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A New Way to Cool Your Attic - Powered Attic Mini-Split Heat Pumps

 
powered attic ventilator mini split heat pump 2

Move over powered attic ventilator. There's a new boss in town. For decades, concerned homeowners have looked for ways to keep their attics cool: gable vents, ridge vents, turtlebacks and whirlybirds. Then they moved from passive to active and latched onto the powered attic ventilator. Now we don't have to settle for a technology that pulls conditioned air up from the house.

The Sad Joke of Higher Furnace Efficiency Standards

 
furnace sealed combustion energy efficiency standard doe

Do you know when the US last raised furnace efficiency standards? It was 1987. Do you know how long the US Department of Energy (DOE) has been trying to change that? At least since 2007. The past eight years have been a sad case of industry heavyweights preventing progress on this important issue. The DOE has just proposed a new rule, so we might finally see some action here. Do you know when it's set to go into effect, if passed?

A Beautiful Solar Home in Utah Nears Net Zero Energy Use

 
near net zero energy home utah 2

I'm writing this on St. Patrick's Day so let me tell you a wee bit about the O'Mearas. Kevin and Svetlana O'Meara live in a beautiful home in Utah that's oh-so-close to being a net zero energy home. After I wrote about how home building is like skiing two years ago, Kevin invited me out to see their home and this year I managed to do so. My wife and I visited them for two days last week and Kevin told me all about the house, including his one major regret.

The Problem of Getting Air for Atmospheric Combustion Appliances

 
hvac furnace atmospheric combustion air building code irc nfpa

Remember those two furnaces I showed you photos of last week? You know, the ones that had ducts placed—or taped, in one case—right in front of them to bring them combustion air. I told you it wasn't a good way to deal with the combustion air issue, but let's go a little further today. Let's look at what building codes say is the right way to do it.

How NOT to Retrofit a Furnace in a Spray Foam Insulated Attic

 
furnace combustion air intake duct spray foam insulated attic

A while back I wrote about the incompatibility of putting an atmospheric combustion furnace in a sealed attic. Most often the attic is sealed by installing spray foam insulation at the roofline, thus bringing the attic inside the building enclosure and turning it into conditioned space (directly or indirectly). The good news is that some installers understand this problem and seek to address it. The bad news is what some of them do.

The Layers and Pathways of Heat Flow in Buildings

 
fiberglass insulation wall cavity johns manville spider

We used to build houses without giving much thought to heat flow through the walls, ceilings, and floors. The main thing was to provide some resistance against wind and rain, and then we'd get a fire going to try to make the indoor temperatures bearable. If you've ever lived in an old, uninsulated house, you know that method didn't work that well so later we started putting insulation into the cavities in building assemblies. Homes with insulated cavities are much more comfortable, but how exactly does heat flow through building assemblies? Turns out there are two ways.

The 3 Types of Heating and Cooling Loads

 
acca manual j 3 types of heating cooling loads

What is it about the number three? You've got the Three Musketeers, the Three Little Pigs, and the Three Stooges. Then there's three strikes (what every pitcher wants), three branches of government (executive, legislative, and judicial), and the three kinds of people (those who can do math and those who can't). And let's not forget three on a match, three wise men, and threepeats. Today we'll look at another big three: the three types of heating and cooling loads. Do you know what they are?

The Fundamentals of Heating and Cooling Degree Days, Part 2

 
balance degree day base temperature

Degree days are a combination of time and temperature. We looked at their uses and where they come from in part 1 of this series, and now it's time to go a little deeper. The temperature enters as a temperature difference, ΔT (delta T), but it's not the ΔT between inside and outside of the building. It's the difference between the outdoor temperature and the base temperature. But what is this thing called base temperature?

The Fundamentals of Heating and Cooling Degree Days, Part 1

 
thermometer heating degree days

Let's say you did some work on your home to make it more energy efficient - air sealing, more attic insulation, and a duct system retrofit. You've got your energy bills for 12 months before and 12 months after you did the work, and now you want to see how much energy you saved. So you sit down with all 24 months worth of utility bills, convert everything to a common unit if you use more than one type of fuel, and take a look at the numbers. Unless, however, you take into account another important factor, you may be led to incorrect conclusions.

Building Enclosure Blunder in the Basement

 
sealed combustion closet unsealed floor joist duct

The photo below shows a common problem in new homes. It's also one that can make it difficult to pass the blower door test required by many building codes these days. If I tell you that the wall pictured here separates two rooms in a basement and one of them is not conditioned, can you see the problem? If so, how many mistakes do you see here?

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