Japanese Woodworking – Insulation with Natural Ventilation [Season 2 – Part 1]

Hello, Shoyan here. I’m a Japanese carpenter. I’ll be working at a new site this time. The framework is already completed. I’ll start with the insulation work. It’s been a while since I finished at the last site, and I start working on a new site from today. The framework is already done, and the exterior load-bearing walls are constructed using Moiss boards. I’d like to start with the insulation work first.

This is the Styrofoam insulation for the walls. I’ll install it between the columns and the studs. It’s 60mm thick and 800mm wide. Divide it in half, and then cut it to fit the dimensions between the columns and the studs. Then, install it firmly in place. Of all the Styrofoam insulation materials, pink Styrofoam is said to perform the best. It’s also recyclable and can be disposed of. I’ll cut the Styrofoam with a handmade tabletop circular saw. It’s dangerous, but this is the best way to cut it. Some may say this cutting method isn’t good, but it’s actually the same as the small splitting method used by a joiner to cut wood.

Now, I’m going to install the insulation that I cut earlier. It needs to be 1mm wider than the distance between the columns. If it were 2mm wider, it would never fit. It’s rather thick, so it’s quite difficult to install. Just 1mm too wide would make it awkward to install. I’ll use a piece of furring strip to widen the middle, and make sure the Styrofoam is firmly installed. Also install the insulation under the windows. I’m taking measurements now as all five or six windows are different heights. The sashes are standardized, but the windows vary in size and height according to their use. As you can see in the video, it takes a lot of force to push and tap.

After two days of this, my body is exhausted. My muscles ache, and by the fourth day I can’t move at all. The roof tile maker is here today, and they’re lifting the tiles onto the roof. It’s so much easier to lift the tiles nowadays. When I was a new carpenter, I don’t think such a winch existed for ladders. In one-story houses, we used to carry the tiles up to the roof by hand. Install insulation in the small triangular part of the room . The triangular part can be a bit tricky. I’ll cut it according to the slope of the roof. Both sides will have the same dimensions from the middle, so you only need to measure the height of one side.

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I’m checking the dimensions now. Use a slope ruler to determine the angle. If you mark one dimension for the high or low point, you can easily cut it using the edge of the ruler as a guide. Install the triangular part so that it fits as tight as possible. The ventilation system, which will open freely, will be attached to the ridge. I’m now cutting out that part. As you can see, the insulation for the roof was installed when the building was first erected.

The roof insulation is 70 mm thick; 10 mm thicker than the wall insulation. The wall insulation is now installed. I hit the Styrofoam pretty hard from the inside, so it’s sticking out more than it should be. So, I’ll hit it from the outside with lumber to move it back into position, and then nail it to the studs. The nails are 50mm N-nails, which are driven in at 100mm intervals on the inside and the outside. So, the wall is stronger than a typical load-bearing wall. Now, I’ll attach the thin pieces of Styrofoam, around the Styrofoam wall using caulk. Press the Styrofoam firmly against the wall and apply caulk around it. Surround the wall with the thin pieces of Styrofoam. It’s like Zokinzuri.* When installing the thin material around it, caulk only the columns.

Then press it down and make sure it’s glued to the caulk. That way, even if the wood shrinks, there will be no gaps. It’s attached to the columns or studs, and not connected to the Styrofoam wall. So even if there’s an earthquake and it moves, it’ll move back. Fill the narrow part of the wall with urethane. It’s difficult to install Styrofoam into this narrow space. At the same time, fill the gaps between the Mendo* with urethane. Then, fill the upper part of the triangular section as well. When filling them with urethane, if you only fill them with a thin layer about 1cm thick, then they may crack. Therefore, it’s necessary to spray more than 2cm. Install the same thin Styrofoam pieces around the large wall. Where the Styrofoam was cut, it has a crumbly surface. Because of this, it attaches to the caulk more easily when pressure is applied to it. It sticks nicely without moving. However, because I have to press hard to get it to stick, my fingertips will be smooth so it won’t leave any fingerprints. After two days of work, my fingertips will start to bleed.

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It’s an easy job, but it can be very tough and painful. Also cover the hardware with urethane. Heat will be transmitted from the foundation to the anchor bolts and then to the air layer. That’s why I cover all the hardware with urethane. This is my favorite snack time. The owner of the house always brings us these. Thank you very much! Now, install the foundation vents. These vents are manually opened and closed. Open and close them twice a year, in spring and fall. Close them in winter and open them in summer. Now, put up the foundation insulation. It’s cut to size in the same way. The thickness is 25mm, which is not as thick as the insulation used in the walls. I’ll put it on the foundation and the lower part of the house. Heat will be transmitted into the house from this concrete.

This type of foundation insulation prevents that from happening. As you can see, I am using a lot of caulking material to attach the Styrofoam insulation. The caulking material smells a little like paint thinner until it hardens, but it’s completely harmless after a week of hardening. Of course, after installing the Styrofoam, make sure that the air can circulate both inside and outside. If the air circulation stops then Styrofoam sweats, and the wood will rot. That’s why we let the air circulate. The air doesn’t enter the living space. It’s kept within the walls and is then circulated to the highest part of the roof that looks like a smoke vent. Carefully apply the urethane around the ventilation. If I apply too much, the vents won’t open and close. Therefore, apply a thin layer of urethane around them carefully to make sure that they can open and close. And finally, apply urethane neatly between the foundation, the base, and the Styrofoam.

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Now the Styrofoam is completely installed. Later, about 100 holes will be drilled in this wall, and a damper with a valve will be attached to it. This is a very labor-intensive method of insulation, but it works very well. So, I’ve finished the first-floor insulation work. I’m only halfway through, I have a long way to go. Next time, I’ll be working on the sash and the eaves. That’s all for today.

Thank you for watching!.

As found on YouTube