The most recent blogs at Green Building Advisor

The Fundamentals of Series and Parallel Heat Flow

Posted on February 25, 2015 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

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.

Deep in the Heat of Texas

Posted on February 24, 2015 by Matt Risinger in Green Building Blog

You may have heard that here in Central Texas, it gets hot. The average temperature rises above 90°F on more than 100 days out of the year. As you might expect, we turn on the air conditioner more often than the furnace.

Foam Shrinks, and Other Lessons

Posted on February 23, 2015 by Joe Lstiburek, GBA Advisor in Green Building Blog

I did a deep-energy retrofit on my barn 16 years ago. Building Science Corp. was young and growing, and we needed a bigger office. The barn would be that office for the next 10 years. In fact, Betsy Pettit wrote about it in “Remodeling for Energy Efficiency” (FHB #194).

Designing for the Future

Posted on February 20, 2015 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

When an architect, residential builder, and owner sit around a table for their first design meeting, their ostensible goal is to begin designing a house. Whether they realize it or not, however, these three people are also predicting the future.

Minisplit Heat Pumps and Blizzards

Posted on February 19, 2015 by Marc Rosenbaum in Guest Blogs

A blizzard (a severe snowstorm and sustained winds of over 35 mph) is a challenging weather condition for a minisplit heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump.. Recall how an air-source heat pumpHeat pump that relies on outside air as the heat source and heat sink; not as effective in cold climates as ground-source heat pumps. works: the outdoor unit has a compressor and a fan that blows air across a coil with refrigerant. In heating mode, the coil is colder than the outdoor air. As air is drawn through the coil, it gives up heat to the coil and leaves the other side colder.

Why Is the HERS Reference Home Based on an Outdated Energy Code?

Posted on February 18, 2015 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

The HERS Index is a number that gives you a measure of how energy-efficient a home is. We can debate how relevant that number is or how accurate is the energy model it's based on, but the fact is that it's being used.

From a Leaky Old House to a Tight New Home

Posted on February 17, 2015 by Andrew Webster in Green Building Blog

Sara and Gareth Ross had spent a decade on the move. Postgraduate degrees and finance work had propelled them from Boston to New York, Philadelphia, and San Francisco. When it came time to settle down, though, they moved to Amherst, Mass., where Sara had grown up. Amherst is a vibrant college town with rural beauty and Japanese restaurants; for the Rosses, it was the perfect place to slow down, nurture roots, and raise children. The Rosses were not tied either to the idea of a new house or to a remodel.

Why Is It So Humid In Here?

Posted on February 16, 2015 by Scott Gibson in Q&A Spotlight

From the sound of it, Andy Chappell-Dick has left no stone unturned in his quest to keep the air inside his house comfortably dry.

His extremely tight new house in northern Ohio (Climate Zone 5) is built with structural insulated panels, and heated and cooled with a pair of ductless minisplit heat pumps. For ventilation, Chappell-Dick has a Venmar Kubix heat-recovery ventilator(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. that pulls exhaust air from two small bathrooms and supplies fresh air to two upstairs bedrooms with a flow rate of between 40 and 80 cubic feet per minute (cfm).

The Evolution of Superinsulation

Posted on February 13, 2015 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

At the recent “Better Buildings By Design” conference in Burlington, Vermont, I attended presentations that epitomized two different approaches to energy-conscious building. I’ll call these two approaches “classic superinsulation” and “the net zeroProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. Calculating net-zero energy can be difficult, particularly in grid-tied renewable energy systems, because of transmission losses in power lines and other considerations. approach.”

The “classic superinsulation” method has been around for about 35 years. It’s the approach that formed the basis of Wolfgang Feist’s PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. standard.

Passive House Perfection

Posted on February 12, 2015 by Justin Pauly in Green Building Blog

After both growing up in California, Mica and Laureen lived together in many other places throughout their busy careers. Their hearts have always been on the West Coast, though, and they longed to return one day. They eventually found a small piece of property in the coastal enclave of Carmel-by-the Sea on the Monterey Peninsula, and they hired me as architect and Rob Nicely of Carmel Building & Design as builder for a new house that will one day be their permanent home.

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