The most recent blogs at Green Building Advisor

Smug About Your Solar Roof? Not So Fast.

Posted on February 8, 2016 by Severin Borenstein in Guest Blogs

If you've installed solar panels on your roof and feel aglow with environmental virtue, you may be in for a rude awakening. There's a good chance someone else has purchased your halo and is wearing it right now.

Choosing Rigid Foam

Posted on February 5, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

Maybe you’ve decided that your floor, wall, or roof assembly needs one or more layers of rigid foam. Which type of foam should you choose: polyisocyanurate, expanded polystyrene (EPSExpanded polystyrene. Type of rigid foam insulation that, unlike extruded polystyrene (XPS), does not contain ozone-depleting HCFCs. EPS frequently has a high recycled content. Its vapor permeability is higher and its R-value lower than XPS insulation. EPS insulation is classified by type: Type I is lowest in density and strength and Type X is highest.), or extruded polystyrene (XPSExtruded polystyrene. Highly insulating, water-resistant rigid foam insulation that is widely used above and below grade, such as on exterior walls and underneath concrete floor slabs. In North America, XPS is made with ozone-depleting HCFC-142b. XPS has higher density and R-value and lower vapor permeability than EPS rigid insulation.)?

The answer depends on several factors, including your R-valueMeasure of resistance to heat flow; the higher the R-value, the lower the heat loss. The inverse of U-factor. target, your local climate, whether the insulation will be in contact with soil, and your level of environmental concern.

Blue Heron EcoHaus: How Small Can We Go?

Posted on February 4, 2016 by Kent Earle in Guest Blogs

Editor's note: Kent Earle and his wife, Darcie, write a blog called Blue Heron EcoHaus, documenting their journey “from urbanites to ruralites” and the construction of a superinsulated house on the Canadian prairies. Their previous blog on GBAGreenBuildingAdvisor.com was called Choosing a Superinsulated Wall System. The blog below was originally published in March 2015.

Looking at the Costs of LEED Version 4

Posted on February 3, 2016 by Stuart Kaplow in Guest Blogs

With the November 1, 2016, deadline approaching when new LEEDLeadership 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. projects must register under the new LEED version 4, the real estate industry has been raising questions about the costs and benefits of LEED v4 compliance.

Foundation and Nailbase Details for a Minnesota House

Posted on February 2, 2016 by Elden Lindamood in Guest Blogs

This is the second part of a blog series by architect Elden Lindamood about the design and construction of his own home. The first installment was called A Low-Energy House for Northern Minnesota.

Why Is It So Cold In Here?

Posted on February 1, 2016 by Scott Gibson in Guest Blogs

J Pritzen's single-story Illinois house was built in the 1950s. It's heated with a gas furnace fully capable of meeting the heating loadRate at which heat must be added to a space to maintain a desired temperature. See cooling load., but somehow it isn't getting the job done.

The single-story brick house has a mostly insulated, but unheated, basement. Warm air is distributed on the main floor by a series of floor registers set near exterior walls, and an energy auditEnergy audit that also includes inspections and tests to assess moisture flow, combustion safety, thermal comfort, indoor air quality, and durability. tells Pritzen the furnace is cranking out 10,000 BtuBritish thermal unit, the amount of heat required to raise one pound of water (about a pint) one degree Fahrenheit in temperature—about the heat content of one wooden kitchen match. One Btu is equivalent to 0.293 watt-hours or 1,055 joules. more per hour than is lost through the walls and roof.

Smart Vapor Retarders for Walls and Roofs

Posted on January 29, 2016 by Martin Holladay, GBA Advisor in Musings of an Energy Nerd

During the winter, when indoor air is usually warm and humid, most 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. is cold. Under these conditions, we really don’t want water vapor to move from the interior of our homes toward the exterior. That’s why builders in the 1980s installed polyethylene on the interior side of walls.

The Effect of Low Oil Prices on Climate Emissions

Posted on January 28, 2016 by David Goldstein in Guest Blogs

Editor's note: The first blog in this two-part blog series was titled How Low Oil Prices Can Be Good for the Environment.

Don’t Let Your Garage Make You Sick

Posted on January 27, 2016 by Allison A. Bailes III, PhD, GBA Advisor in Building Science

The odds are high that the indoor air quality is worse in a home with an attached garage than in a home without one. Just take a look at the photo here to see some of the potential sources of pollutants that can get into your home's air. How many do you see?

Ditch the Tax Credits for Renewables

Posted on January 26, 2016 by Tristan Brown in Guest Blogs

Congress last month extended valuable tax credits to producers of electricity from wind turbines and purchasers of solar equipment, a move that came as a relief to an industry that has experienced rapid growth in recent years.

A tax credit for wind power producers had lapsed almost a year ago, and the credit for solar power was scheduled to decline sharply at the end of 2016. Now, renewable electricity generators have several years of unprecedented stability: the renewed wind and solar power credits don’t expire until 2020 and 2022, respectively.

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