It is now a given that high-performance houses have high levels of insulation. It is not uncommon for a new cold-climate home to have R-40 walls and an R-60 roof, as builders do their best to lower a home’s energy requirements.
But is this premise in favor of thick insulation weighted toward houses in cold climates, where heating is a higher priority than cooling? Does it make just as much sense to insulate houses as heavily in hot, humid climates? Or does a lot of insulation actually make it more difficult to keep the house cool?
Those are the intriguing questions raised in a recent Q&A post at Green Building Advisor, and the topic for this week’s Q&A Spotlight.
Reading a long thread on a website called Design By Many about a Passivhaus project in New Orleans, John Brooks had come across this comment: “In a cooling climate, the delta T is much smaller than in a heating climate, and due to the internal heat gains insulation actually starts to work against you at a certain point. I think anything up to R-30ish is doable/defendable for all components, including roof and suspended floor. Beyond that it will only add to your cooling problem.”
Brooks gets the conversation rolling with this: “I understand how insulation can ‘work against you’ in a building without air conditioning….
“Or when the conditions outside are ‘better’ than conditions inside. The problem is that most Southerners DO air condition their buildings in order to be comfortable …. and for many of the hours during the cooling season the conditions outside are ‘WORSE’ than conditions inside.”
The issues is humidity
High humidity makes air feel uncomfortably sticky. Even…
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