Log — Recent notes
Technical Log
Notes on structural calculation, passive houses, and thermal design (64 articles)
Sep 22, 2026#Tools #JWW #StructureTwo free browser tools are now live
A JWW Viewer that opens Jw_cad .jww drawings on a Mac or tablet, and a Beam Notch Loss calculator for a girder notched by joists and a column tenon. Both run entirely in your browser — files never leave your device.
Sep 19, 2026#AIAn architecture studio building its own software, with AI
In 141 days starting May 2026, we built 28 apps for the daily work of an architectural design office. I am not a professional programmer. What I chose, what it costs, and why the calculation is the one thing we do not leave to AI — written from measured numbers.
Apr 7, 2026I participated in the PHJ National Convention.
https://cms.passivehouse.com/en/training/directory/designers/detail/p21824I have now been certified as a Certified Passive House Designer. I will continue to wo
Apr 7, 2026Duct planning using BIM
At our company, we utilize BIM for tasks such as duct planning and checking for interference with structural elements.By utilizing BIM (Building Information Mod
Mar 7, 2026Passive House Japan National Conference - Breakout Sessions
I served as a lecturer for a breakout session at the PHJ National Conference. (2026/03/06)Subcommittee 3: "Considering Ventilation and Air Conditioning in Passi
Jan 15, 2026Passive House Japan Tokai Branch study session is coming up
Passive House Japan Tokai Branch study session is coming up. Feb 3 (Tue) 13:30–17:00 on Zoom. Speaker: Nobuyuki Tanaka (Dainaga Co.). In our detailing at L'art de vie studio, we leave an "ant-path inspection zone" on the foundation — analyzed with Ψ to verify there's no thermal issue.
Aug 1, 2025We introduced thermal-bridge analysis software Flixo
We introduced "Flixo," software dedicated to building thermal-bridge (heat-bridge) analysis. Now we can precisely design for warm winters and cool summers. We're preparing to take on thermal-bridge analysis as a service for others as well.
Jul 26, 2025Passive House seminar on Wednesday, September 24
Please join us.
Jun 16, 2025Visualizing our order pipeline
We don't showcase order history much, but I made the work-in-progress visible. Renewed sense that we need a proper division of labor. New orders are also moving to higher-spec work. Prioritizing talent development.
May 15, 2025Interior coordination
A request for industrial-style design — so I did some interior coordination work for the first time in a while. It was fun. Curious how the client will react...
May 7, 2025The foundation is a tuning point for the thermal plan
On a small addition project, the builder forgot the insulation. Thermal-bridge analysis showed ~20% performance drop unprepared, ~7% with insulation reinforcement. But at PH levels in Region 6, thinner slab insulation can actually lower annual heating+cooling load by reducing cooling demand. "Thicker is always better" isn't true.
Feb 26, 2025Published a floor-plan drafting manual
A video manual focused on efficiently drafting floor plans by leveraging BIM features. It's primarily an internal manual, but since we made it, we've published it publicly. Few will be interested, but please subscribe to the channel if you find it useful.
Jan 14, 2025Our second Passive House has been registered
Our second Passive House is registered, in Hamamatsu. The details were complex and the Ψ-value calculations were a struggle. Cooling/dehumidification demand was on the edge. Winter is almost a no-heat reality in the Chubu region — next, the general answer for cooling and dehumidification.
Nov 23, 2024Drawing in 15 minutes
We use BIM to produce drawings like this. Once you're freed from the drafting itself, the studio can put more energy into other considerations and the design density goes up.
Nov 22, 2024My working environment
We will introduce the work environment.As a Mac user, I use the trackpad with my left hand and the trackball with my right hand.Also, when I'm working on CAD, I
- Nov 11, 2024
We also do container architecture
Container architecture is one of the new approaches bringing innovation to the construction industry. Eco-friendly and cost-effective compared to conventional building. Reusable containers promote recycling and reduce waste — so an AI tells us.
Sep 19, 2024Thanks to everyone — our team has grown
Three new staff members will be joining us. With that, recruitment is closed.
Aug 21, 2024Updated job information
It's a very white-collar workplace. If you're interested in learning about energy conservation, structures, BIM, etc., why not come work for us?It may also be a
Apr 7, 2024Attending airtightness measurements
Yesterday we conducted airtightness measurements in Hamamatsu City.This property is scheduled to be certified as a Passive House, an international standard.Our
Apr 7, 2024I gave a seminar on thermal bridge analysis.
I was in charge of an intermediate to advanced level seminar as an optional study group for Passive House Japan.It took more than a month of preparation to crea
Apr 7, 2024Oh no! A staff member is quitting at the end of May.
We have a staff member who started as an intern in his second year of university and has been here for almost five years, but he is quitting because he wants to
Jul 30, 20233D design is the way to go
I started in 3D for my thesis 25 years ago — Vectorworks (then MiniCAD). My career skipped 2D. For modern design, 3D is essential. But I output as white models — fine textures eat time and white better invites the viewer's imagination.
Jul 18, 2023First BIM collaboration
On the current project, we're exchanging data with the MEP engineer using IFC, BIM's common format. We've spent considerable time on BIM until now — finally we're reaching the phase of external collaboration via BIM.
- Jun 24, 2023
Started sharing VR
Twinmotion launched a VR cloud-sharing service at some point, so we're using it. Even without a high-spec PC, clients can check the design in 360° from their phone. Producing it takes effort, but you can go all the way to coordination, which may save time overall.
Oct 27, 202224-hour ventilation vs. CO2 concentration, compared by airflow
I simulated airflow vs. CO2 in a 120 m² (36 tsubo) home with my own simulator. For a 3-person family, you can drop the ventilation rate to ~0.3 ACH with no real issue — but the law requires 0.5 ACH minimum.
Sep 7, 2022Ua-value isn't a silver bullet
Ua-value is getting attention. But "just keep improving Ua-value" ignores economics. What matters is balancing insulation, solar gain, and equipment performance. We use PHPP for proper analysis going forward.
Aug 31, 2022"Almost Passive House" begins construction
New project breaking ground in Toyota City, Aichi. Annual heating demand is under 15 kWh/m²a; cooling+dehumidification is slightly over 22 kWh/m²a. Clearing PH certification would cost too much, so we're skipping certification for cost-effectiveness this time.
Jul 25, 2022Passive House Japan Tokai Branch convention
On Tuesday July 26 I'm presenting a case study of the Nagoya Passive House. Unfortunately, members-only.
Feb 19, 2022Effective slenderness ratio of wooden columns
Rarely we're asked to submit a slenderness-ratio check for wooden columns. As long as the spacing between horizontal members doesn't exceed 4.5 m, a 105 mm column is fine — but you have to demonstrate it. Lately, boat-bottom roof structures push the ridge column past 4.5 m, so the ratio actually matters.
Jan 7, 2021CO2 concentration simulation
I simulated how CO2 in a private room evolves. Conclusion: 20–30 m³/h per person per room is enough. The lump-sum "0.5 ACH overall" rule is a bit rough. Demand-controlled ventilation works for high-traffic homes — but smell becomes an issue when no one is there.
Dec 21, 2020Exterior plan for my own house
The year is closing with me running around with my hair on fire. Exterior works at my own office/home keep getting pushed back — the dyer's white pants, as we say. Half a rush job, but I put the plan together and made a movie for the exterior contractor. Modeled in Vectorworks, rendered in Twinmotion.
Jul 3, 2020Converting wood-house foundation beams to flat beams
To accommodate under-floor air conditioners and ducts, we often want to reduce the foundation upstand. The usual move is an inverted (upward) beam — but that's costly and complicates under-slab insulation. Our office uses flat beams where extra strength isn't needed.
May 9, 2020We got a 3D printer
We got the 3D printer we've been wanting. After some trial and error, we found we can even produce 1/100 models, though for precision and readability 1/75 is best. For a 100 m² house with the design progressed enough, modeling takes under 2 hours and printing takes about 3 days.
Feb 17, 2020"Almost Passive House" is nearly complete
A project where we fully designed plan, structure, and environment is almost done. Started summer 2018 from a client request for "Ua ≤ 0.4." Before we knew it, the project had become an ultra-high-performance house at Passive House levels.
Jul 26, 2018Benefits of ultra-high-performance windows
Even aluminum windows can be high-performance overseas. Window performance comes down to Uw (heat transmittance) and η (solar shading). Top windows reach Uw ≤ 0.8. Used right, they function like a heater.
May 29, 2018Housing Performance Evaluation
Housing Performance Evaluation is an objective indicator born from the 1999 Quality Assurance Act. Built around a "ruler" for housing quality. It's optional, but most useful for the structural and energy categories.
May 14, 2018#Structural calcDesign and structure
We often take on jobs that are purely structural and energy calculations. Some designers are great at design but weak on structure and construction. The era of taking structure seriously in wooden houses is coming.
May 10, 2018Heat loss through the foundation slab
Japan's envelope calculation ignores heat loss through the foundation slab. So it's widely believed slab insulation is unnecessary. At Passive House levels, though, this loss matters — you can't clear PH without it.
May 8, 2018#Energy standardThe 2020 energy-saving standard
From 2020, meeting the energy-saving standard becomes mandatory for new houses. It's a loose bar — you can clear it even with aluminum windows and no foundation insulation. The worry is that the bar becomes the ceiling.
May 7, 2018#Anchors #Corner hardwareHardware on the sill plate
Recent corner hardware can be rated to 20 kN, but the sill anchors that transfer that uplift to the foundation often don't have enough strength. Don't leave it to the carpenter's experience — instruct properly on the site.
Apr 26, 2018#Ua valueThe meaning of U-value
Buildings are now described by Ua-value (average heat transmittance). U-value is per-element insulation; Ua is the area-weighted average. What does U-value actually mean? A summary from that angle.
Apr 25, 2018#Slab rebar #FoundationHow to think about the foundation bottom slab
A quick sketch on which way the slab rebar should go on top. You can also design so that either orientation is fine, but site supervisors should understand the basics. I hope this helps supervisors and architects who are not strong on structure.
Apr 24, 2018About foundations
There are still many people who underdetstand house foundations. The mat slab has a bottom slab (ground reaction → load transfer) and an upstand (which carries the wood frame AND functions as a beam). The beam role is what matters most.
Apr 22, 2018#Structural calc #Load-bearing wallsMinimum length of load-bearing walls (shear walls)
Some people summarize the rule as "load-bearing walls need to be at least 60 cm." That's misleading. The actual rule (from the bible of wooden structural design) depends on bracing type and floor-to-floor height.
- Apr 17, 2018
Off Grid House Project
A project we'd started with a trading company to build a Passive House from shipping containers stalled financially. We're continuing it in-house with the added idea of making wooden containers. The know-how will be released open-source.
- Apr 15, 2018
House performance: 03 Reducing deterioration
The "Reducing deterioration" performance category. The standards are fairly loose — any decent builder is already doing this. But to be certified as a "Long-Life Quality Housing," these items have to be explained to a third party with drawings.
- Apr 12, 2018
House performance: 01 Structure
An overview of the 10 categories of Japan's Housing Performance Indication Standard, with a deep dive into "01 Structure" — including seismic and wind classes, and the difference between wall-quantity calculation and allowable-stress design.
- Apr 11, 2018
What I'd like clients to think about
Without a client who can articulate sensible needs, we can't propose a sensible design. Most reasons to build are for child-rearing, but build for yourself instead — what you like, your habits, your everyday self. Communicate that clearly to your architect.
- Apr 9, 2018
The case against underfloor air conditioning
As insulation improves, at some point internal heat gain balances heat loss to the outside. That balance is what Passive House aims for. At that level, underfloor heating may become a burden — and a wood-burning fireplace becomes an expensive interior accessory that compromises airtightness.
Dec 30, 2017Mainstream Japanese windows vs. ultra-high-performance windows
A comparison of a mainstream Japanese high-grade window with a Passive House-spec window for a typical 160×200cm patio door. Savings, surface temperature, and condensation differences.
Nov 29, 2017Pay attention to thermal mass
Insulation has metrics like thermal conductivity, thermal mass, vapor resistance, and moisture content. Thermal mass dampens indoor temperature swings and shifts the timing of peak heat load — important in Japan's summer.
Nov 24, 2017Starting container house design
We've decided to take on container house design. Not from used containers, but designed from the ground up. Manufactured in Qingdao, China. Targeting under ¥4M for a 20-ft unit, all-in.
Nov 1, 2017#WindowsA trip to Qingdao, China for a meeting
A short video from a meeting trip to Qingdao, China, related to high-performance windows.
Oct 30, 2017#European windows #Resin windows #Japanese windowsComparing European and Japanese windows, Part 1
A short video comparing European-spec windows with Japanese resin-frame windows.
Oct 30, 2017#Anchors #Wood-fiber insulationSpiral anchor installation
A short video showing on-site installation of spiral anchors used to fix wood-fiber insulation.
Feb 26, 2017#Quality controlOn single-pour foundations for houses
Clients sometimes request it, and builders sometimes promote it. If you're aiming for the highest quality, I'm against single-pour foundations.
Feb 22, 2017Thinking about the best exterior wall, Part 1
For some years I've been thinking about exterior wall construction. For the base, wood-fiber insulation is my top pick. For the finish, I'm considering NHL (natural hydraulic lime).
- Nov 29, 2016
Inspiration
Design is the work of amplifying what you notice or what flashes through your mind, then giving it form. Designing a house feels a bit like searching for a partner — neither is decided by conditions alone.
- Oct 31, 2016
See the ideal as an extension of reality
When discussing house plans with clients, I often think about how we frame the ideal versus reality. People imagine a space and assume the new space will change their habits — but life rarely changes that suddenly.
- Oct 18, 2016
I design houses
After majoring in architecture at university, I've been doing this work for more than 20 years. These days I've narrowed my focus to wooden housing.
- Oct 17, 2016
Starting the blog
Starting a blog today. I'd like to write whatever I want without worrying about who reads it.
Passive House
A site visit with insulation peers, at a house aiming for Passive House certification. The level of insulation was as expected — high — and achieved relatively inexpensively using 16K-grade high-performance glass wool.
We've started selling drawings on this site
Buy a plan and take it to a builder to construct. We've uploaded LAV200201, a Passive House plan — valuable data for those considering ultra-high-performance housing.
Recommendation: true-north surveying
One topic that makes architects flinch a bit is true north. Anyone who has computed the north-side setback line in low-rise residential zones roughly knows how strict it is. For those who want true north precisely, there is a method called true-north surveying.