Last week was Groundhog Day, and my question that day was, How can Punxatawney Phil (the weather predicting groundhog) or General Beauregard (his Southern counterpart) say anything at all about more winter when we haven't really had a winter at all? Yes, it's been quite warm this winter, especially in comparison to last year. So I thought I'd check to see just how much warmer it's been.

First of all, looking at the number of Heating Degree Days (HDD) is a great way to compare the cold weather of one year to another. There are two websites I'm aware of where you can get the Heating Degree Days for you location:

• Degreedays.net
• kWIQly.com

You should definitely check them out.

Heating Degree Days are a way of looking at how much time your area has spent below a given temperature, called the baseline temperature. The most commonly used baseline here in the States is 65° F, so here's how it works:

• 1 minute at 64° F gets you 1 Heating Degree Minute.
• 1 hour at 60° F would be 5 Heating Degree Hours.
• 24 hours at 30° F accumulates 35 Heating Degree Days.

See how it works?

One way that you can use these numbers is to calculate the amount of heating your home needs. Since your heating load depends on how cold it is outside, the more Heating Degree Days you have, the more heating you have to pay for. The basic equation for this is:

The number of Heating Degree Days tells you the ΔT over a given time period.

So, here in Atlanta, we had a total of 3396 HDD in the 2010-11 winter. It was really cold last year, and we actually had snow three times. We normally get one little snow a year, but we even got shut down for a whole week with snow that turned to ice on the roads and then stuck around. Our 30 year average is about 3000 HDD, so last year was colder than normal.

This year however, if we look just at December and January, we find a huge difference:

The 37% number in the title of this article comes from comparing the HDD of just those two months. We had 1714 HDD in those months in 2010-11 and 1076 HDD this winter. It's great for heating bills and getting outside and doing stuff here. Not so great killing bugs though.

How do your Heating Degree Days this winter compare to last winter?

Photo by AlicePopkorn2 from flickr.com, used under a Creative Commons license.

In today’s blog post, I’m gonna talk about fashion!

Why? 'Cause I'm cool like that! Believe it or not, fashion is a part in what I do as an architect and HVAC designer. Another reason...'Cause I'm cool like that! And, I’m going to New York Fashion Week this week with 18 other elite designers, architects, and savvy writers, compliments of Brizo, premium faucet manufacturer. They’ve promised an action-packed design-focused three day experience, and I am stoked! There's more! We'll have the opportunity to learn from and spend time with fashion designer Jason Wu, which includes an afternoon at his fashion show.

It might seem strange to someone who reads this blog regularly that I would be taking part in such an event. You might ask, "what does fashion have to do with high performance homes and HVAC systems?" I thought you’d never ask…

CLOTHING AS A STATEMENT

According to his website, fashion designer Jason Wu is “driven by a curiosity to learn about construction, workmanship and perfecting every detail of his designs.” V.I.P.’s like Michelle Obama, Diane Kruger, and Natalie Portman regularly sport his creations. Though, he has also found a way to translate his high fashion and attention to detail to everyday items like bathroom fixtures and department store clothing.

In 2006, the faucet manufacturer, Brizo, started collaborating with Jason for their Jason Wu for Brizo collection. And, just yesterday, Target launched the Jason Wu for Target collection.

FAUCETS AS ARTWORK

Brizo is known for its fashion-forward approach to kitchen and bathroom fixtures, even before hooking up with Jason Wu. They’re recognized for bringing form to the everyday function of controlling and delivering water.

Like Jason Wu, Brizo combines high design with function and effeciency. They have been recognized by the EPA as 2011’s WaterSense Partner of the Year for their commitment to water efficiency.

HOUSE AS A SYSTEM

People care what the inside of their home looks like, and I care a lot about that. They also care that they are comfortable and live in a well-built and well-designed home. Some of you know that I specialize in innovative HVAC systems and building science practices in my designs. These things MUST be and are incorporated with form and every day function. It requires good design to create something that matches a homeowner's lifestyle and taste.

Like Jason Wu and Brizo, it's about taking something as everyday as a home, garment, or plumbing fixture, and turning it in to something exceptional. In today's market, high performance homes and high efficiency HVAC systems are exceptional. Exeptional things will always require good design to remain functional and timeless.

THANK YOU, BRIZO...

...for inviting this group to Fashion Week. We are honored to be a part of this event, and can't wait to help make a difference! 

 -from the desk of Energy Vanguard's architect dude, Chris Laumer-Giddens

- Follow the Brizo 19 on Twitter at #BrizoFW

On Friday, the New York Times published an article about the Hartfords, an elderly couple in Dixfield, Maine who couldn't afford to pay for fuel oil for their leaky, inefficient home. I heard about it through social media from a couple of my friends up in Maine. Peter Troast of Energy Circle is one of those, and he's written about the local response their plight.

The story in the Times is heart rending, not only because of the couple, who even offered the title of their car as payment because they still owed for their last two deliveries, but also because of the owner of the fuel oil company, who can't afford to give his product away and stay in business. The stress has really gotten to him.

Peter reported on his Facebook page that there's been a huge outpouring of support to help the couple. He's also written a great article about the deeper implications and how we must address the real issues. Just raising money to allow them to continue buying fuel oil for a grossly inefficient is not the answer. As Peter wrote, "Paying for people's oil, a commodity virtually guaranteed to continue its annual 18% per year price march, is utterly unsustainable."

Peter is putting his principles into action and has gone up to Dixfield today with Upright Frameworks, a weatherization company, and DeWitt Kimball of Complete Home Evaluation Services. They're going to do a complete home energy audit and come up with a plan to help them heat their home more affordably.

I love the response to this story and that this couple is getting a lot of help. The fuel oil company has had a lot of offers of money and gifts coming in, and Peter's group will help the couple improve the energy efficiency of their home. But let's also keep in mind that for each story that gets this kind of publicity and response, there are countless others out there who are still struggling. These are tough economic times, and this story reminds of the way people helped each other during the Great Depression and World War II.

You really should go read those two articles now:

In Fuel Oil Country, Cold that Cuts to the Heart by Dan Barry of the New York Times

Helping the Hartfords and Finding a Path to More Energy Efficient Homes by Peter Troast of Energy Circle. Peter has promised to update his story with their findings and what they do with them.

The photo at the top is one that I've taken and is not from the Hartford's home. The photo of the Blower Door test is from the energy audit of their home, taken by Peter Troast of Energy Circle.

Rule #1: You do not talk about Building Science Fight Club.

Building science is not an objective subject to be discussed in a rational, calm way, always coming to the same conclusions. Yes, it's based on principles of physics that were settled long ago, but buildings are complex. They intermingle structure, HVAC, plumbing, an electrical system, materials for controlling heat, air, and moisture, and more.

Does heat rise? Or should we never say that because the second law of thermodynamics says that heat responds only to temperature differences, moving from warmer to cooler?

Does setting your thermostat back help lower your bills? Or should you just leave the thermostat alone?

Should we insulate old buildings? Surely, no one who understands building science could say no to that, right? Wrong.

Rule #2: You DO NOT talk about Building Science Fight Club.

I hope you'll excuse me now. I've got someone standing out on my porch waiting for our HERS rater class to start. It won't be long before we're going mano a mano (short for manometer a manometer).

Photo by nilsrinaldi from flickr.com, used under a Creative Commons license.

Heat rises. Everyone knows that, right? It's absolutely true. Heat does rise. The problem is that sometimes people say this as if the flow of heat is driven by its wanting to rise. It's not. Heat can move up, down, or sideways, depending on the situation. What the laws of thermodynamics tell us is that heat moves from areas of higher temperature to areas of lower temperature. Put a torch to the top of a steel pole, and heat will travel downward by conduction. So, temperature difference is really what drives heat to move in any given direction.

When you're dealing with fluids, you have to account for density and buoyancy as well. Air is the fluid we live in, and this time of year we spend a lot of money pumping heat into it in our homes and workplaces. When we heat air, the molecules jiggle and zip around faster, which causes them to spread out. When a mass of air takes up more space, it has a lower density. When you have a lower density fluid immersed in a higher density fluid, the lower density fluid rises and the higher density fluid falls.

Think of air bubbles in water, as shown in the photo above. Think of a helium balloon. Think of a hot air balloon. Now, imagine an object with higher density immersed in a fluid. Put Wile E. Coyote's anvil in the air above his head, and it turns him into a pancake.

The point here is that it's easy to get confused by heat in the building science of air movement. Warm air rises when it's surrounded by cold air because of its lower density. Yes, that's due to heat, but density is the main factor causing the movement here. The name for this phenomenon is stack effect. Two factors affect how much stack effect a building experiences:

• Temperature difference between inside and out (because density depends on temperature)
• Height of the building

The problem with stack effect in buildings is that buildings aren't vacuum chambers. They leak. Obviously, a house isn't going to start floating up into the air like a balloon (although I recall with great fondness the Disney movies of my childhood that showed such magical events). But the low density air inside the house will move up and out into the cold, dense winter air when given the chance.

Try this experiment if you don't believe me. Open your pull-down stairs or scuttle hole to the attic on a cold day when your home is warm. Climb up into the attic and then put your face over the hole. You'll feel the stack effect pushing lots of warm air into the attic.

So, in winter, the warm, low density air inside your house wants to rise...if it can. If your house has no leaks, the warm air can't escape and do its thing. There's still a pressure difference across the building envelope, but that's OK if the air barrier's good. Positive pressure inside the house with nowhere to go because there are no pathways.

What happens in reality is that homes leak. Your nice warm air finds way to leak out (exfiltration) and cold air leaks in (infiltration). Because of its lower density, the warm air will leak out the top of the house if there are leaks there. When a cubic foot leaks out, however, it has to be made up by a cubic foot leaking in. As the warm air leaks out at the top, cold air leaks in at the bottom. The leakier your house is, the more temperature difference you'll notice between the top and bottom of the house.

All this happens because the warm air inside your home in winter is less dense than the cold air outside. In summer, the dense air is inside your home because that's where the temperature is lower, especially if you're air conditioning your home. What that means is that leaks in your house bring warm air in at the top and allow cool air to fall out at the bottom.

Ah, warm air falls! Heat sinks. That old expression, "Heat rises," is not a basic truth after all. As with many aspects of building science, you have to look at the full context to understand what's going on.

Related Articles

What Is Pressure? - Understanding Air Leakage

Rats to You, Daniel Bernoulli! - Understanding Air Pressure (with a cool video!)

Infiltration Occurs at the Surface, Not in the Volume

It's the Hole - Understanding What a Blower Door Is for

Building Science 101

Photo of water bubbles by Christian Haugen from flickr.com, used under a Creative Commons license.