As homeowners, contractors, builders and architects prepare for new construction or renovations, insulation is one of the most important considerations. Along with air and moisture barriers and external coatings, insulation helps to form a building envelope – separating the conditioned air on the inside from the temperature changes of the outdoors. It doesn't matter which season it is or what sort of climate zone the building is in – all of them require insulation of one type or another.
Having said that, not all insulation is created equal. Certain materials are inherently more effective than others. Additionally, continuous insulation is better at protecting a building than just filling in wall cavities, because it neutralizes areas where thermal bridging might occur. But those who believe they can attain higher energy savings simply by packing in more insulation are also mistaken. At a certain point, more insulation only generates higher upfront cost for lower ROI.
"The more insulation, the higher the R-value – up to a point."
The diminishing returns from increased insulation
Logic says, the more insulation, the higher the R-value. And that's technically true, to a point. According to Energy Vanguard, insulation has a huge impact on an uninsulated wall, but as the heat flow decreases, more insulation does less and less. Every addition of R-2 insulation does lower the heat flow, but in increasingly smaller increments.
To take a closer look, Energy Vanguard used an uninsulated 2X4 as a starting point. With the addition of R-2 insulation, the heat flow factor went from about 53 MMBTU to just over 25 MMBTU. But another R-2 step of insulation only brought the heat flow down to around 17 MMBTU. The heat flow declines by only 1 or 2 MMBTU from R-14 to R-16, and less and less from there on out. This is to say that at a certain point, it doesn't make financial sense to keep insulating. If a building still has performance issues with ample insulation, adding more might not be the solution. Instead, builders should examine other possible issues.
A better answer
As previously mentioned, the type of insulation can have an effect on performance. While R-14 or spray foam might be comparable to R-14 of fiberglass, those two will vary significantly in cost, installation requirements, best uses and long-term impact. But neither can stand up to the best insulation from Sto Corp that acts as a blanket around the entire exterior of a building.
That's because continuous insulation is part of a comprehensive building performance system geared toward solving insulation needs as well as other airtightness issues. But it also takes a different approach to insulation than materials that builders place on the interior or in wall cavities. In these instances, any nails, studs, staples or other fasteners provide an easy channel through which heat may escape or infiltrate. Continuous insulation cuts off that path by encasing the structure in material with high thermal resistance.
In short, it's important to insulate at least as much as regulations require, based on climate zone and other factors. But going above and beyond won't necessarily net corresponding savings. Rather, use a strategic approach through continuous insulation to save on energy payments and create a high-performance building.