Is a higher R-value good or bad?

A higher R-value is generally good because R-value measures resistance to heat flow, and higher resistance means better insulating performance, lower energy bills, and improved comfort. The higher the R-value, the slower heat moves through the material, so in winter more heat stays inside and in summer more heat stays outside. This is why building codes set minimum R-values that increase in colder climates. However, higher R-value is not always better without limit because of diminishing returns, cost, and space constraints. Going from R-0 to R-19 saves a huge amount of energy, going from R-19 to R-38 saves a significant additional amount, but going from R-38 to R-60 saves much less for the same added cost and thickness. Also, simply chasing a higher R-value without first air sealing leaks is inefficient because air leakage can bypass insulation entirely. Extremely high R-value materials like vacuum insulated panels can also be fragile and expensive. So within practical limits, higher is better for thermal performance, but you should balance R-value with air sealing, ventilation, moisture control, and budget to achieve the best overall building performance rather than just the highest number.