Dabbing my sweaty brow with my Bedouin scarf gnat shield---careful not to spill my precious, freshly picked raspberries---I pause as I reach the ridgetop. Nope! Not a breeze, not even here on the usually windswept spine of the prairie. In this heat, I wish I could feel as happy and energetic as this big bluestem, how he thrusts his stem skyward! If only I too were a warm season C4 plant---like the corn beyond the hedgerow and so many grasses here on the prairie---all day yelling “bring it on” to the sun, then all night laughing and partying as I do my grow dance. No, I’m a good Minnesotan: a cool season C3. No problem with winter. I wither and shrink in the heat.
So as I gaze down at Home the Land Built I wonder how hot it is already in there. Throughout our two year Home the Land Built design, we kept saying to Locus Architect Paul, “We got solar alright. And we got winter covered; throw another log on the fire. But how will we ever keep cool?” That may have been our biggest fear and was certainly mine now as I entered the west porch and opened the door.
Ah-ah-ah-ah-ah. That feels so good. Not yet trusting my own body, I stroll down the corridor to the wall thermostat. 80F! How could 80F feel so good? Partly it’s my bare feet upon the floor, our 5” thick concrete slab, which according the thermostat, is 77F. But mostly I’ve come to realize that there’s nothing magic about 72F. In fact, what is magic is feeling some variation. Unlike the unreal sameness of 72F, the variation in temperature connects me to the Land. Not too much mind you. I’m not looking for miserable. But anywhere from 60F to 80F is just fine. Wool socks and a sweater at 60F, a low-speed fan and iced tea at 80F.
Always needing more data, I click on weather.com and shout, “Its’ 96F! Thank you Architect Paul.” I imagined being back at 4140, dreading going to bed and sweating atop the sheets. So how did we do it? How does Home the Land Built stay so cool when it nears 100 during the day and barely drops below 80 at night? Off-grid. No air conditioning. Not a single shade tree (it’s actually 115F, yikes!). I’m no HVAC expert, but I’ve broken our success down into my 3 Principles of Passive Cooling and tell you how we do it.
3 Principles of Passive Cooling
1. Keep outside heat outside.
Insulation. Ceiling: R60 blown insulation. Walls: R40. Two stud walls (most homes claim higher than actual wall R-value because 10% of wall is actually un-insulated studs). Sandwiched between the two walls are polystyrene blocks (a million McDonald’s cups worth) sprayed with foam sealer. Windows: R5 fiberglass from Serious.
Reflection. Steel roof. Low solar gain windows on east and west. 2’ roof overhang shades the big bank of south-facing windows in summer.
2. Eliminate inside heat.
Electrical efficiency. This is huge. What I used to refer to as “inefficient” I should actually have called “heat I don’t want but pay for anyway”. Our old 4140 fridge got caught in a vicious cycle. The more the kitchen heated up, the more the fridge ran, heating the kitchen all the more until the fridge became a space heater. Literally. According to my calculation our old fridge was like running a 1000 watt space for 2 hours a day. By comparison, our new kitchen’s Sunfrost R10 fridge is that same heater for 5 minutes a day. And that’s just the fridge. On average, 4140 consumed 1000 watts per hour, much of it converted to heat due to inefficiency. Now we’re at 150 watts with very little converted to heat. The only way to afford off-grid is super high-efficiency everything. LED lights. Freezer and backup fridge in much cooler cellar. “Don’t put a heater in our kitchen!” we told Paul. So now I love the sound of our Sunfrost fridge whirring atop the kitchen counter. The sound of coolness.
Less gas heat. On hot sunny days, we get all our hot water from the sun. Want a hot bath? Come on over! So our LP backup water heater never runs. We try to use the LP stove less. Its hard because Linda loves to cook and I love to eat (especially her cooking). We grill more, of course. Just made the best beets ever: apple-smoked. Featured in a recipe from Trout Caviar----Roasted Beet Salad with Aioli and Walnuts---they stole the show at a picnic. Sun tea is always refreshing. And, speaking of solar cooking, today I fired up the solar oven, a Solar Oven Society gift from my dear friend Randy. I’m doing my usual uninspired trick: put all remaining CSA veggies in one pot and cook ‘em.
3. Invite cold in.
Ventilation. Okay, this is where, in many homes, AC shines. Not off-grid. At night, if it ever finally cools down outside, we open the windows. Standing in the stairway, I love to feel the warm air rising past me on its way out the yoga loft window. With windows closed during most of these hot days, we rely on our simple ventilation system for fresh air. Every day of the year, 20 minutes out of every hour, our Whisper bathroom fan quietly and efficiently exhausts air out of the bathroom (never a bad idea with a composting toilet). Outside air is sucked in through a ceiling vent above the kitchen stove. Just yesterday I made that air a little cooler. Instead of coming straight in from outside, I vented the air first down into the root cellar, where it stays below 70F, then up. We’ll see how much that helps. Another great experiment for Home the Land Built.
Conduction. The south and west sides of our home are partly beneath the earth. Most of the home is slab on grade. Thus, we pull coolness out of the earth and into our home. It is the coolness of the earth my feet feel upon the slab. How wonderfully connecting to the Land!
So how are we doing right now as I write the blog. At 12:43PM its 89F outside according to weather.com. Up here in the yoga loft, the warmest room in the house, I feel comfortable though my back is getting a little sticky. Time to go downstairs, where according to the thermostat, the air is 77F while the slab underfoot is 76F. I’ll adjust the angle of the solar oven, pour a glass of iced tea, and kick back with a book in front of a sluggish fan. Here at Home the Land Built, midday in midsummer is like a winter’s eve, except I need a new name for these relaxing inward hours. I don’t even want to mention a “cocoon”.