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All Over the Map — The Imprecision of 24 California HERS Ratings

 
stockton research project hers rating discrepancy grange

A home energy rating is supposed to tell you how energy efficient your home is. A certified home energy rater goes to the home and collects all the data relevant to energy consumption in the home (well, all the data included in the rating anyway, which is almost everything). Then they enter the data into energy modeling software and get the results: consumption for heating, cooling, water heating, lights, and appliances plus this thing called a HERS Index. But what if the results were off by 50%, 100%, or even more?

This Thermostat Setting Can Cost You Money and Make You Sick

 
air conditioner thermostat fan on temperature 600

I've been experimenting with my family lately. Or is it, experimenting on my family? In either case, I've got the data to confirm something I wrote in a 2011 article. But before I tell you what I did, first let me show you what happened. Here is Exhibit A: A Moisture Mystery. What do you think happened to cause the humidity (blue data) in the air in our condo to rise like that?

My Big Fat Oversized Air Conditioner

 
hvac oversized air conditioning system massive enormous condenser

Back in 2009, I had a new air conditioner installed our condo. The previous one was an ancient 25 years old and barely limping along. It wasn't cooling much, and the summer electric bills had risen. So, I did a Manual J load calculation on our condo to find out what size we should replace it with. I wanted to install one that wouldn't be too big so it would have long runtimes and keep our place cool and dry. Well, I put one of my new data loggers to use this summer to find out if I succeeded. The (doctored) photo below, which is not our condo, might give you a hint how well I did.

Why Is RESNET Limiting Its Options for Improvement?

 
How can RESNET improve the consistency of the HERS Index?

In case you haven't heard, last year RESNET created a task force to look at ways to improve the consistency of results among certified home energy raters (aka HERS raters). One week ago, executive director Steve Baden sent an email about the latest developments in the process. He also attached a document titled Quality Improvement Working Group RESNET QA Options (pdf) that outlines the areas of consensus and gives three options for changing the way quality assurance (QA) is done. Unfortunately, there's a glaring omission from the list.

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Moisture and the Quirkiness of OSB

 
oriented strand board osb permeability

Oriented strand board (OSB) gets blamed for a lot of problems that are really the fault of the designers and builders. Part of the problem, of course, is the perrenial confusion between correlation and causality. OSB hit the market as we really started getting serious about insulation and air sealing. As I described in the story of painters refusing to paint insulated homes, building assemblies that keep the exterior sheathing and cladding colder restrict its ability to dry. Is that the fault of the OSB? Or the insulation? Or the lack of a vapor barrier? Or something else altogether?

5 Reasons to Attend the Passive House Conference in California

 
north american passive house conference california 2014 phius

The 9th annual North American Passive House Conference is less than a month away. You knew it's going to be in California, right? It's unfortunate that the other passive house group has chosen to use the same name PHIUS has been using since 2006, but I've already discussed that confusion. All you need to know is that the main passive house conference is in California, not in Maine. And here's why you ought to get yourself registered for it ASAP.

Why Is Clark Howard Giving Bad Energy-Saving Advice?

 
clark howard diy ways save energy bill

Clark Howard is the penny pincher's guru. My wife loves his radio show and website for all the money-saving tips he provides. Naturally, anyone trying to help people save money at home has to address energy use, and Howard does, too. Unlike some others, though, he's generally well educated on the topic because he's hung around the Southface Energy Institute enough to know the basics. (I don't know if he ever used the clip, but he filmed me teaching how to do a blower door test there a few years ago.)

Are You Making This Mistake with Humidity?

 
water words vocabulary dew point psychrometrics hygroscopic

I want you to think about humidity today. Look at the photo below. What do you see? Dew drops on blades of grass. Where did that water come from? Out of the air. What was it about the air that caused the water to go from the vapor state to the liquid state? Wait! Don't answer! If you go any further, you're likely to make the mistake that so many people do.

Matt Risinger's Building Science Summer Camp Interviews

 
Table talk at Building Science Summer Camp

August for me is dominated by Building Science Summer Camp. It's a great event with lots of learning, great discussions, and meeting friends, old and new. I'll be writing about Dr. Chris Timusk's presentation on his OSB research later and possibly one or two other topics. Hal Levin spoke most of Tuesday, and, after his rambling, two-hour introduction, his talk on indoor air pollution was full of useful information. Today, though, let me just give you this nice little video that Matt Risinger put together from interviews he did with me, Joe Lstiburek, and Mark Laliberte.

The Pen Test — A Control Layers Tool for Architects and Contractors

 
pen test liquid water control layer epa moisture guide 550

I listened to the IAQ Radio podcast a couple of weeks ago when they interviewed Lew Harriman and Terry Brennan, who were discussing the new moisture control guide published by the EPA last year. Brennan is the lead author of the document, and it's a really great resource full of useful information about indoor air quality, fundamental building science principles, and how to control moisture. If you have anything to do with buildings, you really should download it now and read it.

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