I’m often asked whether you need thermal mass in a certified passive house. The question came up in recent open days.
The answer is no. You don’t. (Although it might be useful in a hot climate!)
Contrast traditional passive solar houses, where thermal mass, like concrete, is needed. It is needed to absorb some heat from the sun, and radiate it back into the house.
Some people complain that buildings should use materials with less “embodied carbon” – they don’t like concrete for that reason alone.
Sometimes, ironically, the complaints about concrete come from advocates of passive solar design.
I guess all building systems involve some carbon footprint. The question is how much, and where does the footprint come from.
The most important question, is how much carbon footprint is caused by the energy consumption of the building. Heating, cooling, and power. Year after year after year.
That’s why it’s said that building the way we usually do – with poorly designed leaky building envelopes – is “an investment in a carbon intensive future”.
It’s hard to get a wholistic picture of our buildings and energy consumption. It’s hard enough to reduce energy consumption generally. Just look at the Paris Climate Talks.
But I keep thinking, regardless of what our world leaders decide, what’s to stop us building passive house buildings from now on?