of a motor or how much light is coming out of a lamp. For example, the luminous efficiency of a candle is something like 0.04%.  In other words, for 10,000 units of energy, 4 of them will turn to light, and 9,996 will come out as heat. Next time you see somebody using candles and calling themselves green, bear this in mind. The rest of the energy is turning into heat, so inefficient electrical appliances mean more heat in the summer. In the winter, this may not be a bad thing, and in fact having a few lamps with incandescent bulbs will make very good back-up heaters for those really cold winter nights.  

Incandescent lights are over 50 times more efficient than candles. Facilitated by Edison's flair for publicity, that's why people stopped using candles and switched to electric light (image of light bulb coming on above head). They are still only 2%-5% efficient, so of those 10,000 units of energy, around 200 are now coming out as light, 9,800 are coming out as heat. The hotter the filament, the more efficient the light is, so very bright lights, such as projector lights, reach 5%, while most bulbs are around 2%. Halogen bulbs are not much more efficient than incandescents. 

Fluorescents light and LEDs are similar in luminous efficiency, around three times better than incandescents. The best fluorescent seems to be Panasonic's spiral tube, reaching 18% http://panasonic.co.jp/corp/news/official.data/data.dir/jn100609-1/jn100609-1.html. The theoretical limit for LED efficiency is up to 40%, and the most efficient currently being manufactured are around 20% efficient.  So now, 2,000 units of energy are coming out as light, and 8,000 as heat. These "lights" are still working better as heaters than illuminators. http://en.wikipedia.org/wiki/Luminous_efficacy

For reference, the sun has 12% luminous efficiency.

The advantage of LEDs over fluorescents is that the light is all pointing in the same direction, which is often down rather than into fittings, walls or ceilings. This can also be seen as a disadvantage but generally it makes LEDs two or three times more efficient than fluorescents. LEDs are also smaller in size, use fewer materials and are simpler to produce so ultimately should be cheaper to manufacture, and they are likely to take over the market.

This leads onto the design of lighting. Generally speaking European lighting, with spotlights and ambient lighting is more efficient by design, while in Japan gains made by use of energy efficient fluorescents are partly lost because everything is bathed in bright light. Work surfaces, such as desks or kitchen tops, need bright light to be able to read or to distinguish between carrots and fingers on the chopping board.  Ceilings, walls, stairwells and corridors generally don't need as much light, so a design based on efficiency would use modest light in corridors, so we can see where we are going, use some ambient light on walls and ceilings, so we don't feel we are in a cave, and focus bright light around chairs, desks, tables and work tops. Flexibility is needed as we don't know exactly where the desks or chairs will be, so adjustable spot lights seem like a good idea.

One of the energy efficiency features of the Panasonic spiral tube is that it will change its brightness depending how much light is in the room. In bright daylight, it will turn off; dim daylight it will come on weakly and at night it will come on fully. As well as light sensors, use of motion sensors, for example in entrances, storage spaces and toilets, will likely stop lights being left on and save electricity. In terms of design and installation, they should also remove the need for light switches on walls, so may be cheaper. This remains to be seen!

Foundation Construction

Watch it being made.

How warm is it going to be?

It should be warm, but to find out we're putting thermometers in each corner and in the middle, in the bottom slab and in the floor slab, a few centimetres higher.

Foundation

Or perhaps "lost and foundation" after waiting a couple of months. Extruded polystyrene going in first, 100mm underneath (two 50mm as that's the thickest they've got here) then 50mm around the sides. Later another 100mm will be put around the sides up to ground floor level to make 150mm.

From the secret entrance

The view from the South East corner of the plot.

From the kimon

According to feng shui (known as fu sui in Japanese) the northeast corner is known as the "kimon" or demon's gate, apparently. Not a good place for an entrance. Or a camera since they moved the grille there.

The drive

This looked like a really good angle for the house, until the portaloo appeared and took pride of place.

From the western approach

The view from the West. It starts with nothing and may end up obscured by the neighbour.

View from the garden

Here are some pictures. The concrete has started to flow. A little bit of snow but it's not so cold and it melts away quickly!