Energy Vanguard Blog

The Cost of Solar Energy Keeps Dropping, But...

Posted by Allison Bailes on Thu, Sep 29, 2016

Solar energy has sex appeal. If you want to show the world you're doing something to reduce pollution, you put photovoltaic (PV) panels on your roof to generate clean electricity. Even better, you drive a plug-in hybrid or an all-electric car and charge your car's batteries with your solar panels. The good news for solar enthusiasts is the cost of installing a solar electric system on your home just keeps falling and falling. Let's take a look at some data. Then I'll throw in a little cautionary note at the end.

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Tags: environment & sustainability, big picture, solar energy

7 Things I Learned at the North American Passive House Conference

Posted by Allison Bailes on Mon, Sep 26, 2016

Yesterday I returned home from the North American Passive House Conference. It was great, as it always is. Wait. No, this was the best one yet. On the 10th anniversary of the first conference, PHIUS put on an amazing conference. It was the biggest one ever, I believe. As I flew home I pondered some of the things I heard and saw in Philadelphia and here are few that stood out for me.

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Tags: fun, conferences, Passive House

Grading an Attempt to Get Ducts Inside Conditioned Space

Posted by Allison Bailes on Wed, Sep 7, 2016

There's a ton of new construction and remodeling going on in Atlanta. On a lot near where I live, a developer tore down the old house and is building two new ones. This weekend, I took the opportunity to check out their progress on the first one and saw the mechanical system roughed in on the first floor. They did some good things in their attempt to keep the air handler and ducts inside conditioned space. They also did some not-so-good things. Let's grade their work.

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Tags: design, heating & cooling distribution, heating & cooling

How Dirty Is Your State's Electricity?

Posted by Allison Bailes on Fri, Sep 2, 2016

I've been working on my presentation for the 10th anniversary of the North American Passive House Conference. It's on the global warming impact of insulation, a followup to my latest article about Alex Wilson's work on that subject. One of the things I wanted to do was to see what difference it made when a home used "dirty electricity," with a high carbon intensity, versus a home using "clean electricity." The Emissions & Generation Resource Integrated Database (eGRID) from the US Environmental Protection Agency, has the data I was looking for.

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Tags: environment & sustainability

More on Air Conditioner Sizing Rules of Thumb

Posted by Allison Bailes on Mon, Aug 29, 2016

Air conditioner sizing rules of thumb must die. That's what I wrote in my last article. The most common rule of thumb is to use 500 square feet per ton to determine the size of air conditioner needed. Or 400 or 600 or some other number in that general vicinity. In my article, I showed a graph of air conditioner sizes, given in square feet per ton, for 40 homes that we did load calculations for. The average of the 40 was 1,431 sf/ton. Now, let me say a bit more about that.

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Tags: heating & cooling

Air Conditioner Sizing Rules of Thumb Must Die

Posted by Allison Bailes on Fri, Aug 26, 2016

We design a lot of heating and air conditioning systems at Energy Vanguard. Alexander Bell, who goes by Andy, is our design wizard, and I've been getting involved with the process again lately. When I talk to potential clients, a lot of them tell me their contractor wants to size their air conditioner using a rule of thumb. The rule is usually something like this: Install one ton of air conditioning capacity for every 500 (or 600) square feet of conditioned floor area. How far off are they? Let's take a look.

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Tags: comfort, heating & cooling

Installing an Exhaust Fan During a Bathroom Remodel

Posted by Allison Bailes on Tue, Aug 23, 2016

Remember my bathroom remodeling project? I took the liberty of gutting our outdated, decaying bathroom while my wife was out of town in April. I found some interesting air leakage pathways when I opened the walls. I fixed that. I found termite damage. I fixed that. Our 1970 condo didn't have an exhaust fan in this bathroom because, hey, who needs a bath fan when you have a window! I fixed that. Here's how.

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Tags: moisture problems, ventilation

3 Reasons to Remove Attic Floor Insulation in a Spray Foam Attic

Posted by Allison Bailes on Tue, Aug 9, 2016

I get asked a lot of questions about spray foam. Do I need an ignition barrier? Should I use open cell or closed cell spray foam? Will open cell spray foam really rot my roof? But the question I get more than any other on this topic is about whether or not the insulation on the attic floor should be removed when insulating the roof deck in an existing home. As you can tell from the title of this article, my answer is to remove it. Here are my three reasons, in increasing order of importance.

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Tags: insulation, air leakage, indoor air quality

Can You Ventilate a Home with Attic Air?

Posted by Allison Bailes on Fri, Aug 5, 2016

I've seen some crazy things done to homes. It's usually someone's attempt to make things better. Sometimes that someone is a homeowner or other occupant. Sometimes it's a contractor. But it always seems to be a solution to a problem that creates other problems. It's just like they say: Our biggest problem is solutions. So what's the problem with this method of ventilating a home?

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Tags: attic, indoor air quality, ventilation, heating & cooling

Only One Person Can Fix the Passive House Rift

Posted by Allison Bailes on Fri, Jul 29, 2016

In the beginning, there was passivhaus. That was way back in the 1990s. Then the Passive House Institute US, having been thrown out of the party for blasphemy, said, no, passive house started in North America in the 1970s and '80s. But wait, others said, a polar exploration ship from the 19th century was truly the beginning of passive house. And Dr. Joe Lstiburek, as you may recall, said it was the Eskimoes who started it.

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Tags: fun, Passive House