Last issue I wrote about energy “leaks” in the building envelope. Buyers spend a lot of money for energy-efficient wall systems. To get the benefits, however, they also need to have an efficient roof, efficient windows and doors, and an efficient foundation. If one or more of these things is suboptimal, large amounts of energy can leak through them and sharply reduce the benefit you were supposed to get from the walls.
But the public chooses concrete walls for other reasons, like interior comfort, resistance to disasters, and sound reduction. And these things are all similar to energy in one way: if you don’t specify products with the same benefits for the other parts of the envelope, you can lose much of the benefit.
Comfort is an easy one to handle because you pretty much take care of it when you look out for energy efficiency. So long as the roof, windows and doors, and foundation have a high R-value, have no uninsulated parts, and are reasonably air-tight, the interior should maintain an even temperature without drafts.
Disaster resistance can be a bit more of a challenge. Roofs may or may not be designed to withstand things like high winds or an earthquake. This can be done—and should be done if the owner is serious about having a disaster-resistant building. But a structural engineer will tell you that by rights the roof should not just save itself, it should be helping the whole building to survive. If it is strong enough and tied in well, the roof diaphragm can reinforce the “box” structure it forms with walls. And the addition to overall building strength is significant.
It’s hard to get people to beef up their roofs structurally because doing this right requires a concrete or heavy steel product. But at the very least they need to know what they are choosing—and what they are doing without—and why.
Windows and doors do not reinforce the structure much against disasters, but impact-resistant glass is now widely available. It may crack, but its tough plastic layer stops projectiles and wind from getting in. It also holds the glass largely in place so shards will not fly through the air, worsening the situation.
Keeping the interior quiet is another job that benefits from energy efficiency measures. A roof that is more heavily insulated without any breaks almost always cuts down on sound transmission, too. Going to a concrete roof makes another quantum leap in improvement, but again there is the question of cost. More energy-efficient windows and doors are also more sound-resistant. So looking for a higher R-value will help here as well. Beyond specifying energy efficiency products, many higher-quality products are carefully designed with features that cut sound transmission even more than you would guess by looking at the R- or U-value.
I am convinced that “completing the envelope” is destined to become a bigger and bigger issue with both buyers and building codes over time. Buyers have shown a real inclination to pay a bit more for concrete walls because of their benefits. They will come to realize that they are only getting half the potential benefits because they are not paying as much attention to the rest of the envelope. People who put up cash have a knack for figuring out things like this.
Building codes have their own knack—the knack for getting stricter over time. And when they want something like energy efficiency or disaster resistance, they don’t care what part of the building it comes from. They want it, and if that means regulating all parts of the envelope, that’s what they will do.
The march to a tighter, stronger building envelope will continue, and that means more scrutiny for all parts of it. Watch this play out over the next 15 years.