We’ve now been living in this house for 3 years and one of the greatest pleasures is walking into the house in winter and instantly feeling the warmth of the house – regardless of whether the wood stove is on or not.
The insulation we installed in the walls, roof and floor of this house, together with the triple glazing, are working beyond our expectations to keep the house warm in winter and cool in summer. While the house isn’t an airtight passive house (or Passivhaus), which generally employ heat exchanging air vent systems, we designed it to perform as close as possible to a true passive house.
In winter, and without any heating, the house only very rarely gets below 15°C, regardless of the temperatures outside. Today (23rd Jan 2017) is a good example. Outside is 0°C and snowing hard. The wood stove was on the previous night only until 11.00pm and without any heating since then, at midday the house temperature is still hovering around 16°C.
More information:
1st year data on the inside and outside temperatures – see Insulation – 1st year’s performance – to give a better picture of how the inside temperature changes are minimized by the effects of the insulation.
And further details of the insulation we used can be found at this other earlier blog entry; Insulation.
Shiga Eco project 
Hi, this is really impressive! That figure of 15 degrees is stunning. I’m about three years behind you, I’ve bought the house but I haven’t started doing it up yet and I’m still finding out about insulation. Thank you for this information!
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Thanks for your feedback. I spent months focused on insulation and the options available to us here in Japan, not just in terms of availability, but cost, effectiveness, viability given Japan’s high humidity etc. In the end I opted for what seemed to be the best in terms of performance and suitability to our situation – but had to be sourced from the UK, so came over in a shipping container we rented along with many many other materials and options we couldn’t source here in Japan. I will look forward to following your progress.
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Hi there, great post on the value of good insulation. I was looking at the picture of your house and noticed you have a roof very similar to ours, do you have the OM Solar system fitted to your house ? They really do contribute a lot of heat to the house through the day, we still use the maki stove but that’s mostly because we just love having a fire at night.
I’m also curious how you heat your hot water, do you use any like the MMC Solar water heater set up or something else similar ?
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Hi, thanks for your feedback. No we don’t have solar OM. I opted for solar PV and to make the house all electric (except the wood stove).
The water is heated using an air source heat pump – uses very little energy for the job. Some of the earliest posts discuss the reasons for the various options the decided on.
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Yeah, the solar panels can take up a lot of real estate on the roof. We had to limit ourselves to 4kw of HIT panels to accommodate the OM Solar type system installed in our house.
I see from your earlier posts you were possibly thinking of adding a solar water heater later, we saw our costs for heating water drop to almost nothing after adding one and reckon on recovering the purchase price in about 3 – 4 years.
How would you say the insulation you imported compares to locally available products like Neoma Foam or the more conventional rockwool insulation, both bats and rolls available from home centers ?
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Making a decision on whether to have solar water heating or not was the most difficult in terms of how many alternatives there were and all the costs and benefits to weigh up.
With regards the insulation, once I decided to imply a shipping container and source stuff for the building from the UK, the choice of insulation become much easier. Having used SuperQuilt now for 3 years I can say it really lives up to all the claims. It is only 1.9cm thick but has the same thermal performance as 28cm of rock wool. So it is extremely versatile. In addition, it prevents all 3 types of heat transfer unlike conventional insulations, so is very effective in summer too (we don’t have/need air conditioning). Another problem with what is available in Japan is that it is often difficult to find the standardized R-Value for thermal efficiency.
So a short answer to your main question, I think there is very little to compare between SuperQuilt and standard insulations – they are in completely different leagues.
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The beauty of the MMC solar water heaters is that being a pressurised tank system it can slot inline with your existing arrangement if you decide to add one at a later date.
The SuperQuilt does sound fairly awesome with it being so thin yet insulating so well. I know what you mean about finding standardised rating for insulation here, that was one of the hardest things we had to deal with when choosing insulation for our house. Luckily our builder specialised in building eco houses so was able to give some very good advice.
All in all your house looks fantastic, your tv appearances showcases it very well indeed. It must be very satisfying having done so much of the work yourself. If you every have the time or inclination please do come and visit us at JapanSimpleLife.com. Would be great to have someone with your experience in environmental issues.
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What insulation did you end up getting? Yes, I will join the your group at JapanSimpleLife.com. Cheers!
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Thank you for joining JSL, it’s a small community but quite friendly. Hope you enjoy.
As for the insulation, we eventually went with Neoma Foam at around 80 – 100mm. It seems to work quite well and certainly keeps the house warm in winter and cool in summer, like yourself we don’t have any aircon and rely on the the roofing system to cool the house during the night and then hold on to that coolness through the day.
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