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Home heating and cooling, explained plainly.

Straight answers from an HVAC engineer: why your system does what it does, and what actually lowers the bill.

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About



CoolPlain explains home heating and cooling. Why the AC runs but the house stays humid, why one room is always cold, whether a new furnace or heat pump is worth the money: the questions homeowners actually ask, answered with real numbers.

Who writes it

I'm an HVAC engineer with years of hands-on experience with heating and cooling systems, from design to troubleshooting in the field. Most homeowners only hear about their system from someone trying to sell them a new one. I started CoolPlain so you can understand what's going on first.

How posts work

Every post starts with the short answer and what you can do about it today. Below that, a "Go deeper" section covers the engineering for anyone who wants the why. Figures are checked against the sources linked at the end of each post.

Posts cover three things: HVAC news that affects homeowners, how your system works, and what actually lowers your energy bill.

A note on safety

CoolPlain is general information, not a service call. Anything involving refrigerant, gas lines, or electrical panels belongs with a licensed technician, and posts say so when that's the case.

Popular posts from this blog

Water Heater Warm to the Touch? That Heat Is on Your Bill

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The touch test: a bare older tank feels warm because heat is leaving it all day; a wrapped one loses far less. Put your hand flat on the side of your water heater. If the steel feels warm, you are paying to heat the basement, one quiet degree at a time. On an older electric tank that warmth can add up to about $40 a year in heat you never use, and a $20 to $30 insulating blanket gets most of it back in a Saturday morning. Newer tanks and gas tanks are a different story, and I will get to them. Why a warm tank is an expensive tank A storage water heater keeps 50 gallons (189 L) of water at about 120 degrees F (49 degrees C) around the clock, whether anyone showers or not. The basement around it might sit at 60 degrees F (16 degrees C). Heat flows from warm to cold, so the tank leaks heat through its walls all night and the element or burner keeps switching on to replace it. Engineers call this standby loss. Think of a mug of coffee. A thin mug gets hot on the outside and the coffe...
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Did You Overpay for Your AC? A Lawsuit Says Maybe

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Price change since January 2020 as stated in the class-action complaint: HVAC equipment, kitchen appliances, and prices in general. Seven companies that make most of the air conditioners, furnaces and heat pumps sold in the United States are being sued for fixing prices. On October 9 they asked a federal judge in Michigan to throw the case out. Here is the short version. Nothing in the case changes what you should do this fall, and the biggest savings on a new system still come from the quotes you collect, not from a courtroom. What the lawsuit says, and what the makers say back The suits were filed this spring by homeowners and by contractors. They name Carrier, Trane, Lennox, Daikin, Rheem, Bosch and AAON, which between them sell most of the heating and cooling equipment in the country. The claim is simple: since 2020 these companies raised prices in step with each other, by more than their costs went up, and signaled their plans to one another through public announcements an...
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A $3 Sheet of Plastic Can Halve a Window's Heat Loss

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Bare glass versus the same window with a taped film: about half the heat loss. Hold your hand near a bare window on a cold night and you can feel the heat leaving the room. The fix is cheaper than almost anything else in home energy: a clear plastic film kit, taped to the window frame and shrunk tight with a hair dryer. On a single-pane window it cuts the heat flowing out through the glass by about half. On a double-pane window, by about a third. Glass is not the insulator. The air is. This is the part that surprises people. A pane of glass barely slows heat at all. Almost all of a bare window's insulating value comes from the thin layer of still air that clings to each side of the glass. Those two air layers do the work. The glass just holds them apart. A film kit adds a second pocket of trapped air, about an inch (2.5 cm) deep, between the film and the glass. That pocket resists heat about as well as the two air layers combined. So the window ends up with roughly double the...
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