Sun-friendly design: gaining solar radiation in winter and blocking it in summer

Here we will summarize window design standards that are easy for everyone to understand, rather than non-intuitive design standards such as ηAc and ηAh values.

• ・The south-facing window should be as large as possible, as long as the load-bearing wall will allow.Instead, the window has a height of 10 cm and a projection of 3 cm.put up a visor.orBe sure to include external sun protection measuresThis ratio will result in the lowest total annual heating and cooling costs. If it is longer than this, it is suitable for summer, and if it is shorter than this, it is suitable for winter.
• ・If the north direction is tilted by more than 20 degreesIn such a case, it is practically very difficult to block sunlight with eaves even on the south side.Sun protection measures are required.
• ・Windows on the east, west and north sides should be as small as possible.However, there is no need to take the risk of being perceived by the client as ignoring ventilation. Two-way ventilation should be ensured for each room. In that case,Each room, except the south-facing one, has one window of less than 0.5 mXNUMX.This is the standard (the author uses one vertical sliding window with width 400mm and height 1170mm as the standard. Although the window is small, the opening rate is 1%, so there is no complaint that it is impairing ventilation.)
• ・Skylights are difficult to block out the sunlight in summer, so they should be considered a last resort.One in the center of the north sidethink
• ・The south side is thermal insulation Low-E, the east, west and north sides are thermal insulation Low-EThe north side is designed as a low-E heat shield because it is exposed to the western sun from 3:7 to XNUMX:XNUMX in summer.
• ・There are cases where you have to install large windows on the east, west, and north sides. In such cases,External solar shading measuresBe sure to set
• ・In the case of installing large windows on the east and west sides and installing external solar shading measures as described above,Making the glass insulating Low-EThis allows for better optimization in winter too.
• From the standpoint of airtightness, there is no need to use sliding windows other than the large windows on the south side.Opening windowsshould be used
• From the above perspectiveGlass louver windows are the window type you should avoid the mostAnother overlooked point is the ventilation door. It is a popular product, but when airtightness is measured, it is found to be extremely weak.

 

First, draw an equal-time shadow map of the neighboring houses other than the north one.

I have noticed something while giving design seminars to hundreds of practitioners.Where is the sunniest place?The reality is that less than 1% of designers can correctly answer a seemingly simple question: "Do you think thatEqual time shadow mapEven if we show them the answer, they don't know how to read it next, so about 3% of them don't know how to read it.

For example, I have asked more than 2 people the question, "In the two cases above, which one gets more sunlight?" The result was that in almost every venue, many hands were raised for the wrong answer.The amount of solar radiation that the neighboring house receives on the site in winter is an extremely important source of energy.Despite this, the majority of professional architects, like amateurs, do not understand it correctly.

"The window is a kotatsu"After I said this in a lecture a few years ago, this phrase started being used everywhere. This was a phrase created to emphasize that "on a sunny day, 600W of solar radiation enters a single bay window that is one room wide and 2m high.""Free energy"So it's best to get as much as you can.

However, to achieve this, it is necessary to place the house in a location that minimizes the influence of the neighboring house's shadow, place the rooms where people spend the most time in the sunshine, and place large windows in the sunniest areas. The tool to achieve this is an equal-duration shadow map.

However, this type of shadow chart only shows the position of the shadow for each hour, so it is not possible to determine the total amount of sunlight received. This is where the equal-hour shadow chart comes in. With an equal-hour shadow chart, you can see at a glance the total amount of sunlight received in a day, such as the amount of time in the shadow for 1 hours, 2 hours, 3 hours, etc.

To answer the previous question, try placing the building on an equal-duration shadow diagram as shown below, and you will immediately find the answer. Placing it on the east side will get more sunlight. The reason why many people get this wrong is simply because they have never drawn an equal-duration shadow diagram. Even if they have, they have only done it a few times, so they do not have a feel for it.

Another issue this time was that the house on the east side was very long and narrow from north to south, and many people overestimated the size of the house on the east side, even though the house on the south side is closer to the west.

How to plan the layout of a building, garage, and garden from an equal-duration shadow map

Once the equal-duration shadow map is complete, the next step is to begin considering the following:

• - The entire building can be placed in the sunniest spot.
• ・The width of the south side should be as wide as possible to maximize the distance between the house and the neighboring house on the south side.
• - To place the living room in the sunniest spot
• - To have a garden in front of the living room (preferably on the south side)
• - The garage can be placed in a location that does not obstruct the view from the living room and provides good access to the entrance.
• - The shape should have as few uneven surfaces as possible (uneven surfaces on the south side will cast a shadow on the building itself. Uneven surfaces on the north side will further cool the already cold north side, increasing the temperature difference between the north and south of the room).

It is difficult to perfectly meet all six of the above criteria. However, it is very important to consider the mutual arrangement of the elements in a way that balances the six criteria at the very beginning, even before entering into the layout of the building.

The south side is designed to avoid the shadow of your own building.

As mentioned briefly in the previous section, when you start thinking about the interior layout, the exterior often ends up being more uneven than necessary. This is not only disadvantageous thermally because the surface area increases, but also tends to weaken the structure.

Furthermore, from the design point of view, the shape is far from simple, and the complex roof shape will lead to poor weatherproofing. It is no exaggeration to say that there is nothing good about it. Among them, the impact of the shadow cast by your own building is an item that can never be measured by national standards, but actually makes a big difference.

The two buildings above (both with the top facing north and the red windows facing south) have the exact same UA value, C value, and south window area. However, when you actually calculate the heating load, one of them will have a heating load 2% less than the other. More people answered this question correctly, and the building on the right will have a smaller heating load. This is because the convex part on the south side of the building on the left casts a shadow on the south window in the northwest in the morning. No one had ever mentioned this until I started talking about it. Just knowing this will make a big difference in how you create your plans.

So, are there any drawbacks to the house on the right? To consider this, let's divide each of the two houses into three areas. Most people cannot answer the question, "Which house has less temperature variation?" If we change the question to, "Where is the building on the left with the greatest temperature difference?" most people will answer, "2 and XNUMX." Similarly, if we ask, "Where is the building on the right with the greatest temperature difference?" most will answer, "XNUMX and XNUMX."

If you ask, "Which is bigger, the temperature difference between 4 and 3, or the temperature difference between 2 and XNUMX?", many people will give the correct answer, "The temperature difference between XNUMX and XNUMX." If the exterior wall has a lot of bumps and grooves, there will inevitably be many parts close to the exterior wall. In the world of buildings, areas close to the exterior wall are called perimeter zones, meaning zones with poor living environments, and the number of such areas will increase. XNUMX is very cold because it is "on the north side, facing the outside air on three sides, but has no south-facing windows." On the other hand, XNUMX is "on the south side, facing the outside air on only two sides, and extremely warm because there is a window on the south side," so the temperature difference between XNUMX and XNUMX will be the largest.

Knowing this will make a big difference in the final plan. This is true not only for the plan shape, but also for the height of the first and second floors. The closer to the second floor, the less the influence of the roof, so the difference in the feeling of heat in summer will be more noticeable, as well as the cold in winter.

Also, when looking at the drawings of various construction companies, you will notice the presence of sleeve walls on both sides of the second floor south balcony and the balcony with an extremely deep roof, such as a 2P. It is important to note that with this type of design, the south window will receive significantly less sunlight, reducing its effectiveness.

The unevenness of the north side increases the temperature difference between the north and south of the room

In the world of building air conditioning, the area 3 to 5 meters from the exterior is called the "perimeter zone" because it is the area that is "susceptible to external influences = hot and cold." The better the insulation performance of the exterior and the better the summer sun protection, the less the adverse effects of the perimeter zone are felt. However, most home designers are not aware that there are many plans that end up with a large number of perimeter zones due to their shape. For example, compare the two floor plans below.

Figure ①

Figure ②

If we assume that one square is 108m, the area of both is XNUMX㎡. The area shown in blue here is the perimeter zone, XNUMXm from the perimeter. Conversely, the red area in the center is the interior zone, which is less susceptible to external influences.

When viewed in this way, Figure 1 has an interior zone of 18 m2 in the center. However, although Figure 2 has been painted red, it is actually a line and no interior zone exists. When viewed in terms of Q value, it is immediately clear that Figure 2 is worse even in terms of numbers. However, when viewed in terms of UA value, no difference is visible, so caution is required.

Next, there are two convex corners in Figure 2. One protruding to the west and one protruding to the north. Both are surrounded by the exterior on three sides, so the conditions are very poor. The north side in particular is in the shadow of the building itself, and the outside temperature is also lower. The shape in Figure 2 does not cast a shadow on the south side, but the southeast corner is a relatively warm room, so the temperature difference with the protruding part on the north side is quite large.

Here I would like to look at an example that I often have people do calculations during my lectures.

All of these buildings have the same total floor area of "8", but the surface area is so different. Building 1.5 has a surface area about 1.5 times that of building 1.5. This simply means that there is XNUMX times the heat loss. Furthermore, the cost of insulation and exterior wall materials is also XNUMX times higher. Any professional knows that the cost per square meter of this shape will be high, but there are very few practitioners who implement this shape with the understanding that it will also increase heating and cooling costs.

If you want to keep the heating and cooling costs at the same level, you need to remember that you need to increase the UA value by 1.5 to break even. To be more precise, you won't even break even if you increase it by 1.5 because your building is in the shadow for a long time.

So is shape 1 the best thermally? It is true if you only consider heat loss. However, the actual warmth is determined by the balance between heat loss and the amount of solar radiation gained from the sun. With a shape like 1, it is difficult to get a large proportion of the window area on the south side.

Considering this, if there are houses like the three above, the house below, which is "slightly elongated from east to west and has as many south-facing windows as the load-bearing walls will allow," can be said to have the best balance of heat intake and exhaust.

Of course, the higher the insulation and airtightness performance, the less likely these differences in shape will be. Another method is to eliminate temperature differences with a good air conditioning plan. However, if possible, the most straightforward approach is to design a shape with "good properties" from the initial planning stage, which is also inexpensive, highly effective, and has almost no chance of failure.