The most recent blogs at Green Building Advisor

What Happens When You Put a Plastic Vapor Barrier in Your Wall?

Posted on April 30, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

A lot of people have heard advice about vapor barriers and vapor retarders. Many of them have walked away confused. A big part of the problem, I think, is that they've been told what to do — "Put it on the warm-in-winter side," or "Never use one" — but they haven't had the physics of what happens explained to them.

Moving to a New House

Posted on April 29, 2014 by Marc Rosenbaum in Guest Blogs

Jill and I got hitched on June 2, 2013, on the beach at the Gay Head Cliffs on Martha's Vineyard. We then spent the next 7 1/2 days packing up our possessions at our old house at Island CohousingDevelopment pattern in which multiple (typically 8 to 30) privately owned houses or housing units are clustered together with some commonly owned spaces, such as a common workshop, greenhouse, etc. Automobiles are typically kept to the perimeter of the community, creating a protected area within where children can play. Usually, residents are closely involved in all aspects of the development, from site selection to financing and design. in preparation to moving to our new place. We closed on the old house on June 10th. Not a recommended honeymoon.

Does a Home with an HRV Also Need Bath Fans?

Posted on April 25, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

A balanced ventilationMechanical ventilation system in which separate, balanced fans exhaust stale indoor air and bring in fresh outdoor air in equal amounts; often includes heat recovery or heat and moisture recovery (see heat-recovery ventilator and energy-recovery ventilator). system — for example, a system with a heat-recovery ventilator (HRV(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. ) or an energy-recovery ventilator (ERV(ERV). The part of a balanced ventilation system that captures water vapor and heat from one airstream to condition another. In cold climates, water vapor captured from the outgoing airstream by ERVs can humidify incoming air. In hot-humid climates, ERVs can help maintain (but not reduce) the interior relative humidity as outside air is conditioned by the ERV.) — exhausts stale air from some rooms in a building, while simultaneously introducing fresh outdoor air to other rooms. The best balanced ventilation systems use dedicated ventilation ductwork. Usually, these systems pull exhaust air from damp, smelly rooms — bathrooms and laundry rooms — and introduce fresh air to the rooms where people spend most of their time — bedrooms and the living room.

Earth Day 2014 and Climate Change

Posted on April 24, 2014 by Alex Wilson in Energy Solutions

With Earth Day having been this week, I’ve been musing about the state of our environment and where we’re heading.

Does Open-Cell Spray Foam Really Rot Roofs?

Posted on April 23, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

Murmurs and hearsay about open-cell spray foam insulation have been gaining traction for a while. It rots roofs, people have told me. Not long ago, someone even told me that in Florida, roofing companies won't let their workers go up on roofs with open-cell spray foam because the roofs are so spongy, the guys fall right through.

Open-cell spray foam is getting a bad reputation among some people in the construction industry. But is it deserved?

My Earth Tube Story

Posted on April 22, 2014 by Malcolm Isaacs in Guest Blogs

I saw my first “earth tube” back in 2004, on a tour of row houses in Darmstadt, Germany — a tour which had been organized by the 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. Institut (PHI) to show international visitors some examples of Passivhaus construction. As a visiting Canadian engineer specializing in residential energy efficiency, this was a novel and, for me, unheard-of way to temper incoming ventilation air from extremes of heat and cold.

Building a Foolproof Low-Slope Roof

Posted on April 21, 2014 by Scott Gibson in Q&A Spotlight

Carolyn Wood is building a house 80 miles north of Vancouver, British Columbia, and if nothing else she'd like to get all the details in the roof assembly right. The question is whether the house is too far along to let her reach that goal.

The roof, with a 2-in-12 pitch, is framed with I-joists, strapped with 2x4s, and sheathed with 1/2-in. plywood. Above the roof 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. , the roofers plan to install NovaSeal roofing underlayment and standing-seam metal roofing.

All About Radiant Floors

Posted on April 18, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

So-called radiant floors have an excellent reputation. Many customers report that this type of heating system is comfortable and quiet. Moreover, some suppliers of radiant floor materials and equipment claim that these systems can save energy.

In spite of the purported benefits of this type of heating system, few green homes include a radiant floor heating system. This article will explore why.

How Much Water Does it Take to Turn on a Light Bulb?

Posted on April 17, 2014 by Alex Wilson in Energy Solutions

In last week's blog I took a look at some of the water conservation features in our new house, but I began the blog by addressing the relationship between water and energy. That got me curious, so I’ve been digging deeper into this water-energy nexus, examining the water-intensity of our different electricity sources.

How to Detect an Internet Solar Energy Scam

Posted on April 16, 2014 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

All I was trying to do was find some sports scores on Yahoo the other day when I saw it. I don't go looking for this stuff, and when I do see it, I try to ignore it. But this one clotheslined me with an unfair term.

That's the ad in question to the right. Have you seen it? I probably shouldn't tell you the name of the website (powerfreedom.com), but the kryptonite term that made my fingers go apoplectic was “free energy.” Seeing it capitalized intensified the effect. And the photo! Is that a diseased wireless router robot surrendering its secrets to me?

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