Column Vol. 2 “The ‘Apertures’ That Support a ‘Breathing Home’ — Why Wald Chooses ‘DAKO’ Windows from Germany”

Column Vol. 2
“The ‘Apertures’ That Support a ‘Breathing Home’ — Why Wald Chooses ‘DAKO’ Windows from Germany”

Ono from Wald

In Volume 1, I discussed the dangers of “interstitial condensation” caused by the conventional pursuit of high airtightness and insulation, and the importance of the “Breathing Home (Breathability)” concept, based on Dr. Padfield’s theories, as a countermeasure.

When considering “insulation” in home building, you might first think of the “thickness” or “type” of insulation material used inside the walls. However, there is a location that we consider to be just as important, if not more so.

That location is the “window,” or the aperture.

The Real Weak Point in a Home

Where does the most heat enter and escape from a house? It’s not the walls or the roof; it is overwhelmingly the “windows.” It is said that in winter, over 50% of a room’s heat escapes through its windows.

No matter how much you increase the insulation performance of the walls and roof, if the windows remain a “weak point,” heat will be relentlessly lost, and severe condensation will simultaneously occur. Windows are the largest “holes” in a house and the biggest “thermal bridges” (weak points where heat is easily transmitted).

The Problem with Standard Japanese Windows

In particular, the “aluminum sash” windows that have long been the standard in Japanese homes present a significant problem from an insulation perspective. Aluminum is a material that conducts heat very easily. Its thermal conductivity is approximately 1,800 times greater than that of wood.

As you may have experienced, on a cold winter day, an aluminum window frame becomes bitingly cold, just like the outside air. The moment the warm indoor air touches this cold frame or glass, the air is cooled to its saturation point, and the water vapor turns into droplets. This is the true cause of “window condensation.”

If this condensation is ignored, the window frame becomes a breeding ground for mold, and eventually, the moisture penetrates the wall interior, leading to the decay of the home’s structure.

Our Prerequisite for a “Breathing Home”

This is why, to achieve the “condensation-free home” and “Breathing Home” I spoke of in Volume 1, our prerequisite is to completely solve the problem of “windows,” the most condensation-prone area in the house.

This is where the high-performance sash windows from “DAKO” in Germany, which clear the stringent European energy-saving standards (Passive House standards), come in as our standard specification.

The reason we choose DAKO is its overwhelming “insulation performance.”

The DAKO Difference: Overwhelming Performance

DAKO windows do not use any heat-conductive aluminum; instead, the frames are made from “resin (PVC),” which has extremely low thermal conductivity.

Furthermore, “triple glazing” (a 3-layer structure) is standard. Argon gas, which transfers heat less readily than air, is sealed between the three panes of glass, and the indoor-facing pane is treated with a special metallic film (Low-E coating).

As a result, the “U-value” (thermal transmittance), which indicates the insulation performance of the window, achieves an astonishing figure of 0.80 W/m²K. (Note: The lower the U-value, the higher the performance.)

Considering that a typical Japanese aluminum sash (double-glazed) window has a U-value of around 4.0 to 6.0, DAKO’s windows are, in fact, 5 to 7 times more insulated.

What This Performance Achieves

What this performance brings is “freedom from condensation.”

Even in mid-winter, when outside temperatures drop below freezing, the interior surface temperature of a DAKO window remains close to room temperature, around 20°C (68°F). The area by the window simply does not get cold.

Because the surface temperature does not drop, the air does not reach its saturation point, and condensation cannot form. This, of course, eradicates the source of mold growth. Moreover, it prevents the uncomfortable “cold draft” (cold air sinking from the window), meaning you can sit right next to a large living room window and feel no cold at all.

The First Step in Moisture Control

A “Breathing Home” is a home that controls moisture.

The first step in achieving this is to thoroughly upgrade the performance of the windows—the greatest thermal weak points in a house and the very places that create moisture in the form of condensation.

Coming Next

Next time, I would like to look inside the walls and talk in detail about the insulation material that forms the core of the “Breathing Home”: “PAVATEX (Wood Fiber).”