The most recent blogs at Green Building Advisor

Do I Really Need a Concrete Basement Floor?

Posted on May 5, 2014 by Scott Gibson in Q&A Spotlight

Rob Rosen is diving into a basement remodel, a job that involves digging out and removing a concrete slab to provide more headroom so the basement can be turned into usable living space.

He'll reinforce the footing and foundation as needed, but when it comes time to build a new floor for the basement, Rosen wonders whether he can go with something other than a concrete slab.

WUFI Is Driving Me Crazy

Posted on May 2, 2014 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Is it possible to describe all of the factors that influence heat and moisture movement through a wall during a single day? Perhaps. We could start by listing the outdoor conditions, including air temperature, relative humidity, wind speed, wind direction, the angle of the sun with respect to the wall (its altitude and azimuth), the cloud thickness, the precipitation rate, and the depth of snow on the ground. Needless to say, many of these factors change from minute to minute.

Taking Action on Climate Change

Posted on May 1, 2014 by Alex Wilson in Energy Solutions

In my previous blog I described the international effort to understand climate change. The United Nations’ IPCC is leading the charge, and efforts like the Kyoto Treaty have grown out of that background work. But are we getting closer to solving the problem?

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.

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