Musings of an Energy Nerd

Making Room for a PV Array

Posted on November 27, 2015 by Martin Holladay, GBA Advisor

Compared to a 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. system, a solar hot water system yields very little energy per dollar invested. I presented that argument in a 2012 article called “Solar Thermal Is Dead.” Two years later, in 2014, an economic comparison between these two solar technologies showed a stronger tilt than ever before in favor of PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow., leading me to write a follow-up article called “Solar Thermal Is Really, Really Dead.”

Wall Sheathing Options

Posted on November 20, 2015 by Martin Holladay, GBA Advisor

For the past 30 years, the majority of new homes in the U.S. have been built with wood-framed walls sheathed with oriented strand board (OSB). Most builders are so comfortable with OSB wall sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. that they never consider using an alternative material.

In fact, a wide range of materials can be used to sheathe a wood-framed wall. In addition to OSB, builders can choose plywood, fiberboard, rigid foam, diagonal boards, and fiberglass-faced gypsum panels. If you’re a dyed-in-the-wool OSB user, it might be time to consider some of the available alternatives to OSB.

Where Does the Air Come From?

Posted on November 13, 2015 by Martin Holladay, GBA Advisor

Most American homes have a bewildering array of diffusers, registers, and grilles that blow air out or suck air in. For many homeowners, these apertures are somewhat mysterious. We all know that there must be a duct behind each grille, but where does the duct lead?

Another North American Magic Box

Posted on November 6, 2015 by Martin Holladay, GBA Advisor

Over the past few years, GBAGreenBuildingAdvisor.com has published several articles on “magic boxes” — a type of combination appliance that functions as a ventilation system, heating system, and cooling system. Most recently, I wrote about the CERV, a magic box manufactured in Illinois. Now a Canadian manufacturer has come out with a magic box that resembles the CERV.

A Backyard Test of Liquid-Applied Flashings

Posted on October 30, 2015 by Martin Holladay, GBA Advisor

Liquid-applied flashings are caulk-like materials that are spread with a trowel. Once cured, these products form a waterproof, airtight, vapor-permeable layer that can prevent air leakage through sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. seams or protect rough window sills from water entry.

Rethinking Durability

Posted on October 23, 2015 by Martin Holladay, GBA Advisor

Does durability matter? Most green building advocates seem to think that green builders should always aim to build durable structures. My own opinion differs; in fact, as I explained in a 2009 article on the topic, it’s hard to see any correlation between durability and “greenness.”

I recently had an opportunity to reconsider the advantages and disadvantages of durability when my wife and I visited the Pont du Gard in Languedoc-Roussillon, France.

Ductless Minisplits May Not Be As Efficient As We Thought

Posted on October 16, 2015 by Martin Holladay, GBA Advisor

A recent monitoring study of ductless minisplits installed in seven New England homes found that these heating appliances had lower airflow rates and lower coefficients of performance (COPs) than expected. The average COP of these air-source heat pumps ranged from 1.1 at the house with the least-efficient minisplit to 2.3 at the house with the most-efficient minisplit.

The results of the study raise at least as many questions as they answer. Perhaps the most useful outcome of the study is that it sets up a framework for recommendations that could enhance minisplit efficiency.

GBA Prime Sneak Peek: Reassessing Passive Solar Design Principles

Posted on October 9, 2015 by Martin Holladay, GBA Advisor

GBAGreenBuildingAdvisor.com Prime subscribers have access to many articles that aren't accessible to non-subscribers, including Martin Holladay's weekly blog series, “Musings of an Energy Nerd.” To whet the appetite of non-subscribers, we occasionally offer non-subscribers access to a “GBA Prime Sneak Peek” article like this one.

Reassessing Passive Solar Design Principles

Posted on October 9, 2015 by Martin Holladay, GBA Advisor

Everybody loves passive solar design. Back in the 1970s, “passive solar” was the essential first step for cold-climate builders. It was considered an approach with obvious advantages over complicated “active solar” schemes that required pumps, fans, and electronic controls.

Naming Building Parts is Tricky

Posted on October 2, 2015 by Martin Holladay, GBA Advisor

This blog is directed to homeowners. If you are a builder or an architect, you should probably click on a different GBAGreenBuildingAdvisor.com article.

Homeowners who send questions to GBA sometimes don't know what to call the parts of their building. (If it's a diffuserIn a forced-air heating/cooling system, the diffuser is a register or grille attached to ducting through which heated or air conditioned air is delivered to the living space. In a tubular skylight or an electric light fixture, the diffuser is a cover plate through which scattered light is delivered., grille, register, or duct termination, there's a fair chance that someone will decide to just call it a "vent.") I've rounded up some of the most confusing terms used by builders and architects and clarified their definitions.

Since a drawing can be a handy way to clarify a definition, I made some quick sketches to illustrate my points.

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