Building a Low-Energy Home

The best solution?

Mark’s beautiful home

I’m really pleased to have another guest post from Mark Brierley for you today (you can see his first one here). Mark is a certified Passivhaus consultant and blogger, and he is generously sharing his knowledge and experience with us today. You can read more of his writing at his excellent blog, or stay tuned for another guest post from Mark next week.


“The easiest and most effective time to insulate a house is when it is being built, and if you are involved in building a house, it makes sense to invest in lower energy use. Even if you can afford to buy a house with cash, the tax breaks you get from having a mortgage in Japan mean that you are better off borrowing money for your house, and following other suggestions in this blog to get higher returns on your own cash.

Financially, there is always a trade-off between the up-front capital cost of insulation, and the running costs for heating or cooling. If you are borrowing money to build your house, then your capital payments are not up-front investments, they are monthly payments. Your energy bills are also monthly payments, but the energy bills will continue after you have paid back the loan. Nobody has a crystal ball, but there is at least a fifty percent chance that energy will become more expensive rather than less expensive. On the other hand, Japanese banks offer cheap fixed-rate loans, so you know exactly how much you will be paying. Investing in insulation means you pay less overall, and you are also insulated from any spikes in energy costs.

Not all insulation is equal

Heat is lazy, and will always find the easiest way to get from hotter places to colder places. The same principles apply to heat whether it is leaving your warm house on a cold winter night, or coming into your cool house on a hot summer day.

Heat has basically two ways of escaping: conducting through the walls, or leaking through gaps as hot air. This means that along with the insulation, your walls, floors, ceilings, doors and windows need to be airtight. If you have an airtight house, you need ventilation. If you use natural ventilation, such as air vents or opening windows you will lose a lot of air and the heat with it when it is windy, and you will not get enough fresh air when it is still.

Mechanical ventilation means that you get the right amount of air for a healthy and comfortable house. Mechanical ventilation can also use heat exchangers which warm up the fresh air coming into your house with the heat from stale air leaving. The electricity used by the fan may seem like a waste of energy, but it uses much, much less than the heat you will save doing this. Mechanical ventilation will only work effectively if your house is airtight. You can imagine how ineffective it would be to suck air through a straw with lots of holes in the sides.   

Elements of a Passive House

​This combination of insulation, air tightness and mechanical ventilation with heat exchange is the basis of the Passive House standard, which I think is a gold standard in low-energy building. Passive House, or Passivhaus in German, came mostly from a German and Scandinavian reaction to the oil shocks of the 1970s. It is built on forty years of research and measurement, and the experience of several failed attempts to build low-energy houses. 

Even if you are not trying to reach the Passive House standard, you can learn a lot from the research into using less energy, and avoid many problems that can come from attempts at low-energy building. You can read more about my experience building and living in a Passive House in Japan here. You will need to research this because unfortunately you can’t just walk into a builder in Japan and pick up a Passive House off the shelf.  

As well as saving money, better insulated houses are more comfortable, healthier, and can last longer since the insulation will also protect the structure. In many countries energy efficient buildings have higher resale values, but building resale values in Japan are low, energy efficient buildings are scarce, and it is difficult to find evidence of this being true in Japan.

Well-insulated houses are cheaper to heat, but partially insulated houses will not necessarily save any money. As mentioned above, all insulation is not equal, and needs to be carefully designed and properly installed to reduce your heating bills.

Actual energy use is often twice the predictions from regular building codes, but the decades of research and measurement of Passive House buildings in a range of European climates mean that energy use is very close to the predictions, and these buildings reliably use up to 90% less energy than conventional houses.

If installed correctly insulation will always make your house more comfortable, but unless you have a well-insulated house you may end up paying the same energy bills as before to make your house comfortable for more of the time. Moderate insulation will give you a choice between comfort or cheaper heating bills. The performance of Passive House means that you can have both comfort and lower energy bills.”
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Thanks again Mark. Lots to think about there. I am planning to build a small Passivhaus in a few years time -hopefully the concept will have become more popular by then!

Any questions for Mark? Feel free to post them in the comments, and stay tuned for next week’s post.
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17 Responses

  1. If he is familiar with the company, I’d like to hear Mark’s thoughts on Sweden House, and how costs compare between them and working with a someone to build your own Passivhaus.

  2. I don’t have any direct experience of Sweden House Japan, but from what I’ve read, for low-energy they are among the best large-scale house builders in Japan, along with Ichijo, and they may get close to, or even meet the Passivhaus standard, but their Q values (measure of insulation) and C values (measure of airtightness) are typically two or three times higher (i.e. lower performance), so you need to compare cost-performance, not just cost.
    If you want a new house in Japan, you basically have a choice between a large-scale “house maker”, a builder (“komuten”) or an architect (“kenchiku sekkei jimusho”).
    House makers are relatively expensive, you usually have limited options to choose from, and variation may be impossible or charged extra for. But what you get will look very similar to the catalogue or the model house, and the support will be good. Actual energy use will often be a lot higher than predicted, but that applies to most non-PassivHaus buildings. If you can find a house maker you like, building through them will be the smoothest path to your own home. Talk to Sweden House and they may be able to build you a Passive House.
    An architect will be able to build anything you ask for, or at least will be able to draw it. In this case, it may cost less, but there is a risk that you may not get what you want, or that you do get what you wanted, but find when you move in that you didn’t want that after all. Building through an architect will often cost less than a house maker, but there is no guarantee here either. This will work best if you find an architect who shares your idea of an ideal home. If you find an architect interested in building passivhaus with some experience in highly-insulated highly-airtight buildings, then it should come out cheaper than the house makers.
    Going straight to a Komuten will give you more freedom than a house maker, but not as much as an architect, and they will probably be cheaper than either. If you can find a Komuten that will build Passive house, you will likely pay less and get higher performance than Sweden House.

    1. Thank you for the in-depth and informative reply. I’ve been looking at Sweden House for a little while, but really didn’t have anything to measure them against. Having more info about passivhaus standards will help.
      I haven’t heard any solid numbers, but I got the feeling from a few satisfied owners that the building costs are about double that of a regular Japanese house. Permanent residence shouldn’t be very far off, which makes me more interested in having a home. However, if I’m going to go to the expense and effort involved in getting a house, I want one that is properly sealed and insulated.

      1. Proper sealing and insulation are not standard in Japanese buildings, but they are possible, and not rocket science. (Proper sealing and insulation are also important in a rocket though!)

    1. Interesting article, but I’m tempted to add it to my large collection of articles on Japan that have little bearing on what is actually happening here! The story behind this is that the building trade in Japan is highly conservative and factionalised, and there is usually more emphasis on gadgets and details than on materials and holistic design.
      The idea of lifecycle carbon minus is great, although I’m not completely convinced with the LCCM Group’s approach. Murakami is a bit deluded by the “Japan is different” rhetoric. Sure it gets hot and humid in the summer, and cold and dry in the winter, but the humidity is always between 100% and 0%, heat and moisture obey the same laws of physics as in Europe, and the comfortable range for humans is similar. Also he doesn’t acknowledge that the “European Climate” ranges from Finnish tundra to islands off the coast of Africa, and Passivhaus has been developed for that range of climates. There is a lot of useful knowledge outside Japan, and if they had taken this approach with the automobile industry, Toyota would probably be a long-bankrupt rickshaw manufacturer!
      The ideas of having big windows for solar gain, buffer zones, and changing things around between seasons were all tried in Europe in the 1980s and the conclusion was that correctly installed insulation is the best strategy. The Passivhaus standard will basically deliver a building that provides maximum comfort using a minimal amount of energy, so it is the best starting point for any low-carbon approach. From there you can try to reduce the carbon footprint of the construction materials, which is a challenge faced by all buildings. Then you can stick some solar panels on the roof and pronounce it carbon neutral.

      1. Nicely rebutted. That article annoyed me, but I wasn’t able to articulate it well 😉

      2. Thanks for your perspective! I know that none of this is the norm, and it’s not surprising to hear that Japan is behind the trends.

  4. I taught a summer course at a university in Austria a few years ago and the building that I taught in was a Passivhaus. It was beautifully designed but I found it to be much too hot to teach in and the students seemed pretty uncomfortable as well. I think it would have been an OK environment to laze around and watch TV in but I didn’t think it made a good working environment. How is your house in the hottest summer months?

    1. I vaguely remember an NPR story years and years ago about passivehaus or similar construction. They mentioned in the story that just the body heat from more people, say during a dinner party, could make the house hot enough in the winter that you would need to open windows.
      On a similar note, I went to a Sweden House open house held in January. The owner was wearing shorts and a t-shirt, and had windows open, with the heater turned off. When I asked him about the windows, he said that with all the people coming for the open house, their body heat caused the temperature to rise enough that he had to open the windows.
      I would rather deal with these problems than live in a traditional, un-insulated building. 🙂

      1. Each person puts out around 100 watts, which in a normal house is not a big deal, but in a super-insulated house in winter will make a difference. Every time you have guests around, it’s a house warming party!
        In the summer though, this means an extra 100 watts of heat that you don’t want. There is a danger with passivhouse of having too much glazing area, and not adding shading, which will lead to overheating. Our house is not too bad, but on a humid day it is better for lazing around than for working, and we’ve been thinking about adding a dehumidifier.

  5. We built our house here in Japan in 2014. I had visited my parents in law many times, and I thought it was absurd that they lived in a house with hollow walls… It was absolutely freezing in winter and boiling in summer, and running heaters or a/c on full during the cold/hot months had no effect if you sat close to the walls or windows. When we went house shopping companies told us about their “advanced insulation” …. styrofoam under the floor, and fiberglass wool in the walls, and they insisted that “in Japan, we don’t need more insulation” or “this is more than enough”. So we went to a company that at that time just started “airtight” houses, coupled with solar panels, double-pane windows, mechanical heat recovery ventilation, electric heat exchanger water boiler, and all LED lighting.
    Our walls from the outside in have regular siding, moisture barrier, 5cm(?) closed cell foam boards with a kind of aluminum laminate around the entire house taped air-tight, then plywood, on the inside of that about 15-20cm of spray foam insulation, then drywall.
    Our electricity bills for the entire house (160 square meters/1700 square feet) including all water heating and cooking, heating and a/c are never over 8,000 yen a month. We run our business here and have the 1-4 air conditioners running all day long. Before we built the house we typically spend 20,000 yen+ for the business alone, plus our apartment electricity + gas. Our 3kw solar system offsets our usage during the day, and what we don’t use for ourselves we sell to the grid, making us about 7,000 yen a month average. Though we’re not really a passive house or trying to go green, it’s a hundred times more comfortable to live in our house than any other house I have been to, even recently built ones here in Japan; freezing feet in winter, drafts, windows with condensation, sweaty and humid summers, huddling infront of a stove to stay warm. When building a new house I can’t recommend enough to build an airtight, foam insulated house, whatever the cost! Rather build smaller than with less insulation.

  6. One thing my cousin taught me (now living in Australia) is that well insulated houses are cheaper to cool with less heat leaking into the house. Particularly important if you live in the southern part of Japan.

  7. Sorry that I am a bit late to this forum, just found it and really like the conversations in here.
    We are building a new house now and the drawings are about to be finished. It will be a 3 stories house with a basement. I really want to spray insulate the house but that one is still up for discussion….Wife is not convinced it is needed….
    However something that I really would like to have are ducts going from the basement all the way up to the top floor. This is to cool the top floors or heat the basement pending on the time of the year. In addition to this I would like to ensure as well as we don’t get that horrible stale smell. We will have a dry area with windows, so the basement can be aired out once in a while.
    However I really feel that the house could benefit from having the ducts.
    The architect has never done anything like it and seem to “forget” about it every time we meet….
    Should I push for this or am I just wrong in wanting to have it since it might not have any effect.
    If someone has any ideas I would really like to hear them.
    Thank you and have a great day.

      1. Japanese houses don’t usually have basements, so your architect may never have made one at all, let alone thought about ventilating it. Japan gets a lot of rain, and often a high water table, so there could be many issues with water coming in, or with water cooling the outside and causing condensation inside! Ventilation is essential, and if you have a whole-house airtightness and insulation approach, then you also need a whole-house ventilation strategy. If you’re thinking about spray insulation after the drawings have been done, I would be concerned about this.
        Air is a relatively poor transmitter of heat so elaborate systems for moving heat around can often be much less effective than you think. Effects will be limited without a well insulated and airtight house, and if you do have a well insulated and airtight house, you need mechanical ventilation, and you should probably be getting a whole-house system with a heat exchanger, including the basement in the system, rather than trying to send air to or from there.
        Japanese houses do usually have a “crawl-space” underneath, which is traditionally ventilated to the outside. In the traditional (ie uninsulated and not airtight) building context, this is a good idea, but when you start to add insulation and make the house airtight you need to make a choice between treating the crawl-space or basement as inside or outside. If it’s outside then you need to keep ventilation open outside, and make the floor airtight and insulated (though you don’t need as much insulation as for the walls or roof). Or, in my opinion a more sensible idea is to insulate around the outside of the foundations, which will keep everything inside the thermal envelope. This means that heat is stored in your basement, and it will keep the house at a more constant temperature.
        If you have a basement, you probably don’t need to insulate underneath since the ground temperature stops changing after you go a few metres, but it would be a good idea to insulate around the outside of the walls down into the ground with something like XPS (solid boards of extruded polystyrene). In Europe and US there are commercial systems for pouring concrete into insulation, but here you will probably have to add boards into the moulds they pour concrete into, and make sure they are carefully joined together so there are no gaps (which by the way can halve the performance of the insulation). As well as storing heat/stabilising temperature, this will likely be cheaper than spraying insulation on the inside after the concrete has been poured, and if the basement/foundation is insulated, it makes it much easier to join the insulation with the rest of the house sitting on top.
        If you want to get in touch with any more questions, please contact me via my blog page: http://minuszeroeco.blogspot.jp/