Building Science


Moisture Sources, Relative Humidity, and Mold

Posted on March 24, 2009 by Peter Yost

A little water goes a long way

We hear a lot about how moisture can be an indoor pollutant in tight houses. But just how much moisture can be a problem; how does boiling a pot of water compare to a 15-minute shower? This keeps some of us mold worrywarts up at night, so I thought it would be a good idea to run some numbers.

thermal bridge - steel

Thermal Bridging

Posted on March 19, 2009 by Peter Yost

Everything is relative — especially when it comes to thermal bridgingHeat flow that occurs across more conductive components in an otherwise well-insulated material, resulting in disproportionately significant heat loss. For example, steel studs in an insulated wall dramatically reduce the overall energy performance of the wall, because of thermal bridging through the steel. . Thermal bridging occurs wherever assembly components with low R-values relative to surrounding materials span from the inside to the outside of a building assembly. Thermal bridging takes place in wood-framed assemblies because, although wood is a pretty good insulator at about R-1 per inch, it is at least three times more thermally conductive than any cavity insulation, which start at about R-3.5 per inch.

Moisture Meter - basement

Pressure-Treated Sill Plates and the Building Code

Posted on March 9, 2009 by Peter Yost

Code requirements for wood-concrete contact treat the symptoms of rot, not the cause

Last week we talked about moisture meters, and I asked readers why the wood in the picture was wet. As it turns out, that photo was taken in the same house on the same day as the two pictures at right.

moisture meter - crawl2

Tools of the Trade: Moisture Meters

Posted on March 2, 2009 by Peter Yost

A moisture meter is a simple, easy-to-use tool for evaluating moisture and mold problems

Moisture meters help you figure out whether your building materials are too wet. They typically use electrical conductivity between a couple of metal pins to assess moisture content; the more moisture in the material, the greater the electrical conductivity. The moisture content is measured as a percentage of total weight.

Solar fan vent

Are Solar-Powered Attic Ventilators Green?

Posted on February 26, 2009 by Peter Yost

At face value, attic exhaust fans make a lot of sense: if your attic is too hot, you force more air through it to cool it down. To be efficient, you use a solar-powered attic exhaust fan. When the sun is shining and heating up your attic, that’s when the photovoltaic(PV) Generation of electricity directly from sunlight. A photovoltaic cell has no moving parts; electrons are energized by sunlight and result in current flow. panel wired to the exhaust fan powers the fan. Pretty slick.

Peter Yost interview on Go Green Radio

Posted on February 18, 2009 by Brian Becker

Listen to Peter and Go Green Radio host Jill Buck discuss what makes a green home. Peter emphasizes the importance of the building process as well as the products used. Also discussed are the new USGBCUnited States Green Building Council (USGBC). Organization devoted to promoting and certifying green buildings. USGBC created the LEED rating systems. LEED for HomesLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. standards, building durability, building value over time, and how builders can develop their own green construction expertise.

Portland, Oregon

Is Saving Energy Expensive?

Posted on February 9, 2009 by Peter Yost

70% energy savings are not only possible, they can be affordable. Why we need, and what we don't know about, deep energy retrofits

At the recent Affordable Comfort conference in Portland, Oregon, I was on a really interesting panel with Linda Wigington of Affordable Comfort, Katrin Klingenberg of the Passive House Institute US, and Alistair Jackson of O’Brien and Company (we—and the audience—had superb “adult supervision” from a leading Portland architect, Nathan Good). The question the panel wrestled with was this: Just how low can we get the total household energy use of existing homes when we do whole-house retrofits on different building types in different climates?


The Time for Building Green Homes has Arrived

Posted on January 9, 2009 by Sam Rashkin

The Link Between Energy Efficiency and Our Country's Best Interests Are Now Well Understood. Here's five reasons why the time is ripe to build and remodel green

In my last semester of architecture school, I took an elective solar and energy-efficiency course. My life changed immediately and forever. And now, almost 35 years later, it appears the building industry has caught up and it’s time for “green.” Why now? I’ve got five reasons:


Video Tip: Self Draining Sill Pans

Posted on January 9, 2009 by Daniel Morrison

Water Can Collect at Window Sills

Installing windows is tricky— A window is basically a big hole in an otherwise continuous surface that's insulated and protected from rain and wind.

Builders have been putting windows in walls for a long time, so there are plenty of time-tested methods. But old houses weren't insulated or air sealed as well as green houses, so drying was easier if the window leaked.

Watch the video

blog-Whats wrong-cut up I-Joist-Ducts093.jpg

I-joists are not ductwork

Posted on November 11, 2008 by Daniel Morrison

What’s wrong with this picture?

a) The rim joist is too heavily notched.
b) Using framing cavities as duct runs is frowned upon by codes and professional associations.
c) This passed the framing inspection.
d) All of the above

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