Green Building

Is R-8 Duct Insulation Enough?

Prime:  prime Subtitle:  Code requirements are always a compromise between what’s best and what’s practical Images: 

If you know a little building science, you've no doubt seen a lot of problems that occur with air distribution systems. Ducts just don't get anywhere near the attention they deserve in most homes.

I've written about ducts quite a bit here and have shown problems resulting from poor design and installation. We all know how stupid some of those problems are. So today I'm going to talk about a problem that doesn't get nearly enough attention: duct insulation — even when the design and installation are perfect.

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Kingspan Kooltherm Phenolic Foam Rigid Insulation

Subtitle:  A deep-energy-retrofit project uses Kooltherm as part of a high-performance attic insulation system Images: 

Improving the thermal performance of an existing attic is often challenging: workers are faced with narrow cavities, low clearances, and claddingMaterials used on the roof and walls to enclose a house, providing protection against weather. systems that make it hard to achieve desired R-values while still maintaining the necessary drying potential of the assembly.

The house at 81 Chapin Street in Brattleboro, Vermont, is no exception. It’s a 100-year-old wood-framed two-story home that Alex Beck and Candace Pearson are determined to comprehensively retrofit to high performance.

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Adjusting Bath Fan Use in Winter

Prime:  prime Subtitle:  Do you really need to run it when you shower? Images: 

You may have heard or read somewhere that you should run your bathroom exhaust fan whenever you take a shower and then let it run for a while after you're done with the shower. Showers increase the humidity in the bathroom. Sometimes it gets high enough to cause condensation to appear on the mirror and other surfaces in the bathroom. And that can result in mold growth.

So you should always run your bath fan when you shower. Or so they say.

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Ventilating a Home in Cold Weather

Prime:  prime Subtitle:  You need fresh air, but bringing in cold outdoor air can cause problems Images: 

When I woke up Saturday morning, the temperature outdoors was -40 degrees. The wind chill was -100 degrees! It was just unbelievably, impossibly, inhumanly cold outside. Fortunately, that was on a mountaintop in New Hampshire and not where I was. I happened to have woken up on a mountaintop in North Carolina, where the temperature was a much warmer -3°F.

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Night Surveys: The Lights Are On, But Nobody is Home

Subtitle:  How Yale University's energy manager uses after-hours walk-throughs to save energy Images: 

Julie Paquette has been Director of Energy Management at Yale University for about 6 years. That means the buck stops at Julie’s desk for the energy consumption of over 400 buildings on campus. Yale has a pretty sophisticated approach to energy, including the Yale Facilities Energy Explorer, an energy dashboard system that shows energy consumption and details for every one of those 400 Yale buildings.

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The Buy-in Problem

Prime:  prime Subtitle:  From code compliance to Passive House certification, getting good work from contractors is hard Images: 

Last week I read a nice little article by Steve Baczek about getting buy-in from the various stakeholders involved with building a home. He's an architect who works closely with the people who build the homes he designs. He's also a former U.S. Marine who understands the importance of what he calls "a ladder of leadership and responsibility."

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Exterior Insulation on 2x4 Walls Versus 2x6 Walls With Cavity Insulation Only

Prime:  prime Subtitle:  A look at some modeling results may help you decide Images: 

If you live in the world of 2x4 walls, as I do, you may have wondered about the savings you'd get by going to a more robust wall assembly. The typical house in southern climes has 2x4 walls with R-13 insulation in the cavities. The two ways to beef that up would be to add continuous exterior insulation or to go to a thicker wall. But which saves more energy? And how do they compare to the plain old 2x4 wall?

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How Does a Heat Pump Get Heat From Cold Air?

Prime:  prime Subtitle:  The physics of heat pumps isn’t really that difficult to understand Images: 

Cold weather is coming back to Atlanta this week, so let’s talk about heat. An increasingly popular way to heat buildings these days is with heat pumps, even in cold climates. But how do they work?

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Extending the Reach of a Moisture Meter

Subtitle:  Simple ways to measure moisture content deeper into building assemblies Images: 

Typical pins on moisture meters are ½ inch long, meaning you can only determine moisture content by weight near the surface of building assemblies and materials (including wood, gypsum wallboard, and concrete). But I often find myself needing to assess moisture content of first condensing surfaces in walls and ceilings or well below the surface of basement slabs.

This article looks at ways to extend the reach of a moisture meter. (For introductory information on moisture meters, see Tools of the Trade: Moisture Meters.)

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Two Rules for Humidity

Prime:  prime Subtitle:  To prevent moisture damage from humid air, just do these two things Images: 

Because I've written so much about moisture in buildings, I get a lot of questions on the topic. Some are about walls. Some are about the attic. Some are about windows. Some are about the crawl space (which generates the most questions on this topic).

The key to answering a lot of those questions boils down to an understanding of how water vapor interacts with materials. Once you know that, it's easy to see the two rules for preventing damage from humidity.

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The Four Laws of Thermodynamics

Prime:  prime Subtitle:  We often talk of the second law, but what are the other three? Images: 

Building science is an odd subject. Few colleges and universities teach it. The majority of those who work on buildings call themselves engineers, architects, and contractors, not building scientists. And many of those who do invoke the term can explain at least one implication of the second law of thermodynamics (we'll get to that below) but may not know what the other laws of thermodynamics are, why their numbering is so peculiar, or even how many there are. Do you?

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How Many Tons of Air Does a 2.5 Ton Air Conditioner Move?

Prime:  prime Subtitle:  And under what conditions would it move exactly 2.5 tons of air? Images: 

We live in this invisible stuff called air. (But of course you knew that.) We pump it into and out of our lungs. We exhaust it from our bathrooms and kitchens. We cycle it through our heating and air conditioning systems. If we're lucky, we live in a home that even brings outdoor air inside as part of a whole-house ventilation system. But we're missing something.

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