66.0% of Custom Homeowners Prioritized Insulation Performance, While Over 80% Were Unfamiliar with “Insulation Grade” and “UA Value”

How much do you think about insulation performance when building a custom home? Have you ever moved into a home and felt that it was hot in summer and cold in winter? Insulation performance, which has a major impact on daily comfort and utility costs, is actually one of the points often overlooked when building a home. In recent years, it has attracted more attention due to revisions to insulation grade standards and growing awareness of energy savings. NEXER Inc. and Tsuchiya Home Co., Ltd. therefore conducted a survey on awareness of insulation performance in custom homes, targeting 150 men and women across Japan who had answered in a preliminary survey that they had built a custom home. Survey overview: The survey was conducted online from March 2 to March 9, 2026. Respondents were men and women across Japan who had previously answered that they had built a custom home. The number of valid responses was 150. ■66.0% said they prioritized insulation performance The survey first asked how much respondents prioritized insulation performance when building their homes. The results showed that 23.3% said they “prioritized it very much,” while 42.7% said they “somewhat prioritized it.” Combined, 66.0% prioritized insulation performance. On the other hand, 27.3% said they “did not prioritize it much,” and 6.7% said they “did not prioritize it at all,” suggesting that about one in three people did not pay much attention to insulation performance. Reasons for prioritizing insulation included: “It affects running costs,” “It saves energy and lowers electricity bills,” “Air conditioning and heating work better, leading to energy savings,” “To live healthily,” and “It affects utility costs during winter.” Reasons for not prioritizing insulation included: “It was not a topic of discussion when I built my home,” “The term ‘insulated home’ did not exist 35 years ago,” “I was young and lacked knowledge,” “I was focused on staying within budget and could not think that far,” and “When building more than 50 years ago, earthquake resistance and insulation were not regarded as issues.” Among those who prioritized insulation, many cited utility cost savings and energy savings. Monthly electricity and gas costs can create a major difference over a long period of residence, and awareness of these running costs appears to be a key reason for prioritizing insulation performance. Meanwhile, those who did not prioritize it pointed to circumstances such as the lack of a widespread concept of insulation performance at the time or budget constraints taking priority. In particular, people who built homes several decades ago appear to have done so in an era when interest in insulation was much lower than it is today. ■80.7% said they did not know the terms “insulation grade” or “UA value” The survey then asked whether respondents knew the terms “insulation grade” and “UA value,” an indicator that numerically shows a home’s insulation performance. The results showed that 80.7% said they did not know these terms, while only 19.3% said they did. Even among people who had built custom homes, awareness of technical terms related to insulation performance was very low. Those who knew the terms were further asked whether they had received an explanation from a homebuilder or construction company. The results showed that 62.1% had received an explanation, while 37.9% had not. This means that even among those with knowledge of the terms, about 40% had obtained that knowledge without receiving an explanation from their builder. Still, choosing a company that proactively explains insulation-related matters appears to be an important point in building a satisfactory home. ■27.3% said they had information they wished they had known earlier or regrets about insulation performance Finally, respondents were asked whether they had any information about insulation performance that they wished they had known earlier, or any regrets. The results showed that 27.3% said yes. About one in four respondents felt some lingering regret regarding insulation performance. Specific comments included: “I wanted to know more about costs earlier,” “It is better to buy high-performance products even if they are expensive,” “I wish I had known more specialized details such as grades,” “Window frame materials and triple sash windows,” “I should have spent more on insulation,” and “The level and effectiveness of insulation materials.” Looking at the regrets, many respondents said they wished they had known more about differences in insulation grades and specifications, should have paid more attention to window and sash performance, or should have chosen higher-performance insulation even at a higher cost. ■Summary The survey found that while 66.0% of people who had built custom homes prioritized insulation performance, only 19.3% knew specific indicators such as “insulation grade” and “UA value.” In addition, about one in four respondents felt that they wished they had known more about insulation earlier. Insulation performance is directly linked to daily comfort and utility costs, and it is also a part of the home that is difficult to change after construction. Those considering building a custom home may want to look not only at floor plans and design, but also at insulation performance figures and grades.