Yesterday was both the summer solstice and the Strawberry moon! Those two events – plus the weekend of sunny, muggy days – has kicked off Summer in Chicago. If you missed it don’t panic, today will be almost as long and the moon nearly as full tonight … and its going to be hot for a while. Here’s how are we going to keep our cool:
What is the Summer Solstice?
The simplest definition of the solstice is the longest day of the year. Technically speaking, it is the moment when the sun is directly above the Tropic of Cancer (and is completely invisible below horizon in the Antarctic circle). We’ve talked about solstices and equinoxes before here.
You might expect the longest day to also be one of the hottest. So why does the solstice only kick off the summer season (and heat wave) rather than marking the center line of summer?
The answer lies in thermal lag – it takes a while for massive elements (the great lakes, the ground, a brick wall, a segment of blacktop, eg) to heat up and to cool back down. That explains why afternoons are hotter than high noon AND why weather norms place the hottest part of summer another three weeks out.
Keep your Cool all summer …
This effect of heat slowly soaking into surfaces and then radiating back is one of the reasons that the Heat Island Effect heats up Chicago so much. Don’t freak out, though. We can plant trees, and even green roofs, to keep the direct sun OFF of masonry, concrete and asphalt around us.
You can crank the thermostat down, and spend the summer slipping from car to house to office to movie theater, but there are lower impact ways to be cool. Here are a few of our favorite strategies:
Did you know that the “heat index” number quoted by the weather websites and TV news is measured in the shade. So on a day marked 94 (like yesterday) standing in the sun could make you feel 10 to 15 degrees warmer. The same is true for your building and even for your whole neighborhood. Houses with 50% cover by light shade have energy costs 10% lower than those in full sun.
If you want to maximize passive cooling, you’ll need to take a little action in your life. Using the days hot-cool cycle to your advantage, you can let cool air into your house at night, then pull all the windows and curtains tight against the heat during the day. Setting your personal spaces up for cross vent (air flowing from one side of the room or building to the other) and for stack cooling (letting hot air rise out high windows while pulling in cooler air from lower ones) will give you a major comfort boost during the evening hours you’re most likely to be at home.
You probably WILL interface with the AC this summer. 87 percent of U.S. households are equipped with AC, and it is a rare work place that doesn’t feature central air. Make sure that the AC is working for you, rather than the other way around. You can use it to supplement your passive cooling – a little concentrated blast to dehumidify the house when you get home from work – and you can make sure your cooling unit is the right size for your space. This is one place where bigger is not better. An oversized AC unit not only costs more energy but results in a clammy chill instead of the comfortable cool you were probably seeking.
… While taking advantage of all that sun
Don’t let us make you think that the sunshine is not your friend. We LOVE the sun. Its energy, warmth, and gravity are all that keeps the Earth from being a frozen and darkened space rock. So before you crawl into a bunker (or hermetically sealed conventional building) to keep yourself safe from Earth’s nearest star … let us persuade you that the sunshine is GREAT … when we plan for it and handle it well.
We may recommend closing the curtains on south facing windows (or other shade devices) when its hot out … but we LOVE bringing natural light into the buildings we design. A north facing window lets in cool, even, indirect light all year. Any sunlight is great, as long as we’ve planned for it properly. Here are a couple of projects where we were able to dramatically improve the natural light access with our re-designs.
Actually nearly ALL of our power comes from the sun. Even when we burn fossil fuels, we’re just burning old sun power but there’s a limited reserve of that stuff … so why not use solar power straight from the source.
We can use the sun’s heat at times that are not the middle of summer. Don’t write it off just because the weather is hot today. Remember that thermal lag we talked about up at the top of the post? We can use that to our advantage like this.
So, thanks, big ball of burning gas in the sky. We appreciate your shiny warmth (even when we avoid it all summer) and we’ll be back to welcoming you gladly into our homes and lives come fall!