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Ask the Architect

The guidelines for insulation


Q. We interviewed three contractors and three architects after recently buying our home. We think we have the right people selected, but wonder why only one architect mentioned energy requirements. We’re not sure it’s necessary to spend extra money on more insulation, since nobody else talked about it. Can you tell us the rule of thumb for insulating? It can get pretty involved, according to the architect, so we only want to spend for just what we need. Please enlighten us.

A. The expression “rule of thumb” has an interesting origin, related to disciplining students in the one-room schoolhouses of early America. When a child misbehaved, he was sent out to select a twig or branch, called a switch, by which he would have his knuckles whipped by the teacher. He was instructed to find a branch no thicker than his thumb, thus the expression. So the “rule of thumb” was to select the stick with which you would get beaten — even though, in your case, by interviewing all those people, you were trying to avoid being beaten.

There are many codes to be followed, and none are an approximate rule of thumb. Just because someone didn’t discuss every aspect of the codes isn’t a good reason to exclude them, although it’s good to know as much as you can before proceeding with a project. Selecting people that you are confident can communicate and follow through to the end should be your best criteria.

The codes have to be followed regardless of whether you know about them or not. The energy codes have become increasingly strict, and even the methods of insulating have changed. The amount of insulation needed to meet the codes, referred to as the resistance, or R value, has gone way up. Previously, for over 30 years, the value for walls was R-11. It increased to R-13 in the past 10 years, and now it’s R-15. Roof values have changed the most, from R-19 for 30 years, to R-38 in the past 10 years, to R-49 in 2018. What those higher numbers mean is thicker insulation and increased size of the wall and roof structure. Because the depth of the wall or roof cavities is so much greater, the real increase you should be concerned with isn’t just the added expense for insulation, but the much greater cost of larger structure.

Sadly, many in the field are unaware of the formulas that need to be applied to make the whole system of energy compliance work, so often clients will relate that somebody told them that the building was over-structured and money could have been saved. That’s when they have to be enlightened that the person unnecessarily alarmed them and is uninformed. It’s a technical balancing act, deciding whether to utilize more expensive, higher-R-value-per-inch foam in order to prevent much greater-costing large structure from being needed. That’s not so simple.

© 2019 Monte Leeper. Readers are encouraged to send questions to yourhousedr@aol.com, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.