Construction and running costs of high-performance housing

Neglecting energy conservation leads to "housing poverty" - 30 million yen cost difference over 270 years

Design offices and construction companies make a living by receiving orders for design and construction from clients. Their number one priority is to make their clients happy and satisfied. In other words,Ensuring economic efficiency, health and comfortis the only definition.

Until now, it was generally thought that "economy = construction cost". However, this may have been for the sake of the company, not the client. If you really think about the client,The aim is to make the total cost of ownership as economical as possible, not just for new construction, but also for the expected life of the house, such as 30 or 40 years.I have to give advice.

However, if they did that, they would lose out to competitors in comparative bids and would have to give time-consuming explanations to clients. To avoid these hassles, I think they were trying to appeal by keeping construction costs low.

It goes without saying that appropriate temperature and humidity are important when pursuing health and comfort, but the reality is that there are very few housing companies in Japan that are able to provide these services effectively.

Luxury vs. Energy Efficiency

Some people think that only those who can afford it should be able to live in good quality housing. However, this is not how things should be in Japan, a developed country.

There are many people who want to build a house even if they are not financially well off. I think that even if you have to forgo "luxury items" such as a high-end kitchen, you can still get the following:If your budget is so tight that you can't meet the two energy-saving requirements, you shouldn't build a detached house in the first place.I think.

① Insulation performance of ceilings, walls, and floors based on 1999 standards (next-generation energy-saving standards) + sashes with an effective U-value of 1.7 or less

② The C value should be at least 2.0 or less, and ideally 1.0 or less.

We will explain the reason. Currently, many low-cost housing companies are touting the "next-generation energy-saving standards." However, the majority of companies limit the "heat transmission coefficient (U-value)" of windows to a level of 4.65. The U-value is an index of the heat insulation of a window, and its unit is W/m2 (square meter) K. It indicates the amount of heat that passes through per 1 m2 per hour, and the smaller the value, the less heat goes in and out, meaning higher performance.

By simply changing the U-value of the windows to 1.7 (resin windows, double-glazed windows, argon Low-E specifications), the heat loss coefficient (Q-value) can be improved from 2.7 to about 1.9. This will greatly improve the indoor environment, not only in terms of temperature and humidity, but also in terms of health. Even so, for a standard home of about 120 m2 (square meters), the difference in initial cost is only about 30 yen.

According to my calculations, taking into account the running costs over 30 years,If you lower the energy-saving specifications, it will cost an extra 270 million yen.It will be.People who, due to financial difficulties, cut down on initial costs and reduce energy efficiency specifications will become even poorer.This is the picture. This is exactly what we call "housing poverty." We should not make the choice to allow this negative cycle to continue.

Fear of a life spent working for heating

If you can't afford the initial cost of 30 yen to upgrade to energy-efficient models, I recommend purchasing a relatively inexpensive apartment on the middle floor of a south-facing apartment building. If building a new building is difficult, you can also buy a used one. In that case, it's a good idea to install an inner window to improve energy efficiency.

Some condominium developers have begun displaying "fuel efficiency" based on the location of each unit.

When building a house, many people consult financial planners about their financial plans. However,Very few financial planners will provide a detailed explanation of the differences in initial and running costs based on the energy-efficient specifications of a home.Isn't it?

Of course, you should consider your mortgage and life plan, but in fact, in Japan, where average annual income is on the decline, it is very important to think about cost comparisons based on energy-efficient home specifications.

In Europe and the US, houses with proper insulation performance are fairly common, whether they are detached houses, condominiums, new buildings, or existing buildings. However, in Japan, the reality is that even new buildings have very few homes that meet the two energy-saving criteria mentioned above. And when it comes to existing homes, the number is virtually zero.

If you live in a middle room on the middle floor of an apartment building, you are surrounded by neighboring units, so even if the insulation is poor, you can maintain a good indoor temperature environment by strengthening the windows. Moreover, there are often balconies on the south side, which can block the summer sun.

When you think about it this way, condominiums have many advantages in terms of the thermal environment, but there is a problem: the colder the region, the fewer condominiums there are in areas where higher insulation performance is required.

Especially in cold regions where there are few apartments, I would like you to give top priority to detached houses that satisfy the two energy-saving criteria mentioned above. It is no exaggeration to say that homeowners who cannot do so will "spend their lives working for heating."

Households with financial difficulties

The tighter the household budget, the more the house should meet the following four requirements in addition to the two requirements for energy efficiency.Although the initial cost is low, the monthly payments end up being high..

③ Winter solar radiation (southern solar radiation)

④ Protection from summer sunlight (south-facing eaves, minimization of windows on the east, west and north sides + low-E heat insulation / south-facing windows are low-E heat insulation

⑤ Selection of water heater (solar water heater + Eco-Jozu or Eco-Cute)

⑥ Cool and heat with air conditioning (make your home air-conditioned. The air conditioner alone can cool and heat + dehumidify)

Regarding ⑤ "Selection of water heater", hot water is the most energy-consuming item in an average house. The selection of water heater is a momentary decision for the designer, but for the resident, it is a matter of deciding how long the water heater will last for 10 to 15 years before it breaks down.It has a big impact on energy costsIt is necessary to consider carefully.

The first item, "②The C value (a measure of the amount of gap in terms of total floor area, expressed in cm2/m2) should be at least 2 or less, and ideally 1 or less," isAir-conditioned homeIn a house with poor gap equivalent area (C value), air conditioners that use air for heating and cooling are extremely ineffective.

Before that, in homes with a C value worse than 2, it becomes impossible to maintain clean air quality with the type 3 ventilation that most homes use. This isIt also poses health risksSo in that sense it's an important item.

All six items must be met

Finally, an often overlooked③ Winter solar radiation gain, ④ Summer solar radiation shieldingI will explain about it. In my opinion,"Gaining solar radiation in winter" accounts for 5% of the factors for staying warm, and "blocking solar radiation in summer" accounts for 7% of the factors for staying cool.This is the most important item that accounts for

For example, if there is one bay window on the south side that is 1 ken wide and 2 m (3.3 m2) high, it will be hot and humid in both summer and winter if the weather is fine.The heat equivalent to that of a single kotatsu goes in and outIn winter, letting heat in = money, and in summer, keeping heat out = money.

If a household has a high annual income, it is possible to design a house that ignores "solar gain in winter" and "solar shading in summer" and still be able to compensate with money (energy). However, I believe that all six of these items should be met unless the household's annual income exceeds 1000 million yen at the very least.

When you read books about financial planning, the only things listed as things to cut are car expenses, insurance expenses, and cell phone expenses. The six items introduced here are not mentioned at all.

A typical household drives a car with a fuel efficiency of 13km/L and travels about 1km per year. This equates to 27GJ (gigajoules) of primary energy consumption. In contrast, homes consume an average of 75GJ, which is about three times as much.

Cars, insurance, and mobile phones can all be changed at very short notice if you want to, and each time you do, the cost usually comes down due to competition and technological innovation.

On the other hand, the six energy-efficient housing measures presented here are all measures that cannot be easily changed once they are adopted, and most homeowners will have to live with them for 6 years or more.

The cost of insulation renovation is higher than that of a new building.Therefore, it is advisable to improve the energy efficiency of a new building. Without taking these things into consideration, there is no way that a proper financial plan can exist.

In Europe and the United States, it is said that three generations pay one mortgage. On the other hand, in Japan, each generation rebuilds their home and takes on a mortgage each time. In order to prevent people from becoming "housing poor" by making their own home, which is the source of their happy lives, a burden, I would like design offices and construction companies to keep in mind the following six points.