In a July that is breaking heat records in many parts of the U.S. and worldwide and a week in which even Vermont is supposed to get into the mid-90s, the implications of a changing climate on building design are brought into focus.
I have long been a fan of passive design—and I still am. After we do our best to minimize energy consumption through energy-conserving design (high levels of insulation, high-performance windows, and such), passive solar heating, passive cooling strategies, and daylighting should dominate our energy design efforts. There are decades of experience we can draw from in passive design, starting with the knowledge gleaned from the passive solar energy conferences of the late 1970s and 1980s—many of which I attended (even editing the proceedings of one or two).
But I’m increasingly feeling that passive cooling won’t be enough as climate change advances and cooling loads increase. I’m now recommending that in most locations, even if passive conditioning is to be relied on initially, buildings be designed so that they can accommodate mechanical cooling measures down-the-road.
It’s getting hotter
Vermont weather this summer has (at least until this week) been very comfortable, but that’s not the case in much of the U.S. and elsewhere. Heat advisories have been issued in parts of the Southeast. Early July saw record heat in the Pacific Northwest: Seattle recording four consecutive days reaching all-time record highs; Boise recording nine consecutive days reaching over 100°F; and Portland approaching a record number of days with temperatures exceeding 90°F.
Western Europe is also having a record-breaking summer. In Germany, a temperature of 104.5°F in early July set an all-time record. Britain recorded its hottest July day ever (at Heathrow Airport—98.1°F), while Paris saw its second-hottest day ever (103.4°F), and Madrid setting a new June record at 103.5°F. In western France, hot weather recently led to power outages, leaving more than 100,000 without power.
In India, a June heat wave resulted in 2,300 deaths—the fifth-deadliest in world history—while a heat wave in Pakistan killed more than 1,200, with temperatures climbing to 113°F. In South America, a June temperature record was set in the Columbian city of Urimitia (107.6°F)
None of these disasters has been as deadly as the August 2003 heat wave that killed as many as 70,000 in Western Europe, and one has to be careful in ascribing specific heat waves to climate change, but the temperatures we’re seeing, coupled with the projections from climate scientists, should be setting off alarm bells.
Implications for building design
Rising temperatures and increasing cooling loads argue, first of all, for redoubling our efforts to incorporate high levels of insulation, cooling-load-avoidance measures, and passive cooling strategies into our buildings. This is particularly important given the prospect of increased risk of power outages during heat waves—as we saw in western France a few weeks ago.
Designing highly energy-efficient buildings is the best way to provide passive survivability, which RDI defines as ensuring that buildings will maintain habitable conditions should they lose power. This is something I’ve written about extensively on the RDI website and through BuildingGreen, including in this Fundamentals article and this 2006 in-depth overview.
Yes, we need to keep doing all that—and doing it better—but we should also be thinking about incorporating efficient mechanical cooling systems. Even if we don’t have near-term plans to rely on mechanical cooling, providing for the eventual use of such systems is smart design.
Fortunately, in residential and light-commercial buildings, that’s become much easier with the advent of high-efficiency air-source heat pumps (mini-splits). In buildings with very small heating loads, such as our Vermont farmhouse, this is often the best option for heating—especially when there’s a solar array to supply the electricity needed on a net-zero-energy basis—and the cooling comes as a sort-of bonus.
In larger buildings, designing for the later installation of cooling systems may require providing ducting or space for a larger heat pump, chiller, evaporative cooler, or some other cooling system to be added later.
We should continue to strive for buildings that don’t require mechanical cooling—which usually means starting with an exceptional building envelope—but we need to be realistic also. If climate change will effectively move our buildings hundreds or even a thousand miles south, in terms of cooling loads and humidity, we need to provide for mechanical cooling.
In my house, with today’s temperature expected to rise to the mid-80s, I’ll close up the house this morning to keep the place cool, and I may lower some window shades to block solar gain (though porches and shade trees do a pretty good job with that already). That should keep the place cool enough so that I don’t need to turn on our mini-split heat pump—but it’s nice to know that it’s there just-the-same.
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Along with founding the Resilient Design Institute in 2012, Alex is founder of BuildingGreen, Inc. To keep up with his latest articles and musings, you can sign up for his Twitter feed. To receive e-mail notices of new blogs, sign up at the top of the page.